Growth kinetic models of five species of Lactobacilli and lactose consumption in batch submerged culture

Abstract Kinetic behaviors of five Lactobacillus strains were investigated with Contois and Exponential models. Awareness of kinetic behavior of microorganisms is essential for their industrial process design and scale up. The consistency of experimental data was evaluated using Excel software. L. bulgaricus was introduced as the most efficient strain with the highest biomass and lactic acid yield of 0.119 and 0.602 g g-1 consumed lactose, respectively. The biomass and carbohydrate yield of L. fermentum and L. lactis were slightly less and close to L. bulgaricus. Biomass and lactic acid production yield of 0.117 and 0.358 for L. fermentum and 0.114 and 0.437 g g-1 for L.actobacillus lactis were obtained. L. casei and L. delbrueckii had the less biomass yield, nearly 11.8 and 22.7% less than L. bulgaricus, respectively. L. bulgaricus (R 2 = 0.9500 and 0.9156) and L. casei (R 2 = 0.9552 and 0.8401) showed acceptable consistency with both models. The investigation revealed that the above mentioned models are not suitable to describe the kinetic behavior of L. fermentum (R 2 = 0.9367 and 0.6991), L. delbrueckii (R 2 = 0.9493 and 0.7724) and L. lactis (R 2 = 0.8730 and 0.6451). Contois rate equation is a suitable model to describe the kinetic of Lactobacilli. Specific cell growth rate for L. bulgaricus, L. casei, L. fermentum, L. delbrueckii and L. lactis with Contois model in order 3.2, 3.9, 67.6, 10.4 and 9.8-fold of Exponential model.

Non-Structured Kinetic Model of Aspergillus niger Growth and Substrate Uptake in a Batch Submerged Culture.

Aims: To investigate cell growth profile of Aspergillus niger in a batch submerged culture medium and then evaluation of cell kinetic behavior using some different non-structured kinetic models. Methodology: Experiments of cell growth and substrate utilization were conducted in batch submerged cultures with identified medium composition. Fitness assessment of experimental data on the cell growth and glucose consumption by models was performed using the curve-fitting tool in Mat Lab software. This report is the first in the kinetic investigation of Aspergillus niger PTCC 5010 with the studied models. This work was performed in Department of Chemical Engineering, Islamic Azad University, Qaemshahr Branch between April 2013 to September 2013. Results: Based on the obtained results; Moser kinetic model with R2 equal to 0.913 and Gompertz kinetic model with R2 equal to 0.949 were the best fitted models to describe the growth behavior of Aspergillus niger PTCC 5010 in the applied culture condition. Maximum specific cell growth rate with Moser and Gompertz kinetic models were 0.024 and 0.003h-1, respectively. Other kinetic constants for all studied models were also determined at the applied culture conditions. The consistency of the experimental data with Monod, Verhulst and Contois kinetic models wasn't in an acceptable range. Conclusion: In scale up biochemical projects by Aspergillus niger PTCC 5010 for some industrial products, Moser and Gompertz kinetic models are able to demonstrate cell growth behavior and its substrate uptake profile. In continuous processes, dilution rate could be determined based on obtained maximum specific cell growth rate equal to 0.024 h-1.