Title : Residual bacteria in cucurbitacin-containing phytonematicides: Molecular identification, performance mechanisms and sustainability
Abstract:
Cucurbitacin phytonematicides are potent eco-friendly alternatives to synthetic chemical nematicides, which have been withdrawn from the agrochemical markets. The products are manufactured through the fermentation process using effective microorganisms which comprise at least six bacteria – each with a specific role, but without information on the residual bacteria and mechanisms involved in promoting the stability and sterility of the products, along with how the test bacteria sustain themselves without compromising the active ingredients of the products. The research focused on identifying bacterial strains associated with the residual bacteria post the active fermentation process and their potential role in avoiding contamination and thus enhancing product sterility and stability, along with related energy pathways. Using a ZymoBIOMICS™ DNA Miniprep Kit for DNA extraction and 16S rDNA primers for PCR amplification. The study identified a dominant Lactobacillus species, with high genetic similarity to the Spanish Lactobacillus strains (HG794492). Phylogenetic analysis clustererd the South African Lactobacillus with L. vini and L. mobilis, with nucleotide sequence similarities ranging from 85 to 87%. Results indicate that Lactobacillus species dominated the mature stage, eliminating the other microbial constituents in the original EM. The study also explored the biochemical processes involved in fermentation, emphasizing the role of Lactobacillus in reducing pH and enhancing product sterility. Additionally, the research examined cucurbitacin degradation under different storage conditions, noting that temperature significantly influenced product stability, with tropical conditions extending the shelf-life, whereas chilled conditions had the opposite effect. The homolactic fermentation pathway at maturity, highlighted the production of copious lactic acids, hydrogen peroxide and adenosine triphosphate (ATP) molecules. In conclusion the findings suggest that the identified Lactobacillus species plays a crucial role in maintaining the efficacy, sterility and stability of cucurbitacin phytonematicides. Further, the study recommends whole-genome sequencing of the identified Lactobacillus species to refine bacterial classification and explore its bioremediation potential.
