c9t11- 和t10c12- 共轭亚油酸抗癌和影响脂质代谢的异同

共轭亚油酸(CLA)是一组位置和构象异构体的总称,异构体c9t11-CLA 和t10c12-CLA 或二者的协同作用赋予了CLA 的许多生理功能,比如抗癌、降低体脂含量、预防糖尿病的发生、降低血脂抑制动脉粥样硬化等;异构体c9t11-CLA 和t10c12-CLA 在结构及来源上存在一定差别--由于双键位置的不同,t10c12-CLA 异构体比c9t11-CLA 异构体更容易氧化;而在生理功能上二者也有差异-- c9t11-CLA 异构体的主要作用是抗癌,而 t10c12-CLA 则是降低体脂、血脂等,大量单一异构体的体外实验研究表明二者在抗癌及脂肪代谢的调节上作用机制也不尽相同。     

优化乳杆菌高产共轭亚油酸的研究进展

共轭亚油酸(CLA)是亚油酸(LA)的一组位置和空间异构体的总称,其中具有生理活性的异构体是c9,t11-CLA和t10,c12-CLA,它们具有丰富的营养价值和医药价值。在乳球菌属和链球菌属等乳酸菌、丙酸杆菌、瘤胃细菌以及其它菌属中,分离纯化得到的亚油酸异构酶,可催化LA异构化为CLA,利用酶法合成CLA可以有效弥补传统化学合成法的缺陷。本文概述了近年来国内外利用紫外、微波、等离子体诱变、离子注入等物理或化学方法诱变、改造亚油酸异构酶,优化产酶条件和酶学特性,还阐述利用定点突变、基因敲除等基因工程方法,对生产菌株进行改造和培养条件优化,提高CLA产量的相关研究,为进一步筛选出高产共轭亚油酸菌株和CLA的产业化应用提供理论依据。     

共轭亚油酸异构体生理功能的差异

介绍了共轭亚油酸不同异构体在降低机体脂肪积累、抗肿瘤、抗动脉粥样硬化以及免疫调节方面的研究,讨论了不同共轭亚油酸异构体,尤其是顺9,反11-共轭亚油酸(c9,t11-CLA)和反10,顺12-共轭亚油酸(t10,c12-CLA)在生理功能上的差异,以期更有效地利用不同CLA异构体实现特有的生理功能。     

响应面优化法尿素包合法分离共轭亚油酸2种异构体

目的优化尿素包合法,对共轭亚油酸2种主要异构体c9, t11-CLA和t10, c12-CLA进行分离(2种异构体比例近1:1)。方法在单因素实验基础上,以温度、尿素与油比例、乙醇与油比例3个因素为自变量,以t10, c12-CLA/c9, t11-CLA为响应值,利用响应面法优化了共轭亚油酸异构体的分离。结果优化后的实验条件为:在乙醇作溶剂的情况下,将共轭亚油酸、尿素和乙醇按1:2.5:5(V:V:V)配比,置于75℃水浴锅中水浴溶解,室温下搅拌冷却结晶。所得样品中t10,c12-CLA与c9,t11-CLA的比值高达2.47,且共轭亚油酸总量为97.3%。结论优化后的尿素包合法可有效分离CLA的2种异构体,提高t10, c12-CLA比例。     

L.helveticus L7生物转化的共轭亚油酸异构体结构分析

利用HPLC分离出L.helveticusL7生物转化的2种CLA异构体单体,通过紫外光谱、傅立叶变换红外光谱、气相色谱-质谱联用分析,确定了L.helveticusL7生物转化形成的两种CLA异构体是t9t11-CLA和c/t-911-CLA。     

乳酸菌制备CLA的研究

我们利用从酸菜汁中分离出的一株植物乳杆菌Lactobacillus plantarumL18转化亚油酸(LA)来制备共轭亚油酸(CLA)。在MRS培养基中添加0.06%(wt/vol)的LA作为诱导剂,获得制备CLA的洗涤细胞。以游离LA为底物,植物乳杆菌Lactobacillus plantarumL18的洗涤细胞为催化剂,厌氧环境有利于生成CLA。0.1M的磷酸钠缓冲液、pH7.0、LA浓度2%(wt/vol)、细胞浓度为20%(wt/vol)、30℃,反应64h,CLA的产量最高。反应液中生成的CLA产物为c9,t11/t9,c11-CLA和t10,c12-CLA异构体的混合物。     

