Accumulation and Transformation of Sulfonated Aromatic Compounds by Rhubarb Cells (Rheum palmatum)

Sulfonated aromatic compounds are released into the environment in large amounts: the main sources of these recalcitrant pollutants are anionic detergents, dyestuffs, and their byproducts, such as sulfonated anthraquinones. Different derivatives of anthraquinones occur naturally in several plant species such as rhubarb. Therefore, this plant could possess enzymes able to accept sulfonated anthraquinones as substrates. Previously, it has been shown that cultured cells isolated from Rheum palmatum are able to efficiently accumulate and transform different mono- and disulfonated anthraquinones. Because rhubarb is a hardy plant species, it may prove a promising candidate in developing new biological processes to decontaminate effluents containing recalcitrant xenobiotics. The ability of rhubarb cells to accumulate and transform other sulfonoaromatics was investigated in this study. Results obtained show that cultured rhubarb cells were able to efficiently accumulate 2-chloro-5-nitro-benzene sulfonate, both 2-hydroxy-4-sulfo- and 2-hydroxy-4-sulfo-6-nitro-naphthalene-diazonium, as well as 1,3-naphthalene disulfonates, containing either an amino or a nitro group in position 7. Rhubarb cells were also able to biotransform four of these compounds without releasing the metabolites formed.