Improving the thermal stability of Proteus mirabilis lipase based on multiple computational design strategies / 生物工程学报

Proteus mirabilis lipase (PML) features tolerance to organic solvents and great potential for biodiesel synthesis. However, the thermal stability of the enzyme needs to be improved before it can be used industrially. Various computational design strategies are emerging methods for the modification of enzyme thermal stability. In this paper, the complementary algorithm-based ABACUS, PROSS, and FoldX were employed for positive selection of PML mutations, and their pairwise intersections were further subjected to negative selection by PSSM and GREMLIN to narrow the mutation library. Thereby, 18 potential single-point mutants were screened out. According to experimental verification, 7 mutants had melting temperature (Tm) improved, and the ΔTm of K208G and G206D was the highest, which was 3.75 ℃ and 3.21 ℃, respectively. Five mutants with activity higher than the wild type (WT) were selected for combination by greedy accumulation. Finally, the Tm of the five-point combination mutant M10 increased by 10.63 ℃, and the relative activity was 140% that of the WT. K208G and G206D exhibited certain epistasis during the combination, which made a major contribution to the improvement of the thermal stability of M10. Molecular dynamics simulation indicated that new forces were generated at and around the mutation sites, and the rearrangement of forces near G206D/K208G might stabilize the Ca2+ binding site which played a key role in the stabilization of PML. This study provides an efficient and user-friendly computational design scheme for the thermal stability modification of natural enzymes and lays a foundation for the modification of PML and the expansion of its industrial applications.

Process optimization for production and purification of a thermostable, organic solvent tolerant lipase from Acinetobacter sp. AU07

ABSTRACT The purpose of this study was to isolate, purify and optimize the production conditions of an organic solvent tolerant and thermostable lipase from Acinetobacter sp. AU07 isolated from distillery waste. The lipase production was optimized by response surface methodology, and a maximum production of 14.5 U/mL was observed at 30 ºC and pH 7, using a 0.5% (v/v) inoculum, 2% (v/v) castor oil (inducer), and agitation 150 rpm. The optimized conditions from the shake flask experiments were validated in a 3 L lab scale bioreactor, and the lipase production increased to 48 U/mL. The enzyme was purified by ammonium sulfate precipitation and ion exchange chromatography and the overall yield was 36%. SDS-PAGE indicated a molecular weight of 45 kDa for the purified protein, and Matrix assisted laser desorption/ionization time of flight analysis of the purified lipase showed sequence similarity with GDSL family of lipases. The optimum temperature and pH for activity of the enzyme was found to be 50 ºC and 8.0, respectively. The lipase was completely inhibited by phenylmethylsulfonyl fluoride but minimal inhibition was observed when incubated with ethylenediaminetetraacetic acid and dithiothreitol. The enzyme was stable in the presence of non-polar hydrophobic solvents. Detergents like SDS inhibited enzyme activity; however, there was minimal loss of enzyme activity when incubated with hydrogen peroxide, Tween 80 and Triton X-100. The kinetic constants (Km and Vmax) revealed that the hydrolytic activity of the lipase was specific to moderate chain fatty acid esters. The Vmax, Km and Vmax/Km ratio of the enzyme were 16.98 U/mg, 0.51 mM, and 33.29, respectively when 4-nitrophenyl palmitate was used as a substrate.

Characterization of biotechnologically relevant extracellular lipase produced by Aspergillus terreus NCFT 4269.10

Abstract Enzyme production by Aspergillus terreus NCFT 4269.10 was studied under liquid static surface and solid-state fermentation using mustard oil cake as a substrate. The maximum lipase biosynthesis was observed after incubation at 30 °C for 96 h. Among the domestic oils tested, the maximum lipase biosynthesis was achieved using palm oil. The crude lipase was purified 2.56-fold to electrophoretic homogeneity, with a yield of 8.44%, and the protein had a molecular weight of 46.3 kDa as determined by SDS-PAGE. Enzyme characterization confirmed that the purified lipase was most active at pH 6.0, temperature of 50 °C, and substrate concentration of 1.5%. The enzyme was thermostable at 60 °C for 1 h, and the optimum enzyme–substrate reaction time was 30 min. Sodium dodecyl sulfate and commercial detergents did not significantly affect lipase activity during 30-min incubation at 30 °C. Among the metal ions tested, the maximum lipase activity was attained in the presence of Zn2+, followed by Mg2+ and Fe2+. Lipase activity was not significantly affected in the presence of ethylenediaminetetraacetic acid, sodium lauryl sulfate and Triton X-100. Phenylmethylsulfonyl fluoride (1 mM) and the reducing, β-mercaptoethanol significantly inhibited lipase activity. The remarkable stability in the presence of detergents, additives, inhibitors and metal ions makes this lipase unique and a potential candidate for significant biotechnological exploitation.

