Fervidobacterium changbaicum Lip1: identification, cloning, and characterization of the thermophilic lipase as a new member of bacterial lipase family V

Structural features, temperature adaptation and industrial applications of microbial lipases from psychrophilic, mesophilic and thermophilic origins

Microbial lipases are very prominent biocatalysts because of their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. Here microbial lipases from different origins (psychrophiles, mesophiles, and thermophiles) have been reviewed. This review emphasizes an update of structural diversity in temperature adaptation and industrial applications, of psychrophilic, mesophilic, and thermophilic lipases. The microbial origins of lipases are logically dynamic, proficient, and also have an extensive range of industrial uses with the manufacturing of altered molecules. It is therefore of interest to understand the molecular mechanisms of adaptation to temperature in occurring lipases. However, lipases from extremophiles (psychrophiles, and thermophiles) are widely used to design biotransformation reactions with higher yields, fewer byproducts, or useful side products and have been predicted to catalyze those reactions also, which otherwise are not possible with the mesophilic lipases. Lipases as a multipurpose biological catalyst have given a favorable vision in meeting the needs of several industries such as biodiesel, foods, and drinks, leather, textile, detergents, pharmaceuticals, and medicals.

Characteration of a novel arylesterase from probiotics Lacticaseibacillus rhamnosus GG with the preference for medium- and long-chain p-Nitrophenyl esters

We prospected a novel arylesterase LggEst from the probiotics Lacticaseibacillus rhamnosus GG by genome mining strategy, and characterized the enzymatic properties in detail. Biochemical characterization revealed that arylesterase LggEst presented high activity at a wide range of temperatures from 25 to 65 °C with maximum activity at 50 °C. LggEst maintained high activity in the pH range from 5.5 to 7.5 with optimum pH of 6.5. LggEst might efficiently hydrolyze a series of aryl substrates p-nitrophenyl esters with different acyl chain lengths. LggEst displayed the V_max from 2.8 to 77.3 μmol min^-1 mg^-1 protein and the k _cat from 1.8 to 48.8 s^-1 with the highest catalytic activity on pNPC6. The K _M of LggEst on different substrates varied significantly from 4.9 μM to 5.6 mM with the highest affinity on pNPC10. LggEst exhibited the preference for medium- and long-chain p-nitrophenyl esters. LggEst showed remarkable thermostability at 45 °C. LggEst could be tolerant of several organic solvents at the concentration of 10% and DMSO and methanol at the concentration of 20%. Catalytic activity of LggEst was improved by 12% in the presence of 20% ethylene glycol. LggEst was resistant to high concentrations of sodium citrate and sodium chloride. Notably, enzymatic activity of LggEst was significantly enhanced in the presence of 0.1% sodium deoxycholate at high temperatures.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03053-7.

The effect of microwave stabilization on the properties of whole wheat flour and its further interpretation by molecular docking

In order to stabilize the whole wheat flour and extend its shelf life, microwave was employed to heat the wheat bran to inactivate the lipase in this paper. The effects of microwave heating of wheat bran on the lipase activities, gluten properties, dough properties and storage stability of the stabilized whole wheat flour, and the quality of steamed bread made of stabilized whole wheat flour were investigated. Furthermore, molecular docking was applied to interpret the mechanism. The results showed that microwave can reduce lipase activity, maintain the quality of whole wheat flour dough and steamed bread, and retard rancidity. The molecular docking results displayed that the conformation of the amino acids chains near the lipase catalytic center changed, which made the substrate difficult to enter the catalytic center and prevented the hydrolysis of the fat substrate.

Changes of lipids in noodle dough and dried noodles during industrial processing

This study investigated the changes of lipids during the industrial preparation of noodle dough and dried noodles, including the hydration, sheeting, and drying processes. The results showed that industrial processing markedly influenced the stability of lipids during the preparation of dried noodles. The contents of total free fatty acids, polyunsaturated fatty acids, and free lipids were reduced, while peroxide values increased during the hydration and sheeting processes, showing the instability of lipids. The increase in lipid oxidation may have been due to the activation of lipoxygenase. Although its activity declined by 45.7% in the hydration process compared to that of the native wheat flour (198.5 ± 20.4 U/g/min), the residue activity should have been high enough to oxidize lipids. Interestingly, lipase activity remained relatively stable. In addition, an obvious increase of carbon-centered free radicals was observed during the entire processing. In conclusion, the industrial processing, especially the hydration process, markedly changed the lipid profile and promoted lipid oxidation during the preparation of dried noodles. PRACTICAL APPLICATION: The present study showed the positive relationship between endogenous lipid degrading enzymes and the degradation of lipids and elucidated the role of industrial processing on lipid stability in noodle dough and dried noodles. The results of the present study will also help us to understand more about the sensory quality of dried noodles during preparation, as well as to develop high quality of wheat-based food products.

