Optimization of biomass production for <i>Pseudomonas chlororaphis</i> P-105-b-a exhibiting antifungal activity against Post-Harvest phytopathogens

Post-harvest fungal diseases are major contributors to crop losses in fruits and vegetables, and although chemical fungicides are commonly used, they pose significant environmental and health risks. Biological alternatives, such as Plant Growth Promoting Rhizobacteria (PGPR), have gained attention for safer disease control. In this study, a total of 154 <i>Bacillus</i> and <i>Pseudomonas</i> strains were screened for antifungal activity against four common post-harvest fungal pathogens (<i>Alternaria papavericola</i>, <i>Botrytis cinerea</i>, <i>Monilinia laxa</i>, and <i>Penicillium italicum</i>) using dual culture and agar well diffusion assays, alongside lytic enzyme activity assessment. Thirty-five strains demonstrated effective antagonistic activity. Laboratory-scale production optimization of <i>Pseudomonas chlororaphis</i> P-105-b-a, the most effective strain, was carried out using Response Surface Methodology, achieving a viable cell count of 3.3 x 10¹⁰ cfu/mL in modified King's B Broth containing 5% glycerol and 2% dry yeast. This study provides insights for the development of PGPR-based biopreparations to enhance post-harvest disease management.