Synthesis of geraniol esters in a solvent-free system catalysed by Candida antarctica lipase

Summary Candida antarctica lipase was investigated for the synthesis of short chain fatty acid esters of geraniol in a solvent-free system. Maximal activity occurred at 60°C. High yields (about 100%) were obtained with propionate and butyrate, while acetate showed much lower reactivity. The enzyme was used in four consecutive batch reactions with only a 10% loss of activity.     

Functional expression of Candida antarctica lipase B in Eschericha coli

Candida antarctica lipase B (CalB) is an important catalyst in bio-organic synthesis. To optimize its performance, either the reaction medium is changed or the lipase itself is modified. In the latter case, mutants are generated in Eschericha coli and subsequently expressed in fungal hosts for their characterization. Here we present the functional expression of CalB in the periplasm of E. coli. By step-wise deletion of the CalB signal and propeptide we were able to express and purify two different variants of CalB (mature CalB and CalB with its propeptide). A N-terminal FLAG and a C-terminal His tag were used for the purification. For the substrates para-nitrophenol butyrate (p-NPB), para-nitrophenol laurate (p-NPL) and carboxyfluorescein diacetate (CFDA) the specific activity was shown to be similar to CalB expressed in Aspergillus oryzae. The kinetic constants k(M), v(max) and k(cat) were determined using the substrates p-NPB and p-NPL. Almost identical k(cat)/k(M) values (0.423-0.466 min(-1) microM(-1) for p-NPB and 0.068-0.071 min(-1) microM(-1) for p-NPL) were obtained for the CalB variants from E. coli and A. oryzae. The results clearly show that CalB can be functionally expressed in E. coli and that the attachment of tags does not alter the properties of the lipase.     

A novel enantioselective epoxide hydrolase from Agromyces mediolanus ZJB120203: Cloning,characterization and application

A new strain Agromyces mediolanus ZJB120203, capable of enantioselective epoxide hydrolase (EH) activity was isolated employing a newly established colorimetric screening and chiral GC analysis method. The partial nucleotide sequence of an epoxide hydrolase (AmEH) gene from A. mediolanus ZJB120203 was obtained by PCR using degenerate primers designed based on the conserved domains of EHs. Subsequently, an open reading frame containing 1167 bp and encoding 388 amino acids polypeptide were identified. Expression of AmEH was carried out in Escherichia coli and purification was performed by Nickel-affinity chromatography. The purified AmEH had a molecular weight of 43 kDa and showed its optimum pH and temperature at 8.0 and 35 °C, respectively. Moreover, this AmEH showed broad substrates specificity toward epoxides. In this study, it is demonstrated that the AmEH could unusually catalyze the hydrolysis of (R)-ECH to produce enantiopure (S)-ECH. Enantiopure (S)-ECH could be obtained with enantiomeric excess (ee) of >99% and yield of 21.5% from 64 mM (R,S)-ECH. It is indicated that AmEH from A. mediolanus is an attractive biocatalyst for the efficient preparation of optically active ECH.     

黑曲霉（Aspergillus niger）F044脂肪酶新型基因lipB的克隆、表达及酶学性质分析

摘要：【目的】本研究拟克隆新型的黑曲霉（Aspergillus niger）脂肪酶（EC 3.1.1.3）基因,实现其在大肠杆菌（Escherichia coli）的高效表达,并对表达产物进行系统的酶学性质分析,为该脂肪酶的工业化生产及应用奠定基础。【方法】通过PCR和RT-PCR克隆脂肪酶基因,并将其开放式阅读框（ORF）克隆入融合表达载体pET28a;表达产物经Ni-agarose纯化后对LipB进行酶学性质分析,并通过圆二色谱进行结构分析。【结果】成功地从A. niger F044中克隆了一个新型的脂肪酶基因lipB,获得了该基因的全基因组序列和cDNA序列（GenBank: FJ536287、FJ536288）,并实现了其在E. coli中的高效表达。LipB分子量约为43.0 kDa,最适底物为pNPC（C8）,酶学动力学常数Km=5.98 mmol/L,最适反应温度为50℃,最适pH为6.0;该酶能在40℃条件下保持稳定,在60℃条件下处理1 h后残余酶活仅为18.8%;该酶对Ca2+敏感,当脂肪酶经2 mmol/L Ca2+处理1 h后,酶活提高了2.6倍。圆二色谱分析表明该酶在Ca2+处理前后具有明显的结构变化。【结论】新型A. niger脂肪酶lipB基因的克隆不仅积累了脂肪酶基因资源,而且为高效基因工程菌的构建及规模化应用奠定基础;对LipB的酶学性质分析表明该酶在食品和油酯化工等领域具有广阔的应用前景。     

