固定化脂肪酶Lipase G 50催化合成甘油二酯的研究

以D380、CAT600、AB-8三种大孔树脂为载体,采用物理吸附法,对偏甘油酯脂肪酶LipaseG50进行了固定化,并利用其催化脂肪酸和甘油酯化合成甘油二酯。结果表明,采用D380固定的脂肪酶酶活最高,用此固定化酶催化反应的最佳条件为:甘油和脂肪酸的摩尔比5∶1,固定化酶酶加量为底物总质量的7.5%,反应温度35℃,在此条件下经过96h的反应,酯化率为76.39%,甘油二酯的含量为43.89%,没有甘油三酯生成。固定化酶重复使用5个批次后酯化率可达65.76%,甘油二酯的含量达到38.45%,具有良好的重复使用稳定性。      

固定化脂肪酶Lipase G 50催化合成甘油二酯的研究

以D380、CAT600、AB-8三种大孔树脂为载体,采用物理吸附法,对偏甘油酯脂肪酶LipaseG50进行了固定化,并利用其催化脂肪酸和甘油酯化合成甘油二酯。结果表明,采用D380固定的脂肪酶酶活最高,用此固定化酶催化反应的最佳条件为:甘油和脂肪酸的摩尔比5∶1,固定化酶酶加量为底物总质量的7.5%,反应温度35℃,在此条件下经过96h的反应,酯化率为76.39%,甘油二酯的含量为43.89%,没有甘油三酯生成。固定化酶重复使用5个批次后酯化率可达65.76%,甘油二酯的含量达到38.45%,具有良好的重复使用稳定性。     

培养条件对黑曲霉脂肪酶选择性合成1,3甘油二酯的影响

从前期筛菌工作中得到的一株能高选择性合成1,3-甘油二酯（1,3-DAG）的产胞内脂肪酶的黑曲霉GZUF36菌株出发,分别研究了培养时间、温度、接种量、装液量和转速对该菌摇瓶发酵的影响,得出合适的培养条件为培养时间72 h,接种量3%,装液量40 mL/250 mL,培养温度28 ℃,转速180 r/min,在此条件下1,3-DAG的得率和选择性分别为23.87%和82.96%。同时也比较了摇瓶发酵和5 L发酵罐发酵的异同,相比于摇瓶发酵,5 L发酵罐发酵的1,3-DAG的得率有所提高,但是发酵罐发酵的时间有所延长。     

无溶剂体系合成1,3-甘油二酯用脂肪酶的筛选及其酯化性质

对不同来源的脂肪酶进行了系统的筛选,并根据位置专一性的差别将脂肪酶分为1,3 特异的、1,3 选择性和非选择性的3类.采用LipozymeRMIM在无溶剂系统中催化甘油、脂肪酸合成1,3 sn 甘油二酯.研究表明脂肪酸、底物醇种类、温度、水分活度对LipozymeRMIM的活力有明显的影响.     

脂肪酶Novozym 435催化合成羟基酪醇油酸酯

羟基酪醇是一种标志性多酚,其油溶性差且容易降解,将羟基酪醇修饰为油酸酯是提高其油溶性的有效途径。对羟基酪醇油酸酯的酶法合成进行了研究,考察了脂肪酶种类、酶添加量、醇酸摩尔比、溶剂(2-甲基-2-丁醇)用量、反应时间对合成反应的影响,并利用Box-Behnken中心组合的响应面设计优化了羟基酪醇油酸酯的合成反应条件。另外,采用质谱和核磁分析对产物进行了表征。结果表明：羟基酪醇油酸酯合成的最佳工艺条件为羟基酪醇500 mg、油酸2.474 g(醇酸摩尔比1∶2.7)、脂肪酶Novozym 435添加量2.2%(以整个反应体系的质量为基准)、溶剂用量2.6 mL、反应温度37℃和反应时间7 h,在此条件下羟基酪醇转化率高达89.6%;质谱和核磁分析证明成功合成了羟基酪醇油酸酯。脂肪酶催化合成羟基酪醇油酸酯的技术突破,可为延伸油橄榄产业链及副产物高值利用提供有力支撑。     

水活度对牛肉中氧化品质的影响

用含15%脂肪的牛肉为材料,通过添加甘油(0%、20%、40%、60%)制备水活度范围为0.84～0.98的香肠,分别在25℃和49℃储存0、4、8周时测定不同水活度香肠中脂质氧化、美拉德非酶促褐变、蛋白质氧化等氧化品质的变化。结果表明,水活度从0.98降至0.84时对脂质氧化、蛋白质氧化及美拉德非酶促褐变三个氧化品质均无显著影响,但该三个指标均受到加速贮藏(49℃)时间和温度的显著影响。因此,中等水活度牛肉制品在加工和贮藏中除尽量降低水活度以抑制微生物生长的前提下,应严格控制贮藏温度和时间从而延长货架期。     

