Investigation into the Active Substance of Bacillus velezensis TRM82367 for Killing Aphis gossypii

A total of 304 bacterial strains were isolated from the Taklamakan Desert. Through screening, strain TRM82367 exhibited potent insecticidal activity against cotton aphids (<i>Aphis gossypii</i>) and was identified as <i>Bacillus velezensis</i>. To explore the primary insecticidal active components of this strain, lipopeptide substances in the fermentation broth were extracted via hydrochloric acid precipitation. The main active components were analyzed using activity-guided fractionation combined with liquid chromatography-mass spectrometry (LC-MS). Our results demonstrated that <i>Bacillus velezensis</i> TRM82367 possessed strong lethal activity against cotton aphids. The crude extract obtained by means of hydrochloric acid precipitation and methanol dissolution showed high insecticidal efficacy. At concentrations of 100, 150, 200, 250, 300, 400, and 500 mg/L, the 48 h corrected mortality rates of cotton aphids were 25.14%, 38.05%, 50.09%, 53.03%, 57.96%, 74.68%, and 88.67%, respectively. The toxicity regression equation was Y = 2.47X - 5.72, with a median lethal concentration (LC₅₀) of 207.616 mg/L and a 95% lethal concentration (LC₉₅) of 1004.673 mg/L. After separation by an ODS chromatographic column and identification by means of mass spectrometry, the main active components were confirmed to be C₁₂-C₁₆ surfactin homologs.