Combined Effects of the Pijolavirus UFJF_PfSW6 Phage and Sodium Hypochlorite for Reducing Pseudomonas fluorescens Biofilm

<i>Pseudomonas</i> are significant spoilage bacteria in raw milk and dairy products, primarily due to their ability to form biofilms and resist disinfection. This study explored the effects of the <i>UFJF_PfSW6</i> phage combined with sodium hypochlorite in reducing <i>Pseudomonas fluorescens</i> biofilms on stainless steel at various temperatures and ages. Biofilms were formed using <i>P. fluorescens</i> UFV 041 in UHT milk, incubated at 4 °C and 30 °C for 2 and 7 days. Two lytic phages were compared, with <i>UFJF_PfSW6</i> showing superior activity, reducing cell counts by 0.8 to 2.0 logs CFU/cm² depending on conditions. Increasing the contact time of the <i>UFJF_PfSW6</i> phage from 4 to 8 h did not significantly affect the reduction in mature biofilms. The individual treatments of the phage and sodium hypochlorite (100 mg/L) reduced bacterial counts by 0.9 and 0.6 log CFU/cm² at 30 °C, and 1.3 and 1.2 log CFU/cm² at 4 °C, respectively. However, their sequential application achieved greater reductions, reaching 1.3 and 1.8 log CFU/cm² for biofilms formed at 30 °C and 4 °C, respectively. These findings suggest a promising strategy for controlling <i>P. fluorescens</i> in the food industry. Our findings suggest that the <i>UFJF_PfSW6</i> phage combined with chlorine improves the removal of <i>P. fluorescens</i> biofilms.