Production of Poly (3-Hydroxybutyric Acid) by Ralstonia eutropha in a Biocalorimeter and its Thermokinetic Studies Subramanian Mohanakrishnan Anusha 1 & Santharam Leelaram 1 & Mahadevan Surianarayanan 1 Received: 11 January 2016 /Accepted: 11 March 2016 # Springer Science+Business Media New York 2016 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 inclu- sions 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 O 2 . 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. Keywords Bioplastic . Poly (3-hydroxybutyric acid) (PHB) . Ralstonia eutropha . Bioreaction calorimeter . Oxycalorific value Nomenclature Symbols A Heat transfer area (m 2 ) DO Dissolved oxygen PHB Poly (3-hydroxybutyric acid) Appl Biochem Biotechnol DOI 10.1007/s12010-016-2049-0 Electronic supplementary material The online version of this article (doi:10.1007/s12010-016-2049-0) contains supplementary material, which is available to authorized users. * Mahadevan Surianarayanan msuri1@vsnl.com 1 Chemical Engineering Department, Central Leather Research Institute (CLRI), Adyar, Chennai, Tamil Nadu, India