Interrogation of a sonogashira cross-coupling of 8-bromoguanosine with phenylacetylene on amberlite:evidence for Pd/Cu ion binding and propagation of Pd/Cu nanoparticles

The reactivity of Amberlite (IRA-67) base "heterogeneous" resin in Sonogashira cross-coupling of 8-bromoguanosine 1 with phenylacetylene 3 to give 2 has been examined. Both 1 and 2 coordinate to Pd and Cu ions, which explains why at equivalent catalyst loadings, the homogeneous reaction employing triethylamine base is poor yielding. X-ray photo-electron spectroscopy (XPS) has been used to probe and quantify the active nitrogen base sites of the Amberlite resin, and postreaction Pd and Cu species. The Pd2Cl3(PPh)2 precatalyst and CuI cocatalyst degrade to give Amberlite-supported metal nanoparticles (average size ∼2.7 nm). The guanosine product 2 formed using the Amberlite Pd/Cu catalyst system is of higher purity than reactions using a homogeneous Pd precatalyst, a prerequisite for use in biological applications. Copyright © Taylor and Francis Group, LLC.

Fundamental studies of the application of wheat for malting and brewing

Wheat (Triticum aestivum L.) has a long tradition as a raw material for the production of malt and beer. While breeding and cultivation efforts for barley have been highly successful in creating agronomically and brew- technical optimal specialty cultivars that have become well established as brewing barley varieties, the picture is completely different for brewing wheat. An increasing wheat beer demand results in a rising amount of raw material. Wheat has been - and still is – grown almost exclusively for the baking industry. It is this high demand that defines most of the wheat breeding objectives; and these objectives are generally not favourable in brewing industry. It is of major interest to screen wheat varieties for brewing processability and to give more focus to wheat as a brewing cereal. To obtain fast and reliable predications about the suitability of wheat cultivars a new mathematical method was developed in this work. The method allows a selection based on generally accepted quality characteristics. As selection criteria the parameters raw protein, soluble nitrogen, Kolbach index, extract and viscosity were chosen. During a triannual cultivation series, wheat varieties were evaluated on their suitability for brewing as well as stability to environmental conditions. To gain a fundamental understanding of the complex malting process, microstructural changes were evaluated and visualized by confocal laser scanning and scanning electron microscopy. Furthermore, changes observed in the micrographs were verified and endorsed by metabolic changes using established malt attributes. The degradation and formation of proteins during malting is essential for the final beer quality. To visualise fundamental protein changes taking place during malting, samples of each single process step were analysed and fractioned according their solubility. Protein fractions were analysed using a Lab-on-a-chip technique as well as OFFgel analysis. In general, a different protein distribution of wheat compared to barley or oat could be confirmed. During the malting process a degradation of proteins to small peptides and amino acids could be observed in all four Osborn fractions. Furthermore, in this study a protein profiling was performed to evaluate changes during the mashing process as well as the influence of grist composition. Differences in specific protein peaks and profile were detected for all samples during mashing. This study investigated the suitability of wheat for malting and brewing industry and closed the scientifical gap of amylolytic, cytolytic and proteolytic changes during malting and mashing.

d13C and d15N stable isotopes values, total nitrogen and C/N ratios of sediment core GeoB4801-1

Rising stable nitrogen isotope ratios (d15N) in dated sediment records of the German Bight/SE North Sea track river-induced coastal eutrophication over the last 2 centuries. Fully exploiting their potential for reconstructions of pristine conditions and quantitative analysis of historical changes in the nitrogen cycle from these sediment records requires knowledge on processes that alter the isotopic signal in non-living organic matter (OM) of sinking particles and sediments. In this study, we analyze the isotopic composition of particulate nitrogen (PN) in the water column during different seasons, in surface sediments, and in sediment cores to assess diagenetic influences on the isotopic composition of OM. Amino acid (AA) compositions of suspended matter, surface sediments, and dated cores at selected sites of the German Bight serve as indicators for quality and degradation state of PN. The d15N of PN in suspended matter had seasonal variances caused by two main nitrate sources (oceanic and river) and different stages of nitrate availability during phytoplankton assimilation. Elevated d15N values (> 20 per mil) in suspended matter near river mouths and the coast coincide with a coastal water mass receiving nitrate with elevated isotope signal (d15N > 10 per mil) derived from anthropogenic input. Particulate nitrogen at offshore sites fed by oceanic nitrate having a d15N between 5 and 6 per mil had low d15N values (< 2 per mil), indicative of an incipient phytoplankton bloom. Surface sediments along an offshore-onshore transect also reflect the gradient of low d15N of nitrate in offshore sites to high values near river mouths, but the range of values is smaller than between the end members listed above and integrates the annual d15N of detritus. Sediment cores from the coastal sector of the gradient show an increasing d15N trend (increase of 2.5 per mil) over the last 150 years. This is not related to any change in AA composition and thus reflects eutrophication. The d15N signals from before AD 1860 represent a good estimation of pre-industrial isotopic compositions with minimal diagenetic overprinting. Rising d13C in step with rising d15N in these cores is best explained by increasing productivity caused by eutrophication.

