Purification and characterization of a thermoalkaliphilic esterase from Bacillus cereus WZZ006 for enantioselective resolution of indoxacarb intermediate

Abridgement of Microbial Esterases and Their Eminent Industrial Endeavors

Esterases are hydrolases that contribute to the hydrolysis of ester bonds into both water-soluble acyl esters and emulsified glycerol-esters containing short-chain acyl groups. They have garnered significant attention from biotechnologists and organic chemists due to their immense commercial value. Esterases, with their diverse and significant properties, have become highly sought after for various industrial applications. Synthesized ubiquitously by a wide range of living organisms, including animals, plants, and microorganisms, these enzymes have found microbial esterases to be the preferred choice in industrial settings. The cost-effective production of microbial esterases ensures higher yields, unaffected by seasonal variations. Their applications span diverse sectors, such as food manufacturing, leather tanneries, paper and pulp production, textiles, detergents, cosmetics, pharmaceuticals, biodiesel synthesis, bioremediation, and waste treatment. As the global trend shifts toward eco-friendly and sustainable practices, industrial processes are evolving with reduced waste generation, lower energy consumption, and the utilization of biocatalysts derived from renewable and unconventional raw materials. This review explores the background, structural characteristics, thermostability, and multifaceted roles of bacterial esterases in crucial industries, aiming to optimize and analyze their properties for continued successful utilization in diverse industrial processes. Additionally, recent advancements in esterase research are overviewed, showcasing novel techniques, innovations, and promising areas for further exploration.

Thermodynamics of a hyperthermostable carboxylesterase from Anoxybacillus geothermalis D9

Hyperthermostable enzymes are highly desirable biocatalysts due to their exceptional stability at extreme temperatures. Recently, a hyperthermostable carboxylesterase EstD9 from Anoxybacillus geothermalis D9 was biochemically characterized. The enzyme exhibited remarkable stability at high temperature. In this study, we attempted to probe the conformational adaptability of EstD9 under extreme conditions via in silico approaches. Circular dichroism revealed that EstD9 generated new β-sheets at 80 °C, making the core of the hydrolase fold more stable. Interestingly, the profiles of molecular dynamics simulation showed the lowest scores of radius of gyration and solvent accessible surface area (SASA) at 80 °C. Three loops were responsible for protecting the catalytic site, which resided at the interface between the large and cap domains. To further investigate the structural adaptation in extreme conditions, the intramolecular interactions of the native structure were investigated. EstD9 revealed 18 hydrogen bond networks, 7 salt bridges, and 9 hydrophobic clusters, which is higher than the previously reported thermostable Est30. Collectively, the analysis indicates that intramolecular interactions and structural dynamics play distinct roles in preserving the overall EstD9 structure at elevated temperatures. This work is relevant to both fundamental and applied research involving protein engineering of industrial thermostable enzymes.

Selection of a pH- and temperature-stable laccase from Ganoderma australe and its application for bioremediation of textile dyes

By virtue of screening, purification, and properties characterization, this study captures a new pH- and temperature-stable laccase, designated Galacc-F, from Ganoderma australe for dye bioremediating applications. The enzyme was purified to homogeneity by salt precipitation, ionic exchange, and size exclusion chromatography with a final specific activity of 22.214 U mg^-1, yielding a purification fold of 23.989 and recovery of 38.44%. Its molecular weight was estimated to be 48.0 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, zymography, Sephadex G-100 column, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, which confirmed its monomeric nature. Galacc-F exhibited high levels of activity and stability over wide ranges of pH (5.0-8.0) and temperature (10-60 °C), which are highly valuable properties in industrial processes. Broad substrate specificity was observed, wherein a better affinity was found for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with a low value of K_m (164.137 μM) and higher k_cat/K_m ratio (1.663 s^-1 μM^-1). Activity was stimulated by Cu²⁺ and β-mercaptoethanol but inhibited by ethylenediaminetetraacetic acid, diethylpyrocarbonate, iodoacetic acid, phenylmethylsulfonyl fluoride, and Hg²⁺, indicating that Galacc-F is a metalloprotease containing a typical histidine-cysteine-serine catalytic triad. It had high tolerance to surfactants, oxidants, and salts. Additionally, a fabricated protocol for native Galacc-F immobilization onto Fe₃O₄@Chitosan composite nanoparticles using glutaraldehyde as a crosslinker was developed. Most importantly, the enzyme was determined to be ideal for use in efficient treatment of dye effluents as compared with the laccases requiring redox mediators.