脂肪酶及其在饲料工业中的应用研究进展

脂肪酶是一种重要的工业用酶,在食品、化工、纸浆、饲料工业等领域广泛应用,脂肪酶主要来源是微生物脂肪酶.对脂肪酶的来源、性质、生产、检测及在饲料工业中的应用研究进行了概述.     

脂肪酶催化制备丁酸乙酯的研究

利用脂肪酶BSL2作为催化剂,在有机介质中催化合成丁酸乙酯.考察了反应温度、底物浓度、底物摩尔比、反应介质和初始水活度等反应条件对酶促合成丁酸乙酯的影响.试验结果表明:以正己烷为溶剂,初始水活度为0.33,加酶量为100 mg,丁酸浓度为40 mM,底物摩尔比(丁酸/乙醇)为1∶1.5,在40℃条件下振荡反应30 h,合成丁酸乙酯的的转化率可达到94.8%.     

电场对脂肪酶紫外光谱的影响及时效性研究

目的为静电宏观生物效应作用机理提供一定的理论依据。方法用不同电场强度处理脂肪酶5 min,处理后分别在第1 d和第10 d测定电场对脂肪酶紫外光谱的影响。结果脂肪酶紫外光谱发生了明显的变化,说明电场可以改变酶的构象。结论电场强度为1.0,2.0,4.0和6.0 kV/cm时,第1 d的紫外光谱的变化幅度强于第10 d的变化幅度;电场强度为3.0和5.0 kV/cm时,第1 d的变化幅度弱于第10 d的变化幅度。     

杜邦嗜热菌脂肪酶在黑曲霉中的异源表达

该文将杜邦嗜热菌脂肪酶TDL2在黑曲霉系统中异源表达,并考察TDL2自带信号肽和pCAMBIA质粒信号肽对脂肪酶TDL2表达的影响.利用PCR和无缝克隆技术,将脂肪酶TDL2的编码序列与质粒pCAMBIA0380线性片段拼接,分别构建利用β-葡萄糖苷酶bgl2的信号肽的重组质粒pCAMBIA-TDL2-1和利用TDL2信号肽序列的重组质粒pCAMBIA-TDL2-2.用根瘤农杆菌介导转化宿主细胞A. niger CICC 2213构建组成型黑曲霉工程菌A. niger/pCAMBIA-TDL2-1和A. niger/pCAMBIA-TDL2-2,在发酵120 h后其发酵单位分别达到18.5 U·mL^-1和38.3 U·mL^-1,实现了脂肪酶TDL2在黑曲霉中的异源表达.SDS-PAGE分析和活力测定结果表明:利用脂肪酶TDL2信号肽的工程菌A. niger/pCAMBIA-TDL2-2比利用bgl2信号肽的工程菌A. niger/pCAMBIA-TDL2-1的表达量更大、发酵单位更高.     

超声波辅助脂肪酶催化拆分丁酸环氧丙酯

利用超声波辅助脂肪酶催化拆分丁酸环氧丙酯,考察了超声发生装置、超声处理方法、超声功率及超声温度等反应条件对酶促拆分反应的影响,筛选得到最适反应条件.结果表明,在最适反应条件下,超声作用可以使酶活提高近4.3倍,立体选择性提高5倍.     

包衣酶在油/水两相体系中催化水解橄榄油反应

用合成的谷氨酸十二烷基酯核糖醇对来源于Candidarugosa的脂肪酶包衣后在油/水两相体系中水解橄榄油为反应模型.确定了最佳水油比范围为1～3,最适pH值为7.0左右,温度为30℃,油相有机溶剂为异辛烷.包衣酶的最大活性达到48.8mmol·min-1·g-1蛋白质,是天然酶活性的1.8倍.对底物选择性研究表明:包衣酶和天然酶的最适底物均为橄榄油,酰基链越长,酶活越高.包衣酶的米氏常数只有天然酶的一半,最大反应速度是天然酶的1.4倍.     

Degradation of a fullerene end-capped polycaprolactone by lipase AK

Using titrimetric method, enzymatic behavior of lipase AK against fullerene end-capped polycaprolactone (C₆₀-PCL) was studied for the first time, compared with polycaprolactone (PCL). The results showed that degradation of both C₆₀-PCL and PCL by lipase followed Mechaelis-Menten equation, with the degradation parameters of PCL and C₆₀-PCL were 0.75 mg mL^–1 and 0.16 mg mL^–1 for Km, and 0.90 mL h^–1 and 0.43 mL h^–1 for Vmax, respectively. C₆₀-PCL had a slower degradation rate than PCL under the same conditions. These data indicated that the introduction of fullerene enabled PCL hard to be degraded by lipase.     

脂肪酶粉催化酯化合成三羟甲基丙烷酯

以辛酸、癸酸和三羟甲基丙烷作为反应底物，利用 Candida sp. 99-125脂肪酶粉催化反应，研究了反应条件对酶法合成三羟甲基丙烷三辛癸酸酯的影响，并在实验中找到一种可以提高酶粉稳定性的添加剂β-环糊精。结果表明，加入0.01 mol三羟甲基丙烷(TMP) (1.34g)，n_{三羟甲基丙烷}/n _{(癸酸+辛酸)}=1∶4，其中n_癸酸∶n_辛酸=1∶1，添加水的质量分数为0.05%(以底物总质量为基准)、脂肪酶粉的质量分数为12%(以底物总质量为基准)、β-环糊精的质量为酶粉质量的1.5倍，40 ℃下在恒温摇床中，振荡反应130 h，转速130r/min。在此条件下，反应产物三羟甲基丙烷三辛癸酸酯(三羟基酯)的质量分数可达到80% 左右，酸与酯分离后收率可达96%；连续使用6批添加了 β-环糊精的脂肪酶粉，三羟基酯的质量分数可保持在60%以上，与固定化酶的使用寿命相当。     

Virtual substrates screening model of triacylglycerol lipase from <Emphasis Type="Italic">Bacillus thermocatenulanatus</Emphasis>

A reliable 3-D structure of Triacylglycerol lipase from Bacillus thermocatenulanatus was constructed by homology modeling. Under molecular dynamics simulation, it was refined and checked. The model was further used as a receptor to search binding sites and carry out flexible docking with a range of substrates, whose enzyme activities were already measured. By inputting a series of docking results, virtual substrates screening models were established and assessed. Monadic nonlinear solution demanded less data but was weak in fitting enzyme activity data with little difference; its mean absolute percentage error (MAPE) of regression was 0.67 and mean square error (MSE) was 1.73 U/mg. Both quadratic stepwise regression and BP neural network were good in regression and prediction; however, more data were required. In the cross-validation of 12 groups, overall MAPE of regression and prediction for the former were 0.18 and 0.49, while the latter was 0.55 and 0.36. MSE values for these two methods were 0.95 and 1.20 U/mg, respectively. Therefore, monadic nonlinear regression model can be used as a preliminary screening one; quadratic stepwise regression and BP neural network approach can be applied to precise screening.     

Enzymatic Modification of Poly （ethylene terephthalate） Fiber with Lipase from Aspergillus oryzae

Lipase preparation from Aspergillus oryzae could act on ester bonds on the surface of poly （ethylene terephthalate） fibers and a possible hydrolytic product mono （2-hydroxyethyl） terephthalate was released. After the iipase modification, there were more carboxyi groups on the treated poly （ethylene terephthalate） fabric surface that resulted in binding with more cationic dyes. Increased hydrophilicity and antistatic ability of poly （ethylene terephthalate） samples were found based on moisture regain, water contact angle and static half decay time.