The potential of the Bacillus genus to antagonize phytopathogens is associated with the production of cyclic lipopeptides. Depending upon the type of lipopeptide, they may serve as biocontrol agents that are eco-friendly alternatives to chemical fertilizers. This study evaluates the biocontrol activity of surfactin-producing Bacillus (SPB) strains NH-100 and NH-217 and purified surfactin A from these strains against rice bakanae disease. Biologically active surfactin fractions were purified by HPLC, and surfactin A variants with chain lengths from C12 to C16 were confirmed by LCMS-ESI. In hemolytic assays, a positive correlation between surfactin A production and halo zone formation was observed. The purified surfactin A had strong antifungal activity against Fusarium oxysporum, F. moniliforme, F. solani, Trichoderma atroviride and T. reesei. Maximum fungal growth suppression (84%) was recorded at 2000 ppm against F. moniliforme. Surfactin A retained antifungal activity at different pH levels (5–9) and temperatures (20, 50 and 121 °C). Hydroponic and pot experiments were conducted to determine the biocontrol activity of SPB strains and the purified surfactin A from these strains on Super Basmati rice. Surfactin production in the rice rhizosphere was detected by LCMS-ESI at early growth stages in hydroponics experiments inoculated with SPB strains. However, the maximum yield was observed with a consortium of SPB strains (T4) and purified surfactin A (T5) treatments in the pot experiment. The outcomes of the present study revealed that surfactin A significantly reduced rice bakanae disease by up to 80%. These findings suggest that purified surfactin A could be an effective biocontrol agent against bakanae disease in rice and should be incorporated into strategies for disease management.

芽孢杆菌属拮抗植物病原体的潜力与环状脂肽的产生有关。根据脂肽的类型，它们可以用作生物防治剂，是生态友好的化学肥料替代品。这项研究评估产生表面活性素的芽孢杆菌（SPB）菌株NH-100和NH-217以及从这些菌株中纯化的表面活性素A对水稻巴卡那病的生物防治活性。通过HPLC纯化具有生物活性的表面活性素级分，并通过LCMS-ESI确认链长为C12至C16的表面活性素A变体。在溶血测定中，观察到表面活性素A的产生与晕圈区域的形成呈正相关。纯化的表面活性素A具有较强的抗真菌活性尖孢镰刀菌，莫氏镰刀菌，茄形镰刀菌，阿特木霉和里氏木霉。最大真菌生长抑制（84％）被记录了在针对2000ppm的串珠镰孢。Surfactin A在不同的pH值（5–9）和温度（20、50和121°C）下仍具有抗真菌活性。进行了水培和盆栽实验，以确定SPB菌株和从这些菌株中纯化的表面活性素A在超级印度香米上的生物防治活性。在接种SPB菌株的水培试验中，通过LCMS-ESI在水稻生长期早期检测到了根际表面肌动蛋白的生成。但是，在盆栽实验中，使用SPB菌株（T4）和纯化的表面活性素A（T5）的联合体观察到了最大产量。本研究的结果表明，表面活性素A最多可将稻卡卡尼病减少多达80％。