Transport mechanism in ionic liquid membranes and the study of thiomersal biodegradation

The initial goal of this work was the development of a supported liquid membrane (SLM) bioreactor for the remediation of vaccine production effluents contaminated with a highly toxic organomercurial – thiomersal. Therefore, two main aspects were focused on: 1) the development of a stable supported liquid membrane – using room temperature ionic liquids (RTILs) – for the selective transport of thiomersal from the wastewater to a biological compartment, 2) study of the biodegradation kinetics of thiomersal to metallic mercury by a Pseudomonas putida strain. The first part of the work focused on the evaluation of the physicochemical properties of ionic liquids and on the SLMs’ operational stability. The results obtained showed that, although it is possible to obtain a SLM with a high stability, water possesses nonnegligible solubility in the RTILs studied. The formation of water clusters inside the hydrophobic ionic liquid was identified and found to regulate the transport of water and small ions. In practical terms, this meant that, although it was possible to transport thiomersal from the vaccine effluent to the biological compartment, complete isolation of the microbial culture could not be guaranteed and the membrane might ultimately be permeable to other species present in the aqueous vaccine wastewater. It was therefore decided not to operate the initially targeted integrated system but, instead, the biological system by itself. Additionally, attention was given to the development of a thorough understanding of the transport mechanisms involved in the solubilisation and transport of water through supported liquid membranes with RTILs as well as to the evaluation of the effect of water uptake by the SLM in the transport mechanisms of water-soluble solutes and its effect on SLM performance. The results obtained highlighted the determinant role played by water – solubilised inside the ionic liquids – on the transport mechanism. It became clear that the transport mechanism of water and water-soluble solutes through SLMs with [CnMIM][PF6] RTILs was regulated by the dynamics of water clusters inside the RTIL, rather than by molecular diffusion through the bulk of the ionic liquid. Although the stability tests vi performed showed that there were no significant losses of organic phase from the membrane pores, the formation of water clusters inside the ionic liquid, which constitute new, non-selective environments for solute transport, leads to a clear deterioration of SLM performance and selectivity. Nevertheless, electrical impedance spectroscopy characterisation of the SLMs showed that the formation of water clusters did not seem to have a detrimental effect on the SLMs’ electrical characteristics and highlighted the potential of using this type of membranes in electrochemical applications with low resistance requirements. The second part of the work studied the kinetics of thiomersal degradation by a pure culture of P. putida spi3 strain, in batch culture and using a synthe tic wastewater. A continuous ly stirred tank reactor fed with the synthetic wastewater was also operated and the bioreactor’s performance and robustness, when exposed to thiomersal shock loads, were evaluated. Finally, a bioreactor for the biological treatment of a real va ccine production effluent was set up and operated at different dilution rates. Thus it was possible to treat a real thiomersal-contaminated effluent, lowering the outlet mercury concentration to values below the European limit for mercury effluent discharges.

Organic load of substrata for wastewater treatment constructed wetlands

In Portugal the use of Constructed Wetlands (CW) for wastewater treatment has been increasing. However a number of these facilities need new strategies to achieve better efficiency. Keeping the culms of reeds on the CW beds not always results as desired, but the use of widely available agro-forest wastes, may be suitable as CW support matrix. This study was performed at lab-scale with dried culms of Phragmites and eucalyptus bark maintained in tap water, to assess them as CW substrata. With a 7 days residence time in water, Phragmites culms added a high organic load (about 400 mg L-1 BOD5) to the medium, while the eucalyptus bark added only, about 60 mg L-1 BOD5. However, by lixiviation, the organic load decreased to about 25 mg L-1 BOD5 in 5 weeks. With the organic load reduction of the leachate water, its surface tension increased, approaching the surface tension of tap water.

Persistent organic chemicals of emerging environmental concern

The use of chemicals and chemical derivatives in agriculture and industry has contributed to their accumulation and persistence in the environment. Persistent organic pollutants (POPs) are among the environmental pollutants of most concern since, when improperly handled and disposed, they can persist in the environment, bioaccumulate through the food web, and may create serious public health and environmental problems. Development of an effective degradation process has become an area of intense research. The physical/chemical methods employed, such as volatilization, evaporation, photooxidation, adsorption, or hydrolysis, are not always effective, are very expensive, and, sometimes, lead to generation/disposal of other contaminants. Biodegradation is one of the major mechanisms by which organic contaminants are transformed, immobilized, or mineralized in the environment. A clear understanding of the major processes that affect the interactions between organic contaminants, microorganisms, and environmental matrix is, thus, important for determining persistence of the compounds, for predicting in situ transformation rates, and for developing site remediation. Information on their risks and impact and occurrence in the different environmental matrices is also important, in order to attenuate their impact and apply the appropriate remediation process. This chapter provides information on the fate of pesticides and polycyclic aromatic hydrocarbons (PAHs), their impact, bioavailability, and biodegradation. © Springer Science+Business Media Dordrecht 2014.

