Degradation of m-cresol via the ortho cleavage pathway by Citrobacter farmeri SC01

• A newly isolated Critrobacter farmeri SC01 can degrade m-cresol effectively.
• LC–MS analysis detected four new peaks and the intermediates were confirmed.
• GC–MS analysis confirmed the presence of 3-hydroxybenzoic acid and 3,4-dihydroxybenzoic acid.
• FT-IR analysis confirmed the formation of muconolactone during the biodegradation of m-cresol.
• The intermediates in m-cresol degradation proved a new orth-cleaving metabolic pathway.

Traditionally two pathways are used to biodegrade m-cresol: (1) a meta; and (2) gentisate. However, my new study shows a promising third pathway. The study first isolates Citrobacter farmeri SC01 from an aerobic basin of a coking wastewater treatment. Then the isolated C. farmeri SC01 was used to study the metabolism of m-cresol. The findings show that the isolated C. farmeri SC01, if grown on m-cresol as the sole carbon source, can metabolically biodegrade m-cresol. By the methods of HPLC, LC–MS, FT-IR and GC–MS, the study identifies the metabolic intermediates of m-cresol biodegraded by C. farmeri SC01 under aerobic process. These intermediates are 3-hydroxybenzoic acid, cis,cis-munconate, and muconolactone, the typical ortho-cleavage metabolites formed and consumed during the degradation of m-cresol. Moreover, when growing on m-cresol as a sole carbon and energy source, C. farmeri SC01 can induce the production of catechol 1,2-dioxygenase. The findings contribute to the study of the characteristics of biodegradation, the metabolic mechanism, the properties of enzymes and the expression, and the regulation of the genes involved in the degradation of m-cresol.

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