Application of ultrasound and technical enzymes during bioethanol production from fresh cassava root

Abstract

The effect of pre-treatment on sugar yield of cassava root as well as application of amylolytic enzymes for conversion of starch to glucose and bioethanol production using yeast were studied. Different pre-treatments, such as ultrasound, sulphuric acid as well as application of technical enzymes (pectolytic/cellulolytic), have effect on starch conversion into glucose. Up to 3% or 8% of free sugar could be observed after ultrasound and technical enzyme treatment, respectively, compared to untreated sample (free sugar 0.5%). Amylolytic enzymes (α-amylase and gluco-amylase) from different companies (Novozymes, Stern, Valley and AB enzymes) investigated in this study were effective to convert starch in glucose. The activity of amylolytic enzymes depended on the concentration of enzymes and treatment time. Up to 100% of starch could be converted in glucose during 3 h saccharification (28.8 g glucose/100 fresh cassava root) and enzyme concentration of 0.1% w/w. Fermentation of enzymatic saccharified cassava starch using Saccharomyces cerevisiae yeast showed the best fermentation condition for cassava root at 30°C and pH 5.0. Up to 11% v/v ethanol could be produced by 3 days fermentation.