Geochemical composition of snow samples from Antarctica, Greenland and northeast Canada

In this paper, we present new detailed data on the trace metal content of more than 200 shallow polar snow samples collected at various depths in numerous locations mainly in Antarctica and Greenland. The samples were collected in ultraclean plexiglass or teflon tubes from the walls of hand dug pits, using stringent contamination free techniques controlled by severe blank tests. They were then analysed for Na, Mg, K, Ca, Fe, Al, Mn, Pb, Cd, Cu, Zn and Ag in clean room conditions by flameless atomic absorption, after a preconcentration step (by non boiling evaporation in teflon bulbs) which includes dissolving any solid particles by concentrated nitric and hydrofluoric acids. The overall precision on the measured concentrations is of the order of 10 % for all the metals except Pb (20 %) and Cd (35 %), using 95 % confidence limits. The data obtained are compared with those published previously in the literature. Part of these previous data are shown to be erroneously too high, probably because of con-tamination problems both during field collection and analysis.

(Table 1) Sample descriptions, carbon contents, and lipid yields across the K/T boundary at DSDP Hole 93-605 and at Stevns Klint, Denmark

This reconnaissance study was undertaken to determine whether the mass extinctions and faunal successions that mark the Cretaceous/Tertiary (K/T) boundary left a discernible molecular fossil record in the sediments of this period. Lipid signatures of sediments taken from above and below the K/T boundary were compared in core and outcrop samples taken from two locations: the U.S. east coast continental margin (western Atlantic Ocean, DSDP Site 605) and Stevns Klint, Denmark. Four calcareous sediments taken from above and below the K/T boundary in DSDP Hole 605, Section 605-66-1, revealed changing lipid signatures between above and below that are characterized by a large component of unresolved naphthenic hydrocarbons and a homologous series of n-alkanes ranging from Ci6 to C33. These lipid signatures are attributed to an influx of a terrestrial higher plant component and to bacterial reworking of the sediments under partially anoxic depositional and/or diagenetic conditions. The outcrop samples from Stevns Klint had extremely low concentrations of indigenous lipids. The fish clay at the K/T boundary contained traces of microbial hydrocarbons and fatty acids, whereas the carbonates above and below had only microbial fatty acids and additional terrestrial resin acids. The data from both sites indicate a perturbation in the deposition of lipid compound classes across the K/T boundary.

(Table 1) Salinity, dissolved organic carbon and absorption characteristics of surface river waters around Hudson Bay

Composition and concentration of colored dissolved organic matter (CDOM) have been determined in Hudson Bay and Hudson Strait by excitation emission matrix spectroscopy (EEM) and parallel factor analysis (PARAFAC). Based on 63 surface samples, PARAFAC identified three fluorescent components, which were attributed to two humic- and one protein-like components. One humic-like component was identified as representing terrestrial organic matter and showed a conservative behaviour in Hudson Bay estuaries. The second humic-like component, traditionally identified as peak M, originated both from land and produced in the marine environment. Component 3 had spectra resembling protein-like material and thought to be plankton-derived. The distribution and composition of CDOM were largely controlled by water mass mixing with protein-like component being the least affected. Distinctive fluorescence patterns were also found between Hudson Bay and Hudson Strait, suggesting different sources of CDOM. The optically active fraction of DOC (both absorbing and fluorescing) was very high in the Hudson Bay (up to 89%) suggesting that fluorescence and absorbance can be used as proxies of the DOC concentration.

Greenlandic Inuit show genetic signatures of diet and climate adaptation

The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes for signatures of adaptation revealed signals at several loci, with the strongest signal located in a cluster of fatty acid desaturases that determine PUFA levels. The selected alleles are associated with multiple metabolic and anthropometric phenotypes and have large effect sizes for weight and height, with the effect on height replicated in Europeans. By analyzing membrane lipids, we found that the selected alleles modulate fatty acid composition, which may affect the regulation of growth hormones. Thus, the Inuit have genetic and physiological adaptations to a diet rich in PUFAs.

