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. 2015:2015:212159.
doi: 10.1155/2015/212159. Epub 2015 Nov 17.

Extracellular Polyhydroxyalkanoate Depolymerase by Acidovorax sp. DP5

S Vigneswari  1 , T S Lee  2 , Kesaven Bhubalan  3 , A A Amirul  4
Affiliations

Extracellular Polyhydroxyalkanoate Depolymerase by Acidovorax sp. DP5

S Vigneswari et al. Enzyme Res. 2015.

Abstract

Bacteria capable of degrading polyhydroxyalkanoates (PHA) by secreting extracellular depolymerase enzymes were isolated from water and soil samples collected from various environments in Malaysia. A total of 8 potential degraders exhibited clear zones on poly(3-hydroxybutyrate) [P(3HB)] based agar, indicating the presence of extracellular PHA depolymerase. Among the isolates, DP5 exhibited the largest clearing zone with a degradation index of 6.0. The highest degradation activity of P(3HB) was also observed with depolymerase enzyme of DP5 in mineral salt medium containing P(3HB). Based on biochemical characterization and 16S rRNA cloning and sequencing, isolate DP5 was found to belong to the genus Acidovorax and subsequently named as Acidovorax sp. DP5. The highest extracellular depolymerase enzyme activity was achieved when 0.25% (w/v) of P(3HB) and 1 g/L of urea were used as carbon and nitrogen source, respectively, in the culture media. The most suitable assay condition of the depolymerase enzyme in response to pH and temperature was tested. The depolymerase produced by strain Acidovorax sp. DP5 showed high percentage of degradation with P(3HB) films in an alkaline condition with pH 9 and at a temperature of 40°C.

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Figures

Figure 1
Figure 1
Clear zone formation produced by Acidovorax sp. DP5 on P(3HB) agar plate. Cells were grown for 4-5 days at 30°C to form clear zone surrounding the bacterial colony.
Figure 2
Figure 2
Neighbour-joining phylogenetic tree of Acidovorax sp. DP5 and related bacteria based on 16S rRNA sequence comparisons. Accession numbers are given.
Figure 3
Figure 3
Effect of P(3HB) concentration (w/v) on the (a) bacterial growth and (b) enzyme activity. Values are mean of two replicates.
Figure 4
Figure 4
Effect of various nitrogen sources on the enzyme activity. N1: NH4Cl, N2: (NH4)2SO4, N3: NH4NO3, N4: (NH4)2HPO4, N5: (NH2)2CO, and N6: control (without nitrogen source). Values are mean of two replicates.
Figure 5
Figure 5
Effect of various pH values on the degradation of P(3HB) films in an aqueous solution of depolymerase at 37°C. Values are mean of two replicates.
Figure 6
Figure 6
Effect of percentage of weight loss (degradation) of P(3HB) films at various temperatures at pH 9. Values are mean of two replicates.
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