Biodegradation of phenol by a novel diatom BD1IITG-kinetics and biochemical studies

A phenol-degrading novel diatom BD1IITG was isolated from petroleum refinery wastewater and characterized (GenBank Accession No. KJOO2533). HPLC analysis showed the diatom could degrade phenol in the concentration range of 50–250 mg/l in Fog’s media. The highest specific growth and degradation rate were achieved at 100 mg/l phenol. It could also mineralize phenol along with aliphatics in petroleum refinery wastewater. Growth kinetic modeling shows that Haldane model best represents the growth behavior of the diatom in nutrient media as well as refinery wastewater. Biokinetic parameters suggest that the diatom possesses higher maximum specific growth rate (μ_max = 0.4 day^-1), better tolerance to toxicity (K_I = 90.24 mg/l) and high phenol affinity (K_s = 20.99 mg/l) in refinery wastewater as compared to Fog’s media confirming practical applicability of the strain for wastewater treatment. FTIR fingerprinting of biomass indicates intercellular phenol uptake and breakdown into its intermediates via phenol degradation pathway. Pathway was elucidated using HPLC, LC–MS and UV–visible spectrophotometry confirming prominence of ortho- over meta pathway for phenol metabolism. The diatom produces biosurfactant with highest emulsifying activity at 100 mg/l phenol which may contribute to highest degradation rate at this concentration. Infrared analysis confirms increased biosynthesis of lipids and polysaccharides in phenol-degrading biomass, indicating its potential use as feedstock of clean ecofriendly energy sources as biodiesel or bioethanol. The phenol degradation capability coupled with potential applicability of the spent biomass as biofuel feedstock makes diatom BD1IITG a potential candidate for a clean environmentally sustainable process.

Keywords
Phenol; Diatom; Biodegradation; Growth kinetics; Pathway; Biosurfactant; Biofuel