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

Thermostable lipases from the extreme thermophilic anaerobic bacteria Thermoanaerobacter thermohydrosulfuricus SOL1 and Caldanaerobacter subterraneus subsp. tengcongensis

Two novel genes encoding for heat and solvent stable lipases from strictly anaerobic extreme thermophilic bacteria Thermoanaerobacter thermohydrosulfuricus (LipTth) and Caldanaerobacter subterraneus subsp. tengcongensis (LipCst) were successfully cloned and expressed in E. coli. Recombinant proteins were purified to homogeneity by heat precipitation, hydrophobic interaction, and gel filtration chromatography. Unlike the enzymes from mesophile counterparts, enzymatic activity was measured at a broad temperature and pH range, between 40 and 90°C and between pH 6.5 and 10; the half-life of the enzymes at 75°C and pH 8.0 was 48 h. Inhibition was observed with 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride and phenylmethylsulfonylfluorid indicating that serine and thiol groups play a role in the active site of the enzymes. Gene sequence comparisons indicated very low identity to already described lipases from mesophilic and psychrophilic microorganisms. By optimal cultivation of E. coli Tuner (DE3) cells in 2-l bioreactors, a massive production of the recombinant lipases was achieved (53–2200 U/l) Unlike known lipases, the purified robust proteins are resistant against a large number of organic solvents (up to 99%) and detergents, and show activity toward a broad range of substrates, including triacylglycerols, monoacylglycerols, esters of secondary alcohols, and p-nitrophenyl esters. Furthermore, the enzyme from T. thermohydrosulfuricus is suitable for the production of optically pure compounds since it is highly S-stereoselective toward esters of secondary alcohols. The observed E values for but-3-yn-2-ol butyrate and but-3-yn-2-ol acetate of 21 and 16, respectively, make these enzymes ideal candidates for kinetic resolution of synthetically useful compounds.

Methods for detection and characterization of lipases: A comprehensive review

Microbial lipases are very prominent biocatalysts because of their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. The chemo-, regio- and enantio-specific behaviour of these enzymes has caused tremendous interest among scientists and industrialists. Lipases from a large number of bacterial, fungal and a few plant and animal sources have been purified to homogeneity. This article presents a critical review of different strategies which have been employed for the detection, purification and characterization of microbial lipases.

A modeling study by response surface methodology and artificial neural network on culture parameters optimization for thermostable lipase production from a newly isolated thermophilic Geobacillus sp. strain ARM

BACKGROUND

Thermostable bacterial lipases occupy a place of prominence among biocatalysts owing to their novel, multifold applications and resistance to high temperature and other operational conditions. The capability of lipases to catalyze a variety of novel reactions in both aqueous and nonaqueous media presents a fascinating field for research, creating interest to isolate novel lipase producers and optimize lipase production. The most important stages in a biological process are modeling and optimization to improve a system and increase the efficiency of the process without increasing the cost.

RESULTS

Different production media were tested for lipase production by a newly isolated thermophilic Geobacillus sp. strain ARM (DSM 21496 = NCIMB 41583). The maximum production was obtained in the presence of peptone and yeast extract as organic nitrogen sources, olive oil as carbon source and lipase production inducer, sodium and calcium as metal ions, and gum arabic as emulsifier and lipase production inducer. The best models for optimization of culture parameters were achieved by multilayer full feedforward incremental back propagation network and modified response surface model using backward elimination, where the optimum condition was: growth temperature (52.3 degrees C), medium volume (50 ml), inoculum size (1%), agitation rate (static condition), incubation period (24 h) and initial pH (5.8). The experimental lipase activity was 0.47 Uml(-1) at optimum condition (4.7-fold increase), which compared well to the maximum predicted values by ANN (0.47 Uml(-1)) and RSM (0.476 Uml(-1)), whereas R2 and AAD were determined as 0.989 and 0.059% for ANN, and 0.95 and 0.078% for RSM respectively.

CONCLUSION

Lipase production is the result of a synergistic combination of effective parameters interactions. These parameters are in equilibrium and the change of one parameter can be compensated by changes of other parameters to give the same results. Though both RSM and ANN models provided good quality predictions in this study, yet the ANN showed a clear superiority over RSM for both data fitting and estimation capabilities. On the other hand, ANN has the disadvantage of requiring large amounts of training data in comparison with RSM. This problem was solved by using statistical experimental design, to reduce the number of experiments.

