Production of fumaric acid by simultaneous saccharification and fermentation of starchy materials with 2-deoxyglucose-resistant mutant strains of Rhizopus oryzae

Abstract

A mutant strain with high glucoamylase activity and insensitive to catabolite repression was developed to produce fumaric acid by simultaneous saccharification and fermentation (SSF) of starch without additional commercial glucoamylase supplementation. A series of mutant strains resistant to the non-metabolizable and toxic glucose analog 2-deoxyglucose (2-DG) were obtained by implanting nitrogen ion (N+) into Rhizopus oryzae ME-F12. Among them, the best mutant strain DG-3 produced 39.80g/L fumaric acid, which is 1.28-fold of that produced by ME-F12, and exhibited higher glucoamylase activity during SSF. Higher fumaric acid production (44.10g/L) was achieved when the initial total sugar concentration of cornstarch was 100g/L. During SSF of cheap, raw bioresource-degermed corn powder (100g/L total sugar) by DG-3, the maximum fumaric acid concentration and productivity were 32.18g/L and 0.44g/(Lh), respectively.