Enzymatic processes coupled with continuous microfluidic techniques have significant application prospects in pharmaceuticals and fine chemicals. It is important to stably load enzymes in microreactors. This study reported a sol-gel method for preparing wall-coated immobilized enzyme microreactors (W-IMERs) by entrapment of Candida antarctica lipase B (CALB). The W-IMERs were simply constructed in one step by a flow coating process in a capillary. Compared with the free enzyme, the tolerance of immobilized enzyme to ethanol and temperature is significantly improved, and the yield of immobilized enzyme activity is 76.12% in the batch reactor. In W-IMERs, the yield of immobilized enzyme activity increased to 82.95%. The W-IMERs maintained stable activity in 10 cycles for up to 30 days. A CFD model was also established to explore the relationship between the internal reaction and the mass transfer in W-IMERs. The relationship between the internal and external diffusion limits of W-IMERs and the overall reaction rate was analyzed by dimensionless numbers. The results indicated that sol-gel flow coating is a simple and effective method for the preparation of enzymatic microreactors. An in-depth understanding of the relationship between diffusion limitation and reaction rate will have a significant impact on the overall performance of enzyme-catalyzed microreactors.

The use of biocatalysts in pharmaceutical production is an important approach for the pharmaceutical industry to achieve green manufacturing. Compared to other lipases, Candida antarctica lipase B (CALB) possesses numerous excellent characteristics due to its unique structure. It exhibits relatively strong catalytic activity toward both water-insoluble and water-soluble substances. It shows high selectivity in hydrolysis and organic synthesis reactions. These properties are crucial for drug synthesis. However, current research shows that the use of CALB as a catalyst still faces challenges such as high cost, poor stability, and difficulty in large-scale production. Therefore, this paper mainly explores the advantages of CALB in the pharmaceutical industry and the challenges that still need to be overcome. It introduces the application progress of CALB in the pharmaceutical industry and finally provides a prospect for future research directions, hoping to provide appropriate references for related research.

Driven by global environmental awareness, biocatalysts are playing an increasingly important role in industrial chemistry. Enzymatic reactive distillation (ERD) combines the high efficiency of enzymatic reaction and distillation separation to reduce the limiting effects of reaction equilibrium, product inhibition, and the difficulty of product recovery due to its thermodynamic constraints. The lipase CALB was immobilized and coated on the theta-ring by sol-gel method. The synthesis of n-butyl acetate by transesterification reaction was selected as the model reaction in the ERD process, and a laboratory scale column was constructed. The Rate-based RadFrac model in Aspen Plus was used to describe the ERD. The results showed that the enzyme-loaded packing showed high long-term stability after 120 days in the reaction system. The deviation of the ERD experiment and simulation results was less than 10 %, which verifies the reliability of simulation. After the parameter sensitivity optimization on the simulation, compared with the batch reactor, the ERD process increased the reactant conversion from 60 % to 94.74 %. This study established a complete process from enzyme immobilization to ERD process, which provided a theoretical basis for the establishment and optimization of ERD process.

The process of immobilized enzyme and the change mechanism of enzyme in magnetic field.

In the entrapment of enzymes by sol-gel method, the special procedures for obtaining the unique structure of xerogel are sometimes destructive to enzymes, while the internal structure of xerogels is easily broken. To solve the above problems, we present an economical, bio-friendly procedure for the entrapment of Candida antarctica lipase B in silica xerogel. In this procedure, an encapsulation-structured enzyme-carrying silica xerogel was produced by controlling the evaporation rate of the solvent at ambient pressure during drying, while tetramethoxysilane and methyltrimethoxysilane were used as the co-precursors. The xerogel synthesis was modified and optimized for improving the stability and reusability of the enzyme, while the xerogel characteristic structure was preserved. Moreover, the effects of the co-precursors amount on the mechanical strength, pore structure, hydrophobicity, enzyme loading, and enzyme stability of the enzyme-carrying silica xerogels were systematically investigated. And the best performance was observed at the co-precursors content of 30.28 wt%. Finally, the catalytic performance of the enzyme-carrying silica xerogels on the transesterification of n-butanol with ethyl acetate was demonstrated.

A magnetic nano-solid acid catalyst Fe3O4-PDA-SO3H was synthetized through an efficient method, as an eco-friendly and more efficient catalyst. The obtained catalyst has uniform core-shell structure, appropriate particle size, and high acid density. Fe3O4-PDA-SO3H was applied to catalyze the esterification of levulinic acid (LA) with alcohols of different chain length to produce the levulinate esters. The catalytic effect was optimized from the aspects of catalyst dosage, reaction temperature, and acid-alcohol molar ratio. Furthermore, the response surface optimization method was used to obtain the optimal conditions. Verified under these conditions, the experimental results showed that the conversion rate of LA can reach 95.87%, which was much higher than common cationic exchange resin Amberlyst 36 and Amberlyst 46. Furthermore, the recovery and reuse of the Fe3O4-PDA-SO3H was demonstrated six times without obvious loss in the activity.

The unique construction of the dividing-wall sic column (DWC) has the potential for both energy and capital cost conservation. A sufficiently robust control strategy is needed to handle the DWC because it is a complex multivariable system with high process nonlinearity and time lag. In this paper, the single-factor, response surface methodology (RSM), and particle swarm optimization (PSO) optimizations are applied to the DWC, and the optimal operating parameters are obtained. Then, a sliding mode control (SMC) method is proposed for DWC. Specifically, the DWC is estimated by a first-order pure lag transfer function, and the SMC controller is developed with the aid of the Interpreted MATLAB Fcn of MATLAB/Simulink. Finally, the dynamic responses of both SMC controller and proportional-integral-derivative (PID) controller are analyzed using the disturbance in the feed flow rate (F). The results show that the settling time, oscillation, and steady-state deviation of the SMC controller are less than those of the PID controller. In this way, the SMC could present a better option for control of a complex distillation process, such as the DWC.

The stability of immobilized enzyme on packing is an important factor to limit the development of enzyme-catalyzed reaction distillation. The modified sol loaded with Candida antarctica lipase B (CALB) was fixed on random packing (316 L stainless steel wire mesh) by spraying method to form an enzyme-loaded coating, which was applied to catalyze the esterification of ethyl acetate and n-butanol. The addition of 1-[3-(trimethoxysilyl)propyl]ureido (UPS) enhanced the stability of the CALB, and the mechanism of its combination was explored from a microscopic perspective. And then, it was confirmed by scratch resistance test that adhesion of enzyme-loaded coating in packing was improved 19%. The esterification reaction showed that the addition of UPS had little effect on the conversion rate while improving the stability of the coating. These results suggest that the effect of UPS treatment on the enzyme-loaded coating performance significantly enhanced the long-term effect of enzyme-loaded packing.