A novel thermostable lipase from basidiomycete Bjerkandera adusta R59: characterisation and esterification studies

Microbial lipases are widely diversified in their enzymatic properties and substrate specificities, which make them very attractive for industrial application. Partially purified lipase from Bjerkandera adusta R59 was immobilized on controlled porous glass (CPG) and its properties were compared with those of the free enzyme. The free and immobilized lipases showed optimal activities at 45 and 50 degrees C, respectively. Both enzyme forms were highly thermostable up to 60 degrees C. The enzymes were stable at pH from 6.0 to 9.0 and their optimal pH for activity was 7.0. The free lipase was more thermostable in n-hexane than in aqueous environment. Both lipase preparations had good stabilities in non-polar solvents and were capable of hydrolysing a variety of synthetic and natural fats. Non-immobilized lipase activity was inhibited by disulphide bond reagents, serine and thiol inhibitors, while EDTA and eserine had no effect on enzyme activity. All anionic detergents tested in experiments inhibited lipase activity. The free lipase showed good stability in the presence of commercial detergents at laundry pH and temperatures. Applications of free and immobilized lipases for esterification were also presented.

Production of L2 lipase by Bacillus sp. strain L2: nutritional and physical factors

A thermophilic bacterium, Bacillus sp. strain L2 was isolated from a hot spring in Perak, Malaysia. An extracellular lipase activity was detected through plate and broth assays at 70 degrees C after 28 h of incubation. The L2 lipase production was growth dependent as revealed by a number of factors affecting the secretion of extracelullar lipase. As for nutritional factors, casamino acids, trehalose, Ca(2+) and Tween 60 were found to be more effective for lipase production. The optimum physical condition for L2 lipase production was obtained at 70 degrees C after 28 h of cultivation time, at pH 7.0, 150 rpm of agitation rate and 1% of starting inoculum size. The activity staining of crude L2 lipase revealed a clearing zone at 39 kDa.

Characterization of a new rhamnogalacturonan acetyl esterase from Bacillus halodurans C-125 with a new putative carbohydrate binding domain

BH1115 is a gene from Bacillus halodurans strain C-125 that hypothetically encodes a rhamnogalacturonan acetyl esterase (RGAE) of the CE-12 family. As confirmation, this gene was cloned, and the product was expressed in Escherichia coli strain Rosetta (DE3) cells and purified. The enzyme obtained was monomeric, with a molecular mass of 45 kDa, and exhibited alkaliphilic properties. A study of the inhibition of the activity by some modulators confirmed that the catalytic triad for the esterase activity was Ser-His-Asp. This enzyme also presents broad substrate specificity and is active toward 7-aminocephalosporanic acid, cephalosporin C, p-nitrophenyl acetate, beta-naphthyl acetate, glucose pentaacetate, and acetylated xylan. Moreover, RGAE from B. halodurans achieves a synergistic effect with xylanase A toward acetylated xylan. As a member of the SGNH family, it does not adopt the common alpha/beta hydrolase fold. The homology between the folds of RGAE from Aspergillus aculeatus and the hypothetical YxiM precursor from Bacillus subtilis, which both belong to the SGNH family, illustrates the divergence of such proteins from a common ancestor. Furthermore, the enzyme possesses a putative substrate binding region at the N terminus of the protein which has never been described to date for any RGAE.

Purification and characterization of two highly thermophilic alkaline lipases from Thermosyntropha lipolytica