On the use of reporter bacteria for measuring availability of organic contaminants

Natural environments are constantly challenged by the release of hydrophobic organic contaminants, which represent a threat for both the ecosystem and human health. Despite a substantial degradation by naturally occurring micro-organisms, a non negligible fraction of these pollutants tend to persist in soil and sediments due to their reduced accessibility to microbial degraders. This lack of 'bioavailability' is acknowledged as a key parameter for the natural and stimulated clean-up (bioremediation) of contaminated sites. We developed a bacterial bioreporter that responds to the presence of polyaromatic hydrocarbons (PAHs) by the production of the green fluorescent protein (GFP), based on the PAH-degrading bacterium Burkholderia sartisoli. We showed in this study that the bacterial biosensor B. sartisoli strain RP037 was faithfully reporting the degradation of naphthalene and phenanthrene (two PAHs of low molecular weight) via the production of GFP. What is more, the magnitude of GFP induction was influenced by change in the PAH flux triggered by a variety of physico-chemical parameters, such as the contact surface between the pollutant and the aqueous suspension. Further experiments permitted to test the influence of dissolved organic matter, which is an important component of natural habitats and can interact with organic pollutants. In addition, we tested the influence of two types of biosurfactants (tensio-active agents produced by living organisms) on phenanthrene's degradation by RP037. Interestingly, the surfactant's effects on the biodegradation rate appeared to depend on the type of biosurfactant and probably on the type of bacterial strain. Finally, we tagged B. sartisoli strain RP037 with a constitutively expressed mCherry fluorescent protein. The presence of mCherry allowed us to visualize the bacteria in complex samples even when GFP production was not induced. The new strain RP037-mChe embedded in a gel patch was used to detect PAH fluxes from a point source, such as a non-aqueous liquid or particles of contaminated soil. In parallel, we also developed and tested a so-called multiwell bacterial biosensor platform, which permitted the simultaneous use of four different reporter strains for the detection of major crude oil components (e.g., saturated hydrocarbons, mono- and polyaromatics) in aqueous samples. We specifically constructed the strain B. sartisoli RP007 (pPROBE-phn-luxAB) for the detection of naphthalene and phenanthrene. It was equipped with a reporter plasmid similar to the one in strain RP037, except that the gfp gene was replaced by the genes luxAB, which encoded the bacterial luciferase. The strain was implemented in the biosensor platform and detected an equivalent naphthalene concentration in oil spilled-sea water. We also cloned the gene for the transcriptional activator AlkS and the operator/promoter region of the operon alkSB1GHJ from the alkane-degrader bacterium Alcanivorax borkumensis strain SK2 in order to construct a new bacterial biosensor with higher sensitivity towards long-chain alkanes. However, the resulting strain showed no increased light emission in presence of tetradecane (C14), while it still efficiently reported low concentrations of octane (C8). RÉSUMÉ : Les écosystèmes naturels sont constamment exposés à nombre de contaminants organiques hydrophobes (COHs) d'origine industrielle, agricole ou même naturelle. Les COHs menacent à la fois l'environnement, le bien-être des espèces animales et végétales et la santé humaine, mais ils peuvent être dégradés par des micro-organismes tels que les bactéries et les champignons, qui peuvent être capables des les transformer en produits inoffensifs comme le gaz carbonique et l'eau. La biodégradation des COHs est cependant fréquemment limitée par leur pauvre disponibilité envers les organismes qui les dégradent. Ainsi, bien que la biodégradation opère partiellement, les COHs persistent dans l'environnement à de faibles concentrations qui potentiellement peuvent encore causer des effets toxiques chroniques. Puisque la plupart des COHs peuvent être métabolisés par l'activité microbienne, leur persistance a généralement pour origine des contraintes physico-chimiques plutôt que biologiques. Par exemple, leur solubilité dans l'eau très limitée réduit leur prise par des consommateurs potentiels. De plus, l'adsorption à la matière organique et la séquestration dans les micropores du sol participent à réduire leur disponibilité envers les microbes. Les processus de biodisponibilité, c'est-à-dire les processus qui gouvernent la dissolution et la prise de polluants par les organismes vivants, sont généralement perçus comme des paramètres clés pour la dépollution (bioremédiation) naturelle et stimulée des sites contaminés. Les hydrocarbures aromatiques polycycliques (HAPs) sont un modèle de COH produits par les activités aussi bien humaines que naturelles, et listés comme des contaminants chroniques de l'air, des sols et des sédiments. Ils peuvent être dégradés par un vaste nombre d'espèces bactériennes mais leur taux de biodégradation est souvent limité par les contraintes mentionnées ci-dessus. Afin de comprendre les processus de biodisponibilité pour les cellules bactériennes, nous avons décidé d'utiliser les bactéries elles-mêmes pour détecter et rapporter les flux de COH. Ceci a été réalisé par l'application d'une stratégie de conception visant à produire des bactéries `biocapteurs-rapporteurs', qui littéralement s'allument lorsqu'elles détectent un composé cible pour lequel elles ont été conçues. En premier lieu, nous nous sommes concentrés sur Burkholderia sartisoli (souche RP007), une bactérie isolée du sol