Synthesis of novel d-glucuronic acid fatty esters using Candida antarctica lipase in tert-butanol

Glucuronic acid n-alkyl esters, a novel class of promising biosurfactants and their corresponding glucose esters with the same side-chain length, were synthesized by direct esterification in a non-aqueous phase (tert-butanol) using an immobilized lipase.     

产碱假单胞菌脂肪酶的克隆表达及酶学性质研究

【目的】克隆产碱假单胞菌的脂肪酶基因,实现其在大肠杆菌中异源表达并进行酶学性质研究。【方法】通过基因文库构建和PCR,获得脂肪酶基因,并以pET30a(+)为表达载体、E.coli BL21(DE3)为宿主菌,在大肠杆菌中进行异源表达,表达产物经HisTrapTM亲和层析柱纯化后进行酶学性质研究。【结果】从产碱假单胞菌中克隆得到一个脂肪酶基因,大小为1 575 bp(GenBank登录号为JN674069)。该酶分子量为55 kD,最适底物为p-NPO,最适反应温度和pH分别为35°C、pH 9.0。重组酶经1 mmol/L的Cu2+处理30 min可使酶活提高至156%。在最适反应条件下重组酶的比活力为275 U/mg,Km和Vmax分别为80μmol/L和290 mmol/(min.g protein)。【结论】产碱假单胞菌脂肪酶基因的克隆与表达不仅积累了脂肪酶基因的资源,并为其在手性拆分中的应用奠定基础。     

Cloning and characterization of the xyl1 gene, encoding an NADH-preferring xylose reductase from Candida parapsilosis, and its functional expression in Candida tropicalis

Xylose reductase (XR) is a key enzyme in D-xylose metabolism, catalyzing the reduction of D-xylose to xylitol. An NADH-preferring XR was purified to homogeneity from Candida parapsilosis KFCC-10875, and the xyl1 gene encoding a 324-amino-acid polypeptide with a molecular mass of 36,629 Da was subsequently isolated using internal amino acid sequences and 5' and 3' rapid amplification of cDNA ends. The C. parapsilosis XR showed high catalytic efficiency (kcat/Km = 1.46 s(-1) mM(-1)) for D-xylose and showed unusual coenzyme specificity, with greater catalytic efficiency with NADH (kcat/Km = 1.39 x 10(4) s(-1) mM(-1)) than with NADPH (kcat/Km = 1.27 x 10(2) s(-1) mM(-1)), unlike all other aldose reductases characterized. Studies of initial velocity and product inhibition suggest that the reaction proceeds via a sequentially ordered Bi Bi mechanism, which is typical of XRs. Candida tropicalis KFCC-10960 has been reported to have the highest xylitol production yield and rate. It has been suggested, however, that NADPH-dependent XRs, including the XR of C. tropicalis, are limited by the coenzyme availability and thus limit the production of xylitol. The C. parapsilosis xyl1 gene was placed under the control of an alcohol dehydrogenase promoter and integrated into the genome of C. tropicalis. The resulting recombinant yeast, C. tropicalis BN-1, showed higher yield and productivity (by 5 and 25%, respectively) than the wild strain and lower production of by-products, thus facilitating the purification process. The XRs partially purified from C. tropicalis BN-1 exhibited dual coenzyme specificity for both NADH and NADPH, indicating the functional expression of the C. parapsilosis xyl1 gene in C. tropicalis BN-1. This is the first report of the cloning of an xyl1 gene encoding an NADH-preferring XR and its functional expression in C. tropicalis, a yeast currently used for industrial production of xylitol.     