The genotypic diversity and lipase production of some thermophilic bacilli from different genera

Abstract Thermophilic 32 isolates and 20 reference bacilli were subjected to Rep-PCR and ITS-PCR fingerprinting for determination of their genotypic diversity, before screening lipase activities. By these methods, all the isolates and references could easily be differentiated up to subspecies level from each other. In screening assay, 11 isolates and 7 references were found to be lipase producing. Their extracellular lipase activities were measured quantitatively by incubating in both tributyrin and olive oil broths at 60 °C and pH 7.0. During the 24, 48 and 72-h period of incubation, the changes in the lipase activities, culture absorbance, wet weight of biomass and pH were all measured. The activity was determined by using pNPB in 50 mM phosphate buffer at pH 7.0 at 60 °C. The lipase production of the isolates in olive oil broths varied between 0.008 and 0.052, whereas these values were found to be 0.002-0.019 (U/mL) in the case of tyributyrin. For comparison, an index was established by dividing the lipase activities to cell biomass (U/mg). The maximum thermostable lipase production was achieved by the isolates F84a, F84b, and G. thermodenitrificans DSM 465T (0.009, 0.008 and 0.008 U/mg) within olive oil broth, whereas G. stearothermophilus A113 displayed the highest lipase activity than its type strain in tyributyrin. Therefore, as some of these isolates displayed higher activities in comparison to references, new lipase producing bacilli were determined by presenting their genotypic diversity with DNA fingerprinting techniques.

Milk-deteriorating exoenzymes from Pseudomonas fluorescens 041 isolated from refrigerated raw milk

The practice of refrigerating raw milk at the farm has provided a selective advantage for psychrotrophic bacteria that produce heat-stable proteases and lipases causing severe quality problems to the dairy industry. In this work, a protease (AprX) and a lipase (LipM) produced by Pseudomonas fluorescens 041, a highly proteolytic and lipolytic strain isolated from raw milk obtained from a Brazilian farm, have been purified and characterized. Both enzymes were purified as recombinant proteins from Escherichia coli. The AprX metalloprotease exhibited activity in a broad temperature range, including refrigeration, with a maximum activity at 37 °C. It was active in a pH range of 4.0 to 9.0. This protease had maximum activity with the substrates casein and gelatin in the presence of Ca+2. The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from 7.0 to 10. It exhibited the highest activity, in the presence of Ca+2, on substrates with long-chain fatty acid residues. These results confirm the spoilage potential of strain 041 in milk due to, at least in part, these two enzymes. The work highlights the importance of studies of this kind with strains isolated in Brazil, which has a recent history on the implementation of the cold chain at the dairy farm.

Thermostable, alkaline and detergent-tolerant lipase from a newly isolated thermophilic Bacillus stearothermophilus.

Lipases are the enzymes of choice for laundry detergent industries, owing to their triglyceride removing ability from the soiled fabric, which eventually reduces the usage of phosphate-based chemical cleansers in the detergent formulation. In this study, a novel thermo-alkaline lipase-producing strain identified as Bacillus stearothermophilus was isolated from the soil samples of olive oil mill. Enhanced lipase production was observed at 55°C, pH 11 and after 48 h of incubation. Among the substrates tested, xylose (a carbon source), peptone (a nitrogen source) and olive oil at a concentration of 1% were suitable substrates for enhancing lipase production. MgSO4 and Tween-80 were suitable substrates for maximizing lipase production. The enzyme was purified to homogeneity by a single CM-Sephadex column chromatography and revealed molecular mass of 67 kDa. The enzyme (BL1) was active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 11.0, exhibited maximal activity at 55°C and retained more than 70% of its activity after incubation at 70°C or pH 13 for 0.5 h or 24 h, respectively. The enzyme hydrolyzed both short and long-chain triacylglycerols at comparable rates. BL1 was studied in a preliminary evaluation for use in detergent formulation solutions. This novel lipase showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and good stability towards oxidizing agents. Additionally, the enzyme showed excellent stability and compatibility with various commercial detergents, suggesting its potential as an additive in detergent formulations.

