Enhanced activity of Rhizomucor miehei lipase by directed saturation mutation of the propeptide

Computer-Aided Design to Improve the Thermal Stability of Rhizomucor miehei Lipase

Lipase, a green biocatalyst, finds extensive application in the food sector. Enhancing the thermal stability of lipase presents both challenges and opportunities within the food industry. This research employed multiple rounds of cross-screening using tools like FoldX and I-Mutant 3.0 to strategically design mutations for Rhizomucor miehei lipase (RML), resulting in eight unique single-point mutation designs. E230I, N120M, and N264M have been confirmed experimentally to be potential combination mutation candidates. The resulting triple mutant N120M/E230I/N264M showed a higher thermal stability, with an optimum temperature of 55 °C, 10 °C higher than that of the wild-type RML. The half-life was extended from 46 to 462 min at 50 °C. Furthermore, the catalytic activity of N120M/E230I/N264M on camphor tree seed oil increased by 140% to 600 U/mg, which aids in the production of novel structured lipids. Using molecular docking and molecular dynamics simulations, we analyzed the molecular mechanism of enhanced thermal stability. This study validated the efficacy and dependability of computer-aided design to generate heat-resistant RML mutants and indicated that RML N120M/E230I/N264M lipase can be used as an effective biocatalyst for fat processing in the food industry.

Efficient Expression and Application of a Modified Rhizomucor miehei Lipase for Simultaneous Production of Biodiesel and Eicosapentaenoic Acid Ethyl Ester from Nannochloropsis Oil

Few reports exist on one-step enzymatic methods for the simultaneous production of biodiesel and eicosapentaenoic acid ethyl ester (EPA-EE), a high-value pharmaceutical compound. This study aimed to efficiently express Rhizomucor miehei lipase (pRML) in Pichia pastoris X-33 via propeptide mutation and high-copy strain screening. The mutated enzyme was then used to simultaneously catalyze the production of both biodiesel and EPA-EE. The P46N mutation in the propeptide (P46N-pRML) significantly boosted its production, with the four-copy strain increasing enzyme yield by 3.7-fold, reaching 3425 U/mL. Meanwhile, its optimal temperature increased to 45-50 °C, pH expanded to 7.0-8.0, specific activity doubled, Km reduced to one-third, and kcat/Km increased 7-fold. Notably, P46N-pRML efficiently converts Nannochloropsis gaditana oil's eicosapentaenoic acid (EPA). Under optimal conditions, it achieves up to 93% biodiesel and 92% EPA-EE yields in 9 h. Our study introduces a novel, efficient one-step green method to produce both biodiesel and EPA-EE using this advanced enzyme.

Using directed evolution to improve hydrogen production in chimeric hydrogenases from algal species

Algae generate hydrogen from sunlight and water utilizing high-energy electrons generated during photosynthesis. The amount of hydrogen produced in heterologous expression of the wild-type hydrogenase is currently insufficient for industrial applications. One approach to improve hydrogen yields is through directed evolution of the DNA of the native hydrogenase. Here, we created 113 chimeric algal hydrogenase gene variants derived from combining segments of three parent hydrogenases, two from Chlamydomonas reinhardtii (CrHydA1 and CrHydA2) and one from Scenedesmus obliquus (HydA1). To generate chimeras, there were seven segments into which each of the parent hydrogenase genes was divided and recombined in a variety of combinations. The chimeric and parental hydrogenase sequences were cloned for heterologous expression in Escherichia coli, and 40 of the resultant enzymes expressed were assayed for H2 production. Chimeric clones that resulted in equal or greater production obtained with the cloned CrHydA1 parent hydrogenase were those comprised of CrHydA1 sequence in segments #1, 2, 3, and/or 4. These best-performing chimeras all contained one common region, segment #2, the part of the sequence known to contain important amino acids involved in proton transfer or hydrogen cluster coordination. The amino acid sequence distances among all chimeric clones to that of the CrHydA1 parent were determined, and the relationship between sequence distances and experimentally-derived H2 production was evaluated. An additional model determined the correlation between electrostatic potential energy surface area ratios and H2 production. The model yielded several algal mutants with predicted hydrogen productions in a range of two to three times that of the wild-type hydrogenase. The mutant data and the model can now be used to predict which specific mutant sequences may result in even higher hydrogen yields. Overall, results provide more precise details in planning future directed evolution to functionally improve algal hydrogenases.

OPFRs in e-waste sites: Integrating in silico approaches, selective bioremediation, and health risk management of residents surrounding

A multilevel index system of organophosphate flame retardant bioremediation effect in an e-waste handling area was established under three bioremediation scenarios (scenario I, plant absorption; scenario II, plant-microbial combined remediation; scenario III, microbial degradation). Directional modification of OPFR substitutes with high selective bioremediation was performed. The virtual amino acid mutation approach was utilised to generate high-efficiency selective absorption/degradation mutant proteins (MPs) in a plant-microbial system under varying conditions. In scenario III, the MP's microbial degrading ability to replace molecules was increased to the greatest degree (165.82%). Appropriate foods such as corn, pig liver, and yam should be consumed, whereas the simultaneous consumption of high protein foods such as pig liver and walnut should be avoided; sweet potato and yam are believed to be prevent OPFRs and substitute molecules from entering the human body through multiple pathways for reduced genotoxicity of OPFRs in the populations of e-waste handling areas (the reduction degree can reach 85.12%). The study provides a theoretical basis for the development of ecologically acceptable OPFR substitutes and innovative high-efficiency bioremediation MPs, as well as for the reduction of the joint toxicity risk of multiple ingestion route exposure/gene damage of OPFRs in high OPFR exposure sites.

Improving the Thermo-Activity and -Stability of Pectate Lyase from Dickeya dadantii DCE-01 for Ramie Degumming

To improve the thermal stability of pectate lyase for ramie degumming, we modified the novel pectate lyase gene (pelG403) derived from the Dickeya dadantii DCE-01 high-efficiency ramie degumming strain by site-directed mutagenesis. Twelve mutants were acquired, wherein a prospective mutant (A129V) showed better enzyme activity and thermal stability. Compared with the wild type (PelG403), the specific enzyme activity and the optimal reaction temperature of A129V in the fermentation broth increased by 20.1%, and 5 °C, respectively. Under the conditions of 55 °C and pH 9.0, the weightlessness rate of ramie raw materials of A129V increased by 6.26%. Therefore, this study successfully improved the enzyme activity and heat resistance of PelG403 in an alkaline environment, which may contribute to the development of enzyme preparations and the elucidation of the mechanism for ramie bio-degumming.