Journal of Microbial & Biochemical Technology

Abstract

Simultaneous Saccharification of Corn Starch in Gluconic Acid Production by Aspergillus niger Immobilized on Nonwoven Fabric in a Pressurized Reactor

Toru Matsui, Katsuya Tooyama and Seigo Sato

Simultaneous saccharification of corn starch and fermentation to gluconic acid (SSF) was examined with Aspergillus niger immobilized on nonwoven fabric under high dissolved oxygen (DO). The starch liquefaction step to maltodextrins by the action of thermostable α-amylase was optimized using the dextrose equivalent value as an index. SSF was carried out using liquefied starch with simultaneous addition of commercial amyloglucosidase, and A. niger for gluconic acid production at DO of 150 mg/l by supplying pressurized oxygen gas. Treatment with α-amylase at 86ºC, followed by amyloglucosidase at 30ºC resulted in nearly 100% saccharification when using 300 g/l corn starch. Under conditions optimized for the saccharification steps, successful repeated batch production of gluconic acid of 272 g/l with space–time yield of 6.1 g/l/h was achieved with higher than 90% production yield from corn starch without significant loss of production activity for 450 h.