Solvent-dependent activity of Candida antarctica lipase B and its correlation with a regioselective mono aza-Michael addition - experimental and molecular dynamics simulation studies

Effect of structural stability of lipase in acetonitrile on its catalytic activity in EGCG esterification reaction: FTIR and MD simulation

In this study, (-)-Epigallocatechin-3-O-gallate (EGCG) esterification reaction was catalyzed by Novozym 435, Lipozyme RM, Lipozyme TLIM, and lipase Amano 30SD in acetonitrile. Fourier transform infrared spectroscopy (FTIR) and molecular dynamic (MD) simulations were used to analyze the structural stability of different lipases in acetonitrile and their effect on EGCG esterification reaction. The results showed that conversion rate of EGCG catalyzed by Lipozyme RM was the highest, followed by Lipozyme TLIM. FTIR indicated that the secondary structure of Lipozyme RM was the most stable. MD simulations suggested that whole structural stability of Lipozyme RM in acetonitrile was superior to Novozym 435 and lipase Amano 30SD and similar to Lipozyme TLIM due to their similar conformation, while the active site of Lipozyme RM is more flexible than that of Lipozyme TLIM, which indicated that lipase with stable whole structure and flexible active site may be more conducive to the esterification of EGCG in acetonitrile. This study provided a direction for rapidly screening lipase to synthetize EGCG or other polyphenols esterified derivatives.

Metagenomic discovery of lipases with predicted structural similarity to Candida antarctica lipase B

Here we employed sequence-based and structure-based screening for prospecting lipases that have structural homolog to Candida antarctica lipase B (CalB). CalB, a widely used biocatalyst, was used as structural template reference because of its enzymatic properties. Structural homolog could aid in the discovery of novel wild-type enzymes with desirable features and serve as a scaffold for further biocatalyst design. The available metagenomic data isolated from various environments was leveraged as a source for bioprospecting. We identified two bacteria lipases that showed high structural similarity to CalB with <40% sequence identity. Partial purification was conducted. In comparison to CalB, the enzymatic characteristics of two potential lipases were examined. A candidate exhibited optimal pH of 8 and temperature of 50°C similar to CalB. The second lipase candidate demonstrated an optimal pH of 8 and a higher optimal temperature of 55°C. Notably, this candidate sustained considerable activity at extreme conditions, maintaining high activity at 70°C or pH 9, contrasting with the diminished activity of CalB under similar conditions. Further comprehensive experimentation is warranted to uncover and exploit these novel enzymatic properties for practical biotechnological purposes.

Candida antarctica lipase B performance in organic solvent at varying water activities studied by molecular dynamics simulations

Applications of lipases in low-water environments are found across a broad range of industries, including the pharmaceutical and oleochemical sectors. This includes condensation reactions in organic solvents where the enzyme activity has been found to depend strongly on both the solvent and the water activity (aw). Despite several experimental and computational studies, knowledge is largely empirical, and a general predictive approach is much needed. To close this gap, we chose native Candida antarctica lipase B (CALB) and two mutants thereof and used molecular dynamics (MD) simulations to gain a molecular understanding of the effect of aw on the specific activity of CALB in hexane. Based on the simulations, we propose four criteria to understand the performance of CALB in organic media, which is supported by enzyme kinetics experiments. First, the lipase must be stable in the organic solvent, which was the case for native CALB and the two mutants studied here. Secondly, water clusters that form and grow close to the active site must not block the path of substrate molecules into the active site. Thirdly, the lipase's lid must not cover the active site. Finally, mutations and changes in aw must not disrupt the geometry of the active site. We show that mutating specific residues close to the active site can hinder water cluster formation and growth, making the lipase resistant to changes in aw. Our computational screening criteria could potentially be used to screen in-silico designed variants, so only promising candidates could be pushed forward to characterisation.

Thermally Stable and Reusable Silica and Nano-Fructosome Encapsulated CalB Enzyme Particles for Rapid Enzymatic Hydrolysis and Acylation

This study reports the preparation of silica-coated and nano-fructosome encapsulated Candida antarctica lipase B particles (CalB@NF@SiO₂) and a demonstration of their enzymatic hydrolysis and acylation. CalB@NF@SiO₂ particles were prepared as a function of TEOS concentration (3-100 mM). Their mean particle size was 185 nm by TEM. Enzymatic hydrolysis was performed to compare catalytic efficiencies of CalB@NF and CalB@NF@SiO₂. The catalytic constants (K_m, V_max, and K_cat) of CalB@NF and CalB@NF@SiO₂ were calculated using the Michaelis-Menten equation and Lineweaver-Burk plot. Optimal stability of CalB@NF@SiO₂ was found at pH 8 and a temperature of 35 °C. Moreover, CalB@NF@SiO₂ particles were reused for seven cycles to evaluate their reusability. In addition, enzymatic synthesis of benzyl benzoate was demonstrated via an acylation reaction with benzoic anhydride. The efficiency of CalB@NF@SiO₂ for converting benzoic anhydride to benzyl benzoate by the acylation reaction was 97%, indicating that benzoic anhydride was almost completely converted to benzyl benzoate. Consequently, CalB@NF@SiO₂ particles are better than CalB@NF particles for enzymatic synthesis. In addition, they are reusable with high stability at optimal pH and temperature.