N-linked glycosylation of thermostable lipase from Bacillus thermocatenulatus to improve organic solvent stability

Potential of Antarctic lipase from Acinetobacter johnsonii Ant12 for treatment of lipid-rich wastewater: screening, production, properties and applications

The present study aimed to screen and optimize lipase production by the Antarctic strain Acinetobacter johnsonii Ant12 for lipid-rich wastewater treatment. Lipase production was successfully enhanced threefold through optimization of culture conditions. The optimum crude lipase activity was observed at 50 °C with high stability in a wide temperature range. The lipase also exhibited high activity and stability in the presence of solvents, metal ions, and surfactants. The crude lipase was used for the treatment of lipid-rich wastewater, which poses a significant challenge, as traditional removal methods are often inefficient or non-eco-friendly. In this study, bioaugmentation with Ant12 resulted in substantial lipid reduction in synthetic as well as real-world wastewater. Multiple linear regression analysis showed that lipid concentration and time were the most significant factors influencing lipid degradation. Bioaugmentation of real-world wastewater with Ant12 cells resulted in 84% removal of lipids in 72 h, while its crude lipase degraded 73.7% of lipids after 24 h. Thus, the specific rate of lipid degradation was higher for crude lipase (0.095/h) than the whole cell treatment (0.031/h). Economic analysis revealed that crude lipase production was much cheaper, faster and more eco-friendly than purified or partially purified lipase production, which justifies its use in wastewater treatment. The high activity of enzyme also implicates its application as a detergent additive. In our knowledge, it is the first study to establish A. johnsonii isolate from Antarctica for lipid-rich wastewater treatment.

Purification and characterization of extracellular lipase from a thermotolerant strain: Bacillus subtilis TTP-06

In current study, lipase from a thermotolerant Bacillus subtilis TTP-06 was purified in a stepwise manner by using ammonium sulfate precipitation and column chromatography. Thenceforth, it was subjected to sodium dodecyl sulfate- and native-polyacrylamide gel electrophoresis to check the homogeneity of the purified enzyme. The ideal substrate concentration, pH, temperature, reaction duration and lipase specificity were identified. With a yield of 11.02%, purified lipase displayed activity of 8.51 U/mg. Thenceforward, the homogeneously purified enzyme was considered to be a homo-dimer of 30 kDa subunits. Enzyme had Km and Vmax value of 9.498 mM and 19.92 mol mg-1 min-1, respectively. Additionally, the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) method was used to investigate the purified lipase and estimate its 3-D structure, which revealed a catalytic triad of serine, aspartate and histidine.

Asn57 N-glycosylation promotes the degradation of hemicellulose by β-1,3-1,4-glucanase from Rhizopus homothallicus

N-glycosylation alters the properties of different enzymes in different ways. Rhizopus homothallicus was first described as an environmental isolate from desert soil in Guatemala. A new gene encoding glucanase RhGlu16B was identified in R. homothallicus. It had high specific activity (9673 U/mg) when barley glucan was used as a substrate, and β-glucan is hemicellulose that is abundant in nature. RhGlu16B has only one N-glycosylation site in its Ala55-Gly64 loop. It was found that N-glycosylation increased its T_m value and catalytic efficiency by 5.1 °C and 59%, respectively. Adding N-glycosylation to the same region of GH16 family glucanases TlGlu16A (from Talaromyces leycettanus) increased its thermostability and catalytic efficiency by 6.4 °C and 38%, respectively. In a verification experiment using GH16 family glucanases BisGlu16B (from Bisporus) in which N-glycosylation was removed, N-glycosylation also appeared to promote thermostability and catalytic efficiency. N-glycosylation reduced the overall root mean square deviation of the enzyme structure, creating rigidity and increasing overall thermostability. This study provided a reference for the molecular modification of GH16 family glucanases and guided the utilization of β-glucan in hemicellulose.

Thermostable lipases and their dynamics of improved enzymatic properties

Thermal stability is one of the most desirable characteristics in the search for novel lipases. The search for thermophilic microorganisms for synthesising functional enzyme biocatalysts with the ability to withstand high temperature, and capacity to maintain their native state in extreme conditions opens up new opportunities for their biotechnological applications. Thermophilic organisms are one of the most favoured organisms, whose distinctive characteristics are extremely related to their cellular constituent particularly biologically active proteins. Modifications on the enzyme structure are critical in optimizing the stability of enzyme to thermophilic conditions. Thermostable lipases are one of the most favourable enzymes used in food industries, pharmaceutical field, and actively been studied as potential biocatalyst in biodiesel production and other biotechnology application. Particularly, there is a trade-off between the use of enzymes in high concentration of organic solvents and product generation. Enhancement of the enzyme stability needs to be achieved for them to maintain their enzymatic activity regardless the environment. Various approaches on protein modification applied since decades ago conveyed a better understanding on how to improve the enzymatic properties in thermophilic bacteria. In fact, preliminary approach using advanced computational analysis is practically conducted before any modification is being performed experimentally. Apart from that, isolation of novel extremozymes from various microorganisms are offering great frontier in explaining the crucial native interaction within the molecules which could help in protein engineering. In this review, the thermostability prospect of lipases and the utility of protein engineering insights into achieving functional industrial usefulness at their high temperature habitat are highlighted. Similarly, the underlying thermodynamic and structural basis that defines the forces that stabilize these thermostable lipase is discussed. KEY POINTS: • The dynamics of lipases contributes to their non-covalent interactions and structural stability. • Thermostability can be enhanced by well-established genetic tools for improved kinetic efficiency. • Molecular dynamics greatly provides structure-function insights on thermodynamics of lipase.

