Abstract
Polyhydroxyalkanoates (PHAs) are intracellular reserve material stored by gram-negative bacteria under nutrient-limited condition. PHAs are utilized in biodegradable plastics (bio-plastics) synthesis due to their similarity with conventional synthetic plastic. In the present study, the effect of addition of saturated and unsaturated fatty acids (palmitic acid, stearic acid, oleic acid and linoleic acid) on the production of PHAs by the soil bacterium Alcaligenes sp. NCIM 5085 was studied. Fatty acid supplementation in basal media produced saturated and unsaturated PHAs of medium and short chain length. Gas chromatography analysis of palmitic acid-supplemented media showed the presence of short chain length (scl) PHAs which could potentially serve as precursors for bio-plastic production. The scl PHA was subsequently characterized as PHB by NMR and FTIR. On the other hand, oleic acid and linoleic acid addition showed both saturated and unsaturated PHAs of different chain lengths. Palmitic acid showed maximum PHB content of 70.8 % at concentration of 15 g l−1 under shake flask cultivation. When shake flask cultivation was scaled up in a 7.5-l bioreactor (working volume 3 l), 7.6 g l−1 PHA was produced with a PHB yield (YP/X) and productivity of 75.89 % and 0.14 g l−1 h, respectively.
Highlights
Polyhydroxyalkanoates (PHAs) are polymers of hydroxyalkanoate that are synthesized and accumulated as intracellular carbon and energy storage in various microorganisms
Gas chromatography analysis of palmitic acid-supplemented media showed the presence of short chain length PHAs which could potentially serve as precursors for bioplastic production
Oleic and lauric acid have been extensively used as nutritional supplements for PHA production in Aeromonas hydrophila (Chen et al 2001), Ralstonia eutropha (Marangoni et al 2000), recombinant Escherichia coli XY1-Blue pSYL105 (Lee et al 1995)
Summary
Polyhydroxyalkanoates (PHAs) are polymers of hydroxyalkanoate that are synthesized and accumulated as intracellular carbon and energy storage in various microorganisms. The effect of addition of saturated and unsaturated fatty acids (palmitic acid, stearic acid, oleic acid and linoleic acid) on the production of PHAs by the soil bacterium Alcaligenes sp. Fatty acid supplementation in basal media produced saturated and unsaturated PHAs of medium and short chain length.
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