Comparative study of ethanol production from sodium hydroxide pretreated rice straw residue using Saccharomyces cerevisiae and Zymomonas mobilis

Rice straw is a suitable alternative to a cheaper carbohydrate source for the production of ethanol. For pretreatment efficiency, different sodium hydroxide concentrations (0.5–2.5% w/v) were tested. When compared to other concentrations, rice straw processed with 2% NaOH (w/v) yielded more sugar (8.17 ± 0.01 mg/ml). An alkali treatment induces effective delignification and swelling of biomass. The pretreatment of rice straw with 2% sodium hydroxide (w/v) is able to achieve 55.34% delignification with 53.30% cellulose enrichment. The current study shows the effectiveness of crude cellulolytic preparation from Aspergillus niger resulting in 80.51 ± 0.4% cellulose hydrolysis. Rice straw hydrolysate was fermented using ethanologenic Saccharomyces cerevisiae (yeast) and Zymomonas mobilis (bacteria). Overall, superior efficiency of sugar conversion to ethanol 70.34 ± 0.3% was obtained with the yeast compared to bacterial strain 39.18 ± 0.5%. The current study showed that pretreatment with sodium hydroxide is an effective method for producing ethanol from rice straw and yeast strain S. cerevisiae having greater fermentative potential for bioethanol production than bacterial strain Z. mobilis .