Ethyl glycolate (EGly) is a platform molecule in various fields, which has been widely applied for the production of various valuable chemicals. Despite being a traditional catalyst for the conversion of diethyl oxalate (DEO) to EGly, Ag/SiO 2 catalyst exhibits insufficient activity. The present study introduces a novel preparation method that couples H 2 O 2 reduction with deposition precipitation to augment the performance of the catalyst. Performance results show that Ag/SiO 2 catalyst prepared by the new method attains a DEO conversion of 95.6% and an EGly selectivity of 78.0%, showing respective improvements of 10.0 and 15.2% over excess impregnation-evaporating solvent method. Characterization results show that the average silver particles size of Ag/SiO 2 catalyst prepared by the new method is 6 nm, which is 1/2 of the excess impregnation-evaporation solvent method. Simultaneously, it contains a greater quantity of Ag 0 . The smaller and more uniform particles offer greater active site density, leading to enhanced DEO conversion. An increased presence of Ag 0 diminishes DEO overactivation and inhibits the dissociative adsorption of H 2 . Moreover, the amplified quantity of Ag 0 could be attributed to the reduced interfacial charge transport triggered by metal-support interactions (MSIs).
Phospholipase D (PLD) is a valuable enzyme in industrial processes for converting phosphatidylcholine (PC) to phosphatidylserine (PS). In this study, a strain of Bacillus cereus was isolated from soil and identified through 16S rRNA sequencing. To enhance PLD activity, various mutagenesis strategies—including chemical treatment, irradiation, and their combinations—were employed, resulting in four high-activity positive mutants (C-7, I-12, CI 7–12, and IC 13–14). Among these, the CI 7–12 mutant exhibited a significantly higher enzymatic activity, showing a 3.12-fold increase (312.2%) compared to the wild-type strain. Fermentation conditions were optimied using response surface methodology (RSM), achieving a PLD activity of 35 U/mL. The enzyme demonstrated stability over a wide temperature range (30–60 °C) and pH range (6–10), with a half-life of 128 days. Kinetic analysis revealed a V max of 20.04 μmol/h and a K m of 7.13 μmol/mL, indicating efficient activity. In bioconversion experiments, the PLD-enriched fermentation broth catalyzed the conversion of PC to PS, achieving a 53.0% conversion rate and a 92.3% selectivity for PS in a two-phase system. These findings expand the potential sources of PLD and underscore its applicability for PS production in biotechnological applications.
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