Yeast based biorefinery for xylitol and ethanol production from sugarcane bagasse

Lignocellulosic biomass is one of the biggest renewable reservoirs for organic carbon that can be exploited as feed for various value-added products like fuel, nutraceuticals enzymes, and proteins. Biofuel is not only valuable but also a top priority target to address the energy crisis. Hence the current work was planned to valorize the cellulose-rich residual biomass (CRB), left after xylitol production for ethanol fermentation by yeast. Xylose-rich hydrolysate was prepared with dilute acid pretreatment (0.1 M H2SO4, 145 degree celsius, and 90 min) for xylitol production and CRB was further processed for enzymatic hydrolysis (crude cellulase). Acid hydrolysis offered maximum reducing sugars of 0.33 +/- 0.01 g & sdot;g(biomass)(-1) comprised of xylose 0.31 +/- 0.01 g & sdot;g(-1) (biomass). Besides sugar, biomass hydrolysis also produced 0.21 +/- 0.01 g.L-1 furans and 0.34 +/- 0.11 g.L-1 acetic acid. Pichia guilliermondii RLV-04 (MH588234.1) have shown 0.90 +/- 0.02 g(xylitol).g(xylose)(-1) conversion of xylose to xylitol. The primary process has left more than 50-55 % biomass that was rich in cellulose. Enzymatic hydrolysis of the CRB using crude cellulase showed maximum glucose recovery of 0.56 +/- 0.02 g & sdot;g(-1) (available cellulose) at 15 FPU at 50 degree celsius, after 12 h. In addition, yeast biomass recovered from xylitol production was hydrolysed and used as a nitrogen source. Under an anaerobic environment, a maximum ethanol yield of 0.36 +/- 0.01 g.g(-1) (glucose) was achieved with commercial baker's yeast while the addition of yeast biomass hydrolysate improved the alcohol yield to 0.48 +/- 0.02 g.g(glucose)(-1). Reutilization of biocatalysts as nitrogen source not only upgraded fermentation processes but also lowered process waste and improved process economics.