Optimisation of cultivation conditions for Bacillus velezensis G7 from mangrove plants and exploration of potential bacteriocins

The optimal culture conditions for <i>B. velezensis</i> G7 are 4.5 g/100 mL glucose, 1.5 g/100 mL yeast, and 1.2 g/100 mL MgSO₄·7H₂O. The stability of the CFS is affected by several factors, including heat, UV treatment and different storage conditions. High temperatures and long UV irradiation treatments significantly reduce the stability of CFS, which is more sensitive to strong acids, bases and enzymatic degradation. The minimum inhibitory concentration (MIC) of purified bacteriocin P7 against <i>S. aureus</i> was determined to be 30.352 μg/mL. On the basis of the results of the haemolytic activity assay, it was concluded that the use of bacteriocin P7 at concentrations equal to or below the 2 × MIC is safe. The addition of organic solvents and inorganic salts did not affect the bacteriocin P7, while the incorporation of SDS could enhance its antimicrobial efficacy. The bacteriocin was subjected to analysis by LC-MS/MS, which revealed that it was similar to the class I bacteriocin amyloliquecidin GF610. The findings of the present study indicate that the endophytic <i>B. velezensis</i> G7 from mangrove plant can produce bacteriocins, thereby providing a reference point for the expansion of novel bacteriocin sources.