Molecular characterization of a proteolysis-resistant lipase from Bacillus pumilus SG2

Proteolysis-resistant lipases can be well exploited by industrial processes which employ both lipase and protease as biocatalysts. A proteolysis resistant lipase from Bacillus pumilus SG2 was isolated, purified and characterized earlier. The lipase was resistant to native and commercial proteases. In the present work, we have characterized the lip gene which encodes the proteolysis-resistant lipase from Bacillus pumilus SG2. The parameters and structural details of lipase were analysed. The lip gene consisted of 650 bp. The experimental molecular weight of SG2 lipase was nearly double that of its theoretical molecular weight, thus suggesting the existence of the functional lipase as a covalent dimer. The proteolytic cleavage sites of the lipase would have been made inaccessible by dimerisation, thus rendering the lipase resistant to protease.

Cloning and characterization of newly isolated lipase from Enterobacter sp. Bn12

A mesophilic Enterobacter sp. Bn12 producing an alkaline thermostable lipase was isolated from soil in Tehran, Iran. The lipase gene (ELBn12) was identified from a genomic library. Sequence analysis of the DNA fragment revealed an open reading frame of 879 bp encoding a lipase with a molecular mass of 31.3 kDa. The deduced amino acid sequence showed 96% identity with a lipase of Enterobacter sp. Ag1 and the identity of their DNA sequences was 88.9%. ELBn12 belongs to the lipase subfamily I.1 and its catalytic triad consists of Ser82, Asp237 and His259. The lipase was expressed in Escherichia coli (BL21) pLysS and partially purified by anion exchange chromatography. The maximum activity of ELBn12 was obtained at temperature of 60 °C and pH 8.0 towards tricaprylin (C8) and its specific activity was around 2900 U/mg. ELBn12 was stable within a broad pH range from 6.0 to 11.0. The enzyme showed high stability in both polar and nonpolar organic solvents at 50% (v/v). The lipase activity was enhanced in the presence of 10 mM of Ca2+, Mg2+ and K+, while heavy metals (Fe3+ and Zn2+) had strong inhibitory effect. ELBn12 showed high activity in the presence of 1% (w/v) nonionic surfactants, however ionic surfactants inhibited the lipolytic activity. ELBn12 characteristics show that it has a potential to be used in various industrial processes.

Concentration, characterization and application of lipases from Sporidiobolus pararoseus strain

Lipases produced by a newly isolated Sporidiobolus pararoseus strain have potential catalytic ability for esterification reactions. After production, the enzymatic extracts (conventional crude and precipitated, 'CC' and 'CP', and industrial crude and precipitated, 'IC' e 'IP') were partially characterized. The enzymes presented, in general, higher specificity for short chain alcohols and fatty acids. The precipitated extract showed a good thermal stability, higher than that for crude enzymatic extracts. The 'CC' and 'CP' enzymes presented high activities after exposure to pH 6.5 and 40 ºC. On the other hand, the 'IC' and 'IP' extracts kept their activities in a wide range of pH memory but presented preference for higher reaction temperatures. Preliminary studies of application of the crude lipase extract in the enzymatic production of geranyl propionate using geraniol and propionic acid as substrates in solvent-free system led to a reaction conversion of 42 ± 1.5%.

Isolation and characterization of novel thermophilic lipase-secreting bacteria

The purpose of the present study was to screen and identify the lipase-producing microorganisms from various regions of Iran. Samples collected from hot spring, Persian Gulf, desert area and oil-contaminated soil, were analyzed for thermophilic extracellular-lipase producing organisms. Six strains with high activity on rhodamine B plates were selected for chemical identification and further study. Among these isolated bacteria, four strains show higher activity in pH-Stat method at 55 °C. These strains were identified by PCR amplification of 16s rRNA genes using universal primers. Fermentation increased the activity up to 50%. The growth medium, designed for lipase production, increased the activity up to 4.55 folds. The crude supernatant of ZR-5 after fermentation and separation the cells, was lyophilized and the activity was measured. Total activity of this strain was 12 kU/g that shows its potential for industrial uses. Further study is required for purification of enzyme and calculation its specific activity. Immobilization is another approach should be considered.