Two thermostable lipases were isolated and characterized from Thermosyntropha lipolytica DSM 11003, an anaerobic, thermophilic, alkali-tolerant bacterium which grows syntrophically with methanogens on lipids such as olive oil, utilizing only the liberated fatty acid moieties but not the glycerol. Lipases LipA and LipB were purified from culture supernatants to gel electrophoretic homogeneity by ammonium sulfate precipitation and hydrophobic interaction column chromatography. The apparent molecular masses of LipA and LipB determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 50 and 57 kDa, respectively. The temperature for maximal activity of LipA and LipB was around 96 degrees C, which is, so far as is known, the highest temperature for maximal activity among lipases, and the pH optima for growth determined at 25 degrees C (pH(25 degrees C) optima) were 9.4 and 9.6, respectively. LipA and LipB at 100 degrees C and pH(25 degrees C) 8.0 retained 50% activity after 6 and 2 h of incubation, respectively. Both enzymes exhibited high activity with long-chain fatty acid glycerides, yielding maximum activity with trioleate (C(18:1)) and, among the p-nitrophenyl esters, with p-nitrophenyl laurate. Hydrolysis of glycerol ester bonds occurred at positions 1 and 3. The activities of both lipases were totally inhibited by 10 mM phenylmethylsulfonyl fluoride and 10 mM EDTA. Metal analysis indicated that both LipA and LipB contain 1 Ca2+ and one Mn2+ ion per monomeric enzyme unit. The addition of 1 mM MnCl2 to dialyzed enzyme preparations enhanced the activities at 96 degrees C of both LipA and LipB by threefold and increased the durations of their thermal stability at 60 degrees C and 75 degrees C, respectively, by 4 h.

Determination and characterization of thermostable esterolytic activity from a novel thermophilic bacterium Anoxybacillus gonensis A4

A novel hot spring thermophile, Anoxybacillus gonensis A4 (A. gonensis A4) was investigated in terms of capability of tributyrin degradation and characterization of its thermostable esterase activity by the hydrolysis of p-nitrophenyl butyrate (PNPB). It was observed that A. gonensis A4 has an esterase with a molecular weight of 62 kDa. The extracellular crude preparation was characterized in terms of substrate specificity, pH and temperature optima and stability, kinetic parameters and inhibition/activation behaviour towards some chemicals and metal ions. Tributyrin agar assay showed that A. gonensis A4 secreted an esterase and V(max) and K(m) values of its activity were found to be 800 U/L and 176.5 microM, respectively in the presence of PNPB substrate. The optimum temperature and pH, for A. gonensis A4 esterase was 60-80 degrees C and 5.5, respectively. Although the enzyme activity was not significantly changed by incubating crude extract solution at 30-70 degrees C for 1 h, the enzyme activity was fully lost at 80 degrees C for same incubation period. The pH-stability profile showed that original crude esterase activity increased nearly 2-fold at pH 6.0. The effect of some chemicals on crude esterase activity indicated that A. gonensis A4 produce an esterase having serine residue in active site and -SH groups were essential for its activity.

Geobacillus zalihae sp. nov., a thermophilic lipolytic bacterium isolated from palm oil mill effluent in Malaysia

BACKGROUND

Thermophilic Bacillus strains of phylogenetic Bacillus rRNA group 5 were described as a new genus Geobacillus. Their geographical distribution included oilfields, hay compost, hydrothermal vent or soils. The members from the genus Geobacillus have a growth temperatures ranging from 35 to 78 degrees C and contained iso-branched saturated fatty acids (iso-15:0, iso-16:0 and iso-17:0) as the major fatty acids. The members of Geobacillus have similarity in their 16S rRNA gene sequences (96.5-99.2%). Thermophiles harboring intrinsically stable enzymes are suitable for industrial applications. The quest for intrinsically thermostable lipases from thermophiles is a prominent task due to the laborious processes via genetic modification.

RESULTS

Twenty-nine putative lipase producers were screened and isolated from palm oil mill effluent in Malaysia. Of these, isolate T1T was chosen for further study as relatively higher lipase activity was detected quantitatively. The crude T1 lipase showed high optimum temperature of 70 degrees C and was also stable up to 60 degrees C without significant loss of crude enzyme activity. Strain T1T was a Gram-positive, rod-shaped, endospore forming bacterium. On the basic of 16S rDNA analysis, strain T1T was shown to belong to the Bacillus rRNA group 5 related to Geobacillus thermoleovorans (DSM 5366T) and Geobacillus kaustophilus (DSM 7263T). Chemotaxonomic data of cellular fatty acids supported the affiliation of strain T1T to the genus Geobacillus. The results of physiological and biochemical tests, DNA/DNA hybridization, RiboPrint analysis, the length of lipase gene and protein pattern allowed genotypic and phenotypic differentiation of strain T1T from its validly published closest phylogenetic neighbors. Strain T1T therefore represents a novel species, for which the name Geobacillus zalihae sp. nov. is proposed, with the type strain T1T (=DSM 18318T; NBRC 101842T).

