Biodegradation of p-nitrophenol by a member of the genus Brachybacterium, isolated from the river Ganges

A p-nitrophenol (PNP) degrading halotolerant, Gram-variable bacterial strain designated as DNPG3, was isolated from a water sample collected from the river Ganges in Hooghly, West Bengal (WB), India, by enrichment culture technique. Based on 16S rRNA gene sequence analysis (carried out at EzTaxon server and Ribosomal data base project site), the strain DNPG3 was identified as Brachybacterium sp., with B. zhongshanense strain JBT (97.08% identity) as it is nearest phylogenetic relative. The strain could tolerate up to 3 mM of PNP, while the optimal growth for the strain was recorded as 0.25 mM. The strain could carry out biodegradation of PNP with concomitant release of nitrite and p-benzoquinone (PBQ) was detected as a hydrolysis product. Under the catabolic condition, it could carry out 36% biodegradation of PNP within 144 h, while, under co-metabolic condition (with glucose), 100% biodegradation was achieved within 48 h at 30 °C. Calcium alginate bead-based cell immobilization studies (of the strain DNPG3) indicated complete biodegradation of PNP (under catabolic condition) within 26 h. This is the first report of PNP biodegradation by any representative strain of the genus Brachybacterium. The study definitely indicated that Brachybacterium sp. strain DNPG3 has biotechnological potential and the strain may be a suitable candidate for developing clean, green, eco-friendly, cost-effective bioremediation processes towards effective removal of PNP from the contaminated sites.