POPULATION-DYNAMICS OF THERMOPHILIC LACTOBACILLI IN MIXED STARTER WHEY CULTURES

The starter used in the production of Parmesan cheese consists of mixe d-strain whey cultures of thermophilic rod lactic acid bacteria, where several strains of each species can be found. The present work was un dertaken to demonstrate the effects on the strain composition of inter actions among individual lactobacilli grown together in cheese whey. T hree strains belonging to Lactobacillus helveticus and Lactobacillus d elbrueckii subsp. bulgaricus and subsp. lactis were cultured in Parmes an cheese whey and counted by a molecular approach based on Random Amp lified Polymorphic DNA (RAPD) fingerprinting. Results showed interacti ons among the three lactobacilli as confirmed by comparison of growth kinetics and pH behaviour of the respective strains in mixed-strain cu lture with single-strain cultures. The present work underlines the imp ortance of noting strain-to-strain interactions among thermophilic lac tobacilli in whey co-cultures. (C) 1997 Canadian Institute of Food Sci ence and Technology. Published by Elsevier Science Ltd.