CONCLUSION

Strain T1T was able to secrete extracellular thermostable lipase into culture medium. The strain T1T was identified as Geobacillus zalihae T1T as it differs from its type strains Geobacillus kaustophilus (DSM 7263T) and Geobacillus thermoleovorans (DSM 5366T) on some physiological studies, cellular fatty acids composition, RiboPrint analysis, length of lipase gene and protein profile.

Purification and characterization of a mesophilic lipase from Bacillus subtilis FH5 stable at high temperature and pH

Lipases are a class of enzymes which catalyze the hydrolysis of long-chain triglycerides. Microbial lipases are currently receiving much attention with the rapid development of enzyme technology. Bacillus subtilis FH5, isolated from tannery wastes, produced a thermostable alkalophilic lipase and was purified to homogeneity as judged by SDS-PAGE. The purification steps included acetone fractionation and sequential column chromatography on DEAE-cellulose, Sephadex G-75 and adsorption chromatography on Hydroxylapatite. The results of chromatographies showed that two types of lipases were present having molecular weights approximately 62 kDa and 24 kDa, respectively. The purified enzyme was found to be 100% stable at pH 10 and about 80% residual activity was present at 60 degrees C. The enzyme was found to be stable in the presence of Mg2+, Mn2+ and Ca2+ ions. Km value was calculated as 5.05 mM and Vmax as 0.416 micromol/ml/min. Bacillus subtilis FH5 was isolated from tannery waste, therefore, enzyme is environmentally compatible for application in leather degreasing process.

Production of lipase by a newly isolated Bacillus coagulans under solid-state fermentation using melon wastes

An extracellular lipase was produced by Bacillus coagulans by solid-state fermentation. Solid waste from melon was used as the basic nutrient source and was supplemented with olive oil. The highest lipase production (78,069 U/g) was achieved after 24 h of cultivation with 1% olive oil enrichment. Enzyme had an optimal activity at 37 degrees C and pH 7.0, and sodium dodecyl sulfate increased lipase activity. NH4NO3 increased enzyme production, whereas organic nitrogen had no effect. The effect of the type of carbon sources on lipolytic enzyme production was also studied. The best results were obtained with starch and maltose (148,932 and 141,629 U/g, respectively), whereas a rather low enzyme activity was found in cultures grown on glucose and galactose (approx 118,769 and 123,622 U/g, respectively). Enzyme was inhibited with Mn+2 and Ni+2 by 68 and 74%, respectively. By contrast, Ca+2 enhanced enzyme production by 5%.

Characterization of a novel D-lyxose isomerase from Cohnella laevoribosii RI-39 sp. nov

A newly isolated bacterium, Cohnella laevoribosii RI-39, could grow in a defined medium with L-ribose as the sole carbon source. A 21-kDa protein isomerizing L-ribose to L-ribulose, as well as D-lyxose to D-xylulose, was purified to homogeneity from this bacterium. Based on the N-terminal and internal amino acid sequences of the purified enzyme obtained by N-terminal sequencing and quantitative time of flight mass spectrometry-mass spectrometry analyses, a 549-bp gene (lyxA) encoding D-lyxose (L-ribose) isomerase was cloned and expressed in Escherichia coli. The purified endogenous enzyme and the recombinant enzyme formed homodimers that were activated by Mn(2+). C. laevoribosii D-lyxose (L-ribose) isomerase (CLLI) exhibits maximal activity at pH 6.5 and 70 degrees C in the presence of Mn(2+) for D-lyxose and L-ribose, and its isoelectric point (pI) is 4.2 (calculated pI, 4.9). The enzyme is specific for D-lyxose, L-ribose, and D-mannose, with apparent K(m) values of 22.4 +/- 1.5 mM, 121.7 +/- 10.8 mM, and 34.0 +/- 1.1 mM, respectively. The catalytic efficiencies (k(cat)/K(m)) of CLLI were 84.9 +/- 5.8 mM(-1) s(-1) for D-lyxose (V(max), 5,434.8 U mg(-1)), 0.2 mM(-1) s(-1) for L-ribose (V(max), 75.5 +/- 6.0 U mg(-1)), and 1.4 +/- 0.1 mM(-1) s(-1) for D-mannose (V(max), 131.8 +/- 7.4 U mg(-1)). The ability of lyxA to permit E. coli cells to grow on D-lyxose and L-ribose and homology searches of other sugar-related enzymes, as well as previously described sugar isomerases, suggest that CLLI is a novel type of rare sugar isomerase.

