Croissance et activité cellulaire du Brevibacterium casei NCDO 2049 dans du perméat de lactosérum
Growth and cellular activity of Brevibacterium casei NCDO 2049 were studied in a whey permeate as basic culture medium. The possible inhibitory effect of the carbone substrate (undiluted or diluted permeate) on growth was investigated as well as the influence of pH of the media (controlled or not) and of the addition of nitrogen sources (organic or inorganic) or growth factors such as yeast extract or vitamin B12. Growth in undiluted permeate produced a maximal biomass (6.5 × 109 cfu/mL) that was nearly twice as much as that in diluted permeate (3.8 × 109 cfu/mL). The carbone substrate (lactose) had no inhibitory effect on growth. In undiluted permeate and an uncontrolled pH, maximal biomass was reached after 36 h of incubation, while in a pH controlled medium, twice as much time was required to obtain an equivalent biomass. In undiluted permeate and an uncontrolled pH, growth in the presence of peptone reached 22.6 × 109 cfu/mL and, in the presence of (NH4)2SO4, 12.4 × 109 cfu/mL. Adding growth factors to media with peptone resulted in the reduction of 90% of initial lactose in the presence of yeast extract and of 75% in the presence of B12 vitamin. This study indicates the possibility of reducing lactose in whey permeate when cultivating strains of the genus Brevibacterium used as maturing bacteria for certain cheese types.Key words: whey permeate, Brevibacterium casei, lactose.[Journal translation]