Biotransformations of HBCDs by Rhodococcus Strain Stu-38 and Identification of Transformation Products

Abstract

1, 2, 5, 6, 9, 10-Hexabromocyclododecanes (HBCDs) are new brominated flame retardants causing serious environmental pollution. Dozens of degradative bacteria have been found with capacity to transform HBCDs. In the present study, an aerobic functional bacterium Rhodococcus strain stu-38 was isolated from enriched culture of mangrove sediment using HBCDs as carbon source. This strain could stereoselectively transform HBCDs, the removal rate was α-＞γ-＞β-HBCD in the mineral salt medium, but was β-＞α- and γ-HBCD in the growth medium, and it selectively transformed γ- HBCD in the seawater. Transformation rate of strain stu-38 was lower than other functional strains, however, seven potential debrominated products of HBCDs were identified by using GC-MS. These debrominated products, included dibromocyclododecadiene, bromocyclododecadienol and bromocyclododecatriene were formed through reductive debromination, hydrolytic debromination and dehydrobromination. Overall, Rhodococcus sp. stu-38 diastereoisomer-specifically transformed HBCDs to various debrominated products in the different cultural media, which highlighted the complicated stereoselective biotransformation of HBCDs.

Rhodococcus strains as a good biotool for neutralizing pharmaceutical pollutants and obtaining therapeutically valuable products: Through the past into the future

“…are capable of oxidation and complete degradation of a wide range of organic compounds, recalcitrant pollutants and toxic compounds, pesticides, emerging pollutants, endocrine disruptors, explosives, flame retardants, plasticizers, defoliants, and plastics, including microplastics. Additionally, they have potential for fuel biodesulfurization, lipid synthesis, and biofuel production ( Coleman et al, 2002 ; Gilan and Sivan, 2013 ; Auta et al, 2018 ; Presentato et al, 2018b ; Pang et al, 2020 ; Alvarez et al, 2021 ; Hirschler et al, 2021 ; Keasling et al, 2021 ; Yu et al, 2021 ; Baek et al, 2022 ; Kamaraj et al, 2022 ). The biochemical potential of rhodococci is intensively studied due to their catabolic flexibility, unique enzymatic capabilities, broad substrate specificity and an effective set of survival strategies ( Larkin et al, 2010 ; Cappelletti et al, 2019 ; de Carvalho, 2019 ; Kuyukina and Ivshina, 2019a ).…”