Abstract:
Abstract: Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline
environments are promising candidates for the recovery of useful biomaterials including polyhydrox
yalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegradable,
biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospection
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 morpho
logical, 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.,
Paracoccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023
isolated 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,
MO22hadamaximumPHAconcentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9%
Citation: Muigano, M.N.; Anami,
S.E.; Onguso, J.M.; Omare, G.M. The
Isolation, Screening, and
Characterization of
Polyhydroxyalkanoate-Producing
Bacteria from Hypersaline Lakes in
Kenya. Bacteria 2023, 2, 81–97.
https://doi.org/10.3390/
bacteria2020007
Academic Editor: Bart C. Weimer
Received: 29 March 2023
Revised: 28 April 2023
Accepted: 2 May 2023
Published: 8 May 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
PHAconversion, 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 candidates for
the production of polyhydroxyalkanoates.