共轭亚油酸的生理功能综述

共轭亚油酸(conjugated linoleic acid,CLA)是一类含有共轭双键十八碳二烯酸异构体混合物的统称,以异构体c9, t11-CLA和t10, c12-CLA的研究最为集中,广泛应用于保健品、功能食品及食品添加剂等领域。本文综述了CLA的生理功能及抗病机制的国内外研究进展,通过全面了解共轭亚油酸的生理功能及抗病机制,有助于更科学、更准确地进行研究,对相关保健产品的开发具有一定的意义。     

一种共轭化植物油的光化学制备方法

对共轭化植物油的光化学制备方法进行了研究,考察了引发剂DPIS用量、溶剂种类、植物油质量浓度、温度等因素对共轭化反应的影响。结果表明:在玉米油40 g,环己烷300 mL,72℃,引发剂用量0.2%条件下,玉米油可在30 min内被完全共轭化。利用核磁共振氢谱和气相色谱分析了光化学共轭化玉米油中脂肪酸的组成,其共轭亚油酸(CLA)异构体主要为t9,t11-CLA(含量39.10%),与碱法共轭产品中CLA主要为c9,t11-CLA和t10,c12-CLA有明显区别。     

乳酸菌洗涤菌体合成共轭亚油酸的研究

为了解瑞士乳杆菌L7(Lactobacillus helveticusL7)洗涤菌体生物合成共轭亚油酸(CLA)的能力,通过单因素和正交优化研究,确定了瑞士乳杆菌L7洗涤菌体合成c9,t11-CLA的最适条件:0.05mol/LPBS缓冲液(pH5.8)、1.00mg/mL亚油酸、23℃反应12h。在最适转化条件下,c9,t11-CLA产量达到0.54mg/mL。结果表明,洗涤菌体合成CLA的产量和分批发酵相近,可以继续进行瑞士乳杆菌L7固定化细胞发酵生产CLA的研究。     

西北牧区牧民自制酸奶中c9,t11-CLA含量的研究

共轭亚油酸（CLA）是亚油酸的一组几何和位置异构体,具有多种生理功能。反刍动物肉、乳制品是c9,t11-CLA丰富的天然来源。本研究用气相色谱法测定青海、甘南、天祝和肃北4个不同牧区牧民自制酸奶中c9,t11-CLA的含量,并与市售酸奶和牦牛乳中的含量进行对比。结果表明：采用该方法使牧区酸奶中c9,t11-CLA得到很好的分离,测得青海、甘南、天祝和肃北牧区酸奶中c9,t11-CLA的含量分别为1．007、0．782、0,987、1．196rag／ml酸奶;牧区自制酸奶中c9,t110CLA的含量与市售酸奶中的含量差异不显著（p〉0．05）：但含量极显著低于牦牛乳（p〈0．01）。     

乙醇胁迫提高植物乳杆菌p-8的共轭亚油酸(CLA)转化率和相关酶转录水平

该文研究了在MRS培养基中添加0.05 mg/mL LA（Linoleic acid,LA）和不同浓度的乙醇时植物乳杆菌p-8的CLA（Conjugated linoleic acid,CLA）转化率和CLA合成相关酶转录水平的差异情况。结果显示,发酵液中的三种CLA异构体转化率都是在添加0.50%乙醇时最高,其中转化cis9,trans11-CLA（t9,t11-CLA）异构体最高,为2.49%,比不添加乙醇增加2.37倍。添加不同浓度乙醇的发酵液中trans10,cis12-CLA（t10,c12-CLA）转化率都是最低的。菌体中产生的CLA非常少,但规律与发酵液的基本一致。添加0.50%乙醇菌体中t9,t11-CLA转化率最高,其转化率仅为0.05%,比不添加乙醇增加了5倍。当乙醇浓度高于0.50%时,各种不同CLA异构体的转化率却都减少。结果表明CLA是在胞液内产生后再被运转到胞外的,一定浓度范围内的乙醇胁迫通过提高CLA合成相关的酶基因转录水平,进而促进了CLA的转化,可见CLA合成相关酶基因转录水平是造成CLA转化率差异的主要原因。结果为阐明植物乳杆菌p-8产CLA的分子机制和寻找有效提高CLA生成的调控手段奠定了基础。     

Conjugated linoleic and linolenic acid production kinetics by bifidobacteria differ among strains