伯克霍尔德氏菌ZYB002脂肪酶lipC24基因的克隆、表达及其酶学性质

【目的】克隆伯克霍尔德菌ZYB002菌株中的新型脂肪酶lip C24基因,测定其基本酶学性质,为后续深入研究该基因在菌株中的生理功能奠定基础。【方法】根据洋葱伯克霍尔德菌JK321菌株的全基因组DNA信息,直接设计引物从伯克霍尔德菌ZYB002菌株基因组中扩增出lip C24基因,并对之进行原核表达、重组蛋白的纯化及酶学性质分析。【结果】lip C24基因全长1317 bp,编码438个氨基酸残基;多肽链中具有保守五肽-G-X1-S-X2-G-序列;重组蛋白Lip C24的分子量为45 k Da;能有效水解各种对硝基苯酯,对中链脂肪酸的对硝基苯酯表现出偏爱性;其催化水解反应的最适温度为40℃,最适p H7.5;40℃下的半衰期为15.72 min,在p H 7.0-8.0的条件下,具有较好的稳定性。【结论】lip C24的编码产物为一个45 k Da蛋白,具有明显的脂肪酶活性,为中温中性脂肪酶。     

Display of Candida antarctica lipase B on Pichia pastoris and its application to flavor ester synthesis

Two alternative cell-surface display systems were developed in Pichia pastoris using the α-agglutinin and Flo1p (FS) anchor systems, respectively. Both the anchor cell wall proteins were obtained originally from Saccharomyces cerevisiae. Candida antarctica lipase B (CALB) was displayed functionally on the cell surface of P. pastoris using the anchor proteins α-agglutinin and FS. The activity of CALB displayed on P. pastoris was tenfold higher than that of S. cerevisiae. The hydrolytic and synthetic activities of CALB fused with α-agglutinin and FS anchored on P. pastoris were investigated. The hydrolytic activities of both lipases displayed on yeast cells surface were more than 200 U/g dry cell after 120 h of culture (200 and 270 U/g dry cell, respectively). However, the synthetic activity of CALB fused with α-agglutinin on P. pastoris was threefold higher than that of the FS fusion protein when applied to the synthesis of ethyl caproate. Similarly, the CALB displayed on P. pastoris using α-agglutinin had a higher catalytic efficiency with respect to the synthesis of other short-chain flavor esters than that displayed using the FS anchor. Interestingly, for some short-chain esters, the synthetic activity of displaying CALB fused with α-agglutinin on P. pastoris was even higher than that of the commercial CALB Novozyme 435.     

Cloning, expression, and biochemical characterization of a thermostable lipase from Geobacillus stearothermophilus JC

A thermophilic lipase gene of Geobacillus stearothermophilus JC was cloned and expressed in a pET 28-a (+) expression vector. The biochemical properties of the recombinant enzyme and its enantioselective hydrolysis of (RS)-1-phenylethyl acetate were studied. Removal of the signal peptide greatly increased the enzyme’s expression level by 4.3 times. The purified JC lipase had an optimum temperature of 55°C and optimum pH of 9. Furthermore, comparisons with other enzymes suggest that a few amino acid alterations may significantly change the thermostability of this enzyme. The hydrolysis of (RS)-1-phenylethyl acetate with the crude recombinant JC lipase at 25°C produce (R)-1-phenylethanol in 97.7% e.e. and 46.1% yield after 24 h, corresponding to an E value of 237.     

Cloning, expression and characterization of a cDNA encoding a lipase from Rhizopus delemar.

A lambda gt11 cDNA library was constructed in Escherichia coli using poly(A)-selected mRNA from the fungus, Rhizopus (Rp.) delemar. Lipase-producing members of the library were identified by means of a phenotypic score wherein the release of fatty acids by lipase causes a characteristic color change in the growth medium. One such isolate contained a 1287-bp insert (LIP cDNA) which hybridizes to 1.25- to 1.35-kb mRNA species from Rp. delemar. The lipase produced in E. coli containing the LIP cDNA exhibits the same substrate selectivity as the authentic fungal enzyme, hydrolyzing ester bonds at the stereospecific numbering (sn) sn-1 and sn-3, but not the sn-2, positions of triglycerides. The complete nucleotide sequence of the LIP cDNA was determined. By reference to the N-terminal sequence of authentic Rp. delemar lipase, the lipase-encoding region was identified within this fragment. The LIP cDNA encodes a putative preprolipase consisting of a 26-amino-acid(aa) signal sequence, a 97-aa propeptide, and a 269-aa mature enzyme. The predicted mature lipase has the same molecular weight and aa composition as that of Rp. delemar, is highly homologous to that produced by the fungus Rhizomucor miehei, and contains the consensus pentapeptide (Gly-Xaa-Ser-Yaa-Gly) which is conserved among lipolytic enzymes. It is concluded that the LIP cDNA is an essentially full-length analogue of the lipase-encoding gene of Rp. delemar. The lipase encoded by the LIP cDNA occupies a cytoplasmic location when synthesized in E. coli. Unprocessed forms of the lipase accumulate in E. coli.     

