Viable counts, characteristic evaluation for commercial lactic acid bacteria products

Abstract

Eight commercial lactic acid bacteria (LAB) products were assayed for their LAB cell counts, acid and bile tolerance, and adherence to human intestinal epithelium. Results showed that the viable cell densities in liquid products, such as fermented milk samples, were higher than those in the solid products. In two solid products, viable LAB counts were not found indicating the incorrect labeling on the package. With a simulated human gastrointestinal digestion system, LAB strains from different commercial products were found to have different acid and bile tolerance. Twenty five LAB isolates from five commercial products were assayed for their antagonistic activities against bacterial pathogens, such as Staphylococcus aureus, Escherichia coli including enterotoxigenic strain, and Salmonella typhimurium. The spent culture supernatant (SCS) from some LAB isolates significantly inhibited the growth of these indicator bacteria. Among these 25 isolates, only five from one commercial product exhibited weak adherence to the human intestinal epithelial cells (Int-407). The rest showed no adherence at all. In conclusion, only few commercial LAB products meet the basic requirements for probiotic functions.