Use of Filamentous Fungi for Wastewater Treatment and Production of High Value Fungal Byproducts: A Review

Conventional biological wastewater treatment generates large amounts of low value bacterial biomass. The treatment and disposal of this excess bacterial biomass, also known as waste activated sludge, accounts for about 40-60% of the wastewater treatment plant operation cost. A different form of biomass with a higher value could significantly change the economics of wastewater treatment. Fungi could offer this benefit over bacteria in wastewater treatment processes. The biomass produced during fungal wastewater treatment has, potentially, a much higher value than that from the bacterial activated sludge process. The fungi can be used to derive valuable biochemicals and can also be used as a protein source. Various high-value biochemicals are produced by commercial cultivation of fungi under aseptic conditions using expensive substrates. Food-processing wastewater is an attractive alternative as a source of low-cost organic matter and nutrients to produce fungi with concomitant wastewater purification. This review summarizes various findings in fungal wastewater treatment, particularly focusing on byproduct recovery during wastewater treatment. This review also provides an overview on performance of fungal treatment systems under various operational conditions. Important factors such as pH, temperature, hydraulic and solids retention time, nonaxenic and axenic operation, and others that affect the fungal treatment system are discussed. Moreover, certain important practical issues such as bacterial contamination under nonaseptic operation are also covered. The goal of the review paper is to evaluate the feasibility of cultivating fungi during wastewater treatment for deriving valuable biochemicals.