et consommatrice de HAP .Cette souche a servi de base à la construction d'un circuit génétique permettant la formation de la protéine autofluorescente GFP dès que les cellules détectent le naphtalène ou le phénanthrène, deux HAP de faible masse moléculaire. En effet, nous avons pu montrer que la bactérie obtenue, la souche RP037 de B. sartisoli, produit une fluorescence GFP grandissante lors d'une exposition en culture liquide à du phénanthrène sous forme cristalline (0.5 mg par ml de milieu de culture). Nous avons découvert que pour une induction optimale il était nécessaire de fournir aux cellules une source additionnelle de carbone sous la forme d'acétate, ou sinon seul un nombre limité de cellules deviennent induites. Malgré cela, le phénanthrène a induit une réponse très hétérogène au sein de la population de cellules, avec quelques cellules pauvrement induites tandis que d'autres l'étaient très fortement. La raison de cette hétérogénéité extrême, même dans des cultures liquides mélangées, reste pour le moment incertaine. Plus important, nous avons pu montrer que l'amplitude de l'induction de GFP dépendait de paramètres physiques affectant le flux de phénanthrène aux cellules, tels que : la surface de contact entre le phénanthrène solide et la phase aqueuse ; l'ajout de surfactant ; le scellement de phénanthrène à l'intérieur de billes de polymères (Model Polymer Release System) ; la dissolution du phénanthrène dans un fluide gras immiscible à l'eau. Nous en avons conclu que la souche RP037 détecte convenablement des flux de phénantrène et nous avons proposé une relation entre le transfert de masse de phénanthrène et la production de GFP. Nous avons par la suite utilisé la souche afin d'examiner l'effet de plusieurs paramètres chimiques connus dans la littérature pour influencer la biodisponibilité des HAP. Premièrement, les acides humiques. Quelques rapports font état que la disponibilité des HAP pourrait être augmentée par la présence de matière organique dissoute. Nous avons mesuré l'induction de GFP comme fonction de l'exposition des cellules RP037 au phénanthrène ou au naphtalène en présence ou absence d'acides humiques dans la culture. Nous avons testé des concentrations d'acides humiques de 0.1 et 10 mg/L, tandis que le phénanthrène était ajouté via l'heptamethylnonane (HMN), un liquide non aqueux, ce qui au préalable avait produit le plus haut flux constant de phénanthrène aux cellules. De plus, nous avons utilisé des tests en phase gazeuse avec des concentrations d'acides humiques de 0.1, 10 et 1000 mg/L mais avec du naphtalène. Contrairement à ce que décrit la littérature, nos résultats ont indiqué que dans ces conditions l'expression de GFP en fonction de l'exposition au phénanthrène dans des cultures en croissance de la souche RP037 n'était pas modifiée par la présence d'acides humiques. D'un autre côté, le test en phase gazeuse avec du naphtalène a montré que 1000 mg/L d'acides humiques abaissent légèrement mais significativement la production de GFP dans les cellules de RP037. Nous avons conclu qu'il n'y a pas d'effet général des acides humiques sur la disponibilité des HAP pour les bactéries. Par la suite, nous nous sommes demandé si des biosurfactants modifieraient la disponibilité du phénanthrène pour les bactéries. Les surfactants sont souvent décrits dans la littérature comme des moyens d'accroître la biodisponibilité des COHs. Les surfactants sont des agents tensio-actifs qui augmentent la solubilité apparente de COH en les dissolvant à l'intérieur de micelles. Nous avons ainsi testé si des biosurfactants (des surfactants produits par des organismes vivants) peuvent être utilisé pour augmenter la biodisponibilité du phénanthrène pour la souche B. sartisoli RP037. Premièrement, nous avons tenté d'obtenir des biosurfactants produits par une autre bactérie vivant en co-culture avec les biocapteurs bactériens. Deuxièmement, nous avons utilisé des biosurfactants purifiés. La co-cultivation en présence de la bactérie productrice de lipopeptide Pseudomonas putida souche PCL1445 a augmenté l'expression de GFP induite par le phénanthrène chez B. sartisoli en comparaison des cultures simples, mais cet effet n'était pas significativement différent lorsque la souche RP037 était co-cultivée avec un mutant de P. putida ne produisant pas de lipopeptides. L'ajout de lipopeptides partiellement purifiés dans la culture de RP037 a résulté en une réduction de la tension de surface, mais n'a pas provoqué de changement dans l'expression de GFP. D'un autre côté, l'ajout d'une solution commerciale de rhamnolipides (un autre type de biosurfactants produits par Pseudomonas spp.) a facilité la dégradation du phénanthrène par la souche RP037 et induit une expression de GFP élevée dans une plus grande proportion de cellules. Nous avons ainsi conclu que les effets des biosurfactants sont mesurables à l'aide de la souche biocapteur, mais que ceux-ci sont dépendants du type de surfactant utilisé conjointement avec le phénanthrène. La question suivante que nous avons abordée était si les tests utilisant des biocapteurs peuvent être améliorés de manière à ce que les flux de HAP provenant de matériel contaminé soient détectés. Les tests en milieu liquide avec des échantillons de sol ne fournissant pas de mesures, et sachant que les concentrations de HAP dans l'eau sont en général extrêmement basses, nous avons conçu des tests de diffusion dans lesquels nous pouvons étudier l'induction par les HAPs en fonction de la distance aux cellules. Le biocapteur bactérien B. sartisoli souche RP037 a été marqué avec une seconde protéine fluorescente (mCherry), qui est constitutivement exprimée dans les cellules et leur confère une fluorescence rouge/rose. La souche résultante RP037-mChe témoigne