Enzymatic hydrolysis and ethanol fermentation of by-products from potato processing plants

Abstract

By-products from potato processing plants were liquefied and partially saccharified using three commercially available enzymes, followed by ethanol fermentation by yeast and then hydrolysis by glucoamylase. From 12% (w/w) of fresh potato peel, about 20 mg/mL ethanol was formed in the supernatant via amylase, pectinase, or an enzyme complex; this yield was slightly increased with combinations of these enzymes. Supplementation of substandard mash to potato peel (1:1) as a raw material enhanced the amount of ethanol formation, increasing it to approximately 50 mg/mL by the mixture of all three enzymes. After the addition of yeast and glucoamylase to the partially saccharified material, ethanol formation proceeded gradually and slowed in 12 h with the consumption of fermentable sugars. Galacturonic acid derived from pectin was not fermented and remained in the fermented broth. In the by-products, the conversion rate of sugars to ethanol was estimated to be 42.5%.