Technological and genetic aspects of Lactobacillus delbrueckii subsp. indicus involved in the production of novel fermented milks.

Four Lactobacillus strains isolated from an Indian fermented milk have recently been grouped in the new subspecies L. delbrueckii subsp. indicus (1). Previous studies have evidenced that these strains ferment lactose constitutively, like L. delbrueckii subsp. bulgaricus (1). However, lactose degradation is probably related to the presence of a peculiar genetic equipment since any amplification of the lac operon genes was achieved. No additional information is currently available on technological and genetic properties of these strains. In the present study, the ability of the four Indian strains to induce pleasant organoleptic traits when grown in milk-based media of different composition was investigated. Physical and chemical parameters were monitored during milk fermentation in order to establish the performances of the examined strains. In addition, sequences of genes encoding some lactose-PTS system components were obtained suggesting that lactose degradation in the Indian strains is probably due to the presence of these genetic determinants. Finally, a comparison of technological and genetic characteristics displayed by the different L. delbrueckii subspecies was conducted. The data obtained indicate that L. delbrueckii subsp. indicus strains show interesting properties and may be applied in association with S. thermophilus for the production of novel fermented milks.