d'une fluorescence rouge constitutive mais n'induit la fluorescence verte qu'en présence de naphtalène ou de phénanthrène. La présence d'un marqueur fluorescent constitutif nous permet de visualiser les biocapteurs bactériens plus facilement parmi des particules de sol. Un test de diffusion a été conçu en préparant un gel fait d'une suspension de cellules mélangées à 0.5 % d'agarose. Des bandes de gel de dimensions 0.5 x 2 cm x 1 mm ont été montées dans des chambres d'incubation et exposées à des sources de HAP (soit dissouts dans du HMN ou en tant que matériel solide, puis appliqués à une extrémité de la bande). En utilisant ce montage expérimental, le naphtalène ou le phénanthrène (dissouts dans du HMN à une concentration de 2.5 µg/µl) ont induit un gradient d'intensité de fluorescence GFP après 24 heures d'incubation, tandis que la fluorescence mCherry demeurait comparable. Un sol contaminé par des HAPs (provenant d'un ancien site de production de gaz) a induit la production de GFP à un niveau comparable à celui du naphtalène. Des biocapteurs bactériens individuels ont également détecté un flux de phénanthrène dans un gel contenant des particules de sol amendées avec 1 et 10 mg/g de phénanthrène. Ceci a montré que le test de diffusion peut être utilisé pour mesurer des flux de HAP provenant de matériel contaminé. D'un autre côté, la sensibilité est encore très basse pour plusieurs sols contaminés, et l'autofluorescence de certains échantillons rend difficile l'identification de la réponse de la GFP chez les cellules. Pour terminer, un des points majeurs de ce travail a été la production et la validation d'une plateforme multi-puits de biocapteurs bactériens, qui a permis l'emploi simultané de plusieurs souches différentes de biocapteurs pour la détection des constituants principaux du pétrole. Pour cela nous avons choisi les alcanes linéaires, les composés mono-aromatiques, les biphényls et les composés poly-aromatiques. De plus, nous avons utilisé un capteur pour la génotoxicité afin de détecter la `toxicité globale' dans des échantillons aqueux. Plusieurs efforts d'ingénierie ont été investis de manière à compléter ce set. En premier lieu, chaque souche a été équipée avec soit gfp, soit luxAB en tant que signal rapporteur. Deuxièmement, puisqu'aucune souche de biocapteur n'était disponible pour les HAP ou pour les alcanes à longues chaînes, nous avons spécifiquement construit deux nouveaux biocapteurs. L'un d'eux est également basé sur B. sartisoli RP007, que nous avons équipé avec le plasmide pPROBE-phn-luxAB pour la détection du naphtalène et du phénanthrène mais avec production de luciférase bactérienne. Un autre est un nouveau biocapteur bactérien pour les alcanes. Bien que nous possédions une souche Escherichia coli DHS α (pGEc74, pJAMA7) détectant les alcanes courts de manière satisfaisante, la présence des alcanes à longues chaînes n'était pas rapportée efficacement. Nous avons cloné le gène de l'activateur transcriptionnel A1kS ainsi que la région opérateur/promoteur de l'opéron alkSB1GHJ chez la bactérie dégradant les alcanes Alcanivorax borkumensis souche SK2, afin de construire un nouveau biocapteur bactérien bénéficiant d'une sensibilité accrue envers les alcanes à longues chaînes. Cependant, la souche résultante E. coli DHSα (pAlk3} n'a pas montré d'émission de lumière augmentée en présence de tétradécane (C14), tandis qu'elle rapportait toujours efficacement de basses concentrations d'octane (C8). De manière surprenante, l'utilisation de A. borkumensis en tant que souche hôte pour le nouveau plasmide rapporteur basé sur la GFP a totalement supprimé la sensibilité pour l'octane, tandis que la détection de tétradécane n'était pas accrue. Cet aspect devra être résolu dans de futurs travaux. Pour calibrer la plateforme de biocapteurs, nous avons simulé une fuite de pétrole en mer dans une bouteille en verre ouverte de 5L contenant 2L d'eau de mer contaminée avec 20 ml (1%) de pétrole brut. La phase aqueuse a été échantillonée à intervalles réguliers après la fuite durant une période allant jusqu'à une semaine tandis que les principaux contaminants pétroliers étaient mesurés via les biocapteurs. L'émission de bioluminescence a été mesurée de manière à déterminer la réponse des biocapteurs et une calibration intégrée faite avec des inducteurs types a servi à calculer des concentrations d'équivalents inducteurs dans l'échantillon. E. coli a été utilisée en tant que souche hôte pour la plupart des spécificités des biocapteurs, à l'exception de la détection du naphtalène et du phénanthrène pour lesquels nous avons utilisé B. sartisoli. Cette souche, cependant, peut être employée plus ou moins selon la même procédure. Il est intéressant de noter que le pétrole répandu a produit une apparition séquentielle de composés dissouts dans la phase aqueuse, ceux-ci .étant détectables par les biocapteurs. Ce profil contenait d'abord les alcanes à courtes chaînes et les BTEX (c'est-à dire benzène, toluène, éthylbenzène et xylènes), apparaissant entre des minutes et des heures après que le pétrole a été versé. Leurs concentrations aqueuses ont par la suite fortement décru dans l'eau échantillonnée après 24 heures, à cause de la volatilisation ou de la biodégradation. Après quelques jours d'incubation, ces composés sont devenus indétectables. Les HAPs, en revanche, sont apparus plus tard que les alcanes et les BTEX, et leur concentration a augmenté de pair avec un temps d'incubation prolongé. Aucun signal significatif n'a été mis en évidence avec le biocapteur pour le biphényl ou pour la génotoxicité. Ceci démontre l'utilité de ces biocapteurs, spécifiquement pour la détection des composés pétroliers, comprenant les alcanes à courtes chaînes, les BTEX et les HAPs légers.

