Production of ethanol from soybean hull hydrolysate by osmotolerant Candida guilliermondii NRRL Y-2075

In this research, we studied the use of soybean hull hydrolysate (SHH) as a substrate for ethanol and xylitol production using an osmotolerant strain of Candida guilliermondii. The best acid hydrolysis of soybean hull achieved a recovery of 85 and 62% of xylose and mannose, respectively. Among detoxification treatments, activated charcoal 10% (w/v) showed the best results. Kinetic parameters obtained from the cultivation on four-fold concentrated SHH have shown that the osmotic pressure of this medium is higher than that supported by most osmophilic yeasts, revealing the osmotolerant characteristic of C. guilliermondii NRRL Y-2075. When cultivations were carried out on two times concentrated SHH, we obtained high yields of ethanol production, showing the prospect of SHH as a candidate for this biofuel production. Although xylose was present in high concentrations, no xylitol was produced, probably due to the presence of furfural acting as external electron acceptor or some varying cofactor preference of xylose reductase in this yeast strain.