Characterization of a Novel Family IV Esterase Containing a Predicted CzcO Domain and a Family V Esterase with Broad Substrate Specificity from an Oil-Polluted Mud Flat Metagenomic Library

Two novel esterase genes, est2L and est4L, were identified from a previously constructed metagenomic library derived from an oil-polluted mud flat sample. The encoded Est2L and Est4L were composed of 839 and 267 amino acids, respectively, without signal peptides. Est2L was a unique fusion type of protein composed of two domains: a domain of the CzcO superfamily, associated with a cationic diffusion promoter with CzcD, and a domain of the acetylesterase superfamily, belonging to family IV with conserved motifs, such as HGG, GXSAG, and GXPP. Est2L was the first fused esterase with a CzcO domain. Est4L belonged to family V with GXS, GXSMGG, and PTL motifs. Native Est2L and Est4L were found to be in dimeric and tetrameric forms, respectively. Est2L and Est4L showed the highest activities at 60 °C and 50 °C, respectively, and at a pH of 10.0. Est2L preferred short length substrates, especially p-nitrophenyl (pNP)-acetate, with moderate butyrylcholinesterase activity, whereas Est4L showed the highest activity with pNP-decanoate and had broad specificity. Significant effects were not observed in Est2L from Co2+ and Zn2+, although Est2L contains the domain CzcD. Est2L and Est4L showed high stabilities in 30% methanol and 1% Triton X-100. These enzymes could be used for a variety of applications, such as detergent and mining processing under alkaline conditions.

Effect of Superheated Steam Treatment on the Lipid Stability of Dried Whole Wheat Noodles during Storage

Dried whole wheat noodles (DWWN) are a kind of nutritious convenience food with broad market prospects. However, due to the presence of high content of unsaturated fatty acids (UFAs) and lipid degrading enzymes, the shelf life and edible quality of DWWN are easily affected. This study explored the effect of superheated steam treatment (SST-155 °C-10 s, SST-170 °C-10 s, SST-190 °C-5 s) on the lipid stability of DWWN. The lipase, lipoxygenase and peroxidase of the DWWN treated with superheated steam were completely passivated during storage. After 12 weeks of storage, the fatty acid value of DWWN increased by 35.1, 17.9, 15.9, 24.6 mg NaOH/100 g in the groups of control, SST-155 °C-10 s, SST-170 °C-10 s, SST-190 °C-5 s, respectively; whereas the content of UFAs decreased by 13.5%, 6.8%, 5.4%, and 2.7%, respectively. The content of 2-pentylfuran in the SST-155 °C-10 s, SST-170 °C-10 s, SST-190 °C-5 s group was 0.7, 0.6, and 0.4-fold than that of the control group, respectively. In addition, the total tocopherol and total volatile compounds of the SST-190 °C-5 s group were 2.4 and 0.7-fold than that of the control group, respectively. Therefore, SST should be a new technology that can improve the lipid stability of DWWN.

Effect of superheated steam treatment on the lipid stability of whole wheat flour

This study aimed to investigate the effect of superheated steam treatment (SST) on lipid stability of whole wheat flour (WWF) during storage. After SST, the lipase and peroxidase of WWF were inactivated, and lipoxygenase activity was lower than 5% of its initial value. The total tocopherols decreased slightly in all SST groups, especially it only decreased by 1.1% at 190 °C for 5 s. Furthermore, the increase of fatty acid value in the control group was over 100-fold than that of the SST groups during storage. The unsaturated fatty acids and total tocopherols in WWF decreased gradually, but the decrease was alleviated by SST at 190 °C for 5 s. After storage, the relative content of hexanal and 2-pentylfuran in the SST groups were 4 and 0.3-fold than those in the control group, respectively. Thus, SST may be a potential approach to stabilise the quality of WWF.

Directed Evolution of Pseudomonas fluorescens Lipase Variants With Improved Thermostability Using Error-Prone PCR

Lipases catalyze the hydrolysis of fats and oils, and have been widely used in various industrial fields. However, bacterial lipases have a lower thermostability in industrial processes, which was a limiting factor in their industrial application. In this study, we obtained an improve variant of Pseudomonas fluorescens lipase (PFL) with enhanced thermostability using classical error-prone PCR. Wild-type PFL showed an optimal temperature and pH of 50°C and pH 7.5, respectively. Due to the low thermostability of PFL, a library containing over 3000 individual mutants as constructed using error-prone PCR. Screening for thermotolerance yielded the mutants L218P and P184C/M243C with T_m values of 62.5 and 66.0°C, which was 2.5 and 6°C higher than that of the WT, respectively. The combination of the two mutants (P184C/M243C/L218P) resulted in an approximately additive effect with a T_m value of 68.0°C. Although the increase of T_m was not substantial, the mutant also had dramatically increased methanol tolerance. Structural analysis revealed that the introduction of a disulfide bond between P184C and M243C and the substitution of Pro to reduce the flexibility of a loop increased the thermostability of PFL, which provides a theoretical foundation for improving the thermostability and methanol tolerance of lipase family I.1 to resist the harsh conditions of industrial processes.

