Application Of Mass Transfer Enhancement Technology In Biocatalytic Synthesis Of Bio-based Chemicals

The high viscosity and diffusion restriction of the immobilized enzyme biocatalytic system,are the bottlenecks that restrict its high conversion rate and industrialization.The impact of internal diffusion is particularly prominent.The objective of this thesis is to solve the above problems.The collision frequency between the substrates and packing was changed to increase contact surface and reduce surface tension in the biocatalytic reaction.The two-layer immobilized enzyme with a core-shell was developed,which could bear stronger mechanical damage of the granular immobilized enzyme coming from the reactor shearing forces.Via the design of metal mesh packing,the enzyme protein was immobilized directly on the mental packing surface,which greatly reduces the diffusion limit in the reaction,but further increased the enzyme lifetime,the conversion rate,and the contact rate between the substrate and catalyst.Based on the above research,a new type of enzymatic reactor with high mass transfer was designed.The enzymatic new rotating packed bed(NRPB)was applied to the series reaction,and a new kind biolubricant with low pour point,high stability and strong antioxidant,was developed.(1)The development of high mass transfer reactor in high-viscosity biocatalytic systemIn view of the traditional reactor defects,such as diffusion limitation and insufficient mass transfer in the high-viscosity biocatalytic reaction,this paper realized the combination between the rotating packed bed(RPB)and the biocatalytic reaction process.After the exploration of the centrifugal force factors and substrate flow rate on the reaction,it was found that the RPB can effectively improve the internal-external diffusion limitation in the biocatalytic process of the immobilized enzyme.The liquid-side mass transfer coefficient of the system conformed to kLa=A(We)a(Re)b=B(R)h(?)i(?)j(?)k(?)l.The internal diffusion Thiele module conforms to ?=Rsi(R/3)2/(DeffCs0)=x(?)i(R/3)2/Deff.The reaction rate of external diffusion conformed to Rsi=kLacs0=x(?)ics0.By changing centrifugal force factors,the effect of internalexternal diffusion could be effectively reduced,further increased the interphase mass transfer,and the catalytic reaction efficiency of the immobilized enzyme.The conclusion and applicability of the above study were verified by taking the biocatalytic process in the high-viscosity of iso-octyl palmitate and wax ester systems.In the RPB system of synthesizing iso-octyl palmitate,the substrate conversion rate of 99.6%was obtained,so as to the enzyme reusability of 9 batches with the production yield still close to 90%,when the centrifugal force factor was 15,substrate flow rate of 100 mL/min,reaction time of 1 h.Compared with the traditional stirring reactor,the high mass transfer characteristics of the RPB promoted the substrate conversion rate by about 30%,shorted the reaction time by 300%and extended the enzyme lifetime by 100%.In the RPB system of synthesizing soybean oil based wax ester,substrate conversion rate of 96.4%was obtained,so as to the enzyme reusability of 9 batches with the production yield still close to 90%,when the centrifugal force factor was 20,substrate flow rate of 100 mL/min,reaction time of 4 h.Compared with the traditional stirring reactor,the high mass transfer characteristics of the RPB promoted the substrate conversion rate by about 14%,shorted the reaction time by 100%and extended the enzyme lifetime by 300%.(2)Development of the two-layer core-shell shear-resistant immobilized enzymeDue to mechanical damage,the traditional granular immobilized enzyme was easily fragile with a shorter lifetime reacted in the RPB.In this paper,a twolayer core-shell shear-resistant immobilized enzyme was developed to reduce the mechanical damage of under the strong shear force.With mycelium waste as the adsorption carrier,the lipase was adsorbed and immobilized with a core structure.It is then covered with calcium alginate to form the shell structure of the immobilized enzyme.The wax ester results of the immobilized enzyme in the RPB showed that 'he substrate conversion rate of 94%was obtained,so as to the enzyme reusability of 15 batches(45 h)with the production yield close to 80%,when the centrifugal force factor was 20,substrate feed flow rate of 100 mL/min,reaction time of 3 h.Compared with the traditional granular immobilized enzyme,its lifetime was increased 7 batches and the use time was extended nearly 1 time.(3)Dual-function packing development of the metal surface immobilized enzymeIn order to overcome the problem of poor distribution uniformity,shear force damage and diffusion restriction of granular immobilized enzyme micropores in RPB,dual-function packing development of the metal surface immobilized enzyme was developed.In this paper,a series reactions was reacted to synthesis the immobilized enzyme,such as mental coordination reaction between the dopamine hydrochloride and the stainless steel surface with oxidation layer,shrink amine reaction of unsaturated fatty acid linker,unsaturated fatty acid carbon double-bonded ring oxidation reaction,and enzyme protein ring opening reaction for immobilization,The near-single molecular layer structure of the immobilized enzyme was formed on the surface of the stainless steel packing,which had the dual functions of reactor packing and catalysis.The reaction of octyl laurate proved that the dual-function packing had a positive function,and the conversion rate was maintained at more than 98%after 14 batches in the RPB system.(4)Application of the NRPB in preparing the high-performance new lubricantsIn this paper,the NRPB was applied in a process development to synthesis a new type of high-performance furan-ring structured biolubricant.In this study,a series of reactions,such as hydrase interface reaction,high viscous esterification reaction,epoxy reaction,ring opening reaction,etc.,were used to modify the linoleic acid for biolubricant.This biolubricant was superior to conventional mineral lubricants in terms of viscosity(VI=109?163),thermal stability(Tonset=298 ??308?)and frictional properties(COF=0.101?0.106).Besides,it also had outstanding low temperature performance(pour point25??-64?).In the hydration reaction,the linoleic acid conversion rate of 96%was obtained 6 hours later,and single-batch hydrase can be used 15 batches with substrate conversion rate still above 90%.The substrate conversion rate of 99.2%was obtained,so as to the enzyme reusability of 10 batches with the production yield close to 97%in the esterification reaction.While the epoxy reaction was balanced at the 6th hour with the production yield about 98.5%,and the RPB reactor improved enzyme life by more than 1 times in compared with the stirring reactor.In summary,application of mass enhancement technology in biocatalytic synthesis of bio-based chemicals was studied in this paper.Compared with the traditional stirring reactor,the RPB greatly improved the mass transfer,reduced the reaction diffusion limitation,increased the production efficiency,prolonged the lifetime of the enzyme and shortened the balance time of the biocatalytic reaction.The designed NRPB was conducive to broadening its application in the biocatalytic field and providing good selectivity for the industrial production.