微生物生产共轭亚油酸的研究

介绍了共轭亚油酸的结构、性质、作用和机理 ,以及微生物生产共轭亚油酸的研究进展     

共轭亚油酸生理功能及其合成方法

共轭亚油酸（CLA）为亚油酸（LA）的异构体,具有抗癌、降脂、调节免疫、抗粥样硬化等重要的生理功能,目前共轭亚油酸（CLA）的生产大都是利用碱催化亚油酸异构而成,但其异构体繁多。利用微生物转化生产的共轭亚油酸（CLA）,异构体较少,与天然食品中的CLA异构体组成相似,具有很好的商业前景。     

共轭亚油酸的生理功能及其合成、纯化研究检测方法

共轭亚油酸是一系列位置和几何异构体的总称，其中的活性异构体具有多种重要的生理功能，近年来受到越来越多的重视。对活性共轭亚油酸异构体的主要生理功能、微生物合成共轭亚油酸的微生物菌种及合成途径中的关键性酶、目前使用的共轭亚油酸的化学合成方法、以及共轭亚油酸的纯化及分析检测方法进行了综述。     

微生物合成共轭亚油酸机理和方法的研究进展

共轭亚油酸是人类近年来发现的最重要的功能性脂肪酸之一,作为一种新发现的营养素,已被广泛的应用到药品和食品中,应用范围正不断扩大。本文系统地总结目前微生物合成共轭亚油酸的研究现状,阐述生物合成共轭亚油酸(conjugated linoleic acid,CLA)的重要性,列举一些合成CLA的重要菌种,总结不同微生物合成CLA的机制,对比4种微生物合成方法的特点,展望微生物合成CLA的未来研究方向。     

共轭亚油酸的功能性质及安全性评价

介绍了共轭亚油酸及其对健康的益处，综述了共轭亚油酸对动物和人体机体组成影响的研究进展，并讨论了共轭亚油酸添加物的安全性问题。研究认为，共轭亚油酸对健康和机体组成等均具有较好的作用，但人体服用共轭亚油酸的安全性问题有待进一步的研究。     

共轭亚油酸氧化稳定性及其影响因素的研究

研究了共轭亚油酸的氧化稳定性及其主要影响因素。共轭亚油酸氧化稳定性低于相应的油脂。变价金属离子（Fe∧3 能够促进共轭亚油酸氧化。考察了几种抗氧化剂对共轭亚油酸的抗氧化性能,BHT、BHA BHT（1：1）对共轭亚油酸的抗氧化效果优于实验的其他抗氧化剂,添加抗氧化剂可是明显改善共轭亚油酸的氧化稳定性。     

共轭亚油酸对畜禽肌肉品质影响的研究进展

共轭亚油酸(Conjugated linoleic acid,CLA)是亚油酸的一组构象和位置异构体。它作为一种新型功能性脂肪酸,具有许多重要的生理功能,其中调节机体脂肪代谢,降低脂质沉积的功效尤为显著。目前国内外研究人员利用此生物活性在动物饲养方面的研究也日益广泛。文章简要介绍了共轭亚油酸的结构、活性及降脂机制。重点结合近年来国内外在共轭亚油酸和畜禽饲养方面的相关研究报道,从畜禽肌肉品质的主要影响因素展开,综述了共轭亚油酸对畜禽肌肉品质和风味的影响。     

共轭亚油酸降脂及分子机理研究进展

共轭亚油酸是一类具有两个共轭双键的十八碳多不饱和脂肪酸混合物的总称,具有确切的减肥降脂活性与可验证的临床安全性,使其成为国际减肥市场的宠儿。简要回顾了共轭亚油酸减肥降脂的研究成果,并从调控能量代谢、脂代谢、骨骼肌代谢和糖代谢,介导脂肪细胞的分化与凋亡以及调节肠道微生物群6个方面总结了共轭亚油酸减肥降脂的作用机制,同时对其存在问题及发展机会做了分析与讨论。共轭亚油酸作为减肥降脂的天然产物,具有更大、更广阔的发展潜力。     

共轭亚油酸酯类衍生物的研究进展

共轭亚油酸酯类衍生物具有抗氧化、抗癌、降低胆固醇、减肥、降血糖血脂等多种生理功能,在食品、化妆品、医药及饲料行业中均具有广阔的应用前景。为了推动共轭亚油酸酯类衍生物的生产应用,综述了共轭亚油酸酯类衍生物的种类及合成方法、分离纯化方法、检测方法、储存稳定性及其应用。指出推动酶法合成共轭亚油酸酯类衍生物工业化、多种分离纯化方法结合以及进一步提高共轭亚油酸酯类衍生物的储存稳定性是今后的重点研究方向。     

