Fermentation of grain sorghum starch by co-cultivation of schwanniomyces occidentalis and saccharomyces cerevisiae

• Published in: Bioresource technology 1992, Vol.42 (1), p.27-31
• Main Authors: Horn, C.H., du Preez, J.C., Kilian, S.G.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; amylases; amylolytic yeast; Biological and medical sciences; Biotechnology; enzyme activity; ethanol; ethanol production; fermentation; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Grain sorghum; grains; saccharification; Saccharomyces cerevisiae; Schwanniomyces occidentalis; Sorghum bicolor; starch; Use of agricultural and forest wastes. Biomass use, bioconversion
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/0960-8524(92)90084-B

The amylases of a Schwanniomyces occidentalis mutant hydrolysed grain sorghum starch completely. Heat pretreatment to effect gelatinization was essential for total starch hydrolysis. Ethanol fermentations were conducted by using a stationary-phase culture of S. occidentalis in conjunction with Sacchromyces cerevisiae to ferment the sugars liberated from the grain sorghum starch by the amylases of S. occidentalis. Increasing the grain sorghum concentration from 8 to 28% (m/v) did not affect the final ethanol yield of 0·45 g ethanol/g glucose equivalents, although the fermentation rate decreased considerably at the higher slurry concentration, requiring 8 days for completion of the fermentation. A 28% grain orghum slurry yielded 12·5% (w/v) ethanol, indicating that nearly 390 l of ethanol could be produced per tonne grain sorghum, with about 430 kg residual biomass containing 43% crude protein.