Organic acid adsorption and mineralization in oxisols with different textures

Organic acids play an important role in the nutritional conditions of plants. Their relevance is related to their formation dynamics, mineralization rate and adsorption by soil colloids. This study was carried out to evaluate the dynamics of mineralization and adsorption of organic acid (acetic acid - AA, citric acid - CA and humic acid - HA) applied to the soil. Samples of two Oxisols were used: Rhodic Haplustox (LV) and Typic Haplustox (LVA). The mineralization experiment was arranged in a 2 x 3 x 5 factorial design, based on the factors: two soils (LV and LVA) x three organic acid (OA) types (AA, CA and HA) x five OA rates (0, 1, 2, 4, and 8 mmol dm-3). Organic carbon mineralization in samples was measured by the C-CO2 efflux, produced by the microbial activity, in a 30-day (measurements after 4, 8, 12, 21, and 30 days) and in a 4-day experiment (measured after 24, 48, 72 and 96 h). Organic acid adsorption was tested in a 2 x 2 x 5 x 4 factorial design, with the factors and levels: two Oxisols; two organic acids (AA and CA); five OA rates (0, 1, 2, 4, and 8 mmol dm-3) and four adsorption periods (6, 24, 48, and 72 h). The C-CO2 production of soil treated with CA was highest. In the adsorption experiment, the affinity of CA to soil adsorption sites was greatest. The adsorption of organic acids to soils may be an important mechanism by which bioavailability and thus mineralization capacity by microbial activity are reduced.

Organic geochemistry of Jurassic-Cretaceous source rocks and oil seeps from the profile across the Adriatic-Dinaric carbonate platform

Organic geochemical and stable isotope investigations were performed to provide an insight into the depositional environments, origin and maturity of the organic matter in Jurassic and Cretaceous formations of the External Dinarides. A correlation is made among various parameters acquired from Rock-Eval, gas chromatography-mass spectrometry data and isotope analysis of carbonates and kerogen. Three groups of samples were analysed. The first group includes source rocks derived from Lower Jurassic limestone and Upper Jurassic ``Leme'' beds, the second from Upper Cretaceous carbonates, while the third group comprises oil seeps genetically connected with Upper Cretaceous source rocks. The carbon and oxygen isotopic ratios of all the carbonates display marine isotopic composition. Rock-Eval data and maturity parameter values derived from biomarkers define the organic matter of the Upper Cretaceous carbonates as Type I-S and Type II-S kerogen at the low stage of maturity up to entering the oil-generating window. Lower and Upper Jurassic source rocks contain early mature Type III mixed with Type IV organic matter. All Jurassic and Cretaceous potential source rock extracts show similarity in triterpane and sterane distribution. The hopane and sterane distribution pattern of the studied oil seeps correspond to those from Cretaceous source rocks. The difference between Cretaceous oil seeps and potential source rock extracts was found in the intensity and distribution of n-alkanes, as well as in the abundance of asphaltenes which is connected to their biodegradation stage. In the Jurassic and Cretaceous potential source rock samples a mixture of aromatic hydrocarbons with their alkyl derivatives were indicated, whereas in the oil seep samples extracts only asphaltenes were observed.

Effects of inorganic nitrogen (NH4Cl) and biodegradable organic carbon (CH3COONa) additions on a pilot-scale seawater biofilter

Biofilters degrade only a small fraction of the natural organic matter (NOM) contained in seawater which is the leading cause of biofouling in downstream processes. This work studies the effects of chemical additions on NOM biodegradation by biofilters. In this work, biofiltration of seawater with an empty bed contact time (EBCT) of 6 min and a hydraulic loading rate of 10 m h-1 reduces the biological oxygen demand (BOD7) by 8%, the dissolved organic carbon (DOC) by 6% and the UV absorbance at 254 nm (A254) by 7%. Different amounts of ammonium chloride are added to the seawater (up to twice the total dissolved nitrogen in untreated seawater) to study its possible effect on the removal of NOM by a pilot-scale biofilter. Seawater is amended with different amounts of easily biodegradable dissolved organic carbon (BDOC) supplied as sodium acetate (up to twice the DOC) for the same purpose. The results of this work reveal that the ammonium chloride additions do not significantly affect NOM removal and the sodium acetate is completely consumed by the biofiltration process. For both types of chemical additions, the BOD7, DOC and A254 in the outlet stream of the biofilter are similar to the values for the untreated control. These results indicate that this biofilter easily removes the BDOC from the seawater when the EBCT is not above 6 min. Furthermore, nitrogen does not limit the NOM biodegradation in seawater under these experimental conditions.