Madeira wine vinification process: analysis and control

The present study was done in collaboration with J. Faria e Filhos company, a Madeira wine producer, and its main goal was to fully characterize three wines produced during 2014 harvest and identify possible improving points in the winemaking process. The winemaking process was followed during 4 weeks, being registered the amounts of grapes received, the fermentation temperatures, the time at which fermentation was stopped and evolution of must densities until the fortification time. The characterization of musts and wines was done in terms of density, total and volatile acidity, alcohol content, pH, total of polyphenol, organic acids composition, sugars concentration and the volatile profile. Also, it was developed and validated an analytical methodology to quantify the volatile fatty acids, namely using SPME-GC-MS. Briefly, the following key features were obtained for the latter methodology: linearity (R2=0.999) e high sensitivity (LOD =0.026-0.068 mg/L), suitable precision (repeatability and reproducibility lower than 8,5%) and good recoveries (103,11-119,46%). The results reveal that fermentation temperatures should be controlled in a more strictly manner, in order to ensure a better balance in proportion of some volatile compounds, namely the esters and higher alcohols and to minimize the concentration of some volatiles, namely hexanoic, octanoic and decanoic acids, that when above their odours threshold are not positive for the wine aroma. Also, regarding the moment to stop the fermentation, it was verified that it can be introduced changes which can also be benefit to guarantee the tipicity of Madeira wine bouquet.

Direct catalytic macrolactonization and application of the phase separation strategy in complex molecule synthesis

Les macrolactones sont des squelettes structuraux importants dans de nombreuses sphères de l’industrie chimique, en particulier dans les marchés pharmaceutiques et cosmétiques. Toutefois, la stratégie traditionnelle pour la préparation de macrolactones demeure incommode en requérant notamment l’ajout (super)stœchiométrique d’agents activateurs. Conséquemment, des quantités stœchiométriques de sous-produits sont générées; ils sont souvent toxiques, dommageables pour l’environnement et nécessitent des méthodes de purification fastidieuses afin de les éliminer. La présente thèse décrit le développement d’une macrolactonisation efficace catalysée au hafnium directement à partir de précurseurs portant un acide carboxylique et un alcool primaire, ne générant que de l’eau comme sous-produit et ne nécessitant pas de techniques d’addition lente et/ou azéotropique. Le protocole a également été adapté à la synthèse directe de macrodiolides à partir de mélanges équimolaires de diols et de diacides carboxyliques et à la synthèse de dimères tête-à-queue de seco acides. Des muscs macrocycliques ainsi que des macrolactones pertinentes à la chimie médicinale ont pu être synthétisés avec l’approche développée. Un protocole pour l’estérification directe catalysée au hafnium entre des acides carboxyliques et des alcools primaires a aussi été développé. Différentes méthodes pour la macrolactonisation catalytique directe entre des alcools secondaires et des acides carboxyliques ont été étudiées. En outre, la stratégie de séparation de phase en macrocyclisation en débit continu a été appliquée lors de la synthèse totale formelle de la macrolactone ivorenolide A. Les étapes-clés de la synthèse incluent une macrocyclisation par le couplage d’alcynes de Glaser-Hay et une réaction de métathèse d’alcènes Z-sélective.

Perturbations in Blood Phosphatidylcholine and Sphingomyelin Fatty Acid Composition in a Sample Population of Cigarette Smokers

Docosahexaenoic (DHA) and arachidonic acids (AA) are polyunsaturated fatty acids (PUFAs), major components of brain tissue and neural systems, and the precursors of a number of biologically active metabolites with functions in inflammation resolution, neuroprotection and other actions. As PUFAs are highly susceptible to peroxidation, we hypothesised whether cigarette smokers would present altered PUFAs levels in plasma and erythrocyte phospholipids. Adult males from Indian, Sri-Lankan or Bangladeshi genetic backgrounds who reported smoking between 20 and 60 cigarettes per week were recruited. The control group consisted of matched non-smokers. A blood sample was taken, plasma and erythrocyte total lipids were extracted, phospholipids were separated by thin layer chromatography, and the fatty acid content analysed by gas chromatography. In smokers, dihomo-gamma-linolenic acid, the AA precursor, was significantly reduced in plasma and erythrocyte phosphatidylcholine. AA and DHA were significantly reduced in erythrocyte sphingomyelin. Relatively short term smoking has affected the fatty acid composition of plasma and erythrocyte phospholipids with functions in neural tissue composition, cell signalling, cell growth, intracellular trafficking, neuroprotection and inflammation, in a relatively young population. As lipid peroxidation is pivotal in the pathogenesis of atherosclerosis and neurodegenerative diseases such as Alzheimer disease, early effects of smoking may be relevant for the development of such conditions.

