A phage powder for postharvest biocontrol of brown blotch disease in mushrooms caused by Pseudomonas tolaasii

Pseudomonas tolaasii , the causative agent of brown blotch disease in Agaricus bisporus , has been shown to cause significant postharvest losses through surface browning and quality degradation. To address this issue, we developed a freeze-dried bacteriophage (phage) powder formulation containing the newly isolated MKPT02 phage, which exhibits strong lytic activity and has high host specificity against P. tolaasii . This formulation incorporates sucrose and whey protein isolate (WPI) as cryo- and matrix-protectants to preserve phage viability under ambient conditions. Moreover, the optimized composition of 5% (w/v) sucrose and 4% (w/v) WPI maintained high phage titers with low water activity and minimal caking after 4 weeks of storage at 25°C. When applied to mushrooms, the phage powder reduced brown blotch symptoms by effectively suppressing the activity of the pathogen. The present study is the first to report a solid-state phage powder specifically designed to control brown blotch disease in A. bisporus , providing a practical alternative to conventional liquid-based treatments. Its long-term stability, scalability, and efficacy without refrigeration suggest its potential for commercial use in mushroom production and distribution. Furthermore, this technology represents a residue-free, sustainable approach to the biological control of P. tolaasii , contributing to postharvest quality preservation and advances in eco-friendly food packaging.