Abstract
In a circular economy approach, edible filamentous fungi (single cell protein) can be cultivated on volatile fatty acids (VFAs) derived from anaerobic digestion (AD) of organic-rich waste streams. In this study, the effect of pH, concentration/distribution of VFAs, nutrient supplementation, and type of waste on Aspergillus oryzae cultivation on synthetic VFAs, and actual VFAs derived from AD of food waste and cow manure were investigated. The optimal pH for A. oryzae growth on VFAs were 6 and 7 with maximum acetic acid consumption rates of 0.09 g/L.h. The fungus could thrive on high concentrations of acetic (up to 9 g/L) yielding 0.29 g dry biomass/gVFAsfed. In mixed VFAs cultures, A. oryzae primarily consumed caproic and acetic acids reaching a biomass yield of 0.26 g dry biomass/gVFAsfed (containing up to 41% protein). For waste-derived VFAs at pH 6, the fungus successfully consumed 81–100% of caproic, acetic, and butyric acids.
Highlights
The above researchers carried out a long-term semi-continuous Anaerobic digestion (AD) of either Food Waste (FW) or Cow Manure (CM) in which submerged micro filtration membranes assisted in-situ recovery of the metabolized volatile fatty acids (VFAs) solution from the mixture of undigested materials
The VFAs produced via anaerobic digestion of various organic waste are attractive compounds that can be used as building block chemicals for the production of a wide range materials, including filamentous fungi such as A. oryzae
The fungus is a versatile microorganism that can grow on a wide array of different substrates, including carboxylate-containing waste streams such as thin stillage and vinasse. This is the first study investigating the use of VFAs solution derived from anaerobic digestion of organic waste as the sole nutrient source for the cultivation of A. oryzae
Summary
Due to the world population growth, demands for human food and animal feed have significantly increased. A. oryzae is widely used in Asian fermented products, such as sake, shoyu, soy sauces in Japan; or Korean and Chinese rice wines (Nout & Aidoo, 2002) Most of these materials come from wellcontrolled industrial environments, and are considered as defined sub strates whose organic compounds are converted into valuable products. To the authors’ knowledge, the application of VFAs so lution derived from anaerobic digestion of organic waste as exclusive carbon sources for the production of edible A. oryzae fungal biomass has not yet been studied. The VFAs solution derived from anaerobic digestion of cow manure and food wastes were used as the sole nutrient source to produce edible A. oryzae fungal biomass
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