The inhibition mechanism of Lactobacillus fermented whey protein and blueberry juice mixture system against Escherichia coli during storage

Abstract This study aimed to identify the antimicrobial effect and mechanism of whey protein and blueberry juice mixture system using lactobacillus fermentation against Escherichia coli during storage. The whey protein and blueberry juice mixture systems using Lactobacillus casei M54, Lactobacillus plantarum 67, Streptococcus thermophiles 99 or Lactobacillus bulgaricus 134 had different antibacterial activity against E. coli during storage. The antimicrobial activity of whey protein and blueberry juice mixture fermentation systems was the highest with inhibition zone diameter of about 230 mm compared with the whey protein or blueberry juice fermentation alone. There was no viable E. coli cells after 7 h with the treatment of whey protein and blueberry juice mixture systems by survival curve analysis. The inhibitory mechanism analysis showed that the release of alkaline phosphatase (AKP), electrical conductivity, protein content, aspartic acid transaminase (AST), alanine aminotransferase (ALT) and pyruvic acid content on E. coli had increased. These results demonstrated that these mixture fermentation systems especially containing blueberry could inhibit the growth of E. coli and even cause cells death by destroying the cell the membrane and cell wall.