Lipase synthesis in hydrocarbon fermentation.

A study was undertaken to establish conditions and relationships for the production of lipases during hydrocarbon fermentation. A culture of Candida lipolytica was isolated by a kerosene enrichment technique from oil-soaked soil and this microbe was used to study the production of lipase on a kerosene-mineral salts medium. The optimum pH, medium, and temperature for lipase synthesis were established and the properties of the isolated enzyme in terms of its activity and lipid specificity were studied.     

Crystal Structure of Proteus mirabilis Lipase,a Novel Lipase from the Proteus/Psychrophilic Subfamily of Lipase Family I.1

Bacterial lipases from family I.1 and I.2 catalyze the hydrolysis of triacylglycerol between 25–45°C and are used extensively as biocatalysts. The lipase from Proteus mirabilis belongs to the Proteus/psychrophilic subfamily of lipase family I.1 and is a promising catalyst for biodiesel production because it can tolerate high amounts of water in the reaction. Here we present the crystal structure of the Proteus mirabilis lipase, a member of the Proteus/psychrophilic subfamily of I.1lipases. The structure of the Proteus mirabilis lipase was solved in the absence and presence of a bound phosphonate inhibitor. Unexpectedly, both the apo and inhibitor bound forms of P. mirabilis lipase were found to be in a closed conformation. The structure reveals a unique oxyanion hole and a wide active site that is solvent accessible even in the closed conformation. A distinct mechanism for Ca²⁺ coordination may explain how these lipases can fold without specific chaperones.     

产脂肪酶菌株筛选及柠檬酸杆菌产酶条件优化

脂肪酶可以催化甘油三酯水解成脂肪酸和甘油,已广泛应用在工业领域,而获得产酶微生物是研究的基础。采用油脂平板法筛选出1株脂肪酶产生菌。经16S rRNA序列分析可知,该菌株属于柠檬酸杆菌(Citrobacter werkman and Gillen)。单因素试验对其进行产酶条件优化,优化后产酶条件（g/L）：淀粉2.0,KH₂PO₄ 1.0,K₂HPO₄·3H₂O 2.2,(NH₄)₂SO₄ 1.0,MgSO₄·7H₂O 0.1,牛肉膏2.0,橄榄油10.0 mL,pH 7.5,接种量1.5%(v/v),37 ℃培养43 h。获得最大酶活为384 U/mL,是优化前的13倍。可以利用该菌制备脂肪酶。     

Lipase from Pseudomonas fragi. II. Properties of the Enzyme

The optimal pH value of a lipase from Pseudomonas fragi was between 7.5 and 8.9, and a high reaction rate was observed at 54 C. Heating the enzyme solution at 63 C for 30 min inactivated only 27.6% of its activity; however, total inactivation was observed at 66 C after 1 hr and at 71 C after 10 min. The lipase was inhibited strongly by Fe⁺⁺⁺ and Fe⁺⁺ ions, and to a lesser extent by Co⁺⁺, Cu⁺⁺, Zn⁺⁺. No inhibition was observed with Ca⁺⁺ or NaF. Ethylenediaminetetraacetate was effective in removing the toxicity of Fe⁺⁺⁺. The activity of the enzyme was inhibited markedly by p-chloromercurobenzoate, but the effects of N-ethylmaleimide and iodoacetate were moderate. The enzyme was able to hydrolyze natural fats, synthetic triglycerides, and alcohol esters. The order of the rate of hydrolysis of some triglycerides under experimental conditions was, from the fastest to the lowest, trilaurin, tricaprin, tricaprylin, tripalmitin, tributyrin, tricaproin, and tristearin. The enzyme was capable of hydrolyzing methyl butyrate, but the rate of hydrolysis was about one-fifth that for triolein and one-thirteenth that for coconut oil. The enzyme lost its activity rapidly when held frozen, at 20 C, and at the extremes in pH. Glutathione, cysteine, and mercaptoethanol did not preserve the activity of the enzyme.     

诱变选育脂肪酶高产菌株及其酶学性质

面包干酵母(Saccharomyces cerevisiae)为出发菌株,对其进行紫外和微波复合诱变,得高产突变菌株DX213,高产突变菌株酶活力为635 U/mL,为出发菌株的1.69倍。菌株富集培养5代,遗传性状稳定。DX213菌株的最优产脂肪酶条件为:培养温度30℃和培养液pH 7.5。酶学性质研究表明:脂肪酶的最适温度40℃、最适pH为7.5、脂肪酶在40℃以下稳定。Fe3+离子对脂肪酶有激活效应,当Fe3+离子浓度为0.03 g/mL时,脂肪酶酶活力高达720 U/mL。     

Lipase from Pseudomonas fragi. I. Purification of the Enzyme

The experimental conditions required to isolate a lipase from Pseudomonas fragi were determined. The organism was grown in a buffered tryptone medium for 4 to 5 days at 20 C. The lipase in the culture supernatant fluid was isolated by fractionation with ammonium sulfate at 60% saturation, followed by acetone precipitation at 30-60% concentration. Further purification was made by using Sephadex G-200 gel-filtration and diethylaminoethyl cellulose chromatography. Electrophoretic analysis of the purified lipolytic fraction showed apparent homogeneity by both cellulose polyacetate and disc electrophoresis. The specific activity of the purified enzyme was about 100 times that of the starting culture filtrate, and the yield was about 1.8% of the original activity.     

