Screening Of Folic Acid Producing Strains,Study On Its Biological Characteristics And Optimization Of Fermentation Condition

The paper mainly focused on screening of folic acid-producing strains, from the soil, spinach and water. After qualitative screening folic acid-producing strains,34strains, which have the ability of producing folic acid, were obtained. Six strains, named Ra-1, Ra-10, Ra-18, Rb-8, Rc-6and Sc-1, producing relatively high folic acid were selected by the high-performance liquid chromatography. According to morphological, physiological, biochemical properties and16S rDNA homology analysis, strain Ra-1, Ra-10, Ra-18Rb-8and Rc-6were identified as Lactobacillus plantarum, while Sc-1was Streptococcus thermophilus.In order to find the best way to produce folic acid, High performance liquid chromatography and fluorescence detection (potassium permanganate and hydrogen peroxide) were chose and compared. The results show that the folic acid standard solution by High performance liquid chromatography was in0.65μg/mL, with the accuracy rate of98.9%, while98%of potassium permanganate oxidation fluorescence method, the hydrogen peroxide oxidation fluorescence method was relatively low, at94.2%. Considering the operability of the experiment and the accuracy rate, fluorescence detection of potassium permanganate was closer to the result of oxidation measured by HPLC and can make the test results stability. So we chose the potassium permanganate oxidation fluorescence method to detect folate amount.Through the growth kinetics of these six bacteria, the optimum growth temperature of Lactic acid bacteria belonged to37℃, while Streptococcus thermophilus was30℃. Then all strains were cultured under the optimum growth conditions to determine the intracellular and extracellular folic acid amount. We could find that the intracellular folate production was2times folic acid of extracellular amount. Besides, the best output time of extracellular folic acid in6strains were different from the intracellular folate production. Considering the feasibility of the experimental operations and costs, the fermentation broth could have a larger of collection. So this study mainly researched on the extracellular production of folic acid and optimization.In the end, the research compared the folic acid production capacity in the case of joined optimization substances and different culture conditions, including three repeated test, Single factor experiments and orthogonal experiments. The addition of PABA resulted in approximately1.5to2times before joining the PABA. The results showed that the optimal fermentation conditions of strain Ra-1were as follows:glucose25g/L, ammonium citrate4g/L, inoculum volume of2%, PABA0.3g/L, fermentation time24h, initial pH6.5, the yield of folic acid production was up to1.92μg/mL; The optimum conditions of Strain Ra-10:glucose20g/L, ammonium citrate4g/L, PABA0.3g/L, inoculum volume of3%(v/v), incubation time48h, initial pH6.0, the folic acid production was1.78μg/mL; Strain Ra-18’s optimum reaction conditions for the production of folic acid:glucose20g/L, peptone3g/L, PABA0.3g/L, inoculum volume of2%(v/v), fermentation time24h, initial pH6.0, folate production was up to1.41μg/mL; the conditions of Strain Rb-8:sucrose20g/L, ammonium citrate4g/L, PABA in0.5g/L, inoculum volume of3%(v/v), fermentation time48h, initial pH6.5, the folic acid production was1.27μg/mL; The best reaction conditions of strain Rc-6was as follows: glucose25g/L, yeast extract4g/L, PABA0.3g/L, inoculum size of3%(v/v), fermentation time48h, initial pH6.5, the yield of folic acid production was1.27μg/mL. The conditions in strain Sc-1:sucrose20g/L, ammonium citrate2g/L, PABA0.3g/L, inoculum volome of2%, fermentation time48h, initial pH5.5, the folic acid production was1.31μg/mL...