A Newly Isolated Organic Solvent Tolerant Staphylococcus saprophyticus M36 Produced Organic Solvent-Stable Lipase

Thirty-eight high lipase activity strains were isolated from soil, seawater, and Brassica napus. Among them, a novel organic solvent tolerant bacterium (strain M36) was isolated from the seawater in Jiangsu, China. Isolate M36 was able to grow at high concentration of benzene or toluene up to 40% (vol/vol), and later identified as Staphylococcus saprophyticus by biochemical test and 16s ribosomal DNA sequence. No work on Staphylococcus producing lipase with organic solvent tolerance has been reported so far. The lipase of strain M36 whose activity in liquid medium was 42 U mL(-1) at 24-h incubation time was stable in the presence of 25% (vol/vol) p-xylene, benzene, toluene, and hexane.

Isolation and characterization of a Geobacillus thermoleovorans strain from an ultra-deep South African gold mine

A thermophilic facultative bacterial isolate was recovered from 3.2km depth in a gold mine in South Africa. This isolate, designated GE-7, was cultivated from pH 8.0, 50 degrees C water from a dripping fracture near the top of an exploration tunnel. GE-7 grows optimally at 65 degrees C and pH 6.5 on a wide range of carbon substrates including cellobiose, hydrocarbons and lactate. In addition to O(2), GE-7 also utilizes nitrate as an electron acceptor. GE-7 is a long rod-shaped bacterium (4-6microm longx0.5microm wide) with terminal endospores and flagella. Phylogenetic analysis of GE-7 16S rDNA sequence revealed high sequence similarity with G. thermoleovorans DSM 5366(T) (99.6%), however, certain phenotypic characteristics of GE-7 were distinct from this and other previously described strains of G. thermoleovorans.

Identification and over-expression of a thermostable lipase from Geobacillus thermoleovorans Toshki in Escherichia coli

A newly isolated thermophilic strain producing thermostable lipase was identified based on 16S rRNA sequencing, where phylogenetic analysis revealed its closeness to Geobacillus thermoleovorans. Thermostable lipase from this bacterium was cloned using consensus degenerate PCR primers. For over-expression in Escherichia coli, the lipase gene was sub-cloned in pET 15b vector with a strong T7 promotor. Lipase activity was approximately 4.5-fold higher than in the wild-type strain. The lipase enzyme was thermostable at 60 degrees C and pH 8, whereas a 30% residual activity was retained when incubated for 1h at 100 degrees C. Optimum lipase expression was obtained in 2 x YT medium after 70min of induction by IPTG.

Production, purification, and characterization of lipase from thermophilic and alkaliphilic Bacillus coagulans BTS-3

A thermophilic isolate Bacillus coagulans BTS-3 produced an extracellular alkaline lipase, the production of which was substantially enhanced when the type of carbon source, nitrogen source, and the initial pH of culture medium were consecutively optimized. Lipase activity 1.16 U/ml of culture medium was obtained in 48 h at 55 degrees C and pH 8.5 with refined mustard oil as carbon source and a combination of peptone and yeast extract (1:1) as nitrogen sources. The enzyme was purified 40-fold to homogeneity by ammonium sulfate precipitation and DEAE-Sepharose column chromatography. Its molecular weight was 31 kDa on SDS-PAGE. The enzyme showed maximum activity at 55 degrees C and pH 8.5, and was stable between pH 8.0 and 10.5 and at temperatures up to 70 degrees C. The enzyme was found to be inhibited by Al3+, Co2+, Mn2+, and Zn2+ ions while K+, Fe3+, Hg2+, and Mg2+ ions enhanced the enzyme activity; Na+ ions have no effect on enzyme activity. The purified lipase showed a variable specificity/hydrolytic activity towards various 4-nitrophenyl esters.

