Microbial interactions and biocontrol for reducing mycotoxin accumulation in stored rice grains under temperature and humidity variations.

Temperature and humidity critically influence microbial dynamics and mycotoxin accumulation in stored rice, posing risks to grain quality and food safety. This study analyzed 150 rice samples from three major Chinese regions (Liaoning, Chongqing, Zhejiang) to assess microbial community shifts and their implications. Geographical factors exerted stronger effects on microbial diversity than storage duration, with bacterial Chao1 indices varying significantly (Chongqing: 322.73 ± 67.59; Zhejiang: 203.47 ± 37.69; Liaoning: 146.28 ± 41.22; P < 0.05), indicating that regional factors including climate, soil properties, farming practices, etc. exert stronger influence on microbial community. Microcosm experiments under simulated storage conditions (15-30 °C, 50-80 % RH) revealed that elevated temperature and humidity promoted fungal proliferation, notably Aspergillus (relative abundance surged from 0.014 % to 61.01 % at 25 °C & 75 % RH), correlating with increased mycotoxins (aflatoxin B1, ochratoxin A). Co-occurrence network analysis identified antagonistic bacterial guilds, particularly Bacillus subtilis, which reduced aflatoxin B1 (26.27 %), ochratoxin A (25.71 %), and zearalenone (13.33 %) levels in inoculated rice samples (P < 0.001). Fungal diversity positively correlated with mycotoxin accumulation (R = 0.54 for ochratoxin A, P = 0.0027), while bacterial diversity negatively impacted toxin levels (R = -0.78, P = 1.3e-06). These findings underscore the ecological role of bacterial-fungal interactions in grain quality and highlight B. subtilis as a sustainable biocontrol agent to mitigate mycotoxin risks. The study provides actionable insights for optimizing storage practices, reducing chemical fungicide reliance, and enhancing food safety in the rice industry.