No abstract

Bioplastic production from microbial sources is an emerging area which provides opportunities even to convert the wastes into bioplastics. Poly (3-hydroxybutyric acid), commonly called as PHB, is a bioplastic, which is stored as intracellular cytoplasmic inclusions in microorganisms. The objectives of this study are to calorimetrically monitor the PHB production and evaluate the thermokinetic data in a bioreaction calorimeter (BioRC1e). Thus, a well-known PHB-producing bacteria Ralstonia eutropha was selected for batch process in a bioreaction calorimeter. The metabolic heat generated was found to be correlated with the biomass, substrate consumption, oxygen uptake rate (OUR), carbon dioxide evolution rate (CER) and PHB production. The OUR pattern explained the oxidative metabolism of the strain R. eutropha. The heat yields due to biomass and glucose consumption during PHB production were found to be 12.56 and 13.56 kJ/g, respectively. The oxycalorific value obtained for the PHB production was 443.80 kJ/mol of O2. The concentration of PHB obtained in BioRC1e was 4.33 g/L with a production rate of 0.09 g/L/h. The chemical structure of the extracted PHB by R. eutropha was confirmed using fourier transform infrared spectroscopy (FT-IR) and (1)H and (13)C nuclear magnetic resonance (NMR) analysis.

No abstract

A metabolic heat-based model was used for estimating the growth of Kluyveromyces marxianus, and the modified Luedeking-Piret kinetic model was used for describing the inulinase production kinetics. For the first time, a relationship was developed to relate inulinase production kinetics directly to metabolic heat generated, which corroborated well with the experimental data (with R values of above 0.9). It also demonstrated the predominantly growth-associated nature of the inulinase production with Luedeking-Piret parameters α and β, having values of 0.75 and 0.033, respectively, in the exponential feeding experiment. MATLAB was used for simulating the inulinase production kinetics which demonstrated the model's utility in performing real-time prediction of inulinase concentration with metabolic heat data as input. To validate the model predictions, a biocalorimetric (Bio RC1e) experiment for inulinase production by K. marxianus was performed. The inulinase concentration (IU/mL) values acquired from the model in were validated with the experimental values and the metabolic heat data. This modeling approach enabled the optimization, monitoring, and control of inulinase production process using the real-time biocalorimetric (Bio RC1e) data. Gas chromatography and mass spectrometry analysis were carried out to study the overflow metabolism taking place in K. marxianus inulinase production.

No abstract