Ethanol Fermentation from Cassava Starch Hydrolysate by Thermotolerant Yeast Pichia kudriavzevii using Batch and Fed-batch Cultures

Abstract

Ethanol fermentation of Pichia kudriavzeii PBB511-1 was completed after the saccharification period through the cassava starch hydrolysate by Talaromyces flavus 21-3 which produced 60-80 gL^-1 of reducing sugar with the following conditions: 30% (w/v) cassava starch, initial pH at 7.5, temperature at 30-31°C and a shaking speed of 130 rpm for 7 days. The fermentation process began by adding yeast inoculum, then allowed to ferment in a 7-L jar fermenter at 45°C in cassava starch hydrolysate media. The batch fermentation that showed the best condition was an agitation speed of 400 rpm without aeration. The ethanol concentration reached 45.44 gL^-1, a productivity of 0.87 gL^-1h^-1 and a yield of 49.39% of theoretical yield. A fed-batch fermentation was also performed, but it was not achieved as batch fermentation. The results showed supplementation for a 1 time of substrate was better than supplemented for 2 and 3 times. It produced 24.85 gL^-1 of ethanol, a productivity of 0.69 gL^-1h^-1 and a yield of 27.01% of theoretical yield. Therefore, T. flavus 21-3 and P. kudriavzevii PBB511-1 could become more influential on ethanol fuel production.