Selection and characterisation of Lactobacillus and Bifidobacterium strains for use as probiotics

A large culture collection of lactic acid bacteria held at NZDRI (of over 2 000 strains) was screened to select strains with functional characteristics typical of probiotic bacteria. Selection criteria employed included the ab ility of strains to withstand environmental conditions similar to the diges tive tract as well as specific biological activites. Following an initial s creening of over 200 strains selected from the collection, four strains wer e identified as putative probiotic strains. Three of the selected strains w ere 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 fav ourably in these respects to two commercial probiotic strains namely Lactob acillus rhamnosus GG and Lactobacillus acidophilus LA-1. Of the 200 strains studied, a higher proportion of strains of human origin were found to be r esistant to both low pH and high concentrations of bile as compared to stra ins of dairy origin. The four putative probiotic strains were characterised by classical microbiological techniques and molecular methodologies includ ing DNA-DNA homology, SDS-PAGE analysis of whole cell proteins, PFGE, speci es-specific probes and RAPD. The strains were identified as Lb. rhamnosus H N001 (also known as DR20), Lb. acidophilus HN017, Lb. rhamnosus HN067 and B ifidobacterium. lactis HN019 (also known as DR10). (C) 1999 Elsevier Scienc e Ltd. All rights reserved.