GROWTH OPTIMIZATION OF THE EXTREMOPHILIC PARACOCUS BARUCHII LBOG37

Abstract

The genus Paracoccus belongs to the α-subdivision of the Alphaproteobacteria, and encompasses over 34 defined species. Members of the genus are known to be versatile organisms that can prevail in any environmental condition due to their nature of adapting their metabolism accordingly. Hence, Paracoccus strains are able to utilize a wide range of organic carbon compounds which serve as carbon and free energy sources during their heterotrophic growth. Paracoccus baruchii LBOG37 has the potency of producing carotenoids that have a wide application in medical fields. However, commercial exploitation of many carotenoid producing bacteria is limited by the biomass. Thus, this study sought to optimize growth conditions of Paracoccus baruchii LBOG37. The isolate was obtained from the Chiromo campus Biochemistry Department of University of Nairobi where it had been cryopreserved. It was revived and confirmed using 16SrRNA analysis. The growth pH, growth temperature and carbon source were optimized using modified Horikoshi medium at different time intervals. The growth was determined using optical density at 600nm. This was aimed at aiding increased production of biomass of the bacteria to necessitate commercial exploitation of the bacteria for carotenoid production using commonly available carbon sources (starch, carboxymethyl cellulose and glucose). The study established that the Paracoccus baruchii LBOG37 grew optimally at a pH of between 9.0 and 9.5 and with its optimum growth temperature recorded at 40°C on Horikoshi medium. With the latter being a relatively thermophilic temperature, some significant growth was also evident at slightly higher thermophilic temperatures and at the mesophilic temperatures providing an almost “aseptic” growth condition for the isolate. It was therefore concluded that Paracoccus baruchii LBOG37 is a thermophilic, alkaliphilic bacterium that utilises carboxymethyl cellulose, starch and D-glucose during its heterotrophic growth.