Selection and Characterisation of Lactobacillus and Bifidobacterium Strains for Use as Probiotics

Abstract A large culture collection of lactic acid bacteria held at NZDRI (of over 2000 strains) was screened to select strains with functional characteristics typical of probiotic bacteria. Selection criteria employed included the ability of strains to withstand environmental conditions similar to the digestive tract as well as specific biological activites. Following an initial screening of over 200 strains selected from the collection, four strains were identified as putative probiotic strains. Three of the selected strains were of dairy origin and one was of human origin. These strains were able to survive at low pH and relatively high bile concentrations and compared favourably in these respects to two commercial probiotic strains namely Lactobacillus rhamnosus GG and Lactobacillus acidophilus LA-1. Of the 200 strains studied, a higher proportion of strains of human origin were found to be resistant to both low pH and high concentrations of bile as compared to strains of dairy origin. The four putative probiotic strains were characterised by classical microbiological techniques and molecular methodologies including DNA–DNA homology, SDS–PAGE analysis of whole cell proteins, PFGE, species-specific probes and RAPD. The strains were identified as Lb. rhamnosus HN001 (also known as DR20), Lb. acidophilus HN017, Lb. rhamnosus HN067 and Bifidobacterium. lactis HN019 (also known as DR10).