微波作用下亚油酸转化为共轭亚油酸工艺的研究

以玉米胚芽油为原料,丙三醇为溶剂,在微波场作用下对亚油酸异构化为共轭亚油酸工艺进行了研究。通过紫外、红外吸收光谱分析,证明微波作用下生成的产物主要是共轭亚油酸,并含有顺式和反式共轭结构。与油浴加热方法比较微波作用异构化生产共轭亚油酸的方法优越可行。通过对影响共轭异构化反应的因素及正交试验的分析,确定了最佳工艺条件,获得了95%以上的共轭异构化转化率。     

乳酸菌合成共轭亚油酸及其应用研究进展

共轭亚油酸(conjugated linoleic acid,CLA)是一种具有多种生理活性的功能性脂肪酸,在食品、保健品中具有广阔的应用前景。然而,天然来源的CLA含量很低,不能满足人类需求。乳酸菌可以合成CLA,且广泛用于食品加工领域,利用乳酸菌开发富含CLA的功能食品是当今的研究热点。为推动CLA功能食品的研究开发,该文对合成共轭亚油酸乳酸菌的研究进展、合成共轭亚油酸乳酸菌的益生性研究以及将产CLA乳酸菌应用到食品和饲料中的研究现状进行综述,并对利用乳酸菌合成CLA进而应用于功能食品进行展望。     

Response of milk fatty acid composition to dietary supplementation of soy oil, conjugated linoleic acid, or both

Thirty-six Holstein cows were blocked by parity and allotted by stage of lactation to 6 treatments to evaluate the effects of dietary soy oil, conjugated linoleic acid (CLA; free acid or calcium salt), or both, on CLA content of milk. Diets were fed for 4 wk and are as follows: (1) control, (2) control + 5% soy oil, (3) control + 1% CLA, (4) control + 1% Ca(CLA)₂, (5) control + 1% CLA + 4% soy oil, and (6) control + 1% Ca(CLA)₂ + 4% soy oil. Rumen volatile fatty acid -concentrations, blood fatty acid concentrations, milk yield, and milk composition were measured weekly or biweekly. Dry matter intake and milk yield were recorded daily. Dietary supplementation of soy oil or CLA had no effect on daily milk yield, milk protein concentration and production, or milk lactose concentration and production. Supplementation of unsaturated fatty acids as soy oil, CLA, or Ca(CLA)₂ increased total fatty acid concentration in plasma, decreased milk fat concentration and production, and had no effect on rumen volatile fatty acid concentrations. The weight percentage of CLA in milk was increased from 0.4 to 0.7% with supplementation of 1% CLA, to 1.2% with supplementation of soy oil, and to 1.3% with supplementation of 1% CLA plus soy oil. Supplementation with Ca(CLA)₂ or Ca(CLA)₂ + soy oil increased the CLA content of milk fat to 0.9 and 1.4%, respectively. In summary, adding 5% soy oil was as effective as supplementing CLA, Ca(CLA)₂, or a combination of 1% CLA (free acid or calcium salt) + 4% soy oil at increasing CLA concentrations in milk fat. Feeding CLA as the calcium salt resulted in greater concentrations of CLA in milk fat than did feeding CLA as the free acid. Dietary supplementation of 5% soy oil or 4% soy oil + 1% CLA as the free acid or the calcium salt increased the yield of CLA in milk.     

Production of conjugated fatty acids by lactic acid bacteria

Conjugated fatty acids have attracted much attention as a novel type of biologically beneficial functional lipid. Some isomers of conjugated linoleic acid (CLA) reduce carcinogenesis, atherosclerosis, and body fat. Considering the use of CLA for medicinal and nutraceutical purposes, a safe isomer-selective process is required. The introduction of biological reactions for CLA production could be an answer. We screened microbial reactions useful for CLA production, and found several unique reactions in lactic acid bacteria. Lactic acid bacteria produced CLA from linoleic acid. The produced CLA comprised a mixture of cis-9,trans-11-octadecadienoic acid (18:2) and trans-9,trans-11-18:2. Lactobacillus plantarum AKU 1009a was selected as a potential CLA producer. Using washed cells of L. plantarum AKU 1009a as a catalyst, CLA production from linoleic acid reached 40 mg/ml under the optimized conditions. The CLA-producing reaction was found to consist of two successive reactions, i.e., hydration of linoleic acid to 10-hydroxy-12-octadecenoic acid and dehydrating isomerization of the hydroxy fatty acid to CLA. On the basis of these results, the transformation of hydroxy fatty acids by lactic acid bacteria was investigated. Lactic acid bacteria transformed ricinoleic acid (12-hydroxy-cis-9-octadecenoic acid) to CLA (a mixture of cis-9,trans-11-18:2 and trans-9,trans-11-18:2). Castor oil, which is rich in the triacylglycerol form of ricinoleic acid, was also found to act as a substrate for CLA production by lactic acid bacteria with the aid of lipase-catalyzed triacylglycerol hydrolysis. L. plantarum AKU 1009a produced conjugated trienoic fatty acids from alpha- and gamma-linolenic acid. The trienoic fatty acids produced from alpha-linolenic acid were identified as cis-9,trans-11,cis-15-octadecatrienoic acid (18:3) and trans-9,trans-11,cis-15-18:3. Those produced from gamma-linolenic were cis-6,cis-9,trans-11-18:3 and cis-6,trans-9,trans-11-18:3. The conjugated trienoic fatty acids produced from alpha- and gamma-linolenic acid were further saturated by L. plantarum AKU 1009a to trans-10,cis-15-18:2 and cis-6,trans-10-18:2, respectively.     

