Rhodococcus aetherivorans IAR1, a new bacterial strain synthesizing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from toluene

Toluene is the volatile organic compound (VOC) that is most abundantly emitted to the environment. Here, we report a new bacterial strain, IAR1, which synthesizes polyhydroxyalkanoate (PHA) from toluene as the sole carbon source. Using physiological tests and phylogenetic analysis, IAR1 was identified as Rhodococcus aetherivorans. Degradation of toluene by resting IAR1 cells followed Michaelis–Menten kinetics. The determined kinetic parameters showed that the degradation ability of IAR1 is slightly lower than that of Acinetobacter sp. Tol 5, which is highly effective for removing toluene from off-gas. PHA synthesized by IAR1 was identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by 1H NMR and gas chromatography. During fed-batch cultivation of resting IAR1 cells, the principal monomer unit shifted from 3-hydroxybutyrate to 3-hydroxyvalerate. PHBV shows flexibility and toughness comparable to conventional thermoplastics, but its production usually requires supplying expensive precursors as a secondary carbon source. Therefore, employment of R. aetherivorans IAR1 in the production of PHBV from toluene as the sole carbon source is an attractive means for production of the practical copolymer. In addition, the utilization of waste toluene as a raw material for the polymer production will achieve further cost reduction alongside the effective utilization of waste material.