Study On Conjugated Linoleic Acid Biosynthesized By Lactobacillus Plantarum In Different Systems

A rapidly expanding body of results obtained in studies of animal models indicates that incorporation of conjugated linoleic acid (CLA) in the diet at a relatively low level confers a number of health benefits,including anti-carcinogenic and anti-atherogenic activity.The research described in this dissertation focuses on the production of CLA biosynthesized by Lactobacillus plantrum in different systems including traditional food system, resting cells system, non-aqueous system.In the traditional food system,skim milk,soybean milk,tomato juice were selected to investigate the problem : (i) the effect of linoleic acid (LA )amount to the growth of Lp;(ii) the effect of added form to the CLA production; (iii) the effect of preincubation to the CLA production.As a result, CLA was produced at 201.05μg per millimeter after 12h culture of Lp preincubated or not in skim milk containg 1 mg LA per milliliter and 2%(v/v) Tween-80; CLA was produced at 152.5μg per millimeter after 48h culture of Lp preincubated in soybean milk containg 1 mg LA per milliliter and 2%(v/v) Tween-80; CLA was produced at 37.35μg per millimeter after 12h culture of Lp not preincubated in tomato juice containg 1 mg LA per milliliter and 2%(v/v) Tween-80.The ratio between cis-9, trans-11 and trans-10,cis-12-CLA was 92.5:7.5 in soybean milk and 97.8:3.2 in skim milk using gas chromatograph(GC).The effects of carbon source, nitrogen source and metal ion on Lp in liquid-state induction were investigated. The composition of meidium was optimized with orthogonal test.The result showed that the optimal medium was as follows: 1%glucose,1.5% (phytone:meat extract=1:1),0.5% yeast extract,0.15%Tween-80, 0.01g FeSO4?7H2O, 5g sodium acetate,2g diammonium citrate.Optium operating conditions are 37℃,substrate of 1mg/mL LA,Tris-HCl buffer pH of 7.5 ,cell concentration of 20mgCDW(cell dry weight) per millimeter,a shake rate of 120r/min and a reaction time of 12h.Under these conditions, CLA was produced at 180.9μg/mL in resting system. The ratio between cis-9, trans-11 and trans-10, cis-12-CLA was 64.7:35.3 in resting cells system using GC.Using immobilized whole cell of Lactobacillus plantrum entrapped in a matrix composed of alginate gel and silica gel, the biosynthesis of CLA was investigated in non-aqueous system.The optimal conditions with orthogonal test were as follows: 1.5% sodium alginate, 0.2M CaCl2, 0.15g per 10millimeter silica gel,3mgCDW per millimeter vector。Suitable condition in non-aqueous system were: 37℃,substrate of 1mg per millimeter LA, cell concentration of 6mgCDW per millimeter ,a cell memory pH of 7.5 , water content of 3.025g/gCDW per millimeter,a shake rate of 120r per minute and a reaction time of 18h. Under these conditions, CLA recovery rate was17.82% in resting system.The ratio between cis-9, trans-11 and trans-10, cis-12-CLA was 98.85:1.15 in non-aqueous system using GC.