Lb.paracasei Hd1.7 Metabolic Regulation Of Synthesis Of L-lactic Acid And L-lactic Acid Extraction And Purification

Lactic acid is one kind of ancient and important organic acid, widely used in the chemical, food, and pharmaceutical industries. As a result of the human body only have L-lactic dehydrogenase, only metabolism L-lactic acid, therefore, with high optical purity L- lactic is required in edible and for medicinal purposes domain. On the macromolecule polymerization materials PLA synthetic industry called L-lactic acid optical activity reache more than 97%, this make PLA costs very high and its application under great restrication.In this dissertation, produces L-lactic acid with Lb.paracasei HD1.7.Through study the enzyme (LDH) character to adjust metabolism condition and union industry need and carry out a new isolation method with ceramics film and nanometer film fiteration removing the protein, power active charcoal in combination with sugar and pigments removal and ion exchange resin method purification lactic acid.Main conclusion of experiment as follows:1. The optimum catalysis temperature of cf LDH which abstract from Lb.paracasei HD1.7 is 35℃, Optimum reaction pH value is 7.5,Mg2+ and Ca2+could increase the activity of LDH, but Mn2+ could reduce its activity.The Km constants based on the substrates of pyruvate and NADH were 1.30×10-4mol/L and8.69×10-4mol/L respectively. Through add 10g/L pyruvate in liquid fermenting in12h, the production of Lactic acid up to 94g/L, the rotation of lactic acid is 97.4%.2. After ceramics film and nanometer film fiteration the protein-removing rate was 87.5% and the loss rate of lactic acid was 4.5%. Having obvious advantage compare with tradition protein removal handicraft. By the comparison of the effects on the removal of residual sugar and pigment in fermentation liquid between the powered activated charcoal and granular activated charcoal particles, the Guangfu power activated charcoal was chosen .By study the temperature, the volume ,stirring speed, reaction time and pH value make sure the best condition.According to the orthogonal experimental design based on the single factor experiments, when the volume of adsorbent added 6%, temperature50 C,pH value6.0, rotational speed 110r/min, time1.5h, the rate of the removal of residual sugar was 90.3%,pigment 96.5% and the loss rate of lactate was 5.8%.3. Choose two kinds of resins from 9 resins which is suitable to isloation lactic acid. The type is 001-7 and D301-R. Through these resins dynamic adsorption curve,study the effect of temperature ,flow rate, different concentration on exchange capacities and adsorption balance, make suer the best reaction condition is: 30℃,flow rate2.0mL/min, etrance lactic acid cocentration is 80g/L for001-7 and 40℃, flow rate1.5mL/min, etrance lactic acid cocentration is 100g/L for D301-R .the recovery of lactic acid could reach 83%.