An oxidant and organic solvent tolerant alkaline lipase by P. aeruginosa mutant: downstream processing and biochemical characterization

An extracellular alkaline lipase from Pseudomonas aeruginosa mutant has been purified to homogeneity using acetone precipitation followed by anion exchange and gel filtration chromatography and resulted in 27-fold purification with 19.6% final recovery. SDS-PAGE study suggested that the purified lipase has an apparent molecular mass of 67 kDa. The optimum temperature and pH for the purified lipase were 45°C and 8.0, respectively. The enzyme showed considerable stability in pH range of 7.0-11.0 and temperature range 35-55 °C. The metal ions Ca2+, Mg2+ and Na+ tend to increase the enzyme activity, whereas, Fe2+ and Mn2+ ions resulted in discreet decrease in the activity. Divalent cations Ca+2 and Mg+2 seemed to protect the enzyme against thermal denaturation at high temperatures and in presence of Ca+2 (5 mM) the optimum temperature shifted from 45°C to 55°C. The purified lipase displayed significant stability in the presence of several hydrophilic and hydrophobic organic solvents (25%, v/v) up to 168 h. The pure enzyme preparation exhibited significant stability and compatibility with oxidizing agents and commercial detergents as it retained 40-70% of its original activities. The values of Km and Vmax for p-nitrophenyl palmitate (p-NPP) under optimal conditions were determined to be 2.0 mg.mL-1 and 5000 μg.mL-1.min-1, respectively.

The potential use of lipases in the production of fatty acid derivatives for the food and nutraceutical industries

The potential of lipases (E.C.3.1.1.3.) as biocatalysts for the production of fatty acid derivatives for the food and nutraceutical industries, such as flavouring esters, fatty acid esters of antioxidants and structured lipids, is enormous, mainly due to their high regio- and stereo-selectivities, in addition to the other well-known advantages of enzymatic processes. The replacement of chemical catalysts by lipases presents great benefits in terms of the nutritional properties of the obtained products and environmental care. The reactions performed for the production of these compounds, as well as the best operation conditions, the biocatalysts used, reactor types and operation mode, are addressed in this review.

Optimization of physical parameters for lipase production from Arthrobacter sp. BGCC#490.

The physical parameters for the production of thermostable, alkaline lipase from Arthrobacter sp. BGCC# 490 were optimized using response surface methodology (RSM), employing face centered central composite design (FCCCD). The design was employed by selecting pH, temperature and incubation period as the model factors and to achieve maximum yield, interaction of these factors was studied by RSM. A second-order quadratic model and response surface method showed that the optimum conditions for lipase production (pH 10.0, temperature 40oC and incubation period 48 h) resulted in 1.6-fold increase in lipase production (13.75 EUml-1), as compared to the initial level (8.6 EUml-1) after 48 h of incubation, whereas its value predicted by the quadratic model was 12.8 EUml-1. Lipase showed stability in the pH range 8-10 and temperature range 40-60oC, with maximum activity at pH 9.0 and temperature 50oC. Lipase activity was enhanced in the presence of K+, Ca2+ and Mg2+ ions, but inhibited by Hg2+ ions. The enzyme exhibited high activity in the presence of acetone, isopropanol and ethanol, but was unaffected by methanol. These properties suggest that the lipase may find potential applications in the detergent industry. The present work also demonstrated the feasibility of using experimental design tools to optimize physical parameters for lipase production by an indigenous Arthrobacter sp.

Comparative esterification of phenylpropanoids versus hydrophenylpropanoids acids catalyzed by lipase in organic solvent media

The esterification of phenylpropanoid and hydrophenylpropanoid acids, catalyzed by candida antarctica lipase B (CAL-B), with several alcohols has demonstrated that the substitution pattern on the aromatic ring has a very significant influence on the reactivity of the carboxyl group due, mainly, to electronic effects, when compared to the unsaturated acids with the hydrogenated acids. It is also clear that in the saturated acids there still remain some unclear effects related to the aromatic substituents.

Yeast lipases: enzyme purification, biochemical properties and gene cloning

Lipases are placed only after proteases and carbohydrases in world enzyme market and share about 5% of enzyme market. They occur in plants, animals and microorganisms and are accordingly classified as plant, animal and microbial lipases. Wherever they exist, they function to catalyze hydrolysis of triglycerides to glycerol and fatty acid. Like carbohydrases and proteases, lipases of microbial origin enjoy greater industrial importance as they are more stable (compared to plant and animal lipases) and can be obtained in bulk at low cost. Majority of yeast lipases are extracelluar, monomericglycoproteins with molecular weight ranging between ~33 to ~65 kD. More than 50% reported lipases producing yeast, produce it in the forms of various isozymes. These lipase isozymes are in turn produced by various lipase encoding genes. Among many lipase producing yeasts Candida rugosa is most frequently used yeast as the source of lipase commercially. This review is aimed at compiling the information on properties of various yeast lipases and genes encoding them.

