产脂肪酶菌株的筛选、鉴定及发酵培养基优化

该研究从自然界筛选出一株脂肪酶产生菌株,鉴定其种属并对其发酵培养条件进行研究。采集富油水样,利用罗丹明B培养基进行初筛,结合形态观察、生理生化试验和16S rDNA序列分析进行菌种鉴定,建立系统发育树。结果表明,筛选出一株产脂肪酶的细菌U5,经鉴定为枯草芽孢杆菌（Bacillus subtilis）。通过单因素试验和响应面试验设计对发酵培养基中三丁酸甘油酯、葡萄糖、尿素添加量进行发酵优化。结果表明,最佳的发酵培养基组分为：三丁酸甘油酯2.0%（V/V）,葡萄糖9 g/L,尿素8 g/L。在此优化条件下,粗脂肪酶酶活为4.3 U/mL,比优化前的酶活提高了16.22%。     

除膻菌株分离鉴定及其对膻味脂肪酸降解能力的研究

为了分离筛选出能作用于膻味脂肪酸的微生物,从火腿和土壤中分离出11株菌,这11株菌均能对羊油脂进行水解。通过形态学、生理生化特征鉴定及16S rRNA基因序列和ITS基因序列分子生物学鉴定,确定为6株细菌和5株霉菌。分别将11株菌接种到加入4-甲基辛酸和4-乙基辛酸的液体培养基进行发酵,发现4-甲基辛酸的减少量达到30%～70%,4-乙基辛酸减少量达到10%～70%。这11株菌对膻味脂肪酸具有不同程度的降解作用,该研究结果可为微生物羊肉除膻提供理论基础。     

微波辐照稳定化处理小麦籽粒及其品质变化的研究

以河北优质白麦为原料,研究了微波辐照功率、辐照时间、润麦水分、润麦时间等参数对全麦粉脂肪酶活动度、湿面筋含量的影响,考察了适度微波辐照对面粉粉质特性和糊化特性的影响。结果表明微波辐照能够显著降低(p<0.05)全麦粉的脂肪酶活动度和湿面筋含量。适度的微波辐照(微波功率420 W,辐照时间90 s,润麦水分14%,润麦时间25 min)能够大幅降低全麦粉脂肪酶活动度,同时对其湿面筋含量损伤较小,并提高面粉粉质稳定时间,降低弱化度,增加了面糊峰值粘度和回生值,改善了面筋强度和面糊稳定性,延缓了全麦粉脂肪酸值的升高。     

用蛋白质工程技术提取和修饰南极假丝酵母脂肪酶B

从南极假丝酵母中提取的脂肪酶B,具有较高的对应异构体选择性,广泛应用在培养基中,作为不对称有机化学的生物催化剂。近年来,一系列组合蛋白质工程研究和扩展了南极假丝酵母脂肪酶的催化和物理特性。这些工程不但生产出了指定的催化剂,还有助于阐明酶的结构一作用关系,并且有助于说明这些酶的对应异构体选择性。进一步的研究将在工程与酶的关系方面展开讨论。     

无溶剂体系两步酶法合成阿魏酰基结构脂

通过对不同途径合成阿魏酰基结构脂的研究,确立了减压旋转生物反应器两步酶法催化合成阿魏酰基结构脂的方法.采用减压旋转生物反应器,通过阿魏酸乙酯与甘油酯交换制备1-阿魏酰甘油酯,1-阿魏酰甘油酯再与油酸酯化,两步合成阿魏酰基结构脂,可显著提高反应速率和产物产率,两步反应平衡时,阿魏酸乙酯的转化率和阿魏酰基结构脂的产率分别达到100%和96%.     

Synthesis of magnetically modified palygorskite composite for immobilization of Candida sp. 99–125 lipase via adsorption

Magnetically modified palygorskite composites were synthesized withγ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac-tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99–125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg·g-1 support and enzyme activity of 2631.6 U·(g support)-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusability compared with free lipase.     

An extra-cellular alkaline metallolipase from Bacillus licheniformisMTCC 6824: Purification and biochemical characterization

An extra-cellular lipase produced by Bacillus licheniformis MTCC 6824 was purified to homogeneity by ammonium sulphate fractionation, ethanol/ether precipitation, dialysis, followed by anion-exchange chromatography on Amberlite IRA 410 (Cl⁻ form) and gel exclusion chromatography on Sephadex G 100 using Tris–HCl buffer (pH 8.0). The crude lipase extract had an activity of 41.7 LU/ml of culture medium when the bacterium was cultured for 48 h at 37 °C and pH 8.0 with nutrient broth supplemented with sardine oil as carbon source. The enzyme was purified 208-fold with 8.36% recovery and a specific activity of 520 LU/mg after gel exclusion chromatography. The pure enzyme is a monomeric protein and has an apparent molecular mass of 74.8 kDa. The lipase had a V_max and K_m of 0.64 mM/mg/min and 29 mM, respectively, with 4-nitro phenylpalmitate as a substrate, as calculated from the Lineweaver–Burk plot. The lipase exhibited optimum activity at 45 °C and pH 8.0, respectively. The enzyme had half-lives (T_1/2) of 82 min at 45 °C, and 48 min at 55 °C. The catalytic activity was enhanced by Ca²⁺ (18%) and Mg²⁺ (12%) at 30 mM. The lipase was inhibited by Co²⁺, Cu²⁺, Zn²⁺, Fe² even at low concentration (10 mM). EDTA, at 70 mM concentration, significantly inhibited the activity of lipase. Phenyl methyl sulfonyl fluoride (PMSF, 70 mM) completely inactivated the original lipase. A combination of Ca²⁺ and sorbitol induced a synergistic effect on the activity of lipase with a significantly high residual activity (100%), even after 45 min, as compared to 91.5% when incubated with Ca²⁺ alone. The lipase was found to be hydrolytically resistant toward triacylglycerols with more double bonds.     

麦胚稳定化处理方法的比较研究

研究了热风干燥、微波干燥、常压蒸气和高压蒸气处理麦胚对其加速储藏期间脂肪酶的钝化效果.在38℃下进行35 d的加速储藏试验,并跟踪检测,以酸值和过氧化值作为钝化脂肪酶的表征参数,对不同方法处理原料的优化结果(酸值和过氧化值)进行了比较.结果表明,脂肪酶的钝化效果:湿热蒸气处理的效果优于微波干燥、明显好于热风干燥处理,酸值和过氧化值均上升缓慢,常压蒸气处理20 min即可达到预定效果.对常压蒸气处理的麦胚原料进行超临界萃取并对得到的麦胚油进行了GC分析,与对照组原料相比,脂肪酸组成与含量均无明显变化.水蒸气是良好的热载体和传热介质,蒸气处理能够有效钝化脂肪酶的活力,提高小麦胚的贮藏稳定性.     

潜力工业催化剂——白地霉脂肪酶

白地霉脂肪酶因具有独特的底物特异性,在油脂改性等领域有着广泛应用。文中概述了白地霉脂肪酶的发酵生产、分离纯化、克隆与表达、底物特异性分子机理及应用等,并展望其未来发展方向,为该工业催化剂的研发与广泛应用提供参考。