一株脂肪酶产生菌的筛选及产酶条件优化研究

通过利用溴甲酚紫显色培养基初筛和酶活测定法复筛得到产脂肪酶的一株细菌HP2,经形态学观察和生理生化测定初步鉴定该菌株为不动杆菌属。并对该菌株的摇床培养产酶条件进行了初步研究,采用正交试验对HP2菌株发酵产脂肪酶的条件进行了优化,得到最佳发酵条件为初始pH为7.7,培养温度为35℃,接种量(V/V)为1.5%,发酵周期为48 h,酶活力达到129.7 U/mL。     

Homologous Expression of the Lipase and ABC Transporter Gene Cluster, tliDEFA, Enhances Lipase Secretion in Pseudomonas spp.

The ABC transporter TliDEF was found to be an efficient secretory apparatus for extracellular lipase TliA in Pseudomonas fluorescens. For the enhanced secretion of the lipase, we tried to coexpress tliA and tliDEF in various Pseudomonas species. Whereas the coexpression of tliA and tliDEF was required for the lipase secretion in P. fragi, the expression of tliA was sufficient for the lipase secretion in P. fluorescens, P. syringae, and P. putida, indicating the existence of compatible ABC transporter in these species. However, P. fluorescens harboring tliDEFA secreted much more lipase than P. fluorescens harboring only tliA, but the tliDEF was functional only at temperatures below 30°C. The recombinant P. fluorescens overexpressing tliDEFA showed the highest secretion level, 217 U/ml · OD (optical density) (28 μg/ml · OD) of lipase in Luria-Bertani medium under microaerated conditions. With the increase of aeration, the lipase production was decreased and the lipase seemed to be degraded as the cells entered the cell death phase. These results demonstrate that P. fluorescens can be used as a host system for the secretory production of the lipase using the ABC transporter, thus producing lipase in over 14% of the total protein.     

根霉菌脂肪酶的生产及酶特性的初步研究

我们在以氢化油为唯一碳源的培养基上培养分离到一株根霉菌,该菌能分泌高温脂肪酶。本文对固态培养条件及产酶工艺条件进行了初步研究。在３６℃培养４２小时,产酶可达１４７ｕｇ＾－１（绝干曲）。该脂肪酶的最佳作用ｐＨ和温度分别为７．２和５８℃。     

Lipase and Esterase Activities of Propionibacterium freudenreichii subsp. freudenreichii

The lipase and esterase activities of eight strains of dairy Propionibacterium freudenreichii subsp. freudenreichii were studied. A lipase activity was detected on whole cells and in the culture supernatant. The highest activity was expressed at 45°C and pH 6.8. An esterase activity was also detected in the culture medium. The electrophoresis of the intracellular fractions of the cells revealed from three to six different esterase activities. Two esterases were common to all the strains. The substrate specificity was dependent on each esterase, but no activity was revealed, in our experimental conditions, on ester substrates with a chain length longer than that of butyrate.     

脂肪酶产生菌分离,鉴定及酶性质的研究

从含油污泥中分离筛选出１７株产脂肪酶菌株,对其中一株进行鉴定,为无花果丝孢酵母（Ｔｒｉｃｈｏｓｐｆｉｇｕｅｒｉａｅ）．研究了该菌的最适产酶条件,并对其部分酶性质进行了研究．     

紫外诱变选育脂肪酶高产菌株及其酶学性质的研究

目的:初步筛选脂肪酶高产菌株.方法:以 1444 粗壮假丝酵母作为出发菌株,对其进行紫外线诱变育种.结果:经紫外诱变的重复处理、摇瓶复筛和遗传稳定性实验,最终得出两株高产酶突变株 Z6 及 Z8,其酶活分别为22.6、25U/ml,酶活力较出发菌株分别提高了 120%和 150%.酶学性质研究表明:Z6、Z8的最适反应温度分别为45、50℃,最适 pH 都为8,在 pH 6～9较稳定.Z6、Z8的热稳定都较好,在50℃下保温 60min 酶基本不失活.结论:经紫外诱变获得的突变株 Z6 及 Z8 有进一步的研究价值.