Production Of2,3-butanediol By Catalytic Hydrolysis And Fermentation Of Stalk

2,3-Butanediol (2,3-BD) is an important biobased bulk chemical. Using stalk as the rawmaterial to produce2,3-BD is very meaningful for promoting high value utilization of stalk.This article used wheat stalk and corncob as the raw materials and removed lignin from thestalks by pretreatment. Cellulose and hemicellulose which were obtained by pretreatment of stalkwere degraded into fermentable sugars such as hexose and pentose via enzymatic hydrolysis.Then, the fermentable sugars were converted to2,3-BD by klebsiella pneumoniae physiologicalmetabolism and finally2,3-BD was separated from fermentation broth.Firstly, pretreatment and enzymatic hydrolysis of stalk were studied. The optimumconditions of pretreatment are: the alkaline H2O2solution containing2%NaOH and1.5%H2O2,the ratio of alkaline H2O2to ethanol of1:1, the ratio of solid to liquid of1:20,80oC, for3h. Theremoval rates of lignin from wheat stalk and corncob reach91.0%and92.8%, respectively. Theoptimum conditions of enzymatic hydrolysis are as follows: temperature of50oC, pH of4.8,substrate concentration of80g/L, cellulase loading of28U/g (substrate), β-Glycosidase enzymeloading of15U/g (substrate) and reaction80h. A reducing sugar yield of87.6%was achieved.The analyses of gas chromatography-mass spectrum on hydrolyzate of wheat stalk and corncobshowed that their main compositions are glucose and xylose.Sencondly, the fermentation conditions of2,3-BD were studied. In the convertion ofglucose into2,3-BD by Klebsiella pneumoniae, the optimum conditions are temperature of30oC, initial pH of7.0, shaking speed of150rpm, time of96h and inoculation amount of8%.When the initial glucose and peptone contents in medium are120g/L and16g/L,2,3-BDconcentration reaches61.78g/L. The optimum fermentation mediums of2,3-BD productionfrom stalk hydrolyzate are as follows: the initial glucose and peptone contents in medium of120g/L and6g/L, adding0.05g/L of CaCO3, keeping pH of6.0-6.5during the process offermentation. The highest concentration of protuct can reach50.97g/L under the aboveconditions. In batch fermentation, the proper supplemental carbon and nitrogen ratio is21. Afterfermentation, the maximum output is91.88g/L，which accounts for86%of the theoretical yield.The utilization rate of reducing sugar can reach94.95%.Finally, extraction of2,3-BD by aqueous two-phase of ethanol and dipotassium hydrogenphsophate system was studied. The optimal conditions for aqueous two-phase system extractionof2,3-BD was composed of25%(w/w) ethanol and26%(w/w) dipotassium hydrogenphsophate. The extraction ratios of2,3-BD is97.86%. Dipotassium hydrogen phosphate wasrecovered by adjusting the pH value and adding ethanol to the bottom phase. The recovery ratioof dipotassium hydrogen phosphate can reach77.1%.