High performance enzymatic synthesis of oleyl oleate using immobilised lipase from Candida antartica

High performance enzymatic synthesis of oleyl oleate, a liquid wax ester was carried out by lipase-catalysed esterification of oleic acid and oleyl alcohol. Various reaction parameters were optimised to obtain high yield of oleyl oleate. The optimum condition to produce oleyl oleate was reaction time; 5 min, organic solvents of log P is greater than or equal to 3.5, temperature; 40-50 ºC, amount of enzyme; 0.2-0.4 g and molar ratio of oleyl alcohol to oleic acid; 2:1. The operational stability of enzyme was maintained at >90 percent yield up to 9 cycles. Analysis of the yield of the product showed that at optimum conditions, >95 percent liquid wax esters were produced.

Production of industrially important enzymes by some actinomycetes producing antifungal compounds.

Seventeen strains of actinomycetes antagonistic to yeast and moulds have been tested for their ability to produce amylase, lipase, gelatinase and caseinase using solid media containing starch, Tween-20, gelatin and skimmed milk, respectively, Enzyme producing potential of test strains is expressed in ternis of relative enzyme activity (REA). Actinomycetes strain Streptomyces somaliensis GS 1242 and Streptomyces sampsonii GS 1322 showed higher amylase production (REA 6.5) while maximum lipase activity was noted in Streptomyces strain SAP 1089 (REA 7.0). Gelatinase activity was noted higher is S. sampsonii GS 1322 (REA 9.6) and S. somaliensis GS 1242 (REA 8.8). Enzyme producing potential of these strains has been discussed in terms of their industrial significance.

Enzyme activity and microbial content of acid fish silage

The activity of acidic cathepsins and lipases were followed during the storage of five sliage samples which were prepared from different raw materials. The hygienic quality of fish silage and the dominant microorganisms were determined. Activity of acidic cathepsins and lipases varied with the differences in the raw materials, Fish silages were free from coagulase positive Staphylococcus aureus, Salmonella sp. and Vibrio parahaemolyticus. The count of yeasts increased with the progress of storage time and Candida rugosa as well as Candida lipolytica were predominated. Penicillium was the predominant genus of mold

Interaction of guanidine hydrochloride and guanidine thiocyanate with wheat germ lipase.

Effect of two classical and potent denaturants, guanidine hydrochloride (GuHCl) and guanidine thiocyanate (GuHSCN) on purified wheat germ lipase has been studied. Lipase was found to be active only up to 5 M GuHCl and 1.5 M GuHSCN. The extent of interaction was determined by the measurement of apparent partial specific volume of the enzyme in presence of these two denaturants. While the preferential interaction parameter (zeta 3) has values of 0.08 +/- 0.02 and 0.14 +/- 0.03 g/g, the interaction parameter (delta m3/delta m2)T,mu 1, mu3 has values of 35 +/- 9 and 50 +/- 10 mole/mole for GuHCl and GuHSCN, respectively. The number of denaturant molecules bound to the enzyme, A3, obtained experimentally were 0.486 +/- 0.020 and 0.348 +/- 0.020 g/g and the calculated values were 0.459 +/- 0.023 and 0.567 +/- 0.030 g/g for 6 M GuHCl and 3 M GuHSCN, respectively. The volume change occurring upon denaturation results in -420 +/- 42 and -462 +/- 84 ml/mole in 6 M GuHCl and 3 M GuHSCN, respectively. The denaturation is accompanied by exposure of hydrophobic groups to the bulk solvent as confirmed by fluorescence emission measurements of the enzyme. The Tm measurements indicated a control value of 56 +/- 1 degree C. In presence of 6 M GuHCl/3 M GuHSCN, the value was 42 +/- 1 degree C. These results explain the retention of lipase activity even at 5 M GuHCl from a mechanistic point of view.

Some physicochemical properties of human milk bile-salt activated lipase.

Influence of pH, deoxycholate and denaturing reagents on human milk bile-salt activated lipase (EC 3.1.1.3) has been studied. It appears that pH between 5.0-8.0 has no significant effect on the secondary structure of this lipase, but its higher order structures are affected. Lipase-dependent 8-anilino-1-naphthalene sulphonate fluorescence has revealed that the deoxycholate activated form of lipase has a surface rich in hydrophobic amino acid residues. Circular dichroism and second derivative electronic absorption spectroscopic observations have also provided an evidence for deoxycholate-induced alterations in the surface conformation of this lipase.