A simple, non-aseptic, low-cost single process had been developed for the treatment of starch processing wastewater (SPW) with the production of fungal protein and glucoamylase enzyme. The selected fungus Rhizopus oligosporus DAR 2710 has the ability to covert more than 95% starch materials in SPW to produce 4.5–5.2 g of dry fungal biomass from a litre of SPW in 14 h cultivation at 35°C and initial pH 4.0. The fungal biomass contained 46% protein and was safe for human and animal consumption. The process using an air lift bioreactor was successfully carried out in a batch system without sterilization and/or preliminary hydrolysis of SPW. In addition to the production of fungal protein and glucoamylase, the removal of 95% COD and total suspended solids would lead to a potential benefit to the environment.