Characterization of esterase activity from an Acetomicrobium hydrogeniformans enzyme with high structural stability in extreme conditions

Impact of imperfect data on protein secondary structure estimates from Far-UV circular dichroism spectra

Circular dichroism [CD] is widely used to rapidly assess protein structure. Deconvolution of the far-UV CD spectrum is widely used to quantify the secondary structural elements [SSEs]. Multiple algorithms are available for this. Imperfections in the experimental CD spectra arising from spectral noise, instrument miscalibration, spectral offsets and non-linearity will impact on the accuracy and precision of derived secondary structure estimates. Analytical validation for use in regulated environments, such as biopharmaceuticals, requires that the impact of imperfect data on these estimates be understood. Limited information on the impact of poor data were available. A series of noise-free simulated spectral datasets with modified intensity, wavelength, noise and intensity linearity and offsets were created from entries in the Protein Circular Dichroism Data Bank. These datasets were analysed using the BeStSel, on-line resource to estimate secondary structure. Data imperfections caused significant change in SSEs, but the spectral range is also important. This study emphasises the importance of analytical method validation and justifiable estimates of uncertainty when reporting results. The datasets created are made available as a resource to validate other secondary structure estimation programs.

Sustainable Biosynthesis of Esterase Enzymes of Desired Characteristics of Catalysis for Pharmaceutical and Food Industry Employing Specific Strains of Microorganisms

Reactions catalysed by sustainably produced enzymes can contribute to the bioeconomy supporting several industries. Low-value compounds can be transformed into added-value products or high-resolution chemicals could be prepared in reactions catalysed by biocatalyst esterase enzymes. These enzymes can be synthesised by purposely isolated or genetically modified strains of microorganisms. Enzymes belonging to the hydrolase family catalyse the formation and hydrolysis of ester bonds to produce the desired esterified molecule. The synthesis of homo-chiral compounds can be accomplished either by chemical or biocatalytic processes, the latter being preferred with the use of microbial esterases. For varied applications, esterases with high stability and retained activity at lower and higher temperatures have been produced with strains isolated from extreme environments. For sustainable production of enzymes, higher productivity has been achieved by employing fast-growing Escherichia coli after incorporating plasmids of required characteristics from specific isolates. This is a review of the isolated and engineered strains used in the biosynthesis of esterase of the desired property, with the objective of a sustainable supply of enzymes, to produce products of industrial importance contributing to the economy.

Composition Characterization and Transformation Mechanism of Dissolved Organic Matters in a Full-Scale Membrane Bioreactor Treating Co-Digestion Wastewater of Food Waste and Sewage Sludge

The membrane bioreactor (MBR) serves as the most widely used technology in anaerobic digestion wastewater treatment, but the composition and transformation of the dissolved organic matters (DOMs) are vague. This study focused on the composition characterization and transformation mechanism of DOMs in real co-digestion wastewater of food waste and sewage sludge from a full-scale MBR via molecular weight cut-off, 3D-EEM, FT-IR, and SPME-GC/MS. The results indicated that the co-digestion wastewater mainly comprised organics with molecular weight (MW) lower than 1 kDa and dominated by tryptophane-protein-like substances. The hydrolytic/acidogenic process improved the biodegradability with the conversion of high-MW organics into low-MW organics, while the two-stage A/O process possessed the highest contribution to the organic removal with the consumption of most DOMs. However, the deficient removal of refractory organics (MW < 5 kDa) in the ultrafiltration unit led to the residual DOMs in the effluent. The potential functional bacteria in the biological processes have also been identified and were principally affiliated with Proteobacteria and Firmicutes. These findings could help to advance the understanding of the co-digestion wastewater and provide fundamental information for the optimization and development of MBR in anaerobic digestion wastewater treatment.

Low-resolution molecular shape, biochemical characterization and emulsification properties of a halotolerant esterase from Bacillus licheniformis

Bacterial esterases are highly versatile enzymes, currently widely used in detergents, biosurfactants, bioemulsifiers and as biocatalysts in paper and food industries. Present work describes heterologous expression, purification, and biophysical and biochemical characterization of a halotolerant esterase from Bacillus licheniformis (BlEstA). BlEstA preferentially cleaves pNP-octanoate and both activity and stability of the enzyme increased in the presence of 2 M NaCl, and also with several organic solvents (ethanol, methanol and DMSO). Furthermore, BlEstA has considerable emulsifying properties, particularly with olive oil as substrate. Our studies also show that the enzyme is monomeric in solution and its small-angle X-ray scattering low-resolution molecular envelope fits well its high-resolution homology model.

Biochemical profiles of two thermostable and organic solvent-tolerant esterases derived from a compost metagenome

Owing to the functional versatility and potential applications in industry, interest in lipolytic enzymes tolerant to organic solvents is increasing. In this study, functional screening of a compost soil metagenome resulted in identification of two lipolytic genes, est1 and est2, encoding 270 and 389 amino acids, respectively. The two genes were heterologously expressed and characterized. Est1 and Est2 are thermostable enzymes with optimal enzyme activities at 80 and 70 °C, respectively. A second-order rotatable design, which allows establishing the relationship between multiple variables with the obtained responses, was used to explore the combined effects of temperature and pH on esterase stability. The response curve indicated that Est1, and particularly Est2, retained high stability within a broad range of temperature and pH values. Furthermore, the effects of organic solvents on Est1 and Est2 activities and stabilities were assessed. Notably, Est2 activity was significantly enhanced (two- to tenfold) in the presence of ethanol, methanol, isopropanol, and 1-propanol over a concentration range between 6 and 30% (v/v). For the short-term stability (2 h of incubation), Est2 exhibited high tolerance against 60% (v/v) of ethanol, methanol, isopropanol, DMSO, and acetone, while Est1 activity resisted these solvents only at lower concentrations (below 30%, v/v). Est2 also displayed high stability towards some water-immiscible organic solvents, such as ethyl acetate, diethyl ether, and toluene. With respect to long-term stability, Est2 retained most of its activity after 26 days of incubation in the presence of 30% (v/v) ethanol, methanol, isopropanol, DMSO, or acetone. All of these features indicate that Est1 and Est2 possess application potential.