Study On The Production Of Conjugated Linoleic Acid By Lactobacillus Sp.

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid (LA). Cis-9, trans-11 conjugated linoleic acid (c9, t11-CLA)and trans-10. cis-12 conjugated linoleic acid (t10, c12-CLA) have been confirmed that they are biologically beneficial functional fatty acids, including enhancing organism immunity, immunomodulatory function, preventing atherosclerosis, antioxidant and so on. CLA has been widely applied in the field of medicine production and food additive.In this research, a strain with high productive ability of CLA was screened. And low temperature plasma technology was used in order to improve the production of CLA by the strain. Finally, medium components and fermentation conditions were optimized to increase the production of CLA. The specific research contents and results are as following:1. Four strains producing CLA were screened from northeast sauerkraut, fresh milk, yogurt, and activated sludge. Strain SC-05, screened from northeast sauerkraut, has the highest CLA producion. Especially, only c9, t11-CLA was found in the fermentation product using SC-05 strain detected by Gas Chromatography method.2. Sequencing and analysis of 16s rDNA sequence of SC-05 strain, showed that it is the closest relative with Lactobacillus. SC-05 strain was identified as a strain of Lactobacillus sp.3. Lactobacillus sp. SC-05 was induced by low temperature plasma, then a mutation strain A-08 was screened out, by which CLA production could reach 119.24 ?g/mL, raised 83.00% compared with in the original strain.4. The medium components for the strain A-08 to produce CLA were optimized by using orthogonal experiment, and fermentation conditions were studied by using the single factor experiment and response surface method (RSM). The optimum medium consisted of glueose 3%, peptone 0.5%, beef extract 2%, yeast extract 2%, diammonium citrate 0.2%, sodium acetate 0.3%, dipotassium hydrogen phosphate 0.2%, magnesium sulfate 0.02%, manganese sulfate 0.02%. The suitable fermentation conditions for the mutation strain A-08 to produce CLA were:LA emulsion liquild 0.38%, temperature 37?, initial pH 6.5, inoculumsize 2%, fermentation time was 44.67 h and micro-aerobic condition. The production of CLA reached 196.27 ?g/mL under the optimized medium and fermentation condition, which was 64.60% higher than that of the original strain.5. Batch fermentation and fed-batch fermentation were carried out in 5 L fermenter to improve cell density. The production of CLA could reach 213.26 ?g/mL under the condition of pH-stat 4.5.