Cultivo de Streptococcus zooepidemicus: modelagem e produção de ácido hialurônico

Abstract

Hyaluronic acid is a biopolymer found in many organisms, which has several biomedical applications, like viscosupplementation and aesthetic procedures. Such applications are associated with its rheological properties, that depend directly on the molar mass. Streptococcus zooepidemicus bacteria can produce hyaluronic acid. However, it is still necessary to determine the best operating conditions for a bioreactor so that higher HA yields are achieved. In the light of this, our work aims to develop kinetic and genome-scale models that describe the microbial production of hyaluronic acid. To reach this objective, information was collected regarding the central carbon metabolism, production, and consumption of amino acids of S. zooepidemicus. To adjust and validate these models, experimental data were obtained from cultures using glucose as carbon source and soybean peptone as nitrogen source in 5 L automated stirred tank bioreactor. To adjust the kinetic model, PSO algorithm was used, while OptFlux software was used to simulate the developed genome-scale model. The agitated tank bioreactor cultures indicated the microorganism consumed other nutrients present in the peptone besides the glucose added to the medium. In addition, an adaptation phase of almost 20 h. This phase was reduced by increasing the concentration of glucose in the inoculum and pre-inoculum. The experimental results also showed that the concentration of amino acids increases at the end of the culture, which can be explained by the action of proteases. Regarding the proposed kinetic model, it could competently describe most of the experimental data, diverging in the last data of cell and lactic acid concentration. This fact is attributed to the more intense consumption of the nutrients of the peptone used. As for the adapted genomic scale model, the major alterations were regarding the reactions related to the formation of acid D- glucuronic and the biosynthesis and consumption of amino acids. The validation tests results diverged from the experimental data. It is possible that consumption of other nutrients in the peptone were responsible for this. However, errors that compromised the simulations were not observed, indicating the developed genome-scale model potential.