Production of ethanol from enzymatically hydrolyzed soybean molasses

Soybean molasses (SM) is a by-product of soybean meal concentrate. It is rich in sucrose, raffinose and stachyose. Stachyose and raffinose are not directly fermentable to ethanol but, when hydrolyzed, can be metabolized by Saccharomyces cerevisiae. In this work, we studied (1) the production of ethanol from natural SM by fermentation with S. cerevisiae, (2) the enzymatic hydrolysis of SM by alpha-galactosidase and the subsequent fermentation with S. cerevisiae (HF), and (3) ethanol production via the simultaneous hydrolysis and fermentation (SHF) of SM. The results showed that, although the fermentation of natural soybean molasses provided a fermentation yield of 72.9% under optimized conditions, hydrolyzed soybean molasses provided a fermentation yield 7.6% higher using the HF process and 8.2% higher using SHF. Both fermentation processes resulted in lower concentrations of residual sugar. (C) 2012 Elsevier B.V. All rights reserved.