Efficacy of Probiotic Lactobacillus Casei in Bio-control of Escherichia Coli O157:H7 in Nono

Abstract

The use of chemical preservatives and non-therapeutic antibiotics for milk preservation has been an aged long practice. Although, there are specified dosages for their uses, overall fact that they are synthetic raises a need for the adoption of bio-control measures which are deemed to be natural. Lactobacillus casei is a probiotic organism indigenous to Nono. Nono is a fermented milk beverage consumed in Nigeria. This research aimed at the use of L. casei as a bio-preservative against E. coli O157:H7 in Nono. L. casei and E. coli O157:H7 isolates were obtained from Nono and identified with 16S rDNA sequencing. The Lactobacillus isolate was assessed for probiotic abilities. It was used in ratios of 1:1, 1:2, 1:3, 1:4, and 1:5 against E. coli in Nano preservation. The time course and pH changes were monitored over a period of 24 h. There was notable decrease in the E. coli counts within 24 h with 1:5 ratio of E. coli to L. casei giving the highest contaminant reduction. Likewise same 1:5 ratio gave the highest L. casei count over the 24 h monitoring. pH monitoring showed that acidity increased with increase in ratio of L. casei, and 1:5 ratio had the highest acidity of 4.0±0.1. This research thus has shown that L. casei can act as a bio-control agent for the preservation of Nono from E. coli contamination. Its activity has been shown to be modulated by competitive inhibition and decrease in pH.