Studies On Screening Of Lactobacillus Planetarium Strain Producing Conjugated Linoleic Acid And Optimization Of The Fermentation Conditions

Conjugated linoleic acid(CLA) have recently attracted much attention as a novel type of biologically beneficial functional fatty acids. Some isomers of CLA were reported to reduce carcinogenesis, atherosclerosis and body fat, enhance organism immunity and promote growth. CLA has been widely used in Health care and production of food additive. The chemical approaches to synthesizing CLA, have been studied early and thoroughly in industry fields, however, the resulting CLA product contained toxic substances, the costs of product purification and use in a large amount were thus very high. In this research,we screened Lactic acid bacterium strains with high CLA producing capacity from food and optimized the fermentation medium and fermentation conditions based on the fast determination method of CLA, and the results of this paper are as following:1. Several strains possible producing CLA were screened from fermentation Chinese sauerkraut juice, lactobin and yogurt. Three strains producing CLA were screened from fermentation Chinese sauerkraut juice, and one strains were screened from lactobin and yogurt respectively by using UV spectrophotometry method. Strain LJ-05, have the highest CLA producing capacity. CLA produced by strain LJ-05 contains 32.15% cis9, trans11-C18:2 isomer and 68.85% trans10, cisl2-C18:2 isomer, and the relative amount of cis9,trans11-C18:2 and trans10,cisl2-C18:2 isomer in extract are 0.81% and 1.79% detected by Gas Chromatography method.2. Identify strain LJ-05 by physiology and biochemistry approaches,then identify strain LJ-05 by Biolog Microbial Identification System(BMIS), compare merit and demerit of this two identification method,and strain LJ-05 was identified as Lactobacillus plantarum finally.3. The fermentation medium and fermentation conditions to produce CLA of Lactobacillus plantarum LJ-05 were studied by using orthogonal experiment and response surface method. The optimum medium consisted of glucose 4%, peptone 1%, beef extract 1%, yeast extract 1%, diammonium Citrate 0.2%, sodium acetate 0.5%, dipotassium hydrogen phosphate 0.2%, magnesium sulfate 0.04%, manganese sulfate 0.025%; The suitable fermentation conditions to produce CLA of Lactobacillus plantarum LJ-05 were:LA emulsion liquild 0.23%, temperature 36℃,initial pH 7.3,inoculum size 3.95%, the best fermentation time was 36h under standing and micro-aerobic condition. The yield of CLA produced by Lactobacillus plantarum LJ-05 reached 510.9μg/(mL fermentation liquid) under the optimized medium and fermentation condition, which was 39.93% higher than that of the original strain.