Abstract: The fermentation medium based on potato powder wastewater for lipopeptides production by Bacillus amyloliquefaciens PC2 strain was optimized by Plackett-Burman design and Box-Behnken response surface methodology. The results showed that contents of total protein, total free amino acids, total free starch and total reducing sugar in wastewater were 16.00 mg/mL, 2.11 mg/mL, 0.18 mg/mL and 1.29 mg/mL, respectively. K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Zn²⁺, Cu²⁺ and Mn²⁺ were present at concentration of 1.07 mg/mL, 0.05 mg/mL, 0.10 mg/mL, 7.10 μg/mL, 2.34 μg/mL, 0.25 μg/mL and 0.09 μg/mL, respectively. The fermentation broth of PC2 strain based on potato powder wastewater alone did not show lipopeptides inhibitory effect. The optimal medium components were as the follows:sucrose 30.2 g, sodium glutamate 3.96 g, (NH₄)₂SO₄ 6.0 g, potato powder wastewater 1000 mL. The inhibitory zone diameter of lipopeptides fermented by the optimal medium against Staphylococcus aureus was 21.74 mm. Moreover, the fermentation conditions were optimized by single factor horizontal and response surface methodology. The optimal fermentation conditions were 6.0% inoculation, 50 mL/250 mL medium capacity, temperature at 31℃, medium initial pH 6.8, rotate rate at 170 r/min and fermentation time for 35 h. The inhibitory zone diameter of the lipopeptides crude extract under the optimized conditions against S. aureus was 22.81 mm, increased by 1.08 mm compared with that before optimization, and the viable bacteria number in the fermentation broth increased from 2.6×10⁸ CFU/mL to 3.2×10¹⁰ CFU/mL. The results suggested the optimized medium based on potato powder wastewater could be used for the low-cost production of lipopeptides by B. amyloliquefaciens PC2.

Key words: potato powder wastewater, Bacillus amyloliquefaciens, lipopeptide, response surface methodology, medium optimization