Ethanol production using concentrated oak wood hydrolysates and methods todetoxify

Ethanol production from concentrated oak wood hydrolysate was carried out t o obtain a high ethanol concentration and a high ethanol yield. The effect of added inhibitory compounds, which are typically produced in the pretreat ment step of steam-explosion on ethanol fermentation, was also examined. p- Hydroxybenzoic aldehyde, a lignin-degradation product, was the most inhibit ory compound tested in this study. Compounds with additional methyl groups had reduced toxicity and the aromatic acids were less toxic than the corres ponding aldehydes. The lignin-degradation products were more inhibitory tha n the sugar-derived products, such as furfural and 5-hydroxymethylfurfural (HMF). Adaptation of yeast cells to the wood hydrolysate and detoxification methods, such as using charcoal and overlime, had some beneficial effects on ethanol production using the concentrated wood hydrolysate. After treatm ent with charcoal and low-temperature sterilization, the yeast cells could utilize the concentrated wood hydrolysate with 170 as well as 140 g/L gluco se, and produce 69.9 and 74.2 g/L ethanol, respectively, with a yield of 0. 46-0.48 g ethanol/g glucose. In contrast, the cells could not completely ut ilize untreated wood hydrolysate with 100 g/L glucose. Low-temperature ster ilization, with or without charcoal treatment, was very effective for ethan ol production when highly concentrated wood hydrolysates were used. Low-tem perature sterilization has advantages over traditional detoxification metho ds, such as using overlime, ion exchange, and charcoal, because of the redu ction in the total cost of ethanol production.