Isolation and characterization of a thermophilic lipase from bacillus thermoleovorans ID-1

Transgenic rice as bioreactor for production of the Candida antarctica lipase B

Candida antarctica lipase B (CALB) is a versatile biocatalyst used for a wide range of biotransformation. Methods for low cost production of this enzyme are highly desirable. Here, we report a mass production method of CALB using transgenic rice seeds as the bioreactor. The transgenic rice transformed with the CALB gene under the control of the promoter of the rice seed storage protein GT1 was found to have accumulated a large quantity of CALB in seeds. The transgenic line with the highest lipolytic activity reached to 85 units per gram of dry seeds. One unit is defined as the amount of lipase necessary to liberate 1 μmol p-nitrophenol from p-nitrophenyl butyrate in 1 min. The rice recombinant lipase (rOsCALB) from this line represents 40% of the total soluble proteins in the crude seed extracts. The enzyme purified from the rice seeds had an optimal temperature of 40 °C, and optimal pH of 8.5, similar to that of the fermentation products. Test of its conversion ability as a biocatalyst for biodiesel production suggested that rOsCALB is functionally identical to the fermentation products in its industrial application.

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.

Thermostable lipase from Geobacillus sp. Iso5: bioseparation, characterization and native structural studies

The extracellular thermoalkaline lipase from Geobacillus sp. Iso5 was purified to homogeneity by ultrafiltration, 6% cross-linked agarose and Phenyl spehrose HIC column chromatography. The final purified lipase resulted in 8.7-fold with 6.2% yield. The relative molecular weight of the enzyme was determined to be a monomer of 47 kDa by SDS-PAGE and MALDI-TOF MS/MS spectroscopy. The purified enzyme exhibit optimum activity at 70 °C and pH 8.0. The enzyme retained above 90% activity at temperatures of 70 °C and about 35% activity at 85 °C for 2 h. However, the stability of the enzyme decreased at the temperature over 90 °C. The enzyme activity was promoted in the presence of Ca(2+) and Mg(2+) and strongly inhibited by HgCl2 , PMSF, DTT, K(+) , Co(2+) , and Zn (2+) . EDTA did not affect the enzyme activity. The secondary structure of purified lipase contains 36% α-helix and 64% β-sheet which was determined by Circular dichromism, FTIR, and Raman Spectroscopy.

Quantitative approach to track lipase producing Pseudomonas sp. S1 in nonsterilized solid state fermentation

Proliferation of the inoculated Pseudomonas sp. S1 is quantitatively evaluated using ERIC-PCR during the production of lipase in nonsterile solid state fermentation an approach to reduce the cost of enzyme production. Under nonsterile solid state fermentation with olive oil cake, Pseudomonas sp. S1 produced 57·9 IU g(-1) of lipase. DNA fingerprints of unknown bacterial isolates obtained on Bushnell Haas agar (BHA) + tributyrin exactly matched with that of Pseudomonas sp. S1. Using PCR-based enumeration, population of Pseudomonas sp. S1 was proliferated from 7·6 × 10(4) CFU g(-1) after 24 h to 4·6 × 10(8) CFU g(-1) after 96 h, which tallied with the maximum lipase activity as compared to control. Under submerged fermentation (SmF), Pseudomonas sp. S1 produced maximum lipase (49 IU ml(-1) ) using olive oil as substrate, while lipase production was 9·754 IU ml(-1) when Pseudomonas sp. S1 was grown on tributyrin. Optimum pH and temperature of the crude lipase was 7·0 and 50°C. Crude enzyme activity was 71·2% stable at 50°C for 360 min. Pseudomonas sp. S1 lipase was also stable in methanol showing 91·6% activity in the presence of 15% methanol, whereas 75·5 and 51·1% of activity were retained in the presence of 20 and 30% methanol, respectively. Thus, lipase produced by Pseudomonas sp. S1 is suitable for the production of biodiesel as well as treatment of oily waste water.