Anaerobic Digestibility of Microalgae : Fate and Limitations of Long Chain Fatty Acids in the Biodegradation of Lipids

La digestion anaérobie est un processus biologique dans lequel un consortium microbien complexe fonctionnant en absence d’oxygène transforme la matière organique en biogaz, principalement en méthane et en dioxyde de carbone. Parmi les substrats organiques, les lipides sont les plus productifs de méthane par rapport aux glucides et aux protéines; mais leur dégradation est très difficile, en raison de leur hydrolyse qui peut être l’étape limitante. Les algues peuvent être une source importante pour la production de méthane à cause de leur contenu en lipides potentiellement élevé. L’objectif de cette étude était, par conséquent, d’évaluer la production en méthane des microalgues en utilisant la technique du BMP (Biochemical méthane Potential) et d’identifier les limites de biodégradion des lipides dans la digestion anaérobie. Le plan expérimental a été divisé en plusieurs étapes: 1) Comparer le potentiel énergétique en méthane des macroalgues par rapport aux microalgues. 2) Faire le criblage de différentes espèces de microalgues d’eau douce et marines afin de comparer leur potentiel en méthane. 3) Déterminer l'impact des prétraitements sur la production de méthane de quelques microalgues ciblées. 4) Identifier les limites de biodégradation des lipides algaux dans la digestion anaérobie, en étudiant les étapes limitantes de la cinétique des lipides et de chacun des acides gras à longues chaines. Les résultats ont montré que les microalgues produisent plus de méthane que les macroalgues. Les BMP des microalgues d'eau douce et marines n'ont montré aucune différence en termes de rendement en méthane. Les résultats des prétraitements ont montré que le prétraitement thermique (microonde) semblait être plus efficace que le prétraitement chimique (alcalin). Les tests de contrôle du BMP faits sur l'huile de palme, l’huile de macadamia et l'huile de poisson ont montré que l'hydrolyse des huiles en glycérol et en acides gras à longues chaines n'était pas l'étape limitante dans la production de méthane. L'ajout de gras dans les échantillons de Phaeodactylum dégraissée a augmenté le rendement de méthane et cette augmentation a été corrélée à la quantité de matières grasses ajoutées.

Characterization of Wastes from Natural Rubber and Rubber Wood Processing Industries and Their Utilization for Biomethanation

The research work which was carried out to characterization of wastes from natural rubber and rubber wood processing industries and their utilization for biomethanation. Environmental contamination is an inevitable consequence of human activity. The liquid and solid wastes from natural rubber based industries were: characterized and their use for the production of biogas investigated with a view to conserve conventional energy, and to mitigate environmental degradation.Rubber tree (flevea brasiliensis Muell. Arg.), is the most important commercial source of natural rubber and in india. Recently, pollution from the rubber processing factories has become very serious due to the introduction of modern methods and centralized group processing practices.The possibility of the use of spent slurry as organic manure is discussed.l0 percent level of PSD, the activity of cellulolytic, acid producing,proteolytic, lipolytic and methanogenic bacteria were more in the middle stage of methanogenesis.the liquid wastes from rubber processing used as diluents in combination with PSD, SPE promoted more biogas production with high methane content in the gas.The factors that favour methane production like TS, VS, cellulose and hemicellulose degradation were favoured in this treatment which led to higher methane biogenesis.The results further highlight ways and means to use agricultural wastes as alternative sources of energy.

Biodegradation of phenolic compounds in different ecosystems in Cochin

The purpose of this study is to determine the ability of specifically adapted bacteria to degrade phenol and to quantify the rate of biodegradation at. Different concentrations by mixed as well as individual isolates. Regular quantitative analysis of phenolics and aerobic phenololytic heterotrophs from five different ecosystems were done during 1990-1991, and the ability of microorganisms isolated from those areas, to utilize phenol, o-cresol and orcinol was also studied. In addition, data on environmental parameters like temperature, dissolved oxygen, salinity, pH, organic carbon and nutrients were also collected during the period of study The present study is one of its first kind in natural aquatic environment and has aimed to bring out some idea about the potential phenol biodegrades in such environments where the phenol concentration is beyond permitted level.

Valorization of date palm (Phoenix dactylifera) fruit processing by-products and wastes using bioprocess technology – Review

The date palm Phoenix dactylifera has played an important role in the day-to-day life of the people for the last 7000 years. Today worldwide production, utilization and industrialization of dates are continuously increasing since date fruits have earned great importance in human nutrition owing to their rich content of essential nutrients. Tons of date palm fruit wastes are discarded daily by the date processing industries leading to environmental problems. Wastes such as date pits represent an average of 10% of the date fruits. Thus, there is an urgent need to find suitable applications for this waste. In spite of several studies on date palm cultivation, their utilization and scope for utilizing date fruit in therapeutic applications, very few reviews are available and they are limited to the chemistry and pharmacology of the date fruits and phytochemical composition, nutritional significance and potential health benefits of date fruit consumption. In this context, in the present review the prospects of valorization of these date fruit processing by-products and wastes’ employing fermentation and enzyme processing technologies towards total utilization of this valuable commodity for the production of biofuels, biopolymers, biosurfactants, organic acids, antibiotics, industrial enzymes and other possible industrial chemicals are discussed

