Self-assembled fungus-biochar composite pellets (FBPs) for enhanced co-sorption-biodegradation towards phenanthrene

Sorption and biodegradation are two major applicable techniques for organic pollutants removal. However, the desorption risk following the sorption process and the low bioavailability of trace pollutants to microbes are still hindering the efficient removal of pollutants. To take full advantages of both sorption (for contaminant accumulation) and microbial degradation, here we introduce a self-assembly method combining carbonaceous sorbents (i.e., biochars: RS350, RS500, and RS700) with fungal hyphae (Phanerochaete chrysosporium) which can efficiently degrade phenanthrene (PHE), one of the typical polycyclic aromatic hydrocarbons. By cultivating Phanerochaete chrysosporium in biochar-containing medium, fungus-biochar composite pellets (FBPs) were successfully synthesized with a 3D macrostructure of abundant hyphae and uniform pellet size (~2.5 mm in diameter). Benefiting from the high sorption ability of biochars, such FBPs showed up to triple sorption ability and 70 folds faster biodegradation rate than pure fungal pellets. The PHE concentration remaining in solution receiving co-sorption-degradation treatment after 22 d was only one third of that receiving sorption treatment alone. Continuous removal experiment indicated that these composite pellets could hold their removal ability of above 90 % in the first 4 cycles. This study points out a simple and promising self-assembly approach that could be easily scaled up to manufacture FBPs with high removal efficiency, fast biodegradation rate, easy separation ability and long-term stability.