Abstract:

Using the fermentation broth bacterial quantity as the screening index, the single-factor method was used to screen the best carbon source, nitrogen source, inoculum amount, pH, temperature, and incubation duration for strain PBSH9. The findings indicated that the best material for strain PBSH9 development was wheat bran. When wheat bran was used to replace soluble starch in Gaoshi 1 medium with a concentration of 1%, the bacterial colony amount of strain PBSH9 in the fermentation broth was 104.3×10⁹ CFU/mL, and the antibacterial rate was 60.3%. Soybean meal powder is most beneficial for the growth of strain PBSH9, When replacing potassium nitrate in Gaoshi 1 culture medium with 0.5% concentration of soybean meal powder, the maximum number of colonies and antibacterial rate were 123.7×10⁹ CFU/mL and 55.6%, respectively. Inoculating a seed solution with a concentration of 1×10⁸ CFU/mL by 4% ratio into Gaoshi 1 culture medium, the fermentation broth had the highest bacterial amount and antibacterial rate, with a colony amount of 144.6×10⁹ CFU/mL and an antibacterial rate of 71.9%; strain PBSH9 in pH 6.0-7.0 had the strongest bacterial inhibition activity, 66.3% and 65.8%, respectively; the fermentation broth had the largest colony size and bacterial inhibition rate at 28 ℃, with a colony size of 101.6×10¹⁰ CFU/mL and 69.1% inhibition rate. When cultured in optimized fermentation medium for six days, the maximum bacterial amount and antibacterial rate (71.9%) were achieved.

Key words: Potato, Potato scab disease, Streptomyces, Biocontrol bacteria, Optimization of fermentation conditions