Substrate uptake, phosphorus repression, and effect of seed culture on glycopeptide antibiotic production: Process model development and experimental validation

Abstract

Actinomycetes, the soil borne bacteria which exhibit filamentous growth, are known for their ability to produce a variety of secondary metabolites including antibiotics. Industrial scale production of such antibiotics is typically carried out in a multi-substrate medium where the product formation may experience catabolite repression by one or more of the substrates. Availability of reliable process models is a key bottleneck in optimization of such processes. Here we present a structured kinetic model to describe the growth, substrate uptake and product formation for the glycopeptide antibiotic producer strain Amycolatopsis balhimycina DSM5908. The model is based on the premise that the organism is an optimal strategist and that the various metabolic pathways are regulated via key rate limiting enzymes. Further, the model accounts for substrate inhibition and catabolite repression. The model is also able to predict key phenomena such as simultaneous uptake of glucose and glycerol but with different specific uptake rates, and inhibition of glycopeptide production by high intracellular phosphate levels. The model is successfully applied to both production and seed medium with varying compositions and hence has good predictive ability over a variety of operating conditions. The model parameters are estimated via a well-designed experimental plan. Adequacy of the proposed model was established via checking the model sensitivity to its parameters and confidence interval calculations. The model may have applications in optimizing seed transfer, medium composition, and feeding strategy for maximizing production.

Correlation between pellet morphology and glycopeptide antibiotic balhimycin production by Amycolatopsis balhimycina DSM 5908

“…In our previous work, it was shown that balhimycin production was signiWcantly inXuenced by phosphate concentration in deWned media [14]. SpeciWcally, increasing phosphate concentration beyond the optimal value led to higher biomass growth but lower balhimycin production.…”

“…Our previous work has shown that the concentration of ammonia has a signiWcant eVect on balhimycin productivity [14]. Therefore, we wanted to investigate whether variation in ammonia aVected morphology.…”

“…Concentration of balhimycin was estimated from the fermentation broth using bioassay and further conWrmed via HPLC as previously described [1,14,15]. In the bioassay, Kocuria rhizophila ATCC9341, old name Micrococcus luteus [28], was used as a test organism to measure antimicrobial activity of balhimycin.…”

“…balhimycina was a kind gift from Prof. Anna Eliasson Lantz, Denmark's Technical University, Denmark. The strain was cultivated and maintained as reported previously [14,15]. BrieXy, 100-ml cultures were grown at 30°C and 150 rpm in single baZed Erlenmeyer Xasks of 500-ml capacity for all the experiments.…”

Strain Improvement of Streptomyces roseosporus for Daptomycin Production by Rational Screening of He–Ne Laser and NTG Induced Mutants and Kinetic Modeling

“…Further, inhibition of glucose was also taken into account. Therefore, the Monod model was modified to account for the inhibitions of substrates and product by incorporating two additional parameters, n and S max , for each substrate and product as proposed by Luong [18] and Maiti et al [19], respectively. The Leudeking-Piret model was used to investigate the product formation for both the wild and mutant strains of S. roseosporus.…”