The autolysis of Streptococcus thermophilus DN-001065 is triggered by several food-grade environmental signals

Streptococcus thermophilus DN-001065 is a highly autolytic strain that spon taneously lyses dramatically after a rapid growth phase in M17 medium. Sinc e starter autolysis appears as a crucial step of flavour development in fer mented dairy products, we examined whether strain DN-001065 could lyse in e nvironmental conditions compatible with dairy technology. Lysis took place to a large extent, although at low rate, at pH around 5 and temperature bel ow 15 degrees C. Addition of 2% NaCl, heat shock (from 42 to 50 or 55 degre es C) as well as cold shock (from 42 to 4 or 8 degrees C) triggered lysis o f DN-001065 exponential growing cells cultured in M17 medium. Lysis was als o evidenced in buffered milk; in these conditions, the lysis triggering eff ect of lactose depletion and NaCl was observed. This work thus highlights t he technological potential of S, thermophilus autolytic strain DN-001065 wh ich undergoes lysis in response to several specific food-grade environmenta l signals, even when grown in milk. (C) 2000 Elsevier Science Ltd. All righ ts reserved.