Produção de hidrogênio por culturas isoladas de Bacillus cereus, Enterococcus faecalis e Enterobacter aerogenes a partir de vinhaça de cana-de-açúcar

Abstract

Vinasse is a residue from the distillation of ethanol from sugarcane that is generated in large quantities by the sugar and ethanol industry. It has high carbon sources and can be reused as a substrate for the biological production of hydrogen and other value added products. Hydrogen is a form of clean and renewable energy and can be obtained by fermentative processes by means of microorganisms in pure cultures or associated in co-cultures obtained from natural sources of inoculum. Thus, the objective of this work was to evaluate the production of hydrogen and volatile fatty acids by isolated strains in Enterococcus faecalis, Bacillus cereus and Enterobacter aerogenes co-cultures, using vinasse as a substrate and using the bioaumentation technique of the consortium. The microorganisms were isolated from hydrogen producing anaerobic granular sludge. The experiments were carried out in flasks with a volume of 60 mL, containing vinasse at concentrations of 30, 50, 70 and 100% and glucose-containing assays for the pure cultures and the co-culture of B. cereus + E. aerogenes + E. faecalis. The microorganisms were inoculated in isolation, in cocultures and compared with the microbial consortium of origin. The cultures were maintained in shaker orbital shaking at 37 ° C for 48 h. Gaseous samples of the headspace and the liquid fraction were evaluated. The pure strains of B. cereus, E. faecalis and E. aerogenes, had the highest production of hydrogen in 100% vinasse, with 85.41 mmolH2. L-1, 79.0 mmol H 2. L-1 and 41.95 mmol H 2. L-1, respectively. The consortium, also in the largest concentration of vinasse, had a production of 54.16 mmolH2. L-1. The co-culture system E. faecalis + E. aerogenes produced more hydrogen (65 mmolH2. L-1) than the consortium. The microbial consortium produced more hydrogen than when it received the bioaumentation of the isolated strains of B. cereus, E. faecalis and E. aerogenes. The acetic and butyric acids were produced in greater quantity and propionic acid was the most consumed in all the experiments, indicating a favorable route chosen by the microorganisms for the production of hydrogen. The results indicate that there was the bioconversion of vinasse in clean energy and volatile fatty acids, providing a sustainable destination for this potentially polluting agroindustrial residue.