Production of Poly (3-Hydroxybutyric Acid) by Ralstonia eutropha in a Biocalorimeter and its Thermokinetic Studies

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.

Water Splitting–Biosynthetic Hybrid System for CO2 Conversion using Nickel Nanoparticles Embedded in N‐Doped Carbon Nanotubes

“…The calculations of biomass, FE, and ECE were performed according to previous publications. [12,17,52] Full details are provided in the Supporting Information. The LSV was conducted using the potentiostat (VSP-300, BioLogic, France) for the electrochemical analysis.…”

“…[6][7][8][9] Nevertheless, severalc hallenges still must be overcome, such as (1) low value of CRR products,( 2) low products selectivity,a nd (3) low energy efficiency. [12][13][14][15][16] Yang et al employed a-NiS as an electrocatalyst for the hydrogen evolution reaction( HER) and Methanosarcina barkeri as ab iocatalyst to realize CO 2 to CH 4 conversion with a low overpotential (360 mV) and high faradaic efficiency (FE, up to 86 %). Inspired by some autotrophic microorganisms (e.g., Sporomusa ovata and Ralstoniae utropha)c apable of converting CO 2 to organic compounds[ i.e.,a cetate, poly-b-hydroxybutyrate (PHB), isopropanol, and alpha-humulene],h ybrid bio-inorganic systemsc ombining water splitting with H 2 -oxidizing autotrophic biosynthesish ave been developed for efficient CO 2 conversion.…”

“…Inspired by some autotrophic microorganisms (e.g., Sporomusa ovata and Ralstoniae utropha)c apable of converting CO 2 to organic compounds[ i.e.,a cetate, poly-b-hydroxybutyrate (PHB), isopropanol, and alpha-humulene],h ybrid bio-inorganic systemsc ombining water splitting with H 2 -oxidizing autotrophic biosynthesish ave been developed for efficient CO 2 conversion. [12][13][14][15][16] Yang et al employed a-NiS as an electrocatalyst for the hydrogen evolution reaction( HER) and Methanosarcina barkeri as ab iocatalyst to realize CO 2 to CH 4 conversion with a low overpotential (360 mV) and high faradaic efficiency (FE, up to 86 %). [11] Another successful example incorporateda ne ngineereds train of Ralstonia eutropha and Co-P alloy/CoP i catalyzed water splitting to convert CO 2 to isopropanol with an energy efficiency exceeding 50 %.…”