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.

Mycotoxin contamination in rice can create a health risk for the consumers. In this study, the measurement of 23 mycotoxins in rice samples (n = 180) was performed using a validated LC–MS/MS method. A food frequency questionnaire was used to get rice consumption data for the assessment of mycotoxin dietary exposure, before calculating the health risk in adults and children of north and south regions of the Pakistani Punjab province. The prevalence of aflatoxin B1 (56%), aflatoxin B2 (48%), nivalenol (28%), diacetoxyscirpenol (23%), fumonisin B1 (42%), zearalenone (15%), HT-2 toxin (10%), deoxynivalenol (8%), and ochratoxin A (6%) was estimated in samples with a mean concentration range between 0.61 and 22.98 µg/kg. Aflatoxin degradation by traditional Pakistani cooking recipes was evaluated and observed to be 41–63%. The dietary exposure to aflatoxins exceeded the tolerable daily intake at all levels, and ochratoxin A and zearalenone posed health risk at high contamination and high consumption levels. The margin of aflatoxin B1 exposure ranged between 10 and 69 in adults and 10 and 62 in children. The mean cancer risk by aflatoxin B1 exposure was 0.070 (adults) and 0.071 (children) cases/year/100,000 people in South Punjab population, and 0.122 (adults) and 0.127 (children) cases/year/100,000 people in North Punjab population. This study will provide new insights for the planning and management of mycotoxins in Pakistan.

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