Isolation and Characterization of Bacillus sp. INT005 Accumulating Polyhydroxyalkanoate (PHA) from Gas Field Soil

A gram-positive bacterium (designated strain INT005) that accumulated polyhydroxyalkano-ate (PHA) was isolated from gas field soil. From its morphological and physiological properties and the partial nucleotide sequence (about 500 bp) of its 16S rDNA, it was suggested that strain INT005 was similar to several species of the genus Bacillus. We confirmed that strain INT005 is a Bacillus sp. The PHA productivities of strain INT005 were higher than those of Bacillus mega-terium and Ralstonia eutropha at 37–45C reported to date, and it was suggested that the PHA syn-thase of INT005 may exhibit moderate thermostability. The bacterium had the ability to produce poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-6-hydroxyhexanoate-co-3-hydroxyhexanoate) from the appropriate carbon sources. The PHA synthase from INT005 showed similar substrate specificity to those of class I and III PHA synthases and strain INT005 produced PHAs with various monomer compo-sitions. From the analysis of monomer composition and PHA accumulation in the presence of acrylic acid, it was suggested that de novo fatty acid synthesis and -oxidation are involved in the PHA synthesis of Bacillus sp. INT005. Since Bacillus sp. INT005 could synthesize PHA even a