Journal Article

Continuous co-production of ethanol and xylitol from rice straw hydrolysate in a membrane bioreactor

Jouzani, Gholamreza Salehi, Tabatabaei, Meisam, Khodaiyan, Faramarz, Abbasalizadeh, Saeed, Zahed, Omid

2016

Overview

The present study was set to develop a robust and economic biorefinery process for continuous co-production of ethanol and xylitol from rice straw in a membrane bioreactor. Acid pretreatment, enzymatic hydrolysis, detoxification, yeast strains selection, single and co-culture batch fermentation, and finally continuous co-fermentation were optimized. The combination of diluted acid pretreatment (3.5 %) and enzymatic conversion (1:10 enzyme (63 floating-point unit (FPU)/mL)/biomass ratio) resulted in the maximum sugar yield (81 % conversion). By concentrating the hydrolysates, sugars level increased by threefold while that of furfural reduced by 50 % (0.56 to 0.28 g/L). Combined application of active carbon and resin led to complete removal of furfural, hydroxyl methyl furfural, and acetic acid. The strains Saccharomyces cerevisiae NCIM 3090 with 66.4 g/L ethanol production and Candida tropicalis NCIM 3119 with 9.9 g/L xylitol production were selected. The maximum concentrations of ethanol and xylitol in the single cultures were recorded at 31.5 g/L (0.42 g/g yield) and 26.5 g/L (0.58 g/g yield), respectively. In the batch co-culture system, the ethanol and xylitol productions were 33.4 g/L (0.44 g/g yield) and 25.1 g/L (0.55 g/g yield), respectively. The maximum ethanol and xylitol volumetric productivity values in the batch co-culture system were 65 and 58 % after 25 and 60 h, but were improved in the continuous co-culture mode and reached 80 % (55 g/L) and 68 % (31 g/L) at the dilution rate of 0.03 L per hour, respectively. Hence, the continuous co-production strategy developed in this study could be recommended for producing value-added products from this hugely generated lignocellulosic waste.

• Publisher: Springer Netherlands,Springer Nature B.V
• Subject: Acetic acid / Applied Microbiology / batch fermentation / Biomass / Biomedical and Life Sciences / Bioreactors / Biorefineries / biorefining / Biotransformation / Candida tropicalis / carbon / Cellulose - metabolism / coculture / Detoxification / Environmental Engineering/Biotechnology / enzymatic hydrolysis / Ethanol / Ethanol - metabolism / ethanol production / Fermentation / furfural / hydrolysates / Hydrolysis / hydroxymethylfurfural / Immunology / Kinetics / Life Sciences / lignocellulose / Membrane reactors / Microbiology / Nitrogen - metabolism / Oryza - metabolism / Oryza - microbiology / Oxygen - metabolism / Rice / Rice straw / Saccharomyces cerevisiae / Saccharomyces cerevisiae - metabolism / Studies / Sugar / Sulfuric Acids - metabolism / value-added products / wastes / xylitol / Xylitol - metabolism / Yeasts