Optimization of fermentation parameters for the production of concentrated starters from nonbitter Streptococcus lactis INIA 12

Streptococcus lactis INIA 12, a selected nonbitter strain, reached its maximum counts and its highest lactic acid production in a culture medium containing 125 g/L skim milk powder, fortified with 5 g/L yeast extract and digested with 10 ppm papain for 20 min at 65°C. Lactose added to the medium did not enhance growth rate or biomass production. A growth temperature of 32°C and the maintenance of pH at 6.80, with 10N NaOH as the neutralizer, were the optimum fermentation parameters in batch cultures. In ten 40‐L fermentations carried out at 32°C and pH 6.80, with a 5% inoculum, a 0.2 kg/cm2 nitrogen head space pressure and a stirring rate of 80 rpm, maximum counts of S. lactis (1010 CFU/mL) were reached after incubation for 6 hr at 32°C and pH 6.80. Copyright © 1988, Wiley Blackwell. All rights reserved