SIGNIFICANCE AND IMPACT OF STUDY

This study presents the first report on the production of thermophilic organic solvent tolerant lipase using agro-industry waste in nonsterile solid state fermentation. Positive correlation between survival of Pseudomonas sp. S1 and lipase production under nonsterile solid state fermentation was established, which may emphasize the need to combine molecular tools and solid state fermentation in future studies. Our study brings new insights into the lipase production in cost-effective manner, which is an industrially relevant approach.

Thermolongibacillus altinsuensis gen. nov., sp. nov. and Thermolongibacillus kozakliensis sp. nov., aerobic, thermophilic, long bacilli isolated from hot springs

Two novel endospore-forming, aerobic bacilli, strains E173aT and E265T, were isolated from soil and sediment samples from Kozakli and Altinsu hot springs, Nevsehir (Turkey). Their young cells in the exponential phase of growth were motile, Gram-stain-positive, straight rods, 0.6–1.1×3.0–8.0 µm in size, but they became strikingly long, approximately 0.6–1.2 by 9.0–35.0 µm, after the stationary phase of growth. Cells varied in tests for oxidase, and had a weakly positive reaction for catalase. Both strains could grow between 40 and 70 °C, with optimal growth at 60 °C (E173aT) and 55 °C (E265T). Growth occurred within the range pH 5.0–11.0 with optimal growth at pH 9.0 (E173aT) and pH 8.5 (E265T). Strain E173aT grew within a salinity range from 0 to1.5 % (w/v) NaCl with optimal growth at 0.5 %, while strain E265T grew within the range 0–5.0 % (w/v), with an optimum at 3.0 %. The new isolates differed from each other in some phenotypic and chemotaxonomic characters as well as repetitive extragenic palindromic element PCR (rep-PCR) fingerprints. 16S rRNA gene sequence similarities suggested distant relationships with other members of the family Bacillaceae (<95.8 %), although the two strains showed 97.5 % sequence similarity between them, and had 55 % relatedness by DNA–DNA hybridization. The DNA G+C contents were 44.8 (E173aT) and 43.5 mol% (E265T). Moreover, the chemotaxonomic data of E173aT and E265T [presence of low amounts of meso-diaminopimelic acid, A1γ to A1γ′ cross-linkage types in peptidoglycan, fatty acids including iso-C15 : 0 (>60 %), iso-C17 : 0 and C16 : 0] supported the consideration of these isolates as members of a novel genus. Based upon phenotypic, phylogenetic and chemotaxonomic characteristics, it is proposed that new isolates represent a novel genus, Thermolongibacillus gen. nov., with two novel species: Thermolongibacillus altinsuensis sp. nov. (type strain E265T = DSM 24979T = NCIMB 14850T) and Thermolongibacillus kozakliensis sp. nov. (type strain E173aT = DSM 24978T = NCIMB 14849T).

Anoxybacillus calidus sp. nov., a thermophilic bacterium isolated from soil near a thermal power plant

A novel thermophilic, Gram-stain-positive, facultatively anaerobic, endospore-forming, motile, rod-shaped bacterium, strain C161ab(T), was isolated from a soil sample collected near Kizildere, Saraykoy-Buharkent power plant in Denizli. The isolate could grow at temperatures between 35 and 70 °C (optimum 55 °C), at pH 6.5-9.0 (optimum pH 8.0-8.5) and with 0-2.5 % NaCl (optimum 0.5 %, w/v). The strain formed cream-coloured, circular colonies and tolerated up to 70 mM boron. Its DNA G+C content was 37.8 mol%. The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. Strain C161ab(T) contained menaquinones MK-7 (96 %) and MK-6 (4 %). The major cellular fatty acids were iso-branched fatty acids: iso-C15 : 0 (52.2 %) and iso-C17 : 0 (28.0 %,) with small amounts of C16 : 0 (7.4 %). Phylogenetic analysis based on the 16S rRNA gene revealed 94.6-96.8 % sequence similarity with all recognized species of the genus Anoxybacillus. Strain C161ab(T) showed the greatest sequence similarity to Anoxybacillus rupiensis DSM 17127(T) and Anoxybacillus voinovskiensis DSM 17075(T), both had 96.8 % similarity to strain C161ab(T), as well as to Anoxybacillus caldiproteolyticus DSM 15730(T) (96.6 %). DNA-DNA hybridization revealed low levels of relatedness with the closest relatives of strain C161ab(T), A. rupiensis (21.2 %) and A. voinovskiensis (16.5 %). On the basis of the results obtained from phenotypic, chemotaxonomic, genomic fingerprinting, phylogenetic and hybridization analyses, the isolate is proposed to represent a novel species, Anoxybacillus calidus sp. nov. (type strain C161ab(T) = DSM 25520(T) = NCIMB 14851(T)).

