Dynamics of rate limiting enzymes involved in the sequential substrate uptake by Pseudomonas putida CSV86: Modeling and experimental validation

Preferential utilization of intracellular nutrients supports microalgal growth under nutrient starvation: multi-nutrient mechanistic model and experimental validation

Microalgae are able to grow even under exhaustion of some key nutrients such as nitrogen and phosphorous. Here, we report a multi-nutrient mechanistic model to predict heterotrophic growth of Chlorella sp. FC2 IITG over two sequential phases of fermentation: nutrient sufficient condition to nutrient starved condition. The model assumes that the growth of the microorganism takes place via sequential utilization of extracellular nutrients (ECN) under nutrient replete condition followed by intracellular stored nutrients under exhaustion of limiting nutrients. Further, intracellular nutrient was assumed to be in three different forms: structural form of nutrient (SFN), readily utilizable nutrient (RUN) and non-readily utilizable nutrient (Non-RUN). After the exhaustion of ECN, microorganism switches to RUN followed by Non-RUN to continue its growth, which was experimentally validated by extracting intracellular nitrate and phosphate compounds. The model also incorporates variability in yield coefficients for nitrate and phosphate utilizations.

Assessment of the metabolic capacity and adaptability of aromatic hydrocarbon degrading strain Pseudomonas putida CSV86 in aerobic chemostat culture

Pseudomonas putida CSV86 utilizes aromatic compounds preferentially over sugars and co-metabolizes aromatics along with organic acids. In the present study, the metabolic capacity and adaptability of strain CSV86 were assessed in a chemostat at benzyl alcohol concentrations ranging from 1 g l(-1) to 3 g l(-1) and in the presence of glucose and succinate by systematically varying the dilution rate. Complete removal of benzyl alcohol was achieved for loadings up to 640 mg l(-1) h(-1) in presence of benzyl alcohol alone. The strain responded within 1 min towards step changes in substrate loading as indicated by an increase in the oxygen uptake rate, presumably as a result of excess metabolic capacity. These results suggest that CSV86 exhibits considerable metabolic elasticity upon increase in substrate load. Metabolic elasticity of the microorganism is an important parameter in wastewater treatment plants due to the changing substrate loads.