Study On Butanol Production From Vinegar Residue By Steam-explosion Pretreatment And Bioconversion

Industrial vinegar residue(VR)is the residue of grain,bran and husk after solid fermentation to produce vinegar.Due to its low cost and availability,it is likely to become an excellent potential raw material in the field of biofuel production in the future.However,compared with lignocellulosic materials from other sources,the application of vinegar residue in the field of energy production has not been fully developed and explored,mainly because:(1)the high biodegradability of vinegar residue hinders the release of monosaccharides by enzymatic hydrolysis;(2)The process of producing energy fuel with vinegar residue as substrate lacks reasonable and effective conversion path.Pretreatment is almost a must in the process of biomass refining and efficient utilization,including vinegar residue.Although steam explosion(SE)has been shown to be effective for the pretreatment of biomass from a variety of sources,few studies have applied steam blasting to the pretreatment of vinegar residue,so much of the relevant knowledge is still unknown.At the same time,in the study of vinegar residue,the conversion process of producing liquid fuel by saccharification fermentation with appropriate microorganisms is also rarely involved.In this paper,a steam explosion pretreatment scheme for vinegar residue was first established,and the effect of steam explosion pretreatment was evaluated by taking the changes of water extract composition,glycan hydrolysis rate,physicochemical properties and enzymatic hydrolysis rate of vinegar residue as the indexes.Then the mechanism of pretreatment and enzymatic hydrolysis was studied and explained by statistical and dynamic analysis.Finally,the adaptive stable strain screened by atmospheric pressure and room temperature plasma(ARTP)mutation method was used to transform and ferment the obtained water extract and enzymatic hydrolysate,successfully realizing the production process of transforming vinegar residue into biobutanol,and providing new research methods and ideas for the efficient utilization of vinegar residue.In the pretreatment process of steam explosion,the pressure conditions were 1.5,2.0 and 2.5 MPa respectively,and the residence time was 1,2,3 and 4 min respectively.Under the optimal pretreatment condition(2.5 MPa-2 min),the hydrolysis rate of dextran in vinegar residue was 29.47%(W/W),the hydrolysis rate of xylan was 71.62%(W/W)and the hydrolysis rate of Arabinan was 22.21%(W/W).In the process of enzymatic hydrolysis,the kinetics analysis showed that the pseudo-second-order kinetics model could well reveal the relationship between the enzymatic hydrolysis rate of vinegar residue(VR)and severity of steam explosion,and the data showed that the enzymatic hydrolysis rate of pretreatment vinegar residue was up to 13 times higher than that of untreated vinegar residue.SEM analysis and porosity analysis showed that steam explosion pretreatment can effectively change the microstructure of vinegar residue and increase the number of pores within the aperture range of 0-30nm.The material balance analysis showed that the maximum yield of 100 g vinegar residue after two steps was 19.60 g glucose,15.21 g xylose and 5.63 g arabinose.Finally,a superior inhibitor tolerant strain,Clostridium acetobutylicum Tust-001,was generated with ARTP treatment.The water extraction and enzymolysis liquid gathered were successfully fermented and achieved butanol titer of 7.98 g/L and ABE titer of 12.59 g/L.