VOCs-mediated allelopathy by Bacillus subtilis on suppressing drainage malodor

Microbial volatile organic compounds (mVOCs) are diverse small molecules produced by microorganisms that mediate complex community interactions via offensive and defensive mechanisms. This study investigated the allelopathic potential of mVOCs emitted by Bacillus subtilis to suppress odorous emissions from drainage-associated bacteria, particularly targeting Pseudomonas aeruginosa. Exposure to B. subtilis-derived mVOCs impaired metabolic, respiratory, and energy-generation processes in P. aeruginosa, significantly reducing its viability. Analysis of coastal drainage microbial communities showed that introducing B. subtilis-derived mVOCs markedly altered volatile emissions, reducing key odor compounds-including methylamine, acetaldehyde, nonane, and dodecane-by over 95 % under both aerobic and anaerobic conditions. Odor intensity (sum of odor intensities, SOI) decreased substantially from over 10-7.8 aerobically and 1.4 anaerobically. Additionally, microbial viability declined by up to 53.5 % under aerobic conditions, accompanied by shifts in community structure with Marinomonas decreasing by 25.9 % and Thalassolituus increasing by 17.8 %. Under anaerobic conditions, viability dropped by up to 76.6 %, alongside a 12.3 % decrease in Psychrosphaera and an 11.8 % increase in Maricurvus. These findings highlight the potential of Bacillus subtilis-derived mVOCs as an innovative biocontrol strategy for mitigating odor issues in complex microbial environments, such as coastal drainage systems.