Isolation and structural characterization of fucoidans from the brown algae Fucus vesiculosus

agricultural, pharmaceutical, cosmetic or bioenergy applications. They contain bioactive compounds, namely, polysaccharides Fucoidan. These polysaccharides are mainly constituted by fucose residues and sulfate esters, and have been reported to possess a broad variety of bioactivities, such as anticoagulant, anti-thrombotic, anti-inflammatory, anti-tumor, antiviral and antioxidant. In this work, the fucoidans from brown seaweed Fucus vesiculosus from “Ria de Aveiro” were isolated and characterized in order to add value to this natural resource of the region. The polysaccharides from the algae were extracted with hot water and fractioned by ethanol precipitation and calcium chloride salts. They were further purified by using anion-exchange chromatography, allowing to separate the neutral polysaccharides (laminaranas) from those negatively charged (sulfated fucoidans and alginate). The purified polysaccharides showed high content of fucose (41 mol%) and sulfates (50 mol%), having also galactose residues (6 mol%), which confirm the presence of only sulfated fucoidans. Glycosidic linkages analysis show the presence of high amounts of terminal fucose (25%) and (1→3,4)-Fuc (26%), allowing to infer that the fucoidans were highly branched. These fucoidans are composed also by (1→2)-Fuc (14%) and (1→3)-Fuc linkages (10-16%). In this work it was also tested an alternative extraction technology, the microwave hydrodiffusion and gravity system, where it was possible to extract sugars, although in low yields. However, this methodology allowed to extract polysaccharides, constituted mainly by fucose and uronic acids, as well as mannitol, without the need to add any solvent, obtaining at the end the dry alga. The current work allowed to characterize the structure of the fucoidans isolated from “Ria de Aveiro” F. vesiculosus. The presence of high content of sulfate residues and the high branch degree of the purified fucoidans allow to infer that these polysaccharides could have potential to be studied for biomedical applications, according to their biological activities.

Biofuels and high value added products from the yeast Rhodosporidium toruloides NCYC 921: Strategies towards a true cost-effective and environmentally sustainable integrated multiproduct driven biorefinery [Poster]

Single-cell oils (SCO) have been considered a promising source of 3rd generation biofuels mainly in the final form of biodiesel. However, its high production costs have been a barrier towards the commercialization of this commodity. The fast growing yeast Rhodosporidium toruloides NCYC 921 has been widely reported as a potential SCO producing yeast. In addition to its well-known high lipid content (that can be converted into biodiesel), is rich in high value added products such as carotenoids with commercial interest. The process design and integration may contribute to reduce the overall cost of biofuels and carotenoid production and is a mandatory step towards their commercialization. The present work addresses the biomass disruption, extraction, fractionation and recovery of products with special emphasis on high added valued carotenoids (beta-carotene, torulene, torularhodin) and fatty acids directed to biodiesel. The chemical structure of torularhodin with a terminal carboxylic group imposes an additional extra challenge in what concern its separation from fatty acids. The proposed feedstock is fresh biomass pellet obtained directly by centrifugation from a 5L fed-batch fermentation culture broth. The use of a wet instead of lyophilised biomass feedstock is a way to decrease processing energy costs and reduce downstream processing time. These results will contribute for a detailed process design. Gathered data will be of crucial importance for a further study on Life-Cycle Assessment (LCA).