无溶剂体系脂肪酶催化合成1,3-丙二醇单酯

在无溶剂体系中,用脂肪酶Novozyme 435催化1,3-丙二醇和油酸合成1,3-丙二醇单酯,同时确立酯化产物及油酸含量的HPLC-RID检测方法。以1,3-丙二醇单酯最大生成量为目的,初步确定反应最优条件为:1,3-丙二醇和油酸摩尔比6∶1,反应温度60℃,摇床转速180 r/min,加酶量1%(以1,3-丙二醇和油酸的总质量为基准),反应时间8 h。该条件下产物中的1,3-丙二醇单酯含量达到48.21%。     

非水相中脂肪酶催化合成乙酸正己酯

研究了用海藻酸钠固定化的脂肪酶在有机溶剂中催化乙酸与正己醇之间的酯化反应。探讨了溶剂、醇酸摩尔比、温度、底物浓度等多种因素对脂肪酶催化乙酸正己酯合成反应的影响规律。研究结果显示,在优化的条件下,即溶剂为正庚烷、醇酸摩尔比为1∶1、底物浓度为0.15mol/L、温度为70℃、pH为7.5、酶湿度为8.9%、吸水剂用量为0.20g/mL时,反应5h后,乙酸正己酯的转化率达88%。     

非水相中脂肪酶催化合成乙酸正己酯

研究了用海藻酸钠固定化的脂肪酶在有机溶剂中催化乙酸与正己醇之间的酯化反应。探讨了溶剂、醇酸摩尔比、温度、底物浓度等多种因素对脂肪酶催化乙酸正己酯合成反应的影响规律。研究结果显示,在优化的条件下,即溶剂为正庚烷、醇酸摩尔比为1∶1、底物浓度为0.15mol/L、温度为70℃、pH为7.5、酶湿度为8.9%、吸水剂用量为0.20g/mL时,反应5h后,乙酸正己酯的转化率达88%。      

脂肪酶催陈白酒应用条件对微量成分影响的研究

以脂肪酶Novozym435作为催化剂,探索了应用脂肪酶进行白酒催陈过程不同反应条件对白酒中微量成分的影响。结果表明,Novozym435对不同酒度白酒均有明显的作用,常规作用温度及转速对催陈影响不明显,加酶量对催陈有着较强的影响。     

乳化剂对无溶剂体系合成1，3-甘油二酯的影响

在无溶剂体系中,通过脂肪酶Novozyme 435催化甘油解法合成功能性油脂1,3-甘油二酯。在底物摩尔比1∶1(甘油与天然谷物调和油比),脂肪酶添加量8%(占底物质量)条件下,研究酶催化反应过程中不同HLB值的蔗糖脂肪酸酯和反应温度对1,3-甘油二酯生成量的影响。研究结果表明,选择HLB值为11的亲水性蔗糖脂肪酸酯,在添加量0.5%,反应温度60℃下反应24 h,1,3-甘油二酯生成量最高,为42.61%。     

1,3-甘油二酯的功能性研究

研究了1,3-甘油二酯对大鼠的减肥和降血脂作用.实验分成5组:对照TAG组,3剂量组分别为100?G组、70?G组、30?G组,阳性对照30%SE组.大鼠喂养6周,每周称体重,最后腔静脉取血,检测血清中血脂水平;将大鼠内脏脂肪全部取出,计算Lee's指数和体脂比.结果表明:从第3周开始,100?G组、70?G组、30%SE组的大鼠体重明显低于对照组,而30?G组与对照组比较在大鼠体重上没有明显差异.各实验组大鼠的Lee's指数和体脂比均显著低于对照组.相比于对照组,100?G组、70?G组、30%SE组可显著降低血清中TC、TAG、LDL-C、Apo-B的水平,明显提高血清中HDLC的水平,30?G组与对照组比较,各指标均无显著差异.各实验组与对照组在血清中ALT、AST水平上无显著差异.实验结果表明,1,3-DAG在不损伤肝功能的情况下具有减肥和降血脂的功能.     

离子液体中脂肪酶活性调控对硬脂酸淀粉酯合成的影响

主要研究了离子液体中脂肪酶活性的调控对硬脂酸淀粉酯合成的影响。结果表明:在离子液体中添加不同水活度(Aw)的水合盐对对脂肪酶催化活性有显著影响,水合盐对为Na_2HPO_4·7H_2O和Na_2HPO_4·2H_2O的混合物,即Aw为0.61,添加量为80%(水合盐对淀粉质量比)时达到最佳的脂肪酶催化效果;冻干酶的pH值、添加量及冻干过程中冻干保护剂的存在对硬脂酸淀粉酯合成过程中脂肪酶活性同样影响显著,冻干酶催化反应的最适pH值为7.1,最适添加量为10.4%(冻干酶淀粉质量比),脂肪酶和有机化合物等冻干保护剂的加入能保护冻干酶的催化活性,提高反应转化率,其中以聚乙二醇效果最佳。     