Identification and characterization of a novel alkalistable and salt-tolerant esterase from the deep-sea hydrothermal vent of the East Pacific Rise

A novel esterase gene selected from metagenomic sequences of deep-sea hydrothermal vents was successfully expressed in Escherichia coli. The recombinant protein (est-OKK), which belongs to the lipolytic enzyme family V, exhibited high activity toward pNP-esters with short acyl chains and especially p-nitrophenyl butyrate. Site-mutagenesis results confirmed that est-OKK contains the nonclassical catalytic tetrad predicted by alignment and computational modeling. The est-OKK protein is a moderately thermophilic enzyme that is relatively thermostable, and highly salt-tolerant, which remained stable in 3 mol/L NaCl for 6 hr. The est-OKK protein showed the considerable alkalistability, displayed optimal activity at pH 9.0 and maintained approximately 70% of its residual activity after incubation at pH 10 for 4 hr. Furthermore, the est-OKK activity was strongly resistant to a variety of metal ions such as Co²⁺ , Zn²⁺ , Fe²⁺ , Na⁺ , and K⁺ ; nonionic detergents such as Tween-20, Tween-80; and organic solvents such as acetone and isopropanol. Taken together, the novel esterase with unique characteristics may give us a new insight into the family V of lipolytic enzymes, and could be a highly valuable candidate for biotechnological applications such as organic synthesis reactions or food and pharmaceutical industries.

Cloning, expression and characterization of the esterase estUT1 from Ureibacillus thermosphaericus which belongs to a new lipase family XVIII

A new esterase gene from thermophilic bacteria Ureibacillus thermosphaericus was cloned into the pET32b vector and expressed in Escherichia coli BL21(DE3). Alignment of the estUT1 amino acid sequence revealed the presence of a novel canonical pentapeptide (GVSLG) and 41-47% identity to the closest family of the bacterial lipases XIII. Thus the esterase estUT1 from U. thermosphaericus was assigned as a member of the novel family XVIII. It also showed a strong activity toward short-chain esters (C2-C8), with the highest activity for C2. When p-nitrophenyl butyrate is used as a substrate, the temperature and pH optimum of the enzyme were 70-80 °C and 8.0, respectively. EstUT1 showed high thermostability and 68.9 ± 2.5% residual activity after incubation at 70 °C for 6 h. Homology modeling of the enzyme structure showed the presence of a putative catalytic triad Ser93, Asp192, and His222. The activity of estUT1 was inhibited by PMSF, suggesting that the serine residue is involved in the catalytic activity of the enzyme. The purified enzyme exhibited high stability in organic solvents. EstUT1 retained 85.8 ± 2.4% residual activity in 30% methanol at 50 °C for 6 h. Stability at high temperature and tolerance to organic solvents make estUT1 a promising enzyme for biotechnology application.

Effects of microwave heating of wheat on its functional properties and accelerated storage

The effect of microwave heating wheat grains (700 W for 0-60 s) on gluten, farinograph, pasting properties and baking (steamed bread and biscuit) of flour was studied. The lipase (LA) and lipoxygenase (LOX) activities of the microwave-treated wheat were monitored, and the accelerated storage at 35 °C of whole wheat flour was also investigated. The results showed that the gluten, farinograph properties and viscosity were influenced to a small extent when microwave treatment time was less than or equal to 20 s and the temperature of the grains was less than or equal to 56 °C. Texture profile analysis indicated that steamed bread made from wheat treated by microwave for 20 s was softer and of better quality. Microwave treatment for longer periods (≥30 s) increased the temperature ≥68 °C, that damaged the gluten and made wheat unsuitable for making steamed bread; however, suitable for making food with lower gluten requirements, such as biscuits. The results obtained from enzyme activity and accelerated storage experiments demonstrated that microwave treatment could inactivate LA and LOX and extend the shelf-life.

Identification and characterization of three novel lipases belonging to families II and V from Anaerovibrio lipolyticus 5ST

Following the isolation, cultivation and characterization of the rumen bacterium Anaerovibrio lipolyticus in the 1960s, it has been recognized as one of the major species involved in lipid hydrolysis in ruminant animals. However, there has been limited characterization of the lipases from the bacterium, despite the importance of understanding lipolysis and its impact on subsequent biohydrogenation of polyunsaturated fatty acids by rumen microbes. This study describes the draft genome of Anaerovibrio lipolytica 5ST, and the characterization of three lipolytic genes and their translated protein. The uncompleted draft genome was 2.83 Mbp and comprised of 2,673 coding sequences with a G+C content of 43.3%. Three putative lipase genes, alipA, alipB and alipC, encoding 492-, 438- and 248- amino acid peptides respectively, were identified using RAST. Phylogenetic analysis indicated that alipA and alipB clustered with the GDSL/SGNH family II, and alipC clustered with lipolytic enzymes from family V. Subsequent expression and purification of the enzymes showed that they were thermally unstable and had higher activities at neutral to alkaline pH. Substrate specificity assays indicated that the enzymes had higher hydrolytic activity against caprylate (C8), laurate (C12) and myristate (C14).