Abstract
The process to obtain starch from wheat requires high amounts of water, consequently generating large amounts of wastewater with very high environmental loading. This wastewater is traditionally sent to treatment facilities. This paper introduces an alternative method, where the wastewater of a wheat-starch plant is treated by edible filamentous fungi (Aspergillus oryzae and Rhizopus oryzae) to obtain a protein-rich biomass to be used as e.g. animal feed. The wastewater was taken from the clarified liquid of the first and second decanter (ED1 and ED2, respectively) and from the solid-rich stream (SS), whose carbohydrate and nitrogen concentrations ranged between 15 and 90 and 1.25–1.40 g/L, respectively. A. oryzae showed better performance than R. oryzae, removing more than 80% of COD after 3 days for ED1 and ED2 streams. Additionally, 12 g/L of dry biomass with protein content close to 35% (w/w) was collected, demonstrating the potential of filamentous fungi to be used in wastewater valorization. High content of fermentable solids in the SS sample led to high production of ethanol (10.91 g/L), which can be recovered and contribute to the economics of the process.
Highlights
Wheat is one of the most important crops in human diet
The wastewater of a wheat-starch plant was investigated as the substrate for the cultivation of A. oryzae and R. oryzae
The effluent of a wheat-starch plant was treated by A. oryzae and R. oryzae
Summary
Wheat is one of the most important crops in human diet. Globally, wheat supplies more protein than poultry, pig, and bovine meat together [1]. The European Union (EU) is the most important producer of wheat in the world, accounting for over 20% of the global production [2]. According to the European starch manufacture, wheat is the most processed crop, accounting for 35.9% of the total 23.6 million tons of crops processed annually. In 2015, wheat yielded 39.6% of the 10.7 million tons of starch produced [3]. Several methods of starch production from wheat were reviewed by Van Der Borght et al [6]. These methods can demand up to 1.8 parts of water per part of wheat flour [6]. This wastewater has to be treated at the end of the process, which represents an environmental challenge due to the large chemical oxygen
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