PERMEABILIZATION OF STREPTOCOCCUS-THERMOPHILUS AND LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS WITH ETHANOL

Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgar icus cultures were treated with ethanol and tested for viability and b eta-galactosidase activity. Exposure of the biomass of test cultures t o 30%-55% ethanol (vol/vol) caused a 100% loss of viability and up to 15-fold Increase in measurable beta-galactosidase activity in both str eptococci and lactobacilli. Ethanol-treated cell suspensions could be stored for up to 6 months without loss of enzyme activity. The nonviab le permeabilized biomass of the more active S. thermophilus was used t o achieve up to 80% hydrolysis of lactose in aqueous solutions and non -fat milk.