A study of the hemin-stimulated respirative growth kinetics of Lactococcus lactis using batch cultivation

Azher Razvi, Université D'Ottawa / University Of Ottawa, Université D'Ottawa / University Of Ottawa
The influence of initial glucose concentration: 60, 80, and 90 g/L on the hemin-stimulated respirative growth of Lactococcus lactis was studied in batch culture. Quantification of substrate consumption, biomass and product formation kinetics revealed that energy-spilling reactions may to contribute to a significant amount of non-growth associated or non-maintenance associated substrate utilization. The maximum specific growth rate was unaffected by initial substrate concentration, while the
more » ... tion, while the maintenance coefficient, mS, and the maximum yield coefficient, YMX/S, were strongly affected. The value of mS increased from 1.56 to 1.73 g glucose/g DCW-h when the substrate concentration was increased. Product formation kinetics were also affected with the growth associated product formation (alpha) increasing from 1.9 to 2.8 g lactate/g DCW, while the non-growth associated product formation (beta) value increasing from 0.74 to 0.81 g lactate/g DCW-h. The total biomass accumulated was also improved by a systematic modification of the growth medium utilized. A 50 % increase in the concentration of yeast extract, peptone, and tryptone against the base medium used increased the final biomass concentration from 4.2 to 6.3 g/L. An analytical solution to the differential equations developed by Pirt for substrate consumption, Leudeking-Piret for production formation, and the differential logistic growth equation was successfully developed in this work. The solution represents a nonlinear system of equations that allows the simultaneous modeling of cell growth, substrate consumption, and product formation for substrate-limited growth. A medium for improved growth of L. lactis and lactic acid bacteria was also developed for small-scale microbiological applications. By modification of a popular commercial medium used for its cultivation, not only was improved growth of L. lactis observed, but the final extracellular environment for long term cell survival was improved. Increasing the concentration of the salt disodium glycerophosphat [...]
doi:10.20381/ruor-12327 fatcat:5uvnhs2pzbevjcbahnh47nvg4q