Simultaneous sago starch hydrolysis and ethanol production by Zymomonas mobilis and glucoamylase

Abstract

Simultaneous saccharification and ethanol fermentation (SSF) of sago starch was studied using glucoamylase (AMG) and Zymomonas mobilis. When compared with a presaccharified two-step process, the SSF process showed higher ethanol yields and productivities. Various SSF processes were tried using free enzyme and cells, free enzyme and immobilized cells, and coimmobilized enzyme and cells. Among these processes, the coimmobilized system proved to be more advantageous than the others with respect to ethanol productivity and enzyme recovery. The maximum ethanol productivity based on total working volume, V//r, was 17. 7 g/L h with 46. 3% of theoretical yield. The continuous production of ethanol could be maintained at the concentration of 44 g/L over 40 days with 93% of theoretical yield.