Bioconversion of lignocellulosic hydrolysate to acetic acid using Moorella thermoacetica

Abstract

A systematic study of bioconversion of lignocellulosic sugars to acetic acid by Moorella thermoacetica strain ATCC 39073 was conducted. Four different hydrolysates obtained after steam pretreatment of lignocellulosic biomass were selected and fermented to acetic acid in batch fermentations. The bacterial strain (ATCC 39073) can effectively ferment xylose and glucose in steam exploded hydrolysates from wheat straw, forest residues, switchgrass, and sugarcane straw to acetic acid. This homoacetogen prefers xylose over glucose. The highest acetic acid yield obtained was in steam pretreated sugarcane straw hydrolysate and the lowest in forest residues hydrolysate (71% and 39% of theoretical respectively based on total sugars). This acetogen can partially consume arabinose, galactose and mannose within 72 h of fermentation. Acetic acid yield in forest residues was adversely affected by high concentration of arabinose, galactose and mannose. Glucose to xylose ratio has a direct effect on production yield. It was also observed that M. thermoacetica can tolerate process derived inhibitory compounds from steam explosion pretreatment (total phenolics up to 3 g/L and furans up to 0.5 g/L).