Mechanistic investigations in ultrasound-assisted biodegradation of phenanthrene

• Published in: Ultrasonics sonochemistry 2020-04, Vol.62, p.104890-104890, Article 104890
• Main Authors: Kashyap, Niharika, Roy, Kuldeep, Moholkar, Vijayanand S.
• Format: Article
• Language: English
• Subjects: Biodegradation; Biodegradation, Environmental; Biological Oxygen Demand Analysis; Candida tropicalis; Candida tropicalis - metabolism; Catechol 2,3-Dioxygenase - metabolism; Electrophoresis, Polyacrylamide Gel; Fungal Proteins - metabolism; Haldane kinetic model; Phenanthrene; Phenanthrenes - metabolism; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - metabolism; Sonication; Spectroscopy, Fourier Transform Infrared; Ultrasound
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2019.104890

[Display omitted] •Biodegradation of polycyclic aromatic hydrocarbon Phenanthrene using yeast, Candida tropicalis.•Statistical optimization of process parameters and kinetic analysis with Haldane model.•Sonication at 33 kHz and 10% duty cycle enhanced phenanthrene removal by 25%•Overexpression of intracellular proteins during sonication analysed by SDS-PAGE.•Degradation of phenanthrene occurred via meta route catalysed by C2,3-D enzyme. This study has addressed the biodegradation of polycyclic aromatic hydrocarbon, phenanthrene using Candida tropicalis. Optimization using central composite statistical design yielded optimum experimental parameters as: pH = 6.2, temperature = 33.4 °C, mechanical shaking = 190 rpm and % inoculum = 9.26% v/v. Sonication of biodegradation mixture at 33 kHz and 10% duty cycle in log phase (12 h per day for 4 days) resulted in a 25% enhancement in phenanthrene removal. Profiles of specific growth rate (µ) and specific degradation rate (q) versus initial substrate concentration were fitted to Haldane substrate inhibition model. Both µ and q showed maxima for initial concentration of 100 mg L−1. Kinetic analysis of degradation profiles showed higher biomass yield coefficient and smaller decay coefficient in presence of sonication. Expression of total intracellular proteins in control and test experiments were analyzed using SDS–PAGE. This analysis revealed overexpression of enzyme catechol 2,3-dioxygenase (in meta route metabolism) during sonication which is involved in ring cleavage of phenanthrene. Evaluation of cell viability after sonication by flow cytometry analysis revealed > 80% live cells. These effects are attributed to enhanced cellular transport induced by intense microturbulence generated by sonication.