Properties of a thermostable extracellular lipase fromBacillus megaterium AKG-1

An extracellular lipase isolated from Bacillus megaterium AKG-1 had an optimum activity at 55 degrees C/pH 7.0. It retained 100% activity at 50 degrees C for 30 min with a half life of 30 min at 70 degrees C. A 20-70% increase in lipase activity was observed in presence of acetone (20% v/v), DMSO (20% v/v) and isopropanol (10% v/v). The enzyme activity was 92, 98 and 107% after 24 h, on treatment with 10% (v/v) acetone, benzene and isopropanol respectively. Deoxycholic acid, sodium deoxycholate, lithocholic acid, rhamnolipid, Brij 52 and cholic acid stimulated the lipase activity by 76, 36, 24, 24, 23.6 and 13%, respectively. Addition of reducing agents like sodium sulphite, sodium metabisulphite and L-cysteine-HCl, at 10 mM concentration stimulated lipase activity by 127, 146 and 150% respectively. The lipase appeared to show enantioselectivity in hydrolyzing racemic 3-acetoxy-beta-lactam as it hydrolyzed only the (+) enantiomer.

Characterization of thermostable lipase from thermophilic Geobacillus sp. TW1

A novel lipase-producing thermophilic strain TW1, assigned to Geobacillus sp. TW1 based on 16S rRNA sequence, was isolated from a hot spring in China. Based on this strain, a lipase gene encoding 417 amino acids was cloned. Subsequently, the lipase gene was expressed in Escherichia coli and purified as a fusion protein with glutathione S-transferase. The results showed that the recombinant lipase had an activity optimum at 40 degrees C and pH at 7.0-8.0. It was active up to 90 degrees C at pH 7.5, and stable over a wide pH ranging from 6.0 to 9.0. The recombinant lipase was stable in 1 mM enzyme inhibitors (EDTA, 2-ME, SDS, PMSF or DTT), as well as in 0.1% detergents (Tween 20, Chaps or Triton X-100). Its catalytic function was enhanced in the presence of Ca(2+), Mg(2+), Zn(2+), Fe(2+) or Fe(3+), but inhibited by Cu(2+), Mn(2+), and Li(+). By comparison with the crude lipase, the recombinant lipase had similar properties and was characteristic of thermostable enzymes. Our study presented a rapid overexpression and purification of the lipase gene from thermophile, aimed at improving the enzyme yield for industrial applications.

Purification, immobilization, and stabilization of a lipase from Bacillus thermocatenulatus by interfacial adsorption on hydrophobic supports

A lipase from Bacillus thermocatenulatus (BTL2) cloned in E. coli has been purified using a very simple method: interfacial activation on a hydrophobic support followed by desorption with Triton. Only one band was detected by SDS-PAGE. The pure enzyme was immobilized using different methodologies. BTL2 adsorbed on a hydrophobic support (octadecyl-Sepabeads) exhibited a hyperactivation with respect to the soluble enzyme, whereas the other immobilized preparations suffered a slight decrease in the expressed activity. The soluble enzyme was very stable, but all immobilized preparations were much more stable than the soluble enzyme, the octadecyl-Sepabeads-BTL2 preparation being the most stable one in all conditions (high temperature or in the presence of organic cosolvents), maintaining 100% of the activity at 65 degrees C or 30% of dioxane and 45 degrees C after several days of incubation. The glyoxyl preparation, the second more stable, retained 80% of the initial activity after 2 days, respectively. The adsorption of this thermophilic lipase on octadecyl-Sepabeads permitted an increase in the optimal temperature of the enzyme of 10 degrees C.

Co-expression of a prophage system and a plasmid system in Bacillus subtilis

A dual expression system for overexpressing two proteins by a single cell strain has been developed in Bacillus subtilis. This dual expression system combines the phi105MU331 prophage system and a plasmid system within a single cell. Protein expression by the prophage system is heat inducible, while that of the plasmid system is constitutive. Three candidate genes, BPN, BT, and amyE, all of Bacillus origin, were used as test models. Seven strains (BPN, BT, AMY, BS168K, MU331K, BPNK, and BTK) were constructed to investigate the influences of the prophage system and the plasmid system on each other, and to compare the efficiency of the individual expression systems with that of the dual expression system. Individually, the yield of the plasmid system is higher than that of the prophage system, which could be attributed to the constitutive nature of the expression of the plasmid system. Nonetheless, for the dual expression strains, the expression of two enzymes in a single fermentation run can reduce costs in facilities, manpower, and utilities. Fed-batch fermentation of BPNK strains confirmed the feasibility of applying this dual expression system in industrial-scale production.

