Future food court in an urban shopping center can supply feedstocks for microbial protein production

Abstract

Food courts in urban shopping centers can be future sources of feedstock for microbial protein production. This study explored whether filamentous fungi Trichoderma reesei, Paecilomyces variotii and Rhizopus oligosporus can be cultivated on growth media prepared from orange peels, soft drink waste-mix, expired bread or spent coffee grounds, all existing and potential by-products of future food courts. Furthermore, artificial urine to describe human urine as a future nitrogen source was investigated. Side stream pretreatments facilitated sugar releases up to 171 g L⁻¹ (expired bread). Cultivation media were prepared from pretreated side streams with 40 g L⁻¹ sugar. Flask cultivations supplemented with nitrogen and micronutrient increased fungal biomass production. From the nitrogen sources tested, yeast extract (10 g L⁻¹) proved effective in media based on soft drink waste-mix and orange peel juice. For the latter artificial urine (5 g L⁻¹ urea) worked as well. The effects of these nitrogen supplements, along with pH, on biomass production were further optimized using design of experiment methodology and validated in lab-scale bioreactor cultivations. The bioreactor cultivations of P. variotii and T. reesei with soft drink waste-mix or orange peel juice supplemented with yeast extract (13 – 15 g L⁻¹) resulted in good biomass production up to 37.8 g L⁻¹ and 15 g L⁻¹ dry weight with total protein contents reaching 25 % and 35 % for P. variotii and T. reesei, respectively. Amino acid analyses