Efficient butanol production using corn-starch and waste Pichia pastoris semi-solid mixture as the substrate

Corn starch is the traditional substrate for butanol production by Clostridium acetobutylicum. However, the production suffers the problems of high substrate price and low sugar utilization yield. Waste P.pastoris semi-solid enriches with carbohydrate/protein and could be potentially used as an alternative substrate. In this study, NaOH was used to treat the waste semi-solid into suspensions. The fermentations were implemented by largely reducing initial starch content, and then adding the suspensions into broth after fermentations entered solventogenesis phase. Using the mixed substrate, final butanol concentrations in a 7 L anaerobic fermentor could reach and stabilize around 9.5-10.5 g/L, which was equivalent to that using 15% pure corn-starch; total sugar utilization yield largely increased from 50% to more than 90%, as disaccharides/trisaccharides were effectively utilized; 53% carbohydrate in the semi-solid was effectively digested which was beneficial for waste amount reduction; 57% expensive corn-starch could be saved.