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Chinese Journal of Biological Control ›› 2021, Vol. 37 ›› Issue (4): 771-784.DOI: 10.16409/j.cnki.2095-039x.2021.09.007

• RESEARCH REPORTS • Previous Articles     Next Articles

Optimization of Fermentation Conditions for Co-culture of Nematocidal Bacillus amyloliquefaciens Sneb709 and Sinorhizobium fredii Sneb183

LI Jiadi1, ZHAO Jinjie1, FAN Haiyan1, ZHU Xiaofeng1, WANG Yuanyuan2, LIU Xiaoyu3, DUAN Yuxi1, CHEN Lijie1   

  1. 1. College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China;
    2. College of Biological Science and Technology, Shenyang Agricultural University, Shenyang 110866, China;
    3. College of Science, Shenyang Agricultural University, Shenyang 110866, China
  • Received:2020-10-10 Published:2021-09-18

Abstract: Root-knot nematodes can cause serious soil-borne diseases of crops, and biological control is an effective measure to sustainability control such diseases. Several strains of Bacillus and Rhizobium with nematicidal activity were obtained in previous work of our laboratory. In this study, Bacillus amyloliquefaciens Sneb709 and Sinorhizobium fredii Sneb183 were co-cultured, and the co-culture fermentation broth had significantly improved activity against Meloidogyne incognita second-stage juveniles (J2). To obtain better biocontrol effects, the fermentation conditions were optimized by response surface methodology. Taking the corrected mortality rate of J2 as an indicator, the single factor method, steepest climbing method and response surface method are used to design and optimize the fermentation broth composition and culture conditions of the co-cultured strains. The most suitable medium composition of the co-culture fermentation broth was determined as follows:sorbose 1.98 g/L, soy flour 1.06 g/L, peanut meal 2.08 g/L. The optimal fermentation conditions were as follows:temperature 30.4℃, initial pH 6.49 and liquid volume 103.15 mL. After the two strains were co-cultured with optimized conditions, the toxic activity of the fermentation broth on J2 was significantly improved, with the mortality of 84.17%. After verification in the fermenter, the toxic activity of the co-culture fermentation broth increased by 24.72%. This result provides a theoretical basis for subsequent studies on separation and extraction of active products of co-cultured strains and the industrialization of nematocidal biocontrol bacteria.

Key words: root-knot nematode, Bacillus, Rhizobium, co-culture, fermentation condition

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