High-level expression and characterization of solvent-tolerant lipase

Characterization of a Highly Solvent-Tolerant SGNH Hydrolase Superfamily Lipolytic Enzyme from Sphaerobacter thermophilus

Thermophilic microbial lipases that retain activity under harsh conditions are a highly desirable tool for catalysis in numerous biosynthetic and biotechnological applications. In this study, a putative SGNH lipase gene, from Sphaerobacter thermophilus (StSGNH1), was overexpressed using a pMCSG7 plasmid in BL21(DE3) cells. The polyhistidine-tagged enzyme was expressed as inclusion bodies that were readily solubilized using Empigen BB detergent, and the protein was purified to homogeneity using immobilized metal affinity chromatography. The classification of StSGNH1 as a thermophilic and alkaliphilic lipase was supported by its ability to optimally catalyze the hydrolysis of medium-length p-nitrophenol esters at elevated temperature (55 °C) and pH (8-11). Evaluation of the StSGNH1 structure generated by AlphaFold indicated that the catalytic domain was composed of a three-layered α/β/α fold, and molecular docking studies yielded insight into which residues proximal to the active site assist in stabilizing the ligand-enzyme interaction and substrate selectivity. Notably, StSGNH1 was able to carry out ester hydrolysis in the presence of elevated concentrations of detergents, chaotropic reagents, and organic solvents, indicating that it would be suitable for employment in industrial reactions. Tryptophan fluorescence measurements in the presence of guanidine hydrochloride were employed to estimate the free energy of folding for StSGNH1 along a reversible folding pathway. The properties of StSGNH1 would be highly desirable for biotechnological applications.

Promoted expression of a lipase for its application in EPA/DHA enrichment and mechanistic insights into its substrate specificity

Expanding toolkits of EPA/DHA enrichment from natural sources is essential for better satisfying increasing demands for them. Lipase K80, from Proteus vulgaris K80, showed an application potential in EPA/DHA enrichment, whereas no desired heterologous expression in generally regarded as safe (GRAS) hosts restricted its relevant applications. In this study, expression of lipase K80 in a well-reputed GRAS host, Pichia pastoris, was achieved and further enhanced via combining disruption of its C-terminal KKL motif with co-expression of N-Acetyltransferase Mpr1, with a cumulative increment of nearly 200% in the secretion level and the volumetric activity. Its application in EPA/DHA enrichment from fish oil was thereafter obtained with merits of low temperature and much less time, yielding an increase of ~31% in their total percentage. To gain mechanistic insights into its substrate chain-length specificity, we performed molecular dynamics simulation and revealed the substrate-dependent significant yet divergent conformational shifts of predominantly distal surface-exposed regions, suggesting a predominant long-range modulation mechanism. Together, this work provided in-depth insights into substrate specificity of lipase K80 and an alternate engineering site, the C-terminal KKL motif, for its expression optimization in P. pastoris, as well as extended toolboxes of EPA/DHA enrichment and application scopes of lipase K80.

High-level expression of lipase from Galactomyces geotrichum mafic-0601 by codon optimization in Pichia pastoris and its application in hydrolysis of various oils

A Galactomyces geotrichum strain with lipolytic activity was isolated and identified by the analysis of internal transcribed spacer (ITS) sequence of 18 s rDNA. Full-length lipase gene of this stain is composed of 1692 base pairs (bp) without intron, which encodes a 563-amino-acid protein. A catalytic triad (Ser²¹⁷-Glu³⁵⁴-His⁴⁶³) was found by constructing the three-dimensional structure of the lipase. In shake flasks, the lipase (LIP) catalytic activity in the supernatant of the recombinant Pichia pastoris increased 48.7% by codon optimization. LIP purified by anion exchange column showed a single protein band on 12% SDS-PAGE. The molecular weight (MW) of LIP was approximately 62 kDa. The specific activity of purified LIP reached 1257.9 U/mg. The optimum temperature and pH of LIP catalysis were 45 °C and pH 8.2, respectively. LIP was stable over the pH range of 4.2-11.2. LIP maintained its activity constantly at 40 °C and 50 °C for 120 min. Zn²⁺ inhibited LIP activity; Ba²⁺, Mn²⁺, Ca²⁺ and EDTA increased the enzyme activity. Referring the amount of hydrolyzed olive oil by LIP as 100%, various oils including lard, peanut oil, rapeseed oil, sunflower oil, soybean oil and linseed oil were efficiently hydrolyzed by 17.24 ± 1.34%, 40.34 ± 2.56%, 105.86 ± 2.78%, 115.51 ± 2.32%, 116.21 ± 2.15%, 120.69 ± 1.98%, respectively. The characteristics allow LIP as a potential biocatalyst in various fields of industry.

Enzymatic Production of Biodiesel: Strategies to Overcome Methanol Inactivation

Lipase-catalyzed transesterification of triglycerides and alcohols to obtain biodiesel is an environmentally friendly and sustainable route for fuels production since, besides proceeding in mild reaction conditions, it allows for the use of low-cost feedstocks that contain water and free fatty acids, for example non-edible oils and waste oils. This review article reports recent advances in the field and focus in particular on a major issue in the enzymatic process, the inactivation of most lipases caused by methanol, the preferred acyl acceptor used for alcoholysis. The recent results about immobilization of enzymes on nano-materials and the use of whole-cell biocatalysts, as well as the use of cell-surface display technologies and metabolic engineering strategies for microbial production of biodiesel are described. It is discussed also insight into the effects of methanol on lipases obtained by modeling approaches and report on studies aimed at mining novel alcohol stable enzymes or at improving robustness in existing ones by protein engineering.