The Isolation, Screening, and Characterization of Polyhydroxyalkanoate-Producing Bacteria from Hypersaline Lakes in Kenya

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Journal of Bacteria
Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline en vironments are promising candidates for the recovery of useful biomaterials including polyhydrox yalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegrada ble, biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospec tion of bacteria isolated from hypersaline-alkaliphilic lakes in Kenya for the potential production of PHAs. In the present study, 218 isolates were screened by Sudan Black B and Nile Red A staining. Of these isolates, 31 were positive for PHA production and were characterized using morphological, biochemical, and molecular methods. Through 16S rRNA sequencing, we found that the isolates belonged to the genera Arthrobacter spp., Bacillus spp., Exiguobacterium spp., Halomonas spp., Para coccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023 iso lated from Lake Magadi had the highest PHA accumulation ability, with an initial biomass-to-PHA conversion rate of 19.14% on a 2% glucose substrate. Under optimized fermentation conditions, MO22 had a maximum PHA concentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9% PHA conversion, equivalent to a PHA yield of 0.02 g/g of biomass. The optimal PHA production media had an initial pH of 9.0, temperature of 35 °C, salinity of 3%, and an incubation period of 48 h with 2.5% sucrose and 0.1% peptone as carbon and nitrogen sources, respectively. This study suggests that bacteria isolated from hypersaline and alkaliphilic tropical lakes are promising candi dates for the production of polyhydroxyalkanoates.
isolation; screening; characterization; polyhydroxyalkanoates; PHA; Lake Magadi; Lake Simbi; Bacillus sp.