There is great interest in conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers because of their supposed health-promoting properties. Therefore, the differences in production kinetics of CLA and CLNA isomers from linoleic acid (LA) and α-linolenic acid (α-LNA), respectively, by bifidobacteria were investigated. Laboratory fermentations, supplemented with LA or α-LNA in the fermentation medium, were performed with Bifidobacterium bifidum LMG 10645, Bifidobacterium breve LMG 11040, B. breve LMG 11084, B. breve LMG 11613, B. breve LMG 13194, and Bifidobacterium pseudolongum subsp. pseudolongum LMG 11595. Conversion of LA and α-LNA to CLA and CLNA isomers, respectively, started immediately upon addition of the substrate fatty acids. During the active growth phase, the c9, t11-CLA isomer and the putative c9, t11, c15-CLNA isomer were formed. Further fermentation resulted in a reduction in the concentration of c9, t11-CLA and c9, t11, c15-CLNA and the subsequent production of the t9, t11-CLA isomer and the putative t9, t11, c15-CLNA isomer, respectively. Modelling of the growth and metabolite data indicated differences in production kinetics among the strains. Some strains displayed a high specific conversion of LA and α-LNA despite poor growth, whereas other strains grew well but displayed lower conversion. Production of specific CLA and CLNA isomers by bifidobacteria holds potential for the production of functional foods and could contribute to their probiotic properties.     

植物乳杆菌ZS2058生物转化产物共轭亚油酸的分析方法的研究

研究了紫外分光光度法、GC、Ag~+-HPLC和GC-MS四种分析方法对植物乳杆菌ZS2058生物转化亚油酸(LA)产生的共轭亚油酸(CLA)检测时的异同点。结果表明,这4种分析方法在对CLA进行检测时各有特色,应用范围也有不同。紫外分光光度法检测成本最低,操作最快速,但检测结果为转化产物中各种CLA异构体的总和,而GC、Ag~+-HPLC和GC-MS能将产物中的各类CLA异构体分开,可对复杂的生物转化产物进行分析。其中,GC的最大优点在于可以检测到转化底物LA,Ag~+-HPLC可将转化产物中c9,t11-CLA和t8,c10- CLA很好的分离,而GC-MS可以将各种异构体与其它副产物明确区分开来。总之,在检测生物转化法产生的CLA时,根据不同的实验需求来选择不同的检测方法,并需将这几种方法灵活的结合起来应用。     

Effects of Linoleic Acid on Conjugated Linoleic Acid Production by Planktonic Rumen Bacteria from Grain-fed Cows

Ruminal conjugated linoleic acid (CLA) production from linoleic acid (LA) was characterized in vitro. Rumen bacteria from grain‐fed cows were more active in BH than those from hay‐fed cows. Particleassociated bacteria produced more hydrogenated products leaving less CLA than the planktonic bacteria (P < 0.05). CLA production by planktonic bacteria did not always correlate to LA given; longer incubations generally decreased CLA concentration and increased c9, t11/t10, c12 ratio, especially at higher LA concentrations. The preincubated cells to LA produced more CLA than the unexposed ones and the increase was more evident with c9, t11 CLA (P < 0.05). This study provides insight into how cattle diet and LA feedings affect ruminal CLA production.     

共轭亚油酸对小鼠肥胖的抑制作用

采用小鼠营养性肥胖模型法,以昆明小鼠为实验动物,设置基础饲料对照组、肥胖模型对照组、共轭亚油酸（conjugated linoleic acid,CLA）高、中、低剂量组,分别连续灌胃6 周,考察小鼠体质量、体内脂肪质量、血脂水平、肝脏脂肪酸合成酶（fatty acid synthase,FAS）含量及脏器的变化,研究CLA对小鼠肥胖的抑制作用。结果表明：CLA各剂量组小鼠的Lee’s指数、脂肪系数和血清甘油三酯（triglyceride,TG）、总胆固醇（totalcholesterol,TC）、低密度脂蛋白胆固醇（low density lipoprotein cholesterol,LDL-C）水平均显著或极显著低于肥胖模型对照组（P＜0.05或P＜0.01）,高密度脂蛋白胆固醇（high density lipoprotein cholesterol,HDL-C）水平均极显著高于肥胖模型对照组（P＜0.01）,各剂量的CLA对小鼠除肝脏以外的其他脏器无显著影响（P＞0.05）,高剂量（0.15 mL/10 g）CLA可使喂食营养饲料小鼠的各项肥胖指标均处于喂食基础饲料小鼠的水平,表明CLA能有效抑制小鼠肥胖,同时对小鼠生长无毒副作用;CLA可极显著降低小鼠肝脏FAS含量（P＜0.01）,降低脂肪酸的合成,从而抑制小鼠肥胖。     

