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Separate hydrolysis and fermentation (SHF) of Prosopis juliflora, a woody substrate, for the production of cellulosic ethanol by Saccharomyces cerevisiae and Pichia stipitis-NCIM 3498

Gupta, Rishi, Sharma, Krishna Kant, Kuhad, Ramesh Chander
Bioresource technology 2009 v.100 no.3 pp. 1214-1220
Scheffersomyces stipitis, hemicellulose, fermentation, lignocellulose, renewable energy sources, delignification, Saccharomyces cerevisiae, cellulose, ethanol production, Prosopis juliflora, enzymatic hydrolysis, proximate composition, acid hydrolysis, biomass, saccharification
Prosopis juliflora (Mesquite) is a raw material for long-term sustainable production of cellulosics ethanol. In this study, we used acid pretreatment, delignification and enzymatic hydrolysis to evaluate the pretreatment to produce more sugar, to be fermented to ethanol. Dilute H₂SO₄ (3.0%,v/v) treatment resulted in hydrolysis of hemicelluloses from lignocellulosic complex to pentose sugars along with other byproducts such as furfural, hydroxymethyl furfural (HMF), phenolics and acetic acid. The acid pretreated substrate was delignified to the extent of 93.2% by the combined action of sodium sulphite (5.0%,w/v) and sodium chlorite (3.0%,w/v). The remaining cellulosic residue was enzymatically hydrolyzed in 0.05M citrate phosphate buffer (pH 5.0) using 3.0 U of filter paper cellulase (FPase) and 9.0 U of β-glucosidase per mL of citrate phosphate buffer. The maximum enzymatic saccharification of cellulosic material (82.8%) was achieved after 28 h incubation at 50 °C. The fermentation of both acid and enzymatic hydrolysates, containing 18.24g/L and 37.47g/L sugars, with Pichia stipitis and Saccharomyces cerevisiae produced 7.13g/L and 18.52g/L of ethanol with corresponding yield of 0.39g/g and 0.49g/g, respectively.