Kinetic analysis and effect of culture medium and coating materials during free and immobilized cell cultures of Bifidobacterium animalis subsp. lactis Bb 12
Microencapsulation technique appears helpful for more protection of Bifidobacteria against acid inhibitory effect. The effect of medium composition and product inhibitory in free cell culture, as well as the effect of the coating materials in immobilized cells, on biomass growth, acid production and substrate utilization kinetics of Bifidobacterium animalis subsp. lactis Bb 12 in uncontrolled batch fermentation was examined. The Monod and the Luedeking and Piret equations with a product inhibition term involving toxic power terms improved model efficiency for both growth and production. The model showed that media and coating materials had an effect on toxic power terms. Cell immobilization had a positive impact on B. animalis culture. Kinetic analysis revealed the permeability of the coating material had a major impact on culture parameters; permeability increased in the following way: Gellan xanthan < Alginate chitosan < K-Carageenan-locust been, and hence growth parameters x m, maximum specific growth rate (h-1) (Âµm) and monod constant (g lactose L-1) (K S) followed the same trend as well as the linking between growth and production. The link between the microbial environment and cell growth was highlighted by the model. It was shown that for an increasing protect effect of coating materials against environmental deleterious factors, namely a decrease of the permeability, transport limitation occurred, which was disadvantageous for cell formation.