A Study of Single Stage Semi‐Dry Anaerobic Digestion of Organic Fraction of Municipal Solid Waste

Solid waste generation is a natural consequence of human activity and is increasing along with population growth, urbanization and industrialization. Improper disposal of the huge amount of solid waste seriously affects the environment and contributes to climate change by the release of greenhouse gases. Practicing anaerobic digestion (AD) for the organic fraction of municipal solid waste (OFMSW) can reduce emissions to environment and thereby alleviate the environmental problems together with production of biogas, an energy source, and digestate, a soil amendment. The amenability of substrate for biogasification varies from substrate to substrate and different environmental and operating conditions such as pH, temperature, type and quality of substrate, mixing, retention time etc. Therefore, the purpose of this research work is to develop feasible semi-dry anaerobic digestion process for the treatment of OFMSW from Kerala, India for potential energy recovery and sustainable waste management. This study was carried out in three phases in order to reach the research purpose. In the first phase, batch study of anaerobic digestion of OFMSW was carried out for 100 days at 32°C (mesophilic digestion) for varying substrate concentrations. The aim of this study was to obtain the optimal conditions for biogas production using response surface methodology (RSM). The parameters studied were initial pH, substrate concentration and total organic carbon (TOC). The experimental results showed that the linear model terms of initial pH and substrate concentration and the quadratic model terms of the substrate concentration and TOC had significant individual effect (p < 0.05) on biogas yield. However, there was no interactive effect between these variables (p > 0.05). The optimum conditions for maximizing the biogas yield were a substrate concentration of 99 g/l, an initial pH of 6.5 and TOC of 20.32 g/l. AD of OFMSW with optimized substrate concentration of 99 g/l [Total Solid (TS)-10.5%] is a semi-dry digestion system .Under the optimized condition, the maximum biogas yield was 53.4 L/kg VS (volatile solid).. In the second phase, semi-dry anaerobic digestion of organic solid wastes was conducted for 45 days in a lab-scale batch experiment for substrate concentration of 100 g/l (TS-11.2%) for investigating the start-up performances under thermophilic condition (50°C). The performance of the reactor was evaluated by measuring the daily biogas production and calculating the degradation of total solids and the total volatile solids. The biogas yield at the end of the digestion was 52.9 L/kg VS for the substrate concentration of 100 g/l. About 66.7% of volatile solid degradation was obtained during the digestion. A first order model based on the availability of substrate as the limiting factor was used to perform the kinetic studies of batch anaerobic digestion system. The value of reaction rate constant, k, obtained was 0.0249 day-1. A laboratory bench scale reactor with a capacity of 36.8 litres was designed and fabricated to carry out the continuous anaerobic digestion of OFMSW in the third phase. The purpose of this study was to evaluate the performance of the digester at total solid concentration of 12% (semi-dry) under mesophlic condition (32°C). The digester was operated with different organic loading rates (OLRs) and constant retention time. The performance of the reactor was evaluated using parameters such as pH, volatile fatty acid (VFA), alkalinity, chemical oxygen demand (COD), TOC and ammonia-N as well as biogas yield. During the reactor’s start-up period, the process is stable and there is no inhibition occurred and the average biogas production was 14.7 L/day. The reactor was fed in continuous mode with different OLRs (3.1,4.2 and 5.65 kg VS/m3/d) at constant retention time of 30 days. The highest volatile solid degradation of 65.9%, with specific biogas production of 368 L/kg VS fed was achieved with OLR of 3.1 kg VS/m3/d. Modelling and simulation of anaerobic digestion of OFMSW in continuous operation is done using adapted Anaerobic Digestion Model No 1 (ADM1).The proposed model, which has 34 dynamic state variables, considers both biochemical and physicochemical processes and contains several inhibition factors including three gas components. The number of processes considered is 28. The model is implemented in Matlab® version 7.11.0.584(R2010b). The model based on adapted ADM1 was tested to simulate the behaviour of a bioreactor for the mesophilic anaerobic digestion of OFMSW at OLR of 3.1 kg VS/m3/d. ADM1 showed acceptable simulating results.

