In this paper, the lipase catalyzed transesterification of citronellol with vinyl acetate was investigated in ionic liquid. Firstly, six kinds of ionic liquids and six kinds of lipases from different sources were screened. The results showed that the lipase from Pseudomonas fluorescens had the best catalytic effect in the ionic liquid [bmimn][TF2]. The factors affecting the transesterification were optimized, and the optimal reaction conditions were as follows: the molar ratio of vinyl acetate to citronellol was 3:1; the reaction temperature was 40 °C; the amount of enzyme was 10 mg/mL; the rotating speed of the shaker was 200 r/min. When the concentration of substrate was below 500 mmol/L, no inhibition of substrate was found, while the inhibition of product was not negligible. The reuse of the lipase was studied, and the results showed that the catalytic activity of the lipase decreased by 20% after 7 times. The kinetic study showed that the reaction was a ping-pong bi-bi reaction mechanism with the inhibition of citronellyl acetate. The reaction kinetics model was established, and the parameters of the model were fitted by MATLAB software. The fitting values and the experimental values were in good agreement, and the relative error was only 7.75%.

In this paper, the optimum conditions and kinetics of lipase-catalyzed transesterification reaction of nerol and vinyl acetate for the synthesis of neryl acetate were investigated in a solvent-free system. The optimum conditions were determined as follows: the reaction temperature was 40 °C, the amount of enzyme was 12 mg/mL, and there was no need to add water. Increasing the stirring speed to 200 r/min can eliminate the external diffusion limitations. There was no substrate inhibition when the substrate concentration was lower than 500 mmol/L. However, the experimental results indicated that the product inhibition effect should be considered. The results of the reaction kinetic analysis indicated that the reaction followed the ping-pong double-double reaction mechanism with product inhibition. Finally, the model parameters were calculated by MATLAB software and the results showed that the experimental values could be in good agreement with the simulated values, and the relative error was 6.98%.

In order to address the challenges associated with free lipase in organic solvents, including aggregation, poor stability, and low catalytic efficiency, this study developed two types of poly(o-phenylenediamine) microspheres (solid and hollow) as supports for immobilizing lipase. The immobilization process utilized an adsorption method, with the poly(o-phenylenediamine) hollow microspheres being identified as the optimal support in a 2:5 enzyme-to-support ratio. On this basis, the lipase was immobilized by the covalent binding method. The immobilization conditions consisted of treating the support with 2% glutaraldehyde and immobilization at 40 °C for 2 h in pH 7.0 buffer. The specific activity of the immobilized enzyme was 5.3 times higher than that of the free enzyme. Covalent-binding immobilized lipase was also used for the preparation of citronellyl acetate by transesterification reaction, and, in optimized reaction conditions where the amount of immobilized enzyme was 0.1 g/mL, the reaction temperature was 50 °C and the shaking speed was 200 r/min during the reaction. Under these conditions, the citronellyl acetate yields can exceed 99% after 2 h. Furthermore, the stability of the immobilized lipase was investigated, and the residual activity of the immobilized enzyme was 95% after seven repetitions, while that of the free enzyme was only 70%. After 56 days of storage at room temperature, the immobilized enzyme retained 60% of its original viability, while the free enzyme retained only 31%.

Deoxyadenosine triphosphate (dATP) is an important biochemical molecule. In this paper, the synthesis of dATP from deoxyadenosine monophosphate (dAMP), catalyzed by Saccharomyces cerevisiae, was studied. By adding chemical effectors, an efficient ATP regeneration and coupling system was constructed to achieve efficient synthesis of dATP. Factorial and response surface designs were used to optimize process conditions. Optimal reaction conditions were as follows: dAMP 1.40 g/L, glucose 40.97 g/L, MgCl2·6H2O 4.00 g/L, KCl 2.00 g/L, NaH2PO4 31.20 g/L, yeast 300.00 g/L, ammonium chloride 0.67 g/L, acetaldehyde 11.64 mL/L, pH 7.0, temperature 29.6 °C. Under these conditions, the substrate conversion was 93.80% and the concentration of dATP in the reaction system was 2.10 g/L, which was 63.10% higher than before optimization, and the concentration of product was 4 times higher than before optimization. The effects of glucose, acetaldehyde, and temperature on the accumulation of dATP were analyzed.