Abstract: One-factor-at-a-time method, Plackett-Burman design and response surface methodology were employed combinedly to optimize a growth medium based on low-cost agricultural by-products, like soybean meal, corn flour, wheat middlings and tomato juice for large-scale cultivation of Lactobacillus plantarum YSQ. The results showed that: 1) According to the results of one-factor-at-a-time experiments, in the culture medium, the carbon source were composed of corn flour, wheat middlings, the nitrogen source was soybean meal, and tomato juice was added as a growth factor. 2) As identified by Plackett-Burman design, the main factor that affect the growth of Lactobacillus plantarum YSQ were wheat middlings, soybean meal, K2HPO4 and MnSO4. 3) Collectively, the results of steepest ascent tests, central composition design and response surface analysis indicated that the optimal growth medium was composed of corn flour 10 g/L, soybean meal 15.5 g/L, bran 1.2 g/L, sucrose 5 g/L, tomato juice 150 mL/L, K2HPO4 1.1 g/L, MnSO4 0.28 g/L, MgSO4 0.3 g/L. The total viable count was 2.68 × 1010 CFU/mL after 18 h of culture in the optimized medium, while that obtained with a medium composed of a mixture of corn flour, soybean meal and bran was only 8.73 × 108 CFU/mL.

Key words: Lactobacillus plantarum YSQ, fermentation medium optimization, Plackett-Burman design, response surface methodology