Enabling butanol production from crude sugarcane bagasse hemicellulose hydrolysate by batch-feeding it into molasses fermentation

Abstract

Butanol is a chemical and advanced biofuel whose fermentative production from hemicellulose hydrolysates is hindered by lignocellulose-derived microbial inhibitory compounds. In this work, Clostridium saccharoperbutylacetonicum DSM 14923 was not able to ferment a sugarcane hemicellulose hydrolysate supplemented with either laboratory-grade nutrients or sugarcane molasses. To circumvent this problem, the crude hemicellulose hydrolysate was fed, after 24 h, to a molasses fermentation containing 45 g/L total reducing sugars. Without the need of supplementing nutrients, the culture was able to co-ferment sucrose, glucose, fructose, and xylose (conversion of sucrose and xylose were 81 and 90 %, respectively) in a fermentation containing a diluted molasses-to-hydrolysate volume ratio of 3:1. Butanol yield (0.31 g/g) was remarkable, and butanol titer was 10.0 g/L after 72 h of fermentation. Therefore, this research demonstrated that sugarcane molasses ‒ a by-product of the sugar industry rich in sucrose and nutrients ‒ can be an efficient feedstock for enabling the production of butanol from sugarcane bagasse hemicellulose hydrolysate.