Abstract: This study aimed to select and optimize the critical medium components and fermentation conditions for the production of folate by Lactococcus lactis KLDS4.0325, isolated from koumiss in Northwest China’s Xinjiang. Folate content in the fermentation broth of this strain was determined by high performance liquid chromatography (HPLC). Using one-factor-at-a-time (OFAT) method, yeast extract and glucose were identified as the optimal nitrogen and carbon sources, respectively, and initial pH, the concentration of p-aminobenzoic acid (pABA) and glutamic acid and culture temperature were identified as main factors that influence folate production. The levels of the four factors were further optimized using response surface methodology with Box-Behnken design. The optimal values for initial pH, pABA concentration, glutamic acid concentration and fermentation temperature were determined as 5.40, 42.0 mg/L, 6.30 g/L and 35.40 ℃, respectively. Under these conditions, the yield of folic acid was 0.814 μg/mL, which was 3.13 times higher than that (0.260 μg/mL) before the optimization. This study provides technical support for the industrial production and application of natural folate.

Key words: response surface methodology, Lactococcus lactis KLDS4.0325, natural folate, medium composition, fermentation conditions