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A comparison of methods of ethanol production from sweet sorghum bagasse

Thanapimmetha, Anusith, Saisriyoot, Maythee, Khomlaem, Chanin, Chisti, Yusuf, Srinophakun, Penjit
Biochemical engineering journal 2019
Saccharomyces cerevisiae, bagasse, cellobiose, endo-1,4-beta-glucanase, enzymatic hydrolysis, enzymatic treatment, ethanol, ethanol production, fermentation, glucose, hydrogen peroxide, hydrolysates, hydrolysis, inoculum, saccharification, sodium hydroxide, sweet sorghum, xylose, yeasts
Ethanol production from sweet sorghum bagasse (SSB) is reported. A two-step pretreatment with hydrogen peroxide followed by NaOH at 121 °C for 20 min, was used prior to enzymatic treatment. Enzymatic treatment was carried out using a commercial cellulase. Enzymatic hydrolysis for 72 h resulted in a hydrolysate containing xylose (5.1 g L―1), glucose (75.3 g L―1) and cellobiose (1.4 g L―1). This hydrolysate was used to produce ethanol by a 72-h fermentation with the yeast Saccharomyces cerevisiae TISTR 5606 at 30 °C. This separate hydrolysis and fermentation (SHF) method was compared with a simultaneous saccharification and fermentation (SSF) method. The SSF process used the pretreated SSB and was carried out in two different ways: (1) In the first method, the enzyme, the substrate and the yeast inoculum were mixed and SSF fermentation took place at 37 °C for 72-h, to produce a final ethanol concentration of 22.3 g L―1; (2) in the second method, termed the ‘delayed simultaneous-saccharification fermentation’ or DSSF, the pretreated SSB was enzymatically hydrolyzed at 50 °C for 6-h, cooled to 37 °C, and then inoculated with the yeast to commence a 66-h fermentation. This gave a final ethanol concentration of 28.3 g L―1. The ethanol productivity was 0.31 g L―1 h―1 for the SHF and SSF processes, but the DSSF had a ˜26% higher productivity.