Study On The Fermentation Character Of A L-Lactic Acid High-Yield Strain Thermophilus Lactobacillus Sp.T-1

In this paper, a L-lactic acid high-yield bacteria strain Lactobacillus sp. T-1 was studied.Some physiological and biochemical experiments were done on T-1. As a result, T-1 was a thermophilus strain and 50℃ was its suitable temperature. It was auxotroph for some vitamin, nuclear acid and amino acid. Something in peptone was its growth factor.The fermentation condition in conical flask of T-1 was optimized. An fermentation form was established. The optimum composition of inoculation medium(g. L^-1): glucose 30, K₂HPO₄ 1, Y.E. 5, peptone 5, CaCO₃ 10. Corn flour was selected from rice flour, corn flour, cassava flour, glucose and xylose as carbon source and energy source. The effect of Y.E., peptone, soybean flour, vegetable juice and wheat bran as nitrogen source on fermentation was studied. The result showed that wheat bran and vegetable juice were not good to fermentation. The optimum composition of culture medium(g. L^-1): glucose(corn) 110, Y.E. 4.3, peptone 4.3, soybean flour 4.9. 100.4g/L L-lactic acid and 91.3% conversion were achieved in this culture, improved by 10.5% and 8.7% respectively. A factorial fractional experimental design was performed to define optimization condition for fermentation. The optimization of inoculation was 10%(V/V). The optimum pH was 5.2-5.4. The optimum volume of the culture in the flask was 150mL. The rotary rate of shakers was 150r/min. The optimum aeration was that shaking cultivation should last 20 hours first, then shaking flasks were put into static state. The glucose concentration was 110 g/L. On this condition, 102.4g/L L-lactic acid were achieved and the conversion reached 93.1%. On the optimized condition, the concentration of dissolved oxygen in culture was 0.15 mg/L and 2.6% at the first 20 hours, then reduced to 0.12 mg/L and 2.1%.The organic acids in broth were detected by HPLC and GC-MC, and the results showed that TCA circle existed in Lactobacillus sp. T-1. The purity of L-Lactic acid reached 98.4% by using HPLC and a L-Lactic acid diagnostic kit to detect.The effect of K₄Fe(CN)₆ on T-1 was studied. 0.05% K₄Fe(CN)₆ could improve the speed of fermentation and the amount of cells. This was similar to fermentation in cassava culture. Cyanide may be the reason caused such a phenomenon.