A novel strategy for D-psicose and lipase co-production using a co-culture system of engineered Bacillus subtilis and Escherichia coli and bioprocess analysis using metabolomics

To develop an economically feasible fermentation process, this study designed a novel bioprocess based on the co-culture of engineered Bacillus subtilis and Escherichia coli for the co-production of extracellular D-psicose and intracellular lipase. After optimizing the co-culture bioprocess, 11.70 g/L of D-psicose along with 16.03 U/mg of lipase was obtained; the glucose and fructose were completely utilized. Hence, the conversion rate of D-psicose reached 69.54%. Compared with mono-culture, lipase activity increased by 58.24%, and D-psicose production increased by 7.08%. In addition, the co-culture bioprocess was explored through metabolomics analysis, which included 168 carboxylic acids and derivatives, 70 organooxygen compounds, 34 diazines, 32 pyridines and derivatives, 30 benzene and substituted derivatives, and other compounds. It also could be found that the relative abundance of differential metabolites in the co-culture system was significantly higher than that in the mono-culture system. Pathway analysis revealed that, tryptophan metabolism and β-alanine metabolism had the highest correlation and played an important role in the co-culture system; among them, tryptophan metabolism regulates protein synthesis and β-alanine metabolism, which is related to the formation of metabolic by-products. These results confirm that the co-cultivation of B. subtilis and E. coli can provide a novel idea for D-psicose and lipase biorefinery, and are beneficial for the discovery of valuable secondary metabolites such as turanose and morusin.

High-efficiency expression of the thermophilic lipase from Geobacillus thermocatenulatus in Escherichia coli and its application in the enzymatic hydrolysis of rapeseed oil

Long-chain fatty acids are widely used in food and chemical industries, and the enzymatic preparation of fatty acids is considered an environmentally friendly process. In the present study, long-chain fatty acids were prepared by the enzymatic hydrolysis of rapeseed oil with a genetically engineered lipase. Because thermophilic lipase has strong stability at higher temperatures, it was more suitable for the industrial production of long-chain fatty acids. Therefore, the thermophilic lipase BTL2 from Geobacillus thermocatenulatus was efficiently expressed in E. coli BL21(DE3) cells with an enzyme activity of 39.50 U/mg followed by gene codon optimisation. Experimental results showed that the recombinant lipase BTL2 exhibited excellent resistance to certain organic solvents (n-hexane, benzene, ethanol, and butanol). The metal cation Ca²⁺ and the non-ionic surfactant Triton-100X enhanced enzyme activity by 7.36% and 56.21% respectively. Moreover, the acid value of the liberated long-chain fatty acids by hydrolysing rapeseed oil was approximately 161.64 mg KOH/g at 50 °C in 24 h, the hydrolytic conversion rate was 91.45%, and the productivity was approximately 6.735 mg KOH/g h. These results suggested that the recombinant lipase BTL2 has excellent hydrolytic performance for rapeseed oil and showed great potential for the enzymatic preparation of long-chain fatty acids.

Biocatalysis at Extreme Temperatures: Enantioselective Synthesis of both Enantiomers of Mandelic Acid by Transesterification Catalyzed by a Thermophilic Lipase in Ionic Liquids at 120 °C

The use of biocatalysts in organic chemistry for catalyzing chemo-, regio- and stereoselective transformations has become an usual tool in the last years, both at lab and industrial scale. This is not only because of their exquisite precision, but also due to the inherent increase in the process sustainability. Nevertheless, most of the interesting industrial reactions involve water-insoluble substrates, so the use of (generally not green) organic solvents is generally required. Although lipases are capable of maintaining their catalytic precision working in those solvents, reactions are usually very slow and consequently not very appropriate for industrial purposes. Increasing reaction temperature would accelerate the reaction rate, but this should require the use of lipases from thermophiles, which tend to be more enantioselective at lower temperatures, as they are more rigid than those from mesophiles. Therefore, the ideal scenario would require a thermophilic lipase capable of retaining high enantioselectivity at high temperatures. In this paper, we describe the use of lipase from Geobacillus thermocatenolatus as catalyst in the ethanolysis of racemic 2-(butyryloxy)-2-phenylacetic to furnish both enantiomers of mandelic acid, an useful intermediate in the synthesis of many drugs and active products. The catalytic performance at high temperature in a conventional organic solvent (isooctane) and four imidazolium-based ionic liquids was assessed. The best results were obtained using 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIMBF4) and 1-ethyl-3-methyl imidazolium hexafluorophosphate (EMIMPF6) at temperatures as high as 120 °C, observing in both cases very fast and enantioselective kinetic resolutions, respectively leading exclusively to the (S) or to the (R)-enantiomer of mandelic acid, depending on the anion component of the ionic liquid.