Biological treatment of vinasse with yeast and simultaneous production of single-cell protein for feed supplementation

Vinasse is the final residue of bioethanol production and presents a low pH (3) and a high Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) in the range of 3000-9000mgL(-1), characterizing this residue as highly polluting. Despite being a highly polluting effluent, vinasse could be used in the production of single-cell proteins and other value-added products due to its high carbon content. Thus, the aim of this work was to propose an aerobic biological treatment for vinasse through the application of a fermentation process in the presence of different yeasts and to simultaneously produce SCP. The optimal conditions were determined by central composite rotational design. Out of ten yeasts selected from the CCMA (Culture Collection of Agricultural Microbiology, Lavras, Brazil), two strains of Saccharomyces cerevisiae (CCMA0187 and CCMA0188) and one strain of Candida glabrata (CCMA0193) and Candida parapsilosis (CCMA0544) presented the highest biomass production at 306, 312, 388 and 306mg L-1, respectively. The generated microbial biomass presented a low anti-nutritional value and, on average, a protein content of 46.85%. The applied biological treatment was promising, demonstrating a reduction in vinasse toxicity or a decrease of 55.8 and 46.9% in BOD and COD, respectively. These results confirmed the potential for using yeasts in the treatment of vinasse while concomitantly producing protein biomass for use in other applications such as animal feed.