Abstract:
Polyhydroxyalkanoates (PHAs) are synthesized by a variety of microorganisms as intracellular storage granules
under imbalanced nutrition and excess carbon. Carbon sources are key contributors to the high cost of PHA
production, hence the need for exploration of cheap and sustainable raw materials for bacteria fermentation. In
the present study, Halomonas alkalicola strain Ext isolated from a hypersaline lake in Kenya was assessed for its
ability to utilize fruit peels hydrolysates (FPH) as sole carbon sources for PHA production. Sugars were extracted
from dried peels of banana, mango, orange, and pineapple fruits through mechanical pretreatment and dilute
acid hydrolysis. Fruit peels pretreated with 3 % H
2
SO
4
at 121℃ were utilized for shake flask fermentation to
produce PHAs by Halomonas alkalicola Ext. At optimal C:N ratios of between 20:1 and 30:1, the bacterium could
produce up to 0.45±0.03, 0.394±0.12, 0.39±0.05, and 0.28±0.0 g/L of PHAs from hydrolysates of orange peels,
mango peels, banana peels, and pineapple peels, respectively. A maximum PHA content of 16.92 % was achieved
on orange peels hydrolysates with 4 % substrate loading. Monomer analysis with gas chromatography-mass
spectrometry (GC-MS) revealed that the bacterium produced a copolymer Poly(3-hydroxybutyrate-co-3-
hydroxyvalerate) (PHBV) with 3-hydroxyvalerate (3HV) contents of 5.77 %, 6.08 %, 6.79 %, 6.845 %, for or
ange peels, pineapple peels, mango peels and banana peels substrates, respectively. The findings of this study
suggest that fruit peels waste is a potential feedstock for sustainable production of PHAs by Halomonas alkalicola.