New application of depth filters for the immobilization of Candida antarctica lipase B

Applied Microbiology and Biotechnology - The objective of this study was to use for the first time depth filters, which are usually intended for clarification of cell culture broth, as a direct...     

Improving the expression yield of Candida antarctica lipase B in Escherichia coli by mutagenesis

Increasing the expression yield of active Candida antarctica lipase B (CAL-B) in Escherichia coli was achieved by using a codon-optimized synthetic gene and by mutagenesis to introduce hydrophilic residues on the surface of CAL-B. Five residues (four leucines and one isoleucine) on the surface of CAL-B were selected and changed with aspartate after codon optimization. While the codon-optimized synthetic gene of CAL-B did not increase the expression yield, the mutation increased the activity of the enzyme three-fold (3.3 mg/l of culture) compared to the wild type. The mutant enzyme had similar hydrolytic activity toward hydrolysis of p-nitrophenyl acetate or p-nitrophenyl butyrate and enantioselectivity toward hydrolysis of (R, S)-1-phenylethyl acetate compared to the wild-type enzyme. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chain length selectivity during the polycondensation of siloxane-containing esters and alcohols by immobilized Candida antarctica lipase B

We have examined the chain length selectivity for a series of acyl donors by lipase B from Candida antarctica (CalB). CalB accepted aliphatic diesters of C4, C6 and C12 chain lengths equally. The introduction of a carbon–carbon double bond into the C4 esters dramatically lowered the rate constant associated with polymerization highlighting the role of geometry in catalysis; fumarate esters were polymerized at a reduced rate compared to the succinate esters, while the maleate esters were not polymerized above 5% over the course of 24 h. A disiloxane-containing diester impeded catalysis by CalB. We examined a series of vinyl siloxane esters and alcohols, and learned that the Z arrangement around the double bond stalled esterification by CalB completely. The distance between the ester carbonyl and the dimethylsiloxy group was shown to be an important factor in mediating catalysis. The rate constants were similar when the methylene spacer was 3, 4, or 5 units in length; beyond 6 methylene units, the rate constants increased. This has been tentatively attributed to the local reduction on the steric bulk when the larger siloxane moiety lies outside of the active site of the enzyme.     

Synthesis of fatty acid ethyl esters with conventional and microwave heating systems using the free lipase B from Candida antarctica

Free Candida antarctica lipase B (Lipozyme, CALB L^®) was used to produce fatty acid ethyl esters (FAEE) from refined soybean oil in solvent-free media using the conventional (CHS) and microwave (MHS) heating systems. Statistical analyses (95% confidence level) for both reaction products, FAEE and free fatty acids (FFA), were performed. An increase in ethanol:oil molar ratio decreased the catalytic performance of CALB L (p?<?.05). The best conditions using the microwave radiation were a molar ratio of ethanol:oil of 3:1, a water content of 20.3?wt.% and an enzyme loading of 3?wt.% and this resulted in a total ester content of 64.7% in 15?min, while the same condition using the conventional heating gave only 21.4%. Moreover, the reaction equilibrium was reached 16 times faster with microwave than with conventional heating. High ethanol:oil molar ratios had a negative effect on FAEE synthesis with both CHS and MHS, probably due to the partial inactivation of the enzymes. MHS improved the reaction performance of CALB L, but other process parameters will have to be optimized to enhance the resulting FAEE yields. The recovery and reuse of CALB L using a MHS was demonstrated. Hence, the use of microwave radiation under the conditions applied in this study was not detrimental to the catalytic performance of CALB L for at least one reuse.     

