Alcohol fermentation of starch by a genetic recombinant yeast having glucoamylase activity

TLDR

A recombinant Saccharomyces cerevisiae strain (SR93) carrying a chromosomally integrated glucoamylase gene (STA1) was cultivated in a fed‑batch process that maintained starch concentrations between 30 and 50 g L⁻¹ to maximize ethanol production. The engineered yeast produced glucoamylase constitutively, converting about 60 % of starch to ethanol with a maximum yield of 0.48 at 50 g L⁻¹ starch, achieving 14.3 g L⁻¹ ethanol—approximately 1.5 times higher than a conventional mixed culture—and the fed‑batch mode increased ethanol output by ~20 % over batch. © 1997 John Wiley & Sons, Inc.

Abstract

Alcohol fermentation of starch was investigated using a direct starch fermenting yeast, Saccharomyces cerevisiae SR93, constructed by integrating a glucoamylase-producing gene (STA1) into the chromosome of Saccharomyces cerevisiae SH1089. The glucoamylase was constitutively produced by the recombinant yeast. The ethanol concentration produced by the recombinant yeast was 14.3 g/L which was about 1.5-fold higher than by the conventional mixed culture using an amylolytic microorganism and a fermenting microorganism. About 60% of the starch was converted into ethanol by the recombinant yeast, and the ethanol yield reached its maximum value of 0.48 at the initial starch concentration of 50 g/L. The fed-batch culture, which maintains the starch concentration in the range of 30 to 50 g/L, was used to produce a large amount of ethanol from starch. The amount of ethanol produced in the fed-batch culture increased about 20% compared to the batch culture. © 1997 John Wiley & Sons, Inc.