A new strategy based on enantioselective acylation properties of relatively unknown penicillin G acylase from Alcaligenes faecalis has been developed for the production of pharmacologically interesting enantiomerically pure d-phenylalanine. In order to get high reaction rate and enantioselectivity, two key factors (pH and temperature) and eight different acyl donors were optimized, and the optimal acylation reaction was carried out at pH 10, 35 °C, using phenylacetamide as the acyl donor. This enantioselective acylating method is also illustrated by the effective production of five different p-substituted phenylalanine derivatives in enantiopure.

In this work, fatty acid ethyl esters were produced from the lipase-catalyzed irreversible transesterification reaction between Jatropha oil and diethyl carbonate (DEC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the five important reaction variables for the irreversible transesterification of Jatropha oil in a solvent-free system. The optimum conditions for the transesterification were a reaction time of 13.3 h, a temperature of 44.5 °C, a lipase amount of 13.7% (w/w), a DEC to Jatropha oil molar ratio of 3.75:1 and no need for adding water. The optimal predicted yield of fatty acid esters was 97.7% and the actual value was 96.2%. The results showed that the RSM based on CCD was adaptable for a fatty acid esters yield study for the current transesterification system.

An efficient approach to synthesize terpene esters using plant lipase-Carica papaya lipase (CPL) as the biocatalyst was developed in this work. The effects of chain length of acyl donor and solvent type on the CPL-catalyzed transesterification reaction were investigated firstly. It was found that CPL showed the highest activity in n-hexane with vinyl octanoate as the best acyl donor. To obtain high yield of terpene esters, the main reaction parameters were studied and further optimized by response surface methodology. Ping–Pong Bi–Bi mechanism with dead end complex of citronellol was found to fit the initial rate data and the kinetic parameters were obtained by regression analysis. The optimal conditions were: 55 °C, 9% (w/w) of CPL based on substrate, equimolar ratio of substrates. Under these conditions, yield of more than 99% was achieved after 8 h reaction. Ionic liquids (ILs) were used to improve the operational stability because the CPL was found to lose its activity markedly during the repeated runs, it showed that the stability of CPL increased about 5 times when it was coated with ionic liquids. The CPL is low cost yet effective, thus the process developed here shows obvious potential for the production of terpene esters industrially.Graphical abstractDownload full-size imageHighlights► Terpene esters of linalool and citronellol were successfully synthesized using Carica papaya lipase. ► The effects of chain length of acyl donor and solvent type were investigated. ► The main reaction parameters were further optimized by response surface methodology. ► Stability of lipase was increased about 5 times when it was pretreated with ionic liquids.

In the context of specifying the origin of enzyme enantioselectivity, the present study explores the lipase enantioselectivity towards secondary alcohols of similar structure from the perspective of substrate binding. By carrying out molecular mechanics minimization as well as molecular dynamics simulation on tetrahedral reaction intermediates which are used as a model of transition state, we identify an unconventional productive binding mode (PBM)—M/H permutation type for Candida antarctica lipase B (CALB). The in silico results also indicate that different PBMs of the slow-reacting enantiomer do exist in one lipase even when there is little structural differences between substrates, e.g. compounds with Ph or CH2CH2Ph group display the M/H permutation type PBM while molecules with CH2Ph show the M/L permutation type PBM. By relating the PBMs of substrates to the experimentally determined E-values obtained by Hoff et al. [16], we find that disparity in PBM of the slow-reacting enantiomer determines why E-values of substrates with CH2Ph were lower than E-values of substrates with Ph or CH2CH2Ph group. The modeling results also suggest that the “pushed aside” effect of the F atom and Br atom accommodates the medium size substituent of the substrate better in the stereospecificity pocket of the enzyme.

A facile pretreatment method was developed to obtain high specific activity of PGA from recombinant E. coli cells for preparing immobilized enzyme with high activity, which coupled selective extraction of PGA with butyl acetate and adsorption of butyl acetate with active carbon. Butyl acetate (5%, v/v) led to a 92.0% release of PGA, the specific activity of which in the extracting solution was twice that obtained by sonication. The negative effect on PGA immobilization due to residual butyl acetate in the extracting solution was removed by adding active carbon (8%, w/v). The final PGA solution meets requirement for industrial immobilization while eliminating the high cost of a traditional purification process. This pretreatment method developed in this work is simple, highly performing and cost-effective. It has been employed in a 10 tons/year immobilized PGA production line.