Alkali Isomerization And Biological Preparation Of Conjugated Linoleic Acid Research

Conjugated linoleic acids (CLA) comprise a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bonds. CLA are isomers of essential fatty acid linoleic acid(cis-9, cis-12, octadecadienoic acid). CLA are the natural fatty acids ,which have many important physiological activities, such as anticancer, antiatherosclerosis, reducing body fat, antioxidant, strengthening immune function, antidiabetic and accelerating growth.Conjugated linoleic acids(CLA) were prepared by alkali isomerization using KOH as catalyst, 1 ,2-propanediol as solvent and walnut oil as raw materials. The concentration and yield of CLA were determined at 233nm by spectrophotometric analysis. Effects of the factors on the yield of CLA have been studied and the mathematical models have been established by using the 23 factorial experiment. A fitted second-order response model in three variables were obtained and the optimum conditions were found: reaction temperature at 174 , reaction time in 2.87 hours, and m(walnut oil): w(KOH) =1.6,when the condition that m(l,2-propanediol): w(KOH) = 3 : 1 , stirring rate at 500r/min and nitrogen protection was given. At the optimum conditions yield of CLA can exceed85.0%.The reaction mechanism of alkali isomerization was discussed. The equation of velocity was speculated by reaction mechanism, and the conclusion was validated by experiment. The apparent kinetic model was also established and equation of velocitywas deduced as dcB/dt = 0.71 67cA. The apparent energy of activation (Ea) is quantified as Ea = 67.22kJ/mol. The constant of reaction rate (k) vs the temperature formula is that67220k = 1. 47456 104s-1e.The strains of bacteria identified as Lactobacillus were isolated from yoghourt, pickle and intestine of domestic animal such as chook, duck and rabbit. 0.1 percent of linoleic acid was added to MRS medium, strains of Lactobacillus isolated and strain of Lactobacillus casei were cultured under microaerobic conditions at 37 for 24h in MRS medium. CLA were extracted from the culture by hexane. The levels of CLA formation were determined by spectrophotometric analysis. The result showed that four strains can produce CLA from linoleic acid, and yield of CLA produced from strain isolated from yoghourt is maximal, which is 0.853%.