Efficient Synthesis Of Furan-Based Alcohol From Fructose And Xylose By Bridging Chemocatalysis And Biocatalysis In A Deep Eutectic Solvent System

In order to solve the problem that tens of thousands of tons of biomass resources are squandered.every year in our country,the development of efficient conversion of biomass resources has become a hot research topic.5-Hydroxymethylfurfural(5-HMF)and furfural(FAL)are the most representative furan platform molecules converted from biomass,and they can synthesize various high value-added chemicals,such as 2,5-bis(hydroxymethyl)furan(BHMF)and furfuryl alcohol(FOL).The current catalytic conversion of biomass to furan-based alcohol often uses conventional catalysts such as expensive metals and inorganic acids.In order to save costs and reduce energy consumption,this study developed a chemical-biological method for the conversion of D-fructose and D-xylose to the high value-added furan-based alcohol chemical BHMF and FOL by using a deep eutectic solvent betaine:benzenesulfonic acid and recombinant E.coli DCF whole cell via tandem catalysis and the required simple operation condition,high product selectivity and catalytic efficiency.Firstly,a novel deep eutectic solvent Bet:BSA was prepared by using betaine and benzenesulfonic acid as a chemical catalyst.~1H NMR and FT-IR analysis were used to characterize Bet:BSA,verifying that the formation of Bet:BSA contributed to the efficiency of the dehydration reaction.By dehydrating D-fructose for 2 min at 120°C with Bet:BSA,124.6m M 5-HMF was obtained in a yield of 62.3%.Dehydration of D-xylose by using Bet:BSA for30 min at 170°C in a reactor resulted in 102.2 m M FAL in a yield of 51.1%.The Bet:BSA from the dehydration reactions were recycled separately and reused,which maintained that Bet:BSA can not only efficiently catalyze D-fructose and D-xylose,but also has good stability and easy to recycle and reuse after five cycles.Secondly,a dual-enzyme co-expression system containing NADPH-dependent reductase from Candida glabrata(Cg CR)and formate dehydrogenase(FDH)was constructed.Recombinant E.coli DCF whole cells were used as biocatalysts.In order to increase the yield of BHMF and FOL,the reaction conditions for bioreduction were optimized.At 40℃,p H 7.5and HCOONa(2.5 mol HCOONa/mol 5-HMF)as a cosubstrate,150 m M 5-HMF was catalyzed to 141.6 m M BHMF using recombinant E.coli DCF whole cells with a yield of94.4%.Furthermore,the recombinant E.coli DCF whole cells were used to catalyze 200 m M FAL into FOL in 99.9%yield and 100%selectivity,indicating that recombinant E.coli DCF whole cells had good catalytic activity.Finally,a sustainable strategy was developed for the chemenzymatic synthesis of high-value BHMF and FOL from biomass-based D-fructose and D-xylose in a one-pot manner.1.8 g D-fructose was converted to 124.6 m M 5-HMF in an oil bath at 120°C within 2min.After p H adjustment,it was converted to BHMF by DCF cells with cosubstrate HCOONa(2.5 mol HCOONa/mol 5-HMF)at 40℃and p H 7.5.The yield of BHMF reached99.6%.1.5 g D-xylose was dehydrated at 170℃for 30 min to obtain 102.2 m M FAL.After p H adjustment,it was converted to FOL under bioreduction condition at 40℃,p H 7.5 and HCOONa(3.5 mol HCOONa/mol FAL)as a cosubstrate.The yield of FOL reached 99.0%.This demonstrated the feasibility of the strategy of synthesizing furan-based alcohol by chemical enzymatic tandem catalysis of D-fructose and D-xylose.In summary,high-value BHMF and FOL were obtained in an environmentally friendly manner by the tandem catalysis of D-fructose and D-xylose by DES Bet:BSA and recombinant E.coli DCF whole cells,and a pathway for the synthesis of furan-based alcohol by chemical enzymatic tandem catalysis was achieved in this study.It saves costs,reduces energy consumption,and explore a green and effective pathway for the synthesis of BHMF and FOL from biomass conversion,which provides a new idea for the synthesis of furan chemicals in mild condition and green environment.