Functional studies of lignin biosynthesis genes and putative flowering gene in Miscanthus x giganteus and studies on indolyl glucosinolate biosynthesis and translocation in Brassica oleracea

The first topic area of this thesis involved studies on the accumulation and translocation of glucosinolates (GSs), bioactive secondary plant compounds, in broccoli plants. Changes in GS accumulation and gene expression levels in response to exogeneous methyl jasmonate (MeJA) treatment were analyzed in different tissue types at different developmental stages of broccoli. Greater accumulation of GSs with MeJA treatment was observed in apical leaves of broccoli seedlings and florets of plants at harvest maturity. Increases in indolyl GS in apical leaves of seedlings and florets were coupled with the up-regulation of indolyl GS biosynthesis genes. The accumulation of indolyl GSs appears to be modulated by MeJA treatment in an organ-specific manner for optimal distribution of defense substances in the plant. Metabolic profiling of hydrophilic metabolites using GC-MS demonstrated increased accumulation of various phenolics, ascorbates and amino acids in broccoli tissues after MeJA treatment. Distinct changes in carbohydrate levels observed between different tissues (vegetative leaves and floret tissues) of broccoli plants after treatment suggest that carbon metabolism is differentially modulated by MeJA treatment in different tissue types depending on sink-source relationships. Reduced levels of hexose sugars and tricarboxylic acid intermediates after MeJA treatment may reflect the increased requirement for carbon and energy needed to drive secondary product biosynthesis to accumulate metabolites for defense against insects and other herbivores. Substantial increases of indolyl and aromatic GSs after exogenous treatment with MeJA in stem and petioles of seedlings and the existence of intact indolyl-GS forms in phloem exudates suggest enhanced de novo synthesis in combination with active transport. Indoly GSs share structural similarities with the auxin, IAA, and may interact with components of the auxin transport system for intra- and extra-cellular transport or translocation. Application of the auxin efflux inhibitor, 1-naphthylphthalamic acid (NPA) reduced MeJA-mediated accumulation of indolyl GSs in broccoli florets and seedling tissues. NPA did not inhibit expression of indolyl GS biosynthesis genes shown to be upregulated by MeJA treatment or the accumulation of tryptophan, the amino acid precursor of indolyl GSs. Exogenous application of benzyl GS to Arabidopsis roots induced ectopic expression of the PIN1 protein associated with the auxin transport system similar to treatment with NPA, again suggesting GS interaction with the auxin efflux carrier system. The inhibitory effect of NPA on MeJA-mediated accumulation of GS may be due to competitive binding of NPA to auxin efflux carrier components and that GS transport is mediated by the auxin transport system. The inhibitory effect of NPA on indolyl and aromatic GS accumulation and the bioactivity of exogenous treatment of these GS compounds in PIN1 localization, Arabidopsis root growth, and gravitrophic response suggest that indolyl and aromatic GSs may be antagonistic to IAA transport and biosynthesis. Indolyl and aromatic GSs can also be potentially converted into IAA by hydrolysis. This intrinsic feature of GSs may be the part of a sophisticated regulatory process where the metabolic pathways in the plant shift from active growth to a reversible defense posture in response to biotic or abiotic stress. It seems likely that indolyl and aromatic GSs are important compounds that provide connections between jasmonate and auxin signaling. Further studies are required to reveal the regulatory mechanism for crosstalk between the two hormones. The third part of this research was to investigate effect of selenium fertilization and MeJA treatment on accumulation of GSs in broccoli florets. Increasing dietary intake of the element selenium (Se) has been shown to reduce the risk of cancer. Simultaneous enhancement of both Se and GS concentrations in broccoli floret tissue were conducted through the combined treatment of MeJA with Se fertilization. A low level of Se fertilization (concentration) with MeJA treatment displayed no significant changes in total aliphatic GS concentrations with 90% and 50% increases in indolyl and total GSs concentrations, respectively. This result suggests that Se- and GS-enriched broccoli with improved health-promoting properties can be generated by this combined treatment. The second topic of this thesis was conducted to provide basic information required to improve biomass quality and productivity and develop tools for gene transformation in Miscanthus x giganteus. The perennial rhizomatous grass, Miscanthus x giganteus is an ideal biomass crop due to its rapid vegetative growth and high biomass yield potential. As a naturally occurring sterile hybrid, M. x giganteus must be propagated vegetatively by mechanicalling divided rhizomes or from micropropagated plantlets. The effect of callus type, age and culture methods on regeneration competence was studied to improve regeneration efficiency and shorten the period of tissue culture in M. x giganteus propagation. Seven lignin biosynthesis genes and one putative flowering gene were isolated from M. x giganteus by PCR reactions using maize othologous sequences. Southern hybridization and nuclear DNA content analysis indicated that the genes isolated from M. x giganteus exist in the genome of other Miscanthus species as multiple copies. Analysis of lignin content and histological staining of lignin deposition indicated that higher lignin content is found in mature stem node tissues compared to young leaves and apical stem nodal tissues. Cell wall lignification is associated with increasing tissue maturity in Miscanthus species. RNAi and antisense constructs harboring sequences of these genes were developed to generate Miscanthus transgenic plants with suppressed of lignin biosynthesis and delayed flowering.

Formation of seep carbonates along the makran convergent margin, northern Arabian sea and a molecular and isotopic approach to constrain the carbon isotopic composition of parent methane

Authigenic carbonate deposits have been sampled with the remotely operated vehicle ‘MARUM-QUEST 4000 m’ from five methane seeps between 731 and 1823 m water depth along the convergent Makran continental margin, offshore Pakistan (northern Arabian Sea). Two seeps on the upper slope are located within the oxygen minimum zone (OMZ; ca. 100 to 1100 m water depth), the other sites are situated in oxygenated water below the OMZ (below 1100 m water depth). The carbonate deposits vary with regard to their spatial extent, sedimentary fabrics, and associated seep fauna: Within the OMZ, carbonates are spatially restricted and associated with microbial mats, whereas in the oxygenated zone below the OMZ extensive carbonate crusts are exposed on the seafloor with abundant metazoans (bathymodiolin mussels, tube worms, galatheid crabs). Aragonite and Mg-calcite are the dominant carbonate minerals, forming common early diagenetic microcrystalline cement and clotted to radial-fibrous cement. The δ18Ocarbonate values range from 1.3 to 4.2‰ V-PDB, indicating carbonate precipitation at ambient bottom-water temperature in shallow sediment depth. Extremely low δ13Ccarbonate values (as low − 54.6‰ V-PDB) point to anaerobic oxidation of methane (AOM) as trigger for carbonate precipitation, with biogenic methane as dominant carbon source. Prevalence of biogenic methane in the seepage gas is corroborated by δ13Cmethane values ranging from − 70.3 to − 66.7‰ V-PDB, and also by back-calculations considering δ13Cmethane values of carbonate and incorporated lipid biomarkers. These calculations (Δδ13Cmethane–carbonate, Δδ13CANME–methane, Δδ13CMOX–methane) prove to be useful to assess the carbon stable isotope composition of seeping methane if this has not been determined in the first place; such an approach represents a useful tool to reconstruct fluid composition of ancient seeps. AOM is also revealed by lipid biomarkers of anaerobic methane oxidizing archaea such as crocetane, pentamethylicosane (PMI), and sn2-hydroxyarchaeol strongly depleted in 13C (δ13C values as low as − 127‰ V-PDB). Biomarkers of sulphate-reducing bacteria are also abundant, showing slightly less negative δ13C values, but still significantly 13C-depleted (average values as low as − 101‰). Other bacterial biomarkers, such as bacteriohopanepolyols (BHPs), hopanols, and hopanoic acids are detected in most carbonates, but are particularly common in seep carbonates from the non-OMZ sites. The BHP patterns of these carbonates and their low δ13C values resemble patterns of aerobic methanotrophic bacteria. In the shallower OMZ sites, BHPs revealed much lower contents and varying compositions, most likely reflecting other sources than aerobic methanotrophic bacteria. 230Th/U carbonate ages indicate that AOM-induced carbonate precipitation at the deeper non-OMZ seeps occurred mainly during the late Pleistocene-Holocene transition, i.e. between 19 and 15 ka before present, when the global sea level was lower than today.

Kinetic study of solid phase demineralization by weak acids in one-step enzymatic bio-refinery of shrimp cuticles

We describe a one-step bio-refinery process for shrimp composites by-products. Its originality lies in a simple rapid (6 h) biotechnological cuticle fragmentation process that recovers all major compounds (chitins, peptides and minerals in particular calcium). The process consists of a controlled exogenous enzymatic proteolysis in a food-grade acidic medium allowing chitin purification (solid phase), and recovery of peptides and minerals (liquid phase). At a pH of between 3.5 and 4, protease activity is effective, and peptides are preserved. Solid phase demineralization kinetics were followed for phosphoric, hydrochloric, acetic, formic and citric acids with pKa ranging from 2.1 to 4.76. Formic acid met the initial aim of (i) 99 % of demineralization yield and (ii) 95 % deproteinization yield at a pH close to 3.5 and a molar ratio of 1.5. The proposed one-step process is proven to be efficient. To formalize the necessary elements for the future optimization of the process, two models to predict shell demineralization kinetics were studied, one based on simplified physical considerations and a second empirical one. The first model did not accurately describe the kinetics for times exceeding 30 minutes, the empirical one performed adequately.