A Comprehensive Study on Chlorella pyrenoidosa for Phenol Degradation and its Potential Applicability as Biodiesel Feedstock and Animal Feed

The present work evaluates the phenol degradative performance of microalgae Chlorella pyrenoidosa. High-performance liquid chromatography (HPLC) analysis showed that C. pyrenoidosa degrades phenol completely up to 200 mg/l. It could also metabolize phenol in refinery wastewater. Biokinetic parameters obtained are the following:growth kinetics, μ max (media) > μ max (refinery wastewater), K s(media) < K s(refinery wastewater), K I(media) > K I(refinery wastewater); degradation kinetics, q max (media) > q max (refinery wastewater), K s(media) < K s(refinery wastewater), K I(media) > K I(refinery wastewater). The microalgae could cometabolize the alkane components present in refinery wastewater. Fourier transform infrared (FTIR) fingerprinting of biomass indicates intercellular phenol uptake and breakdown into its intermediates. Phenol was metabolized as an organic carbon source leading to higher specific growth rate of biomass. Phenol degradation pathway was elucidated using HPLC, liquid chromatography–mass spectrometry (LC-MS) and ultraviolet–visible (UV–visible) spectrophotometry. It involved both ortho- and meta-pathway with prominence of ortho-pathway. SEM analysis shows that cell membrane gets wrinkled on phenol exposure. Phenol degradation was growth and photodependent. Infrared analysis shows increased intracellular accumulation of neutral lipids opening possibility for utilization of spent biomass as biodiesel feedstock. The biomass after lipid extraction could be used as protein supplement in animal feed owing to enhanced protein content. The phenol remediation ability coupled with potential applicability of the spent biomass as biofuel feedstock and animal feed makes it a potential candidate for an environmentally sustainable process.