无溶剂体系甘油解法制备乳脂1,3-甘油二酯

以乳脂为原料,在无溶剂体系下,采用Box-Behnken试验设计对酶法(诺维信435)甘油解反应制备富含1,3-甘油二酯的改性乳脂的工艺条件进行优化。该方法利用固定化酶在无溶剂体系中反应,具有高效安全的优点。优化技术参数为:反应时间12.24 h、酶添加量6.08%、反应温度54.64℃、醇油摩尔比3.6∶1,甘油解反应后的乳脂产物中1,3-甘油二酯的含量可达49.04%。     

The structure functional catalytic activity of rice bran lipase in the presence of selenium and lithium

Rice bran lipase (RBL), an esterase (EC 3.1.1.3) is a versatile enzyme that catalyzes the hydrolysis of ester linkages, primarily in neutral lipids, such as triglycerides. The catalytic activity of RBL in the presence of selenium and lithium has been investigated. Lipase isolated from rice bran was treated with different concentrations of selenium and lithium ions and further subjected to activity determination, along with the kinetics of inhibition of RBL in conjunction with structure–function relationship of the enzyme. Both ions showed competitive inhibition of RBL activity in a concentration-dependent manner (1 μM to 1 mM). At 1 mM concentration of SeO₂ and Li₂SO_4, the enzyme loses its activity by 78 and 71%, respectively. From the analysis of the kinetic data, the inhibition constant K _i is found to be 4 μM for Li₂SO_4, and 1 μM for SeO₂, respectively. Spectrofluorimeter analysis and far UV-CD data showed minor changes in the emission intensity and conformation of the RBL in the presence of these ions at the above concentration. The results suggest that both selenium and lithium specifically inhibit RBL by probably binding near to the catalytic site or distorting the geometry of the active site of the RBL triad.     

Assessment of lipoprotein activators of skim milk lipoprotein lipase and the relationship between lipoprotein lipase activity and milk fat synthesis

Bovine plasma and lipoproteins isolated by gel filtration chromatography were examined for their ability to activate skim milk lipoprotein lipase. Addition of equal amounts of protein from either triglyceride-rich lipoprotein, low density lipoprotein, high density lipoprotein or plasma to a lipoprotein lipase assay resulted in 6.0, 2.2, 2.5, or 1.1% hydrolysis of radiolabelled triglyceride emulsion. Lipoprotein lipase activity in skim milk was evaluated as an indicator of mammary lipid secretory capacity. Skim milk lipoprotein lipase activity was significantly lower immediately prepartum as compared with activity immediately postpartum (.2 vs. 5.4% of substrate hydrolyzed). Skim milk lipoprotein lipase was significantly higher during the final 12 d of lactation than in samples obtained 12 d after machine milking was terminated (5.6 vs. less than 1% of substrate hydrolyzed). Although skim milk lipoprotein lipase activity appeared positively related to mammary lipid secretory capacity during the time immediately surrounding initiation and cessation of copious milk production, activity between those periods was not correlated to milk fat percentage, milk fat yield, or stage of lactation.     

催化氧化合成葡萄糖酸钾工艺技术研究

以葡萄糖为原料，用Pd-Bx／C作催化剂，通过催化氧化的方法，合成了葡萄糖酸钾，产品收率97.8％。探讨了催化剂、葡萄糖质量浓度、氧气量、搅拌参数对葡萄糖转化率的影响。     

D-异抗坏血酸棕榈酸酯(IP)的抗氧化特性研究

考察了酶法合成的D-异抗坏血酸棕榈酸酯(IP)在模拟体系和食用油中的抗氧化能力,并和常用抗氧化剂进行了对比。结果表明:IP的抗氧化能力呈一定的剂量效应关系;与L-抗坏血酸棕榈酸酯(AP)、特丁基对苯二酚(TBHQ)、叔丁基对甲氧酚(BHA)及叔丁基对甲苯酚(BHT)相比,IP具有更强的羟基自由基清除能力和还原能力,但清除超氧阴离子及DPPH·自由基方面,略低于TBHQ;在油脂加速氧化实验中,IP能够显著抑制大豆油和菜籽油的氧化酸败。     

Effects of whole cottonseed or niacin or both on casein synthesis by lactating Holstein cows.

Forty Holstein cows in late lactation were offered diets containing niacin and whole cottonseed: 1) 0 g/d, 0%; 2) 0 g/d, 15%; 3) 6 g/d, 0%; and 4) 6 g/d, 15%, to evaluate effects on milk casein synthesis. Cows fed diet 1 had the highest DMI. The FCM (21.4 vs. 18.7 kg/d) and milk fat percentage (4.08 vs. 3.81) were higher for cows fed diet 1 than for those fed diet 4. Milk protein percentage (3.61 vs. 3.50) was higher for cows fed diet 1 than for those fed diet 2. Casein N, as a percentage of total N, was higher (71.9 vs. 68.0%) in milk from cows fed diet 1 than those fed diet 3. Insulin tended to be elevated in cows on the diets containing niacin, but glucose was not affected. Plasma niacin was elevated in cows on the diets supplemented with niacin compared with diet 1. Plasma AA were changed only slightly by treatments. The beneficial effect of niacin on milk casein synthesis, noted in our earlier work when cows were fed whole cottonseed, was not evident in this study with cows in late lactation and during hot weather.