乳酸菌产共轭亚油酸研究现状

共轭亚油酸(conjugated linoleic acid, CLA)是十八碳二烯酸的异构体。通过食物摄入的CLA不能达到每日推荐摄入量,而CLA又具有减肥、抗癌、抗Ⅱ型糖尿病等多种生理功能,故CLA逐渐成为研究热点。与化学合成CLA相比,微生物合成CLA更具有优势。乳酸菌(lactic acid bacteria, LAB)具有安全性和益生功能,利用乳酸菌合成CLA是一个理想的途径。目前已发现多种产CLA乳酸菌,人们使用乳酸菌发酵油酸、牛乳、植物油合成CLA,并取得了良好的效果。亚油酸异构酶(linoleate isomerase, LAI)对乳酸菌合成CLA起重要作用,但其对乳酸菌合成CLA的作用机理还不明确。一些学者对乳酸菌合成CLA的中间产物进行了研究,发现乳酸菌合成CLA有多种中间产物。乳酸菌合成CLA的代谢机制目前尚不清楚。乳酸菌合成CLA对食品工业有重要意义,也为功能性食品的开发提供了新机遇。本文主要对CLA的生理功能、产CLA乳酸菌、乳酸菌合成CLA的底物、乳酸菌合成CLA的途径进行了概述。     

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.     

Conjugated linoleic acid: A potent fatty acid linked to animal and human health

Conjugated linoleic acid (CLA) is a mixture of isomers of linoleic acid (C18:2 n-6), which is mostly found in the ruminant meat and dairy products. The CLA is known to have many potential health benefits, and considered a potent powerful fatty acid, which is linked to animal and human health. The present work aims to discuss the source and production, mechanism of action, and effects of CLA on humans, poultry, and ruminants by reviewing the recent studies carried out on CLA. Despite most of the recent studies indicating beneficial effects of CLA on improving body weight control parameters, its effects on reducing risk factors of cardiovascular diseases (CVD), inflammation, blood glucose, and insulin are still controversial, and need to be further studied in different hosts.     

产共轭亚油酸丙酸菌的筛选及转化条件初探

通过富集培养、梯度密度稀释和液体培养发酵,采用紫外分光光度法测定共轭亚油酸(CLA),从市售奶酪中筛选获得1株转化生成CLA能力相对较高的菌株P9:考察了菌体接种量、亚油酸(LA)的添加量、反应温度、反应体系pH值以及乳化剂种类等因素对菌株P9 CLA生成量的影响.通过对菌株P9的菌落和形态特征、产丙酸特性及生理生化特性分析,初步鉴定该菌株为费氏丙酸杆菌(Propionibacterium frudenreichii).研究结果显示,菌株P9在菌体接种量10%(v/v),LA添加量0.75mg/mL,pH值为6.8,反应温度30℃,Tween-80作为乳化剂的条件下,CLA生成量为63.371μg/mL,亚油酸转化率为8.45%,表现出较好的产共轭亚油酸能力.     

Conjugated Linoleic Acid Reduces Lipid Oxidation in Aerobically Stored, Cooked Ground Beef Patties

ABSTRACT: The effect of direct addition of conjugated linoleic acid (CLA) on lipid oxidation was studied. CLA and/or fat trim (4% by weight) were added to the lean trim (96%). Thiobarbituric acid reactive substances (TBARS) were determined on days 0, 3, and 7 for cooked or raw patties stored aerobically at 4 °C. Addition of CLA during the grinding process increased CLA isomers in both raw and cooked ground beef and decreased TBARS production ( P < 0.01). CLA caused a greater reduction in TBARS over storage time in cooked patties than in raw patties ( P= 0.006). The concentrations of 18:2n–6 and CLA isomers decreased with storage time. CLA increased 18:2n-6, whereas most fatty acids were decreased by the addition of CLA. CLA did not affect percentages of fat and moisture, cooking loss, or meat color (L*, a *, b *) ( P > 0.60).     

产共轭亚油酸乳酸菌的筛选及生产条件的研究

从分离到的乳酸菌中筛选到1株共轭亚油酸高产菌株,乳杆菌L1(Lactobacillus sp.),在MRS培养基上,乳杆菌L1产生共轭亚油酸的最适亚油酸的浓度是0.1%(v/v),最适培养时间是42h,参与共轭亚油酸形成的酶是胞内酶,并且可能是由多种酶共同作用的结果.建立了共轭亚油酸的紫外光谱扫描和高效液相色谱检测方法.