Hydrogen sulfide producing bacteria (SPB) in raw animal by-products are likely to grow and form biofilms in the rendering processing environments, resulting in the release of harmful hydrogen sulfide (H2S) gas. The objective of this study was to reduce SPB biofilms formed on different surfaces typically found in rendering plants by applying a bacteriophage cocktail. Using a 96-well microplate method, we determined that 3 SPB strains of Citrobacter freundii and Hafnia alvei are strong biofilm formers. Application of 9 bacteriophages (107 PFU/mL) from families of Siphoviridae and Myoviridae resulted in a 33%–70% reduction of biofilm formation by each SPB strain. On stainless steel and plastic templates, phage treatment (108 PFU/mL) reduced the attached cells of a mixed SPB culture (no biofilm) by 2.3 and 2.7 log CFU/cm2 within 6 h at 30 °C, respectively, as compared with 2 and 1.5 log CFU/cm2 reductions of SPB biofilms within 6 h at 30 °C. Phage treatment was also applied to indigenous SPB biofilms formed on the environmental surface, stainless steel, high-density polyethylene plastic, and rubber templates in a rendering plant. With phage treatment (109 PFU/mL), SPB biofilms were reduced by 0.7–1.4, 0.3–0.6, and 0.2–0.6 log CFU/cm2 in spring, summer, and fall trials, respectively. Our study demonstrated that bacteriophages could effectively reduce the selected SPB strains either attached to or in formed biofilms on various surfaces and could to some extent reduce the indigenous SPB biofilms on the surfaces in the rendering environment.
AHLs Regulate Biofilm Formation and Swimming Motility of Hafnia alvei H4