Production, purification, characterization, and applications of lipases

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) 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. The many applications of lipases include speciality organic syntheses, hydrolysis of fats and oils, modification of fats, flavor enhancement in food processing, resolution of racemic mixtures, and chemical analyses. This article discusses the production, recovery, and use of microbial lipases. Issues of enzyme kinetics, thermostability, and bioactivity are addressed. Production of recombinant lipases is detailed. Immobilized preparations of lipases are discussed. In view of the increasing understanding of lipases and their many applications in high-value syntheses and as bulk enzymes, these enzymes are having an increasing impact on bioprocessing.

Analysis of Bacillus megaterium lipolytic system and cloning of LipA, a novel subfamily I.4 bacterial lipase

The lipolytic system of Bacillus megaterium 370 was investigated, showing the existence of at least two secreted lipases and a cell-bound esterase. A gene coding for an extracellular lipase was isolated and cloned in Escherichia coli. The cloned enzyme displayed high activity on short to medium chain length (C(4)-C(8)) substrates, and poor activity on C(18) substrates. On the basis of amino acid sequence homology, the cloned lipase was classified into subfamily I.4 of bacterial lipases.

A new type of thermoalkalophilic hydrolase of Paucimonas lemoignei with high specificity for amorphous polyesters of short chain-length hydroxyalkanoic acids

A novel type of hydrolase was purified from culture fluid of Paucimonas (formerly Pseudomonas) lemoignei. Biochemical characterization revealed an unusual substrate specificity of the purified enzyme for amorphous poly((R)-3-hydroxyalkanoates) (PHA) such as native granules of natural poly((R)-3-hydroxybutyrate) (PHB) or poly((R)-3-hydroxyvalerate) (PHV), artificial cholate-coated granules of natural PHB or PHV, atactic poly((R,S)-3-hydroxybutyrate), and oligomers of (R)-3-hydroxybutyrate (3HB) with six or more 3HB units. The enzyme has the unique property to recognize the physical state of the polymeric substrate by discrimination between amorphous PHA (good substrate) and denatured, partially crystalline PHA (no substrate). The pentamers of 3HB or 3HV were identified as the main products of enzymatic hydrolysis of native PHB or PHV, respectively. No activity was found with any denatured PHA, oligomers of (R)-3HB with five or less 3HB units, poly(6-hydroxyhexanoate), substrates of lipases such as tributyrin or triolein, substrates for amidases/nitrilases, DNA, RNA, casein, N-alpha-benzoyl-l-arginine-4-nitranilide, or starch. The purified enzyme (M(r) 36,209) was remarkably stable and active at high temperature (60 degrees C), high pH (up to 12.0), low ionic strength (distilled water), and in solvents (e.g. n-propyl alcohol). The depolymerase contained no essential SH groups or essential disulfide bridges and was insensitive to high concentrations of ionic (SDS) and nonionic (Triton and Tween) detergents. Characterization of the cloned structural gene (phaZ7) and the DNA-deduced amino acid sequence revealed no homologies to any PHB depolymerase or any other sequence of data banks except for a short sequence related to the active site serine of serine hydrolases. A classification of the enzyme into a new family (family 9) of carboxyesterases (Arpigny, J. L., and Jaeger, K.-E. (1999) Biochem. J. 343, 177-183) is suggested.

Lipolytic enzymes LipA and LipB from Bacillus subtilis differ in regulation of gene expression, biochemical properties, and three-dimensional structure

Bacillus subtilis secretes the lipolytic enzymes LipA and LipB. We show here that they are differentially expressed depending on the composition of the growth medium: LipA is produced in rich and in minimal medium, whereas LipB is present only in rich medium. A comparison of biochemical characteristics revealed that LipB is thermostable at pH 11 but becomes thermolabile at pH 5. However, construction of a variant carrying the substitution A76G in the conserved lipase pentapeptide reversed these effects. The atomic coordinates from the LipA crystal structure were used to build a three-dimensional structural model of LipB, which revealed that 43 out of 45 residues different from LipA are surface-located allowing to rationalize the differences observed in the substrate preferences of the two enzymes.