Resistance of two Lactobacillus paracasei bacteriophages of temperate origin to thermal treatments, high pressure homogenization and chemical biocides of industrial application. POSTER

MERCANTI, D.; GUGLIELMOTTI, D.; REINHEIMER, J.; QUIBERONI, A.

Buenos Aires

Congreso; XIII Congreso Argentino de Ciencia y Tecnología de Alimentos; 2011

AATA

Temperate bacteriophages ф iLp84 and ф iLp1308, isolated after mitomycin C induction of Lactobacillus paracasei strains 84 and 1308, respectively, were tested for their resistance to several physical and chemical treatments of application in dairy industry. Lb. paracasei strains INL3 and A14 were used as host of ф iLp84 and ф iLp1308, respectively. Both phages were tested for their survival at different temperatures of storage, and after thermal treatments of 63ºC, 72ºC and 90ºC in three different media for up to 45 min. Their resistance to high pressure homogenization (HPH) and to either classic (ethanol, sodium hypochlorite and peracetic acid) or five new commercial sanitizers, namely A (quaternary ammonium chloride), B (hydrogen peroxide, peracetic acid and peroctanoic acid), C (alkaline chloride foam), D (p toluensulfonchloroamide, sodium salt) and E (ethoxylated nonylphenol and phosphoric acid), was also studied. Both phages showed very good survival rates during long-term (1 year) storage at 4ºC, -20ºC and  -80ºC, but a fast decay (about 5 log orders) was observed after six months of room temperature storage (25ºC). Phage iLp1308 showed higher thermal resistance than ф iLp84, though none was detected after 2 min at 90ºC. Slight variations among different suspension media were observed only for iLp1308. Best chemical inactivaction was accomplished by using peracetic acid or biocides A, C and E, followed by sodium hypochlorite, whereas ethanol was less efficient and biocides B and D had no effect on phage viability. Phage iLp1308 was more resistant than ф iLp84 to biocide A, but the opposite was true for sodium hypochlorite. Both phages survived well HPH treatments, likewise previously reported phages of Lb. paracasei and Lb. plantarum, being noticeably more resistant than phages infecting other genera of lactic acid bacteria. In summary, our results would help to select better chemical agents and physical treatments to effectively fight against phage infections in dairy plants.