植物乳杆菌p-8转化亚油酸为共轭亚油酸的分析

研究植物乳杆菌（Lactobacillus plantarum）p-8的菌体、菌体破碎液和重组亚油酸异构酶系转化亚油酸（linoleic acid,LA）为共轭亚油酸（conjugated linoleic acid,CLA）的能力和机制。结果表明：L. plantarum p-8在含有LA的MRS上清液和菌体破碎液体外催化LA时,都可以低效产生cis9,trans11-CLA（c9,t11-CLA）、trans10,cis12-CLA（t10,c12-CLA）和trans9,trans11-CLA（t9,t11-CLA）,但菌体中只有很少的t10,c12-CLA。实时聚合酶链式反应结果表明,亚油酸异构酶系的表达水平较低可能是CLA产量较低的原因。独立表达的重组亚油酸异构酶系成员、黄素腺嘌呤二核苷酸（flavin denine dinucleotide,FAD）和烟酰胺腺嘌呤二核苷酸都存在才可完成LA转化为c9,t11-CLA、t10,c12-CLA和t9,t11-CLA,转化途径与L. plantarum AUK1009一致。L. plantarum p-8的亚油酸水合酶经同源建模后有3 个结构域,底物结合位点与FAD位点位于3 个结构域连接处的疏水空腔中,M76和Y180是2 个必需基团。     

Conjugated linoleic acid conversion by six Lactobacillus plantarum strains cultured in MRS broth supplemented with sunflower oil and soymilk

Six strains of Lactobacillus plantarum, isolated from traditional dairy products of minority nationalities, were evaluated for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid in vitro. All the 6 strains were found to be capable of converting linoleic acid to CLA when using sunflower oil as substrate or during soymilk fermentation. The inhibitory effect of linoleic acid on the growth of the L. plantarum was also discussed. The production of CLA was increased with adding high concentration of substrate in sunflower oil and IMAU60042 produced the highest CLA both in sunflower oil and soymilk. The CLA was composted by 2 isomers: cis9, trans11-CLA and tran10, cis12-CLA, and cis9, tran s11-CLA covered the most part of the total CLA formed except for L. plantarum P8. The production of CLA was decreased during the storage of fermented soymilk. The CLA contents decreased significantly in the first week, also more quickly in 2 wk. Especially, tran10, cis12-CLA decreased more rapidly than cis9, tran11-CLA. No dramatic change was observed among other 8 fatty acids in soymilk. The proportion of unsaturated fatty acids varied after fermentation with different L. plantrum strains, but all decreased the during storage. The research on the ability of converting CLA of L. plantrum strains could be basis for the future research and development of fermented soymilk products. PRACTICAL APPLICATION: Desirable probiotic traits, such as acid and bile tolerance, aggregation activity, and antibacterial activity, have been proved for the 6 Lactobacillus plantarum strains. The 6 L. plantarum strains might be used in the fermentation of soymilk to produce multifunctional probiotic soymilk products, especially the rich CLA contents.     

Production of free conjugated linoleic acid by Lactobacillus acidophilus and Lactobacillus casei of human intestinal origin

A gas chromatographic procedure was used for analysis of conjugated linoleic acid (CLA) isomers cis-9, trans-11-octadecadienoic; trans-10, cis-12 octadecadienoic; and trans-9, trans-11-octadecadienoic (c9t11, t10c12, t9t11) produced by lactobacilli. Four different cultures, two strains each of Lactobacillus acidophilus and Lactobacillus casei were tested for their ability to produce CLA from free linoleic acid in MRS broth supplemented with linoleic acid. Different concentrations of linoleic acid (0, 0.05, 0.1, 0.2 and 0.5 mg/ml) were added to MRS broth, inoculated with the lactobacilli, and incubated at 37 degrees C. Viable counts and amounts of individual isomers of CLA (c9t11, t10c12, t9t11) were measured at 0, 24, 48, and 72 h. All the cultures were able to produce free CLA in media supplemented with linoleic acid. Maximum production of CLA (80.14 to 131.63 microg/ml) was observed at 24 h of incubation in broth containing 0.02% of free linoleic acid. No significant (P > 0.05) increases in total CLA levels were observed after 24 h of incubation. The ability of the cultures to produce CLA in skim milk supplemented with 0.02% free linoleic acid also was studied. In this medium, the total amounts of free CLA after 24 h of incubation ranged from 54.31 to 116.53 microg/ml. The use of lactic acid bacteria able to form free CLA in cultured dairy products may have potential health or nutritional benefits. Free CLA in the products likely would be more readily available for absorption from the digestive tract than if it were incorporated into the cells of the starter culture.