Isolation and characterization ofBacillus sp. INT005 accumulating polyhydroxyalkanoate (PHA) from gas field soil

Abstract

A gram-positive bacterium (designated strain INT005) that accumulated polyhydroxyalkanoate (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 genusBacillus. We confirmed that strain INT005 is aBacillus sp. The PHA productivities of strain INT005 were higher than those ofBacillus megaterium andRalstonia eutropha at 37–45°C reported to date, and it was suggested that the PHA synthase 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 compositions. From the analysis of monomer composition and PHA accumulation in the presence of acrylic acid, it was suggested thatde novo fatty acid synthesis and β-oxidation are involved in the PHA synthesis ofBacillus sp. INT005. SinceBacillus sp. INT005 could synthesize PHA even at 45°C and PHAs with various monomer compositions, and only one report on the cloning of the synthesis-related genes from aBacillus species (B. megaterium) has been published;Bacillus sp. INT005 is thought to be very valuable source of PHA synthesis-related genes.