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Bioconversion of sugarcane bagasse and dry spent yeast to ethanol through a sequential process consisting of solid-state fermentation, hydrolysis, and submerged fermentation

Khonngam, Thipsuda, Salakkam, Apilak
Biochemical engineering journal 2019 v.150 pp. 107284
Aspergillus niger, Saccharomyces cerevisiae, amino nitrogen, biotransformation, cellulose, ethanol, ethanol fermentation, ethanol production, feedstocks, hydrolysates, hydrolysis, reducing sugars, solid state fermentation, submerged fermentation, sugar industry, sugarcane bagasse, yeasts
Sugarcane bagasse (SB), a by-product from the sugar industry, is considered a promising feedstock for ethanol production, owing to its high cellulose content and its ready availability. In this study, chemically pretreated SB was mixed with dry spent yeast (DSY) at a mass ratio of 60:40 before being fermented under solid-state fermentation (SSF) by Aspergillus niger TK1. The fermented solids at a concentration of 24 g/L (on a dry basis) was subsequently hydrolyzed to produce a hydrolysate, which was concentrated to contain 29.7 ± 0.6 g/L of reducing sugar and 585.1 ± 6.5 mg/L of free amino nitrogen. The concentrated hydrolysate was fermented by Saccharomyces cerevisiae TISTR 5339, yielding 8.98 ± 0.2 g/L of ethanol. An ethanol yield on reducing sugar was 0.46 g/g, which was 90.33% of the theoretical yield. Based on the results, a bioconversion process consisting of SSF followed by hydrolysis of fermented solids and submerged ethanol fermentation is proposed. In this process, ethanol yield on SB-DSY mixed substrates was 0.08 g/g.