Bioconversion of degraded husked sorghum grains to ethanol

Abstract

Efficient starch saccharification is an essential step towards achieving improved ethanol yields by fermentation. Sorghum grains are important starch sources for bioconversion to ethanol. In the present study, disease degraded (spoilt) husked grains from Nigerian sorghum cultivars were obtained from field sites and subjected to bioprocessing to ethanol. The crude husked grains (comprising husks, spikelet, awn, rachis and pubescence materials) were hammer milled and each meal separately mashed with enzyme cocktails comprising amylase, glucanase and protease enzymes. The saccharified worts obtained were then fermented with the yeasts, Saccharomyces cerevisiae and Pichia stipitis (aka Scheffersomyces stipitis), without exogenous nutrient supplementation. Sugars liberated during mashing were determined and it was found that enzymatic hydrolysis of milled sorghum grains was effective in yielding favourable levels of fermentable sugars up to 70g sugar/100g substrate with one particular cultivar (KSV8). Ethanol and carbon dioxide production was measured from subsequent trial fermentations of the sorghum mash and it was found that S. cerevisiae produced ethanol levels equating to 420 L/t that compares very favourably with yields from wheat and barley. Our findings show that crude degraded sorghum grains represent favourable low-cost feedstocks for bioconversion to ethanol with reduced energy input and without additional costs for nutrient supplementation during fermentation. Consequently, our results suggest some economic benefits could be derived from spoilt or degraded sorghum grains.

Bioethanol Production from Various Lignocellulosic Materials by Encapsulated Saccharomyces cerevisiae NCIM 3095

“…Simple sugars, which can be immediately turned into ethanol, need to be pretreated [8]. A mixture of fermentable sugars and possible inhibitory substances found in the biomass structure are released during pretreatment and hydrolysis [9,10]. The most efficient way to release simple sugars from cellulosic materials is through hydrolysis employing the right enzymes, however, process rates must be improved and enzyme production costs must be reduced [11].…”

Study on the Effective Application of Bacterial α-Amylase for Batch Liquefaction

“…Currently, the literature contains only recommendations for the use of Hitempase 2XL in the production of ethyl alcohol. Nasidi et al [7] showed that the mixture of EP (Promalt, Bioglucanase ME1250L, Hitempase 2XL, Promalt 4TR and Termamyl 120L) allows to convert the spoiled grains of sorghum into bioethanol. The main attention was paid to the influence of the type of raw material on the technological parameters of the process.…”