Cloning, expression, and characterization of a cold-adapted lipase gene from an antarctic deep-sea psychrotrophic bacterium, Psychrobacter sp 7195

A psychrotrophic strain 7195 showing extracellular lipolytic activity towards tributyrin was isolated from deep-sea sediment of Prydz Bay and identified as a Psychrobacter species. By screening a genomic DNA library of Psychrobacter sp. 7195, an open reading frame of 954 bp coding for a lipase gene, lipA1, was identified, cloned, and sequenced. The deduced LipA1 consisted of 317 amino acids with a molecular mass of 35,210 kDa. It had one consensus motif, G-N-S-M-G (GXSXG), containing the putative active-site serine, which was conserved in other cold-adapted lipolytic enzymes. The recombinant LipA1 was purified by column chromatography with DEAE Sepharose CL-4B, and Sephadex G-75, and preparative polyacrylamide gel electrophoresis, in sequence. The purified enzyme showed highest activity at 30 degrees C, and was unstable at temperatures higher than 30 degrees C, indicating that it was a typical cold-adapted enzyme. The optimal pH for activity was 9.0, and the enzyme was stable between pH 7.0-10.0 after 24 h incubation at 4 degrees C. The addition of Ca2+ and Mg2+ enhanced the enzyme activity of LipA1, whereas the Cd2, Zn2+, Co2+, Fe3+, Hg2+, Fe2+, Rb2+, and EDTA strongly inhibited the activity. The LipA1 was activated by various detergents, such as Triton X-100, Tween 80, Tween 40, Span 60, Span 40, CHAPS, and SDS, and showed better resistance towards them. Substrate specificity analysis showed that there was a preference for trimyristin and p-nitrophenyl myristate (C14 acyl groups).     

Cloning and characterization of a gene from Pasteurella haemolytica A1 involved in lipopolysaccharide biosynthesis

Abstract A Pasteurella haemolytica A1 gene involved in the biosynthesis of a moiety on the core of the lipopolysaccharide molecule has been cloned and characterized. Escherichia coli clones which carry this gene showed an alteration of its lipopolysaccharide migration profile on tricine SDS-PAGE and exhibited resistance to the core-specific phage U3. In addition, lipopolysaccharide extracted from the E. coli clones was recognized by an anti-corespecific antiserum, but not by antiserum specific for the O antigen of P. haemolytica A1 lipopolysaccharide. Nucleotide sequence analysis of the cloned DNA identified an open reading frame ( lpsA ) coding for a protein of 263 amino acids which showed significant homology with a Haemophilus influenzae type b lipooligosaccharide biosynthesis gene. PCR amplification of genomic DNA, using primers based on the P. haemolytica A1 lpsA sequence, yielded products from only the A biotypes of P. haemolytica .     

Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68-90% and of 9.5×10^-2-72×10^-2 mmol l^-1 h^-1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^-2 mmol l^-1 h^-1), with these acids the conversion yields and initial rates were lower and in the range of 10-45% and of 0.7×10^-2 to 12.1×10^-2 mmol l^-1 h^-1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^-2 mmol l^-1 h^-1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68–90% and of 9.5×10^?2–72×10^?2 mmol l^?1 h^?1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^?2 mmol l^?1 h^?1), with these acids the conversion yields and initial rates were lower and in the range of 10–45% and of 0.7×10^?2 to 12.1×10^?2 mmol l^?1 h^?1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^?2 mmol l^?1 h^?1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

南极假丝酵母脂肪酶A的表面展示及酶学性质研究

采用a凝集素作为载体蛋白,首次将南极假丝酵母脂肪酶A展示在酿酒酵母细胞表面,通过MD平板筛选获得表面展示型的CALA酵母工程菌株。免疫荧光检测显示CALA被成功展示在酵母细胞壁表面,重组子经诱导后能在三丁酸甘油酯板上形成透明圈,说明展示的CALA具有活性。重组酵母在液体培养基培养72 h,活性达到最高,为80.4 U/g干细胞。酿酒酵母展示的CALA最适温度及pH值为70°C和pH 8.0。经50°C保温2 h,仍含有60%水解酶活力。展示的CALA在pH 7.0和pH 8.0溶液中比较稳定。经DMSO处理2 h,展示的CALA仍保持70%的活性。以上结果表明酵母展示的CALA可作为一种有潜质商业用途的全细胞催化剂。