How Rhodococcus Ruber Accelerated Biodegradation of Benzophenone-3

Benzophenone-3 (2-hydroxy-4-methoxybenzophenone, BP-3) poses risks to human health and natural ecosystems, and means to improve its biodegradation are necessary. When a small mass of Rhodococcus ruber, isolated from BP-3-acclimated biomass, was bioaugmented into the acclimated biomass, BP-3 removal was accelerated by 120 %. The first step of BP-3 biodegradation generates either 2,5-dihydroxy-4-methoxybenzophenone (5-OH-BP-3) or benzophenone-1 (2,4-dihydoxybenzophenone, BP-1). BP-1 is generated by sequential demethylation, hydroxylation, and dehydrogenation reactions, while 5-OH-BP-3 is generated by one mono-oxygenation reaction. Of the two intermediates, 5-OH-BP-3 exhibited stronger inhibition than BP-1 or the original BP-3. Gene-completion mapping showed that R. ruber contains genes for demethylase, hydrolase, dehydrogenase, and mono-oxygenase reaction, which means that R. ruber could generate the less-toxic BP-1. Thus, bioaugmentation of R. ruber into BP-3-acclimated biomass eliminated the accumulation of 5-OH-BP-3 and, consequently, accelerated of BP-3 biodegradation via BP-1.