Bioconvertion Of Linoleic Acid Into The Conjugated Linoleic Acid By A Lactobacillus Acidophilus

A high conjugated linoleic acid (CLA) producing mutant L.S1 was screened fromLactobacillus acidophilus 1.1854 after UV and chemical mutation. And preliminary studieson characteristics of LS1 were conducted.Optimization of LS1 synthesizing conjugatedlinoleic acid was researched to search for optimum conditions. In addition, CLA formationconditions of fermentation skim milk was studied by L.S1.Which had a certain theoreticmeaning and practical value.1. The growth curve of L.S was studied.The OD value was determined each two hours. Theresult showed that the front four hours were lag phase. And then logarithmic growth phasewas confirmed from four hours to sixteen hours, and gradually entered stationary phaselater.2. The fatality rate of L.S was studied by UV and DES on flat count. The result indicatedthat the lethal ratio reached to 72% and 75% respectively when UV treated five secondsand DES used thirty minutes.3. The character of L.S1 was researched after induced mutation by UV and DES. The resultindicated that the growth period of L.S1 changed a little, and logarithmic growth phase wasshortened and the stationary phase was extended. And the cell of L.S1 became larger andlonger and the titratable acidity was strengthened.The stability of L.S1 producing CLA wasbetter than others.4. Five factors quadric orthogonal rotatable design were used to study the influence ofreaction temperature, pH, the concentration of linoleic acid, inoculation dosage andincubation time on CLA production.The result indicated that the optimum conditionswere reaction temperature 37℃, pH 4.74, the concentration of linoleic 0.1%, inoculationdosage 6% and incubation time 24h and the yield of conjugated linoleic acid was 31.2%.Y=29.66-0.37X₁+2.5X₂-1.53X₃+1.07X₅-0.1X₃X₅-0.15X₄X₅-4.67X₁²-3.62X₂²-2.94X₃²-1.67X₄²-2.94X₅².5.The effect of inducing, shaking, little oxygen and Tween-80 on Lactobacillus acidophilusproducing CLA were studied. The result indicated that inducing, shaking, little oxygen andTween-80 could improve CLA production to some extent.6. Fermentation dynamics curve was obtained by the study of the Lactobacillus acidophilusfermentation in MRS culture medium. The cells growth of Lactobacillus acidophilus,production CLA accumulation,pH value change and glucose metabolism were studied bysingle factor test.The results exhibited that the cells of Lactobacillus acidophilus grew slowly firstly ,and developed rapidly from three hours to fifteen hours, which enteredlogarithmic growth phase. And which gradually entered stationary phase later. Glucosemetabolism was consumed rapidly after three hours.Then glucose metabolism sloweredgradually.CLA production was few in front of three hours, then increased rapidly, CLAproduction reached a peak in twenty-four hours.7. Skim milk added linoleic acid(LA) was fermented by L.S1 after chemical mutation, andthe CLA formation conditions were optimized using three factors quadric orthogonalrotatable design. the optimum conditions were reaction temperature 37℃, pH 5.5, andincubation time 28h.Under the optimum conditions the yield of CLA was 33.4%.Y=32.55+2.71X₁+0.75X₂+4.13X₃+0.24X₁X₂+0.16X₂X₃-7.36X₁²-2.95X₂²-6.09X₃²...