Characterization of polyhydroxyalkanoate and the phaC gene of Paracoccus seriniphilus E71 strain isolated from a polluted marine microbial mat

Abstract

Polyhydroxyalakanote (PHA) was produced by the marine bacteria Paracoccus seriniphilus Strain E71. Three methods were used for screening PHA in this strain: (1) microscopic analysis, (2) specifically designed primers for amplify fragments of phaC gene from Gram negative bacteria, and (3) measurements using spectroscopy, calorimetry, thermogravimetry, and rheology. The polyhydroxyalkanoic acid synthase gene (phaC) sequence had 77% identity with the phaC gene of P. denitrificans PD1222 strain. Additionally, the translated sequence showed an 86% similarity with the amino acid sequence of the phaC gene N-terminal portion of the P. denitrificans PD1222 strain. Our phaC sequence was closely related to two phaC sequences that correspond to P. denitrificans; therefore, this is the first report of a sequence of phaC that codifies a poly-(3-hydroxyalkanoate) synthase class I, specifically a poly-beta-hydroxybutyrate polymerase from the marine bacteria Paracoccus seriniphilus. The polymer PHA of E71 melts at 167.86°C (T m), which corresponded to the fusion of the crystalline polymer and thermally degrades at 296.52°C, indicating that the biopolymer has good thermal stability. Rheology showed that this polymer behaves as a nonNewtonian fluid. All these characteristics suggest that the E71 strain produces a PHA that corresponds to the crystalline thermoplastic polymer PHB type.