Management approaches in organic potato and tomato production

The presented thesis considered three different system approach topics to ensure yield and plant health in organically grown potatoes and tomatoes. The first topic describes interactions between late blight (Phytophthora infestans) incidence and soil nitrogen supply on yield in organic potato farming focussing in detail on the yield loss relationship of late blight based on results of several field trials. The interactive effects of soil N-supply, climatic conditions and late blight on the yield were studied in the presence and absence of copper fungicides from 2002-2004 for the potato cultivar Nicola. Under conditions of central Germany the use of copper significantly reduced late blight in almost all cases (15-30 %). However, the reductions in disease through copper application did not result in statistically significant yield increases (+0 – +10 %). Subsequently, only 30 % of the variation in yield could be attributed to disease reductions. A multiple regression model (R²Max), however, including disease reduction, growth duration and temperature sum from planting until 60 % disease severity was reached and soil mineral N contents 10 days after emergence could explain 75 % of the observed variations in yield. The second topic describes the effect of some selected organic fertilisers and biostimulant products on nitrogen-mineralization and efficiency, yield and diseases in organic potato and tomato trials. The organic fertilisers Biofeed Basis (BFB, plant derived, AgroBioProducts, Wageningen, Netherlands) and BioIlsa 12,5 Export (physically hydrolysed leather shavings, hair and skin of animals; ILSA, Arizignano, Italy) and two biostimulant products BioFeed Quality (BFQ, multi-compound seaweed extract, AgroBioProducts) and AUSMA (aqueous pine and spruce needle extract, A/S BIOLAT, Latvia), were tested. Both fertilisers supplied considerable amounts of nitrogen during the main uptake phases of the crops and reached yields as high or higher as compared to the control with horn meal fertilisation. The N-efficiency of the tested fertilisers in potatoes ranged from 90 to 159 kg yield*kg-1 N – input. Most effective with tomatoes were the combined treatments of fertiliser BFB and the biostimulants AUSMA and BFQ. Both biostimulants significantly increased the share of healthy fruit and/or the number of fruits. BFQ significantly increased potato yields (+6 %) in one out of two years and reduced R. solani-infestation in the potatoes. This suggests that the biostimulants had effects on plant metabolism and resistance properties. However, no effects of biostimulants on potato late blight could be observed in the fields. The third topic focused on the effect of suppressive composts and seed tuber health on the saprophytic pathogen Rhizoctonia solani in organic potato systems. In the present study 5t ha-1 DM of a yard and bio-waste (60/40) compost produced in a 5 month composting process and a 15 month old 100 % yard waste compost were used to assess the effects on potato infection with R. solani when applying composts within the limits allowed. Across the differences in initial seed tuber infestation and 12 cultivars 5t DM ha-1 of high quality composts, applied in the seed tuber area, reduced the infestation of harvested potatoes with black scurf, tuber malformations and dry core tubers by 20 to 84 %, 20 to 49 % and 38 to 54 %, respectively, while marketable yields were increased by 5 to 25 % due to lower rates of wastes after sorting (marketable yield is gross yield minus malformed tubers, tubers with dry core, tubers with black scurf > 15% infested skin). The rate of initial black scurf infection of the seed tubers also affected tuber number, health and quality significantly. Compared to healthy seed tubers initial black scurf sclerotia infestation of 2-5 and >10 % of tuber surface led in untreated plots to a decrease in marketable yields by 14-19 and 44-66 %, a increase of black scurf severity by 8-40 and 34-86 % and also increased the amount of malformed and dry core tubers by 32-57 and 109-214 %.

Biodegradation of polyethylene glycol (PEG) in three tropical soils using radio labelled PEG

Polyethylene glycol (PEG) may be added to forage based diets rich in tannins for ruminant feeding because it binds to tannins and thus prevent the formation of potentially indigestible tannin-protein complexes. The objective of this work was to determine the in vitro biodegradation (mineralization, i.e., complete breakdown of PEG to CO2) rate of PEG. C-14-Polyethylene glycol (C-14-PEG) was added to three different tropical soils (a sandy clay loam soil, SaCL; a sandy clay soil, SaC; and a sandy loam soil, SaL) and was incubated in Bartha flasks. Free PEG and PEG bound to tannins from a tannin rich local shrub were incubated under aerobic conditions for up to 70 days. The biodegradation assay monitored the (CO2)-C-14 evolved after degradation of the labelled PEG in the soils. After incubation, the amount of (CO2)-C-14 evolved from the C-14-PEG application was low. Higher PEG mineralization values were found for the soils with higher organic matter contents (20.1 and 18.6 g organic matter/kg for SaCL and SaC, respectively) than for the SaL soil (11.9 g organic matter/kg) (P < 0.05). The extent of mineralization of PEG after 70 days of incubation in the soil was significantly lower (P < 0.05) when it was added as bound to the browse tannin than in the free form (0.040 and 0.079, respectively). (c) 2005 Elsevier B.V. All rights reserved.

The role of root exuded low molecular weight organic anions in facilitating petroleum hydrocarbon degradation: current knowledge and future directions

Rhizoremediation is a bioremediation technique whereby enhanced microbial degradation of organic contaminants occurs within the plant root zone (rhizosphere). It is considered an effective and affordable ‘green technology’ for remediating soils contaminated with petroleum hydrocarbons (PHCs). This paper critically reviews the potential role of root exuded compounds in rhizoremediation, with emphasis on commonly exuded low molecular weight aliphatic organic acid anions (carboxylates). The extent to which remediation is achieved shows wide disparity among plant species. Therefore, plant selection is crucial for the advancement and widespread adoption of this technology. Root exudation is speculated to be one of the predominant factors leading to microbial changes in the rhizosphere and thus the potential driver behind enhanced petroleum biodegradation. Carboxylates can form a significant component of the root exudate mixture and are hypothesised to enhance petroleum biodegradation by: i) providing an easily degradable energy source; ii) increasing phosphorus supply; and/or iii) enhancing the contaminant bioavailability. These differing hypotheses, which are not mutually exclusive, require further investigation to progress our understanding of plant–microbe interactions with the aim to improve plant species selection and the efficacy of rhizoremediation.