In situ production of pediocin PA-1 like bacteriocin by different genera of lactic acid bacteria in soymilk fermentation and evaluation of sensory properties of the fermented soy curd

The lactic acid bacteria (LAB) are found to produce bacteriocins with enhanced nutritive properties in the fermented foods. In the present study, the ability of LAB cultures (Pediococcus acidilactici NCIM 5424, Enterococcus faecium NCIM 5423 and Lactobacillus plantarum Acr2) to produce pediocin PA-1 like bacteriocin was evaluated during soymilk fermentation. The isolates E. faecium NCIM 5423 and Lb. plantarum Acr2 were able to produce bacteriocin as well as ferment soymilk within 6 h of incubation. Upon plating the cultures E. faecium NCIM 5423 and Lb. plantarum Acr2 in soymilk were found to be viable even after 15 days of storage at 4 °C. No significant variation was observed in the viable counts of E. faecium NCIM 5423 and Lb. plantarum Acr2 (P>0.05). The effect of crude bacteriocin on Listeria cells was evidenced through scanning electron microscope (SEM) photographs wherein cell membrane damage was observed. On co-cultivation of E. faecium NCIM 5423 and Lb. plantarum Acr2 individually with Listeria monocytogenes ScottA a decrease in the Listeria count was observed within 24 h of incubation. However, during co-cultivation of ScottA with P. acidilactici NCIM 5424, no significant difference was observed in the viable counts (P>0.05). The pH, titratable acidity, pediocin activity, anti-oxidant property and sensory attributes for E. faecium NCIM 5423 were studied. It was observed that E. faecium NCIM 5423 fermented soymilk had an acceptable sensory score during storage period. Hence, such culture can be an ideal starter for development of functional foods with longer shelf life.