Production and characterization of a halo-, solvent-, thermo-tolerant alkaline lipase by Staphylococcus arlettae JPBW-1, isolated from rock salt mine

Studies on lipase production and characterization were carried out with a bacterial strain Staphylococcus arlettae JPBW-1 isolated from rock salt mine, Darang, HP, India. Higher lipase activity has been obtained using 10 % inoculum with 5 % of soybean oil as carbon source utilizing a pH 8.0 in 3 h at 35 °C and 100 rpm through submerged fermentation. Partially purified S. arlettae lipase has been found to be active over a broad range of temperature (30-90 °C), pH (7.0-12.0) and NaCl concentration (0-20 %). It has shown extreme stability with solvents such as benzene, xylene, n-hexane, methanol, ethanol and toluene up to 30 % (v/v). The lipase activity has been found to be inhibited by metal ions of K(+), Co(2+) and Fe (2+) and stimulated by Mn(2+), Ca(2+) and Hg(2+). Lipase activity has been diminished with denaturants, but enhanced effect has been observed with surfactants, such as Tween 80, Tween 40 and chelator EDTA. The K m and V max values were found to be 7.05 mM and 2.67 mmol/min, respectively. Thus, the lipase from S. arlettae may have considerable potential for industrial application from the perspectives of its tolerance towards industrial extreme conditions of pH, temperature, salt and solvent.

Unraveling the lipolytic activity of thermophilic bacteria isolated from a volcanic environment

In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70–80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern.

Isolation of lipase producing thermophilic bacteria: optimization of production and reaction conditions for lipase from Geobacillus sp

Lipases catalyze the hydrolysis and the synthesis of esters formed from glycerol and long chain fatty acids. Lipases occur widely in nature, but only microbial lipases are commercially significant. In the present study, thirty-two bacterial strains, isolated from soil sample of a hot spring were screened for lipase production. The strain TS-4, which gave maximum activity, was identified as Geobacillus sp. at MTCC, IMTECH, Chandigarh. The isolated lipase producing bacteria were grown on minimal salt medium containing olive oil. Maximal quantities of lipase were produced when 30 h old inoculum was used at 10% (v/v) in production medium and incubated in shaking conditions (150 rpm) for 72 h. The optimal temperature and pH for the bacterial growth and lipase production were found to be 60°C and 9.5, respectively. Maximal enzyme production resulted when mustard oil was used as carbon source and yeast extract as sole nitrogen source at a concentration of 1% (v/v) and 0.15% (w/v), respectively. The different optimized reaction parameters were temperature 65°C, pH 8.5, incubation time 10 min and substrate p-nitrophenyl palmitate. The Km and Vmax values of enzyme were found to be 14 mM and 17.86 μmol ml-1min-1, respectively, with p-nitrophenyl palmitate as substrate. All metal ions studied (1 mM) increased the lipase activity.

