BIOETHANOL PRODUCTION FROM SWEET SORGHUM STALK JUICE BY ETHANOL-TOLERANT SACCHAROMYCES CEREVISIAE STRAINS: AN OVERVIEW

Sweet sorghum (Sorghum bicolor (L.) Moench) represent an emerging alternative feedstock with great potential for bioethanol production. Sweet sorghum stalks can be crushed to extract the sugar-rich juice (containing mainly sucrose, glucose and fructose) which can be directly fermented into ethanol with high efficiency by Saccharomyces cerevisiae yeast. This fast-acting microorganism with high ethanoltolerance displays high ethanol yields and maintains high cell viability during the fermentation under very high gravity conditions (with high total sugar concentrations). The objective of this study is to review the current state of knowledge on the bioethanol production from stalk juice of different sweet sorghum varieties by Saccharomyces cerevisiae (industrial and isolated yeast strains), assessing also the effects of process variables, nutrient supplementation and feeding systems (batch and fed-batch fermentations) on the final ethanol concentration.