Identification and liquid fermentation of biocontrol Bacillus isolated from wolfberry (Lycium barbarum) rhizosphere soil

Na Xi^1,2Tengda Liu³Yuzhou Zhang^3,4Kuo Liu³Huaying Du³Peiwen Gu³Zeyang Yu^3*Yuyang Song¹

• ¹Northwest Agriculture and Forestry University, Yangling, China
• ²Ningxia Rural Science and Technology Development Center, Yinchuan, China
• ³Ningxia University, Yinchuan, China
• ⁴Ningxia Forest Pest Control and Quarantine Station, Yinchuan, China

In this study, a strain of Bacillus subtilis was identified by morphology, physiology, biochemistry, and molecular biology and was named LK-1. It had sound preventive and control effects against many kinds of Fusarium. The antagonistic curve showed that the best antagonistic fermentation time was 48 h. The fermentation broth and bacterial suspension of LK-1 both had sound antagonistic effects on the mycelium or spores of F. oxysporum; when the mycelium or spores of F. oxysporum were treated by LK-1, they grew abnormally. Compared to fermentation broth, the antagonistic effect of sterile filtrate was lower. In addition, compared to the L. barbarum seedlings in the CK group, the plant height, root length, fresh weight above-ground, fresh weight underground, dry weight above-ground, dry weight underground, and leaf area indexes of L. barbarum seedlings treated with LK-1 fermentation broth (1×108 cfu/mL) were all significantly increased. The strain LK-1 cultivated for 24 h was detected as the seed solution. Through the one-way test, Plackett-Burman test and Box-Behnken test, the fermentation medium and fermentation conditions of strain LK-1 were finally determined as 0.5% glucose, 2% beef paste, 2% NaCl, 0.5% yeast powder, fermentation time of 46 h, inoculum amount of 1%, pH 6.6, rotational speed of 170 rpm, and the validation test showed that the bacterial inhibition reached 62.5%, which was 1.43% higher than the theoretical value and 8.06% higher than the unoptimized value (54.44%).