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.
