Enriched microbial consortia for dark fermentation of sugarcane vinasse towards value-added short-chain organic acids and alcohol production

The role of sugarcane vinasse as a nutrient source and the impacts of different inoculum pretreatment methods (acid-thermal and thermal treatment) were assessed in acidogenic systems aiming to produce value-added short-chain organic acids (SCOA) and alcohols. In-depth microbiome characterization was also conducted by high-throughput sequencing of the 16S rRNA gene using the Miseq Illumina platform. SCOA production was 47.3 % higher in vinasse-fed reactors, with isobutyric (up to 10.3 g L−1) and butyric (up to 10.6 g L−1) acids as the primary metabolites most likely resulting from lactate conversion. Ethanol comprised the main product from solventogenic pathways in all conditions, with values ranging between 2.7 and 5.2 g L−1, whereas no butanol was detected. Microbial analyses revealed high relative abundance values for the Clostridium, Lactobacillus, Bacillus and Ruminococcus genera, with the predominance of the Clostridium genus (17%) in acid-thermal treatment reactors and the Lactobacillus genus (37%) in thermal treatment reactors. Overall, vinasse proved to be a suitable substrate for value-added SCOA production, which characterizes a potential management approach to this wastewater stream. In this sense, the biochemical production of butyrate from vinasse could diversify the product portfolio of sugarcane biorefineries, also minimizing bioenergy losses by converting residual carbon fractions1275594601FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2016/16438-3; 2012/09785-8The authors acknowledge Dr. Eloisa Pozzi and Dr. Isabel Kimiko Sakamoto (LPB/EESC/USP), who assisted in the DNA extraction step. This work was supported by the São Paulo Research Foundation (FAPESP) [grant numbers 2016/16438-3 and 2012/09785-8]. The authors declare no conflict of interes