Purification and Characterization of a Thermostable Lipase from Geobacillus thermodenitrificans IBRL-nra

Thermostable lipase from Geobacillus thermodenitrificans IBRL-nra was purified and characterized. The production of thermostable lipase from Geobacillus thermodenitrificans IBRL-nra was carried out in a shake-flask system at 65°C in cultivation medium containing; glucose 1.0% (w/v); yeast extract 1.25% (w/v); NaCl 0.45% (w/v) olive oil 0.1% (v/v) with agitation of 200 rpm for 24 hours. The extracted extracellular crude thermostable lipase was purified to homogeneity by using ultrafiltration, Heparin-affinity chromatography, and Sephadex G-100 gel-filtration chromatography by 34 times with a final yield of 9%. The molecular weight of the purified enzyme was estimated to be 30 kDa after SDS-PAGE analysis. The optimal temperature for thermostable lipase was 65°C and it retained its initial activity for 3 hours. Thermostable lipase activity was highest at pH 7.0 and stable for 16 hours at this pH at 65°C. Thermostable lipase showed elevated activity when pretreated with BaCl(2), CaCl(2), and KCl with 112%, 108%, and 106%, respectively. Lipase hydrolyzed tripalmitin (C16) and olive oil with optimal activity (100%) compared to other substrates.

Purification and characterisation of an F16L mutant of a thermostable lipase

A mutant of the lipase from Geobacillus sp. strain T1 with a phenylalanine to leucine substitution at position 16 was overexpressed in Escherichia coli strain BL21(De3)pLysS. The crude enzyme was purified by two-step affinity chromatography with a final recovery and specific activity of 47.4 and 6,315.8 U/mg, respectively. The molecular weight of the purified F16L lipase was approximately 43 kDa by 12% SDS-PAGE analysis. The F16L lipase was demonstrated to be a thermophilic enzyme due its optimum temperature at 70 °C and showed stability over a temperature range of 40-60 °C. The enzyme exhibited an optimum pH 7 in phosphate buffer and was relatively stable at an alkaline pH 8-9. Metal ions such as Ca(2+), Mn(2+), Na(+), and K(+) enhanced the lipase activity, but Mg(2+), Zn(2+), and Fe(2+) inhibited the lipase. All surfactants tested, including Tween 20, 40, 60, 80, Triton X-100, and SDS, significantly inhibited the lipolytic action of the lipase. A high hydrolytic rate was observed on long-chain natural oils and triglycerides, with a notable preference for olive oil (C18:1; natural oil) and triolein (C18:1; triglyceride). The F16L lipase was deduced to be a metalloenzyme because it was strongly inhibited by 5 mM EDTA. Moderate inhibition was observed in the presence of PMSF at a similar concentration, indicating that serine residues are involved in its catalytic action. Further, the activity was not impaired by water-miscible solvents, including methanol, ethanol, and acetone.

Optimization of extracellular thermophilic highly alkaline lipase from thermophilic bacillus sp isolated from hotspring of Arunachal Pradesh, India

Studies on lipase production were carried out with a bacterial strain (Bacillus sp LBN 2) isolated from soil sample of hotspring of Arunachal Pradesh, India. The cells were cultivated in a mineral medium with maximum production at 1% groundnut oil. The optimum temperature and initial medium pH for lipase production by the organism were 50⁰C and 9.0 respectively. The molecular mass was found to be 33KDa by SDS PAGE. The optimal pH and temperature for activity were 10 and 60⁰C respectively. The enzyme was found to be stable in the pH range of 8–11 with 90% retention of activity at pH 11. The enzyme retained 90% activity at 60⁰C and 70% of activity at 70⁰C for 1h. The lipase was found to be stable in acetone followed by ethanol. The present findings suggested the enzyme to be thermophilic alkaline lipase.

Purification and characterization of an extracellular lipase from Mucor hiemalis f. corticola isolated from soil

We have screened 39 microfungi isolates originated from soil in terms of lipolytic activity. Out of all screened, a novel strain of Mucor hiemalis f. corticola was determined to have the highest lipase activity. The extracellular lipase was produced in response to 2% glucose and 2.1% peptone. The lipase was purified 12.63-folds with a final yield of 27.7% through following purification steps; ammonium sulfate precipitation, dialysis, gel filtration column chromatography and ion exchange chromatography, respectively. MALDI-TOF MS analysis revealed 31% amino-acid identity to a known lipase from Rhizomucor miehei species. The molecular weight of the lipase was determined as 46 kDa using SDS-PAGE and analytical gel filtration. Optimal pH and temperature of the lipase were determined as 7.0 and 40°C, respectively. The enzyme activity was observed to be stable at the pH range of 7.0-9.0. Thermostability assays demonstrated that the lipase was stable up to 50°C for 60 min. The lipase was more stable in ethanol and methanol than other organic solvents tested. Furthermore, the activity of the lipase was slightly enhanced by SDS and PMSF. In the presence of p-NPP as substrate, K(m) and V(max) values of the lipase were calculated by Hanes-Woolf plot as 1.327 mM and 91.11 μmol/min, respectively.

Purification and characterization of a highly thermostable esterase from the actinobacterium Geodermatophilus obscurus strain G20

Intracellular thermostable esterase produced by the extremophilic Geodermatophilus obscurus G20 was purified to homogeneity by a heat treatment, followed by an anion-exchange chromatography, and then characterized. The molecular weight of the purified enzyme determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was shown to be approximatively 55 kDa. The enzyme showed an optimal activity between pH 8.0 and 9.0 and was stable in the pH range 7.0-10.0. Moreover, it is highly thermostable, with a residual activity greater than 90% after incubation at 80 °C for more than 10 h. The enzyme showed preference for esters of p -nitrophenol with short chain fatty acid. When the p -nitrophenyl acetate (C2) was used as substrate, the Michaelis-Menten constant (K(m) ) and maximum velocity for the reaction (V(max) ) of esterase were 400 μM and 2500 U/mg protein, respectively. The effect of phenylmethanesulphonyl fluoride (PMSF), a serine-specific inhibitor, on the enzyme activity suggested that the thermostable esterase belong to the serine hydrolase group. Because of its high thermostability, activity at alkaline pH, tolerance to methanol and various metal ions and specificity for short chain fatty acids, this enzyme showed high potential for use in biocatalysis. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

Screening and characterization of a novel alkaline lipase from Acinetobacter calcoaceticus 1-7 Isolated from bohai bay in china for detergent formulation

A novel alkaline lipase-producing strain 1–7 identified as Acinetobacter calcoaceticus was isolated from soil samples collected from Bohai Bay, China, using an olive oil alkaline plate, which contained olive oil as the sole carbon source. The lipase from strain 1–7 showed the maximum activity at pH 9.0 under 40 °C. One interesting feature of this enzyme is that it exhibits lipase activity over a broad range of temperatures and good stability. It is also stable at a broad range of pHs from 4.0 to 10.0 for 24 h. Its catalytic activity was highly enhanced in the presence of Ca²⁺, Mg²⁺ and K⁺, but partially inhibited by Cu²⁺, Al³⁺, Fe³⁺, Ba²⁺and Zn²⁺. The fact that it displays marked stability and activity in the presence of TritonX-100, Tween-20, Tween-80, SDS, Hydrogen peroxide, Sodium perborate, Sodium hypochlorite, Sodium citrate, Sodium taurocholate, Glycerine and NaCl suggests that this lipase is suitable as an additive in detergent formulations.

High level expression and characterization of a novel thermostable, organic solvent tolerant, 1,3-regioselective lipase from Geobacillus sp. strain ARM

The mature ARM lipase gene was cloned into the pTrcHis expression vector and over-expressed in Escherichia coli TOP10 host. The optimum lipase expression was obtained after 18 h post induction incubation with 1.0mM IPTG, where the lipase activity was approximately 1623-fold higher than wild type. A rapid, high efficient, one-step purification of the His-tagged recombinant lipase was achieved using immobilized metal affinity chromatography with 63.2% recovery and purification factor of 14.6. The purified lipase was characterized as a high active (7092 U mg(-1)), serine-hydrolase, thermostable, organic solvent tolerant, 1,3-specific lipase with a molecular weight of about 44 kDa. The enzyme was a monomer with disulfide bond(s) in its structure, but was not a metalloenzyme. ARM lipase was active in a broad range of temperature and pH with optimum lipolytic activity at pH 8.0 and 65°C. The enzyme retained 50% residual activity at pH 6.0-7.0, 50°C for more than 150 min.

Characterization of a novel lipase from Bacillus sp. isolated from tannery wastes

Kinetics of a lipase isolated from Bacillus sp. was studied. The enzyme showed maximum activity at pH 9 and temperature 60°C. The Michaelis constant (KM 0.31 mM) obtained from three different plots i.e., Lineweaver-Burk, Hanes-Wolf and Hofstee, was found to be lower than already reported lipases that confirmed higher affinity of the enzyme for its substrate p-NPL (p-nitrophenyl laurate). Vmax of the enzyme was found to be 7.6 µM/mL/min. Energy of activation calculated from Arrhenius plot was found to be 20.607 kJmol(-1). Activation enthalpy (ΔH*) had negative trend and the value for the hydrolysis of p-NPL by the enzyme at optimum temperature was -2.748 kJmol(-1). Activation entropy (ΔS*) and free energy of activation (ΔG*) of the enzyme were found to be 1.468 Jmol(-1)K(-1) and -3.237 kJmol(-1), respectively at optimum temperature. Low value of Q10 (0.04788) shows high catalytic activity of the enzyme. Mn(2+), Fe(2+) and Mg(2+) enhanced the lipase activity whereas Cu(2+), Na(+) and Co(2+) inhibited the enzyme activity. However, the enzyme activity was not affected significantly by K(+) ions. EDTA and SDS also significantly inhibited the lipase activity. Activity of the enzyme was increased in n-hexane while decreased with increase in concentration of acetone, chloroform, ethanol and isopropanol.

Effect of Tween 80 on the growth, lipid accumulation and fatty acid composition of Thraustochytrium aureum ATCC 34304

Thraustochytrium aureum ATCC 34304 was grown in the presence and absence of polyoxyethylene sorbitan monooleate (Tween 80). The aim of this work was to obtain basic knowledge about the effect of Tween 80 on growth, lipid accumulation and fatty acid composition in T. aureum. The addition of Tween 80 to a culture medium significantly enhanced the growth of T. aureum, and the biomass increased with an increase of Tween 80 content. Total lipid content and total fatty acid content were significantly higher in 1.0% Tween 80 in comparison with the control (absence of Tween 80). The fatty acid profile showed that the content of C18:1n-9 (oleic acid) significantly increased as a result of the addition of Tween 80. These results indicated that part of the Tween 80 added to the medium was utilized as a carbon source or that the oleate included in Tween 80 was directly incorporated into T. aureum cells as a fatty acid. Neither the DHA content nor the percentage of DHA did not change in spite of the addition of Tween 80. However, the DHA yield significantly increased because the biomass increased due to the addition of Tween 80.

Characterization of an extracellular alkaline lipase from Pseudomonas mendocina M-37

A strain of Pseudomonas mendocina producing extracellular lipase was isolated from soil. The bacterium accumulates lipase in culture fluid when grown aerobically at 30 °C for 24 h in a medium composed of olive oil (1%) as substrate. Pseudomonas mendocina lipase was optimally active at pH 9.0, temperature of 50 °C and was found to be stable between pH 7.0-11.0. The lipase was inhibited by detergents such as SDS and Tween-80. The enzyme was stable in various organic solvents tested with maximum stability in chloroform followed by toluene and exhibited 1-3 regiospecificity for hydrolytic reaction. This lipase was capable of hydrolyzing a variety of lipidic substrates and is mainly active towards synthetic triglycerides and fatty acid esters that possess a butyryl group. Metal ions like Mg(2+), Ca(2+) and Na(+) stimulated lipase activity, whereas, Cu(2+), Mn(2+) and Hg(2+) ions caused inhibition.

In silico characterization of thermostable lipases

Thermostable lipases are of high priority for industrial applications as they are endowed with the capability of carrying out diversified reactions at elevated temperatures. Extremophiles are their potential source. Sequence and structure annotation of thermostable lipases can elucidate evolution of lipases from their mesophilic counterparts with enhanced thermostability hence better industrial potential. Sequence analysis highlighted the conserved residues in bacterial and fungal thermostable lipases. Higher frequency of AXXXA motif and poly Ala residues in lid domain of thermostable Bacillus lipases were distinguishing characteristics. Comparison of amino acid composition among thermostable and mesostable lipases brought into light the role of neutral, charged and aromatic amino acid residues in enhancement of thermostability. Structural annotation of thermostable lipases with that of mesostable lipases revealed some striking features which are increment of gamma turns in thermostable lipases; being first time reported in our paper, longer beta strands, lesser beta-branched residues in helices, increase in charged-neutral hydrogen bonding pair, hydrophobic-hydrophobic contact and differences in the N-cap and C-cap residues of the α helices. Conclusively, it can be stated that subtle changes in the arrangement of amino acid residues in the tertiary structure of lipases contributes to enhanced thermostability.

Purification and characterization of organic solvent and detergent tolerant lipase from thermotolerant Bacillus sp. RN2

The aim of this study was to characterize the organic solvent and detergent tolerant properties of recombinant lipase isolated from thermotolerant Bacillus sp. RN2 (Lip-SBRN2). The isolation of the lipase-coding gene was achieved by the use of inverse and direct PCR. The complete DNA sequencing of the gene revealed that the lip-SBRN2 gene contains 576 nucleotides which corresponded to 192 deduced amino acids. The purified enzyme was homogeneous with the estimated molecular mass of 19 kDa as determined by SDS-PAGE and gel filtration. The Lip-SBRN2 was stable in a pH range of 9-11 and temperature range of 45-60 °C. The enzyme was a non metallo-monomeric protein and was active against pNP-caprylate (C8) and pNP-laurate (C12) and coconut oil. The Lip-SBRN2 exhibited a high level of activity in the presence of 108% benzene, 102.4% diethylether and 112% SDS. It is anticipated that the organic solvent and detergent tolerant enzyme secreted by Bacillus sp. RN2 will be applicable as catalysts for reaction in the presence of organic solvents and detergents.

Purification and characterization of a low molecular mass alkaliphilic lipase of Bacillus cereus MTCC 8372

A low molecular mass alkaliphilic extra-cellular lipase of Bacillus cereus MTCC 8372 was purified 35-fold by hydrophobic interaction (Octyl-Sepharose) chromatography. The purified enzyme was found to be electrophoretically pure by denaturing gel electrophoresis and possessed a molecular mass of approximately 8 kDa. It is a homopentamer of 40 kDa as revealed by native-PAGE. The lipase was optimally active at 55 °C and retained approximately half of its original activity after 40 min incubation at 55 °C. The enzyme was maximally active at pH 8.5. Mg2+, Cu2+, Ca2+, Hg2+, Al3+ and Fe3+ at 1 mM enhanced hydrolytic activity of the lipase. Interestingly, Hg2+ ions synergized and Zn2+ and Co2+ ions antagonized the lipase activity. Among surfactants, Tween 80 promoted the lipase activity. Phenyl methyl sulfonyl fluoride (PMSF, 15 mM) decreased 98% of original activity of lipase. The lipase was highly specific towards p-nitrophenyl palmitate and showed a Vmax and Km of 0.70 mmol.mg⁻¹.min⁻¹ and 32 mM for hydrolysis of pNPP.