Bioethanol Production from Yam (Dioscorea Rotundata) Using Simultaneous Saccharification and Fermentation (SSF)

Abstract

Yam is a starchy tuber mainly used in food preparation but with high potential applications in other fields such as pharmaceutical and bioplastic production. Colombia is among the top twelve yam producing countries worldwide and ranked first in terms of yield of tons per hectare planted. Yam production has specifically been concentrated in the Caribbean region, which is why this tuber is very little known in the inland regions. In this study, we evaluated Simultaneous Saccharification and Fermentation (SSF) for bioethanol production from yam (Dioscorea rotundata) using Saccharomyces bayanus. Ethanol production technologies involve the fermentation and hydrolysis of consumable raw materials (i.e., sugar cane and corn) which are quite mature around the world. For this reason, the process under analysis combined three phases: 60 min of gelatinization, enzymatic hydrolysis (divided into 40 min of liquefaction with α-amylase and 20 min of saccharification with glucoamylase), and 27 h of fermentation with no enzyme recovery. We used different yam concentrations (10, 12.5, 15, and 18 % w/w) in a wet basis. SSF was monitored along time, and total reducing sugars and ethanol concentration were quantified. The hydrolysis yield, was calculated based on the theoretical starch available in the tuber, was 90 % of starch mass for samples with a yam concentration of 10 and 15 % w/w. Regarding ethanol, the best result (a productivity of 0.19 g/Lh-1) was obtained with the sample with a yam concentration of 10 % w/w. Therefore, yam is a starchy material suitable to produce bioethanol via SSF.