Effects of utilizing sawdust on non-ligninolytic degradation of high concentration of n-hexadecane by white-rot fungi: Kinetic analysis of solid-phase bioremediation

Abstract

Abstract A bioremediation system with intermitted aeration was employed to investigate the biodegradation capability of newly isolated wild-type white-rot fungi (WRF) in the solid-phase soil highly contaminated with n-hexadecane (HXD). At the end of the 120-day experimental period, almost complete removal was observed in free cells of fungus 1TK (identified as Schizophyllum commune MK875535) and fungus 4TK. The ability to decompose phenanthrene as well introduced these two strains as potential biodegrader of crude oil contaminants. Although lignin-containing substrate addition enhances polycyclic aromatic hydrocarbons (PAHs) degradation by WRF, little is known about its effect on a linear contaminant. Sawdust was selected as the immobilization support and biostimulator to yield higher degradation. Additionally, a kinetic model was developed enabling the comparison of the degradation rates. The process was best fitted with zero-order kinetic, which attributed the highest rate to cultures without lignocellulose. The results revealed that since alkane degradation pathway is non-ligninolytic, immobilization on sawdust has negative or no effect on bioremediation despite the expectations. This suggests that ligninolytic enzymes secretion, which was stimulated with pre-growing on sawdust, might lead to a higher degradation of preferable lignocellulosic substrate rather than favoring HXD degradation.