Allestimenti di reattori multistadio per la digestione anaerobica dei reflui agro-industriali e confronto con processo convenzionale

This study fits into the context of activities aim at waste bioremediation and valorization through the production of energy according to principles of environmental sustainability. The experimental work was carried out at the laboratories of the Department of Civil Engineering, Environmental and Materials (DICAM) of the Faculty of Engineering. The main objective was to enhance the treatment of high organic loading waste, such as manure and cheese whey, through advanced anaerobic digestion systems in order to obtain biogas rich in methane. On the basis of the premise that the environmental conditions pertaining in most anaerobic wastewater digesters are not optimal for both fermentative and methanogenic microorganisms, the research was particularly focused on the implementation of two-phase anaerobic digesters. In fact a two-phase process permits selection and enrichment of different bacteria in each digester by independently controlling the digester operating conditions. Thus, the first phase (acidogenesis) can be operated to optimize acidogenic growth and the second phase (methanogenesis) to optimize methanogenic growth. (Ince O. , 1998). Before reactors’ set up, , some lab scale experiments were carried out to identify the best manure and whey ratio and the best conditions of temperature, pH, hydraulic retention time of acidogenesis an methanogenic phases.

Attivita tirosina decarbossilasica in enterococcus mundtii

Le ammine biogene sono il prodotto della decarbossilazione degli amminoacidi da parte di enzimi microbici. Tra essi vi è la tirosina decarbossilasi, caratterizzata dalla possibilità di utilizzare, in assenza di tirosina, la fenilalanina, ottenendo la 2-feniletilamina. In particolare, la tiramina è responsabile della comparsa di importanti sintomi tossicologici, raggruppati con il termine “cheese reaction”. In questa sperimentazione sono stati presi in considerazione 2 ceppi di Enterococcus mundtii (C46 e C53) coltivati in BHI in presenza o assenza di tirosina per caratterizzarne l’attività decarbossilasica. Sono state monitorate la crescita microbica, mediante densità ottica e la produzione di tiramina e 2-feniletilamina mediante tecnica HPLC. Dai risultati ottenuti è emerso che entrambi i ceppi producono tiramina sia in presenza che in assenza del precursore. La concentrazione massima rilevata per il ceppo C46 è stata di 797 mg/l e 767 mg/l per C53. È inoltre emerso che essi possono decarbossilare la fenilalanina, ma solo dopo 8 e 24 ore di incubazione per il ceppo C46 e C53. Per quanto concerne la crescita, entrambi i ceppi hanno raggiunto il massimo valore di densità ottica dopo 6-8 ore a 37°C, con una durata della fase lag ridotta, seguita da un rapido aumento della densità ottica. Non sono state riscontrate differenze significative in termini di massima densità ottica raggiunta (A) e durata della fase lag (λ) tra i due ceppi, mentre C53 ha presentato valori inferiori per quanto riguarda la velocità incremento della densità ottica in fase esponenziale (µmax). Dagli studi genici è emerso che l’organizzazione dell’operone dei ceppi considerati corrisponde con quella filogeneticamente riconosciuta per il genere Enterococcus, ma nonostante la similarità, l’operone manca del gene codificante per l’antiporto Na+/H+. È stata inoltre evidenziata nel genoma dei ceppi considerati un’altra regione che contiene geni codificanti per un ulteriore sistema decarbossilasico.

Optimization of a polyhydroxyalkanoates production process using a halotolerant mixed microbial culture

The rate at which petroleum based plastics are being produced, used and thrown away is increasing every year because of an increase in the global population. Polyhydroxyalkanoates can represent a valid alternative to petroleum based plastics. They are biodegradable polymers that can be produced by some microorganisms as intracellular reserves. The actual problem is represented by the production cost of these bioplastics, which is still not competitive if compared to the one of petroleum based plastics. Mixed microbial cultures can be fed with substrates obtained from the acidogenic fermentation of carbon rich wastes, such as cheese whey, municipal effluents and various kinds of food wastes, that have a low or sometimes even inexisting cost and in this way wastes can be valorized instead of being discharged. The process consists of three phases: acidogenic fermentation in which the substrate is obtained, culture selection in which a PHA-storing culture is selected and enriched eliminating organisms that do not show this property and accumulation, in which the culture is fed until reaching the maximum storage capacity. In this work the possibility to make the process cheaper was explored trying to couple the selection and accumulation steps and a halotolerant culture collected from seawater was used and fed with an artificially salted synthetic substrated made of an aqueous solution containing a mixture of volatile fatty acids in order to explore also if its performance can allow to use it to treat substrates derived from saline effluents, as these streams cannot be treated properly by bacterias found in activated sludge plants due to inhibition caused by high salt concentrations. Generating and selling the produced PHAs obtained from these bacterias it could be possible to lower, nullify or even overcome the costs associated to the new section of a treating plant dedicated to saline effluents.