Continuous co-production of ethanol and xylitol from rice straw hydrolysate in a membrane bioreactor.
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.
Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), SPII Campus, Mahdasht Road, Karaj, P.O. Box: 31535-1897, Iran.|Department of Food Science, Engineering and Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran.
Omid
O
Zahed
Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), SPII Campus, Mahdasht Road, Karaj, P.O. Box: 31535-1897, Iran. gsalehi@abrii.ac.ir.
Gholamreza Salehi
GS
Jouzani
Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), SPII Campus, Mahdasht Road, Karaj, P.O. Box: 31535-1897, Iran.
Saeed
S
Abbasalizadeh
Department of Food Science, Engineering and Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran.
Faramarz
F
Khodaiyan
Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), SPII Campus, Mahdasht Road, Karaj, P.O. Box: 31535-1897, Iran.|Biofuel Research Team (BRTeam), Karaj, Iran.
Meisam
M
Tabatabaei
D018533:Biomass; D019149:Bioreactors; D001711:Biotransformation; D002482:Cellulose / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D006868:Hydrolysis; D007700:Kinetics; D009584:Nitrogen / Q000378:metabolism; D012275:Oryza / Q000378:metabolism* / Q000382:microbiology*; D010100:Oxygen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013464:Sulfuric Acids / Q000378:metabolism; D014993:Xylitol / Q000378:metabolism*
D013464:Sulfuric Acids; D000431:Ethanol; D002482:Cellulose; D009584:Nitrogen; C033158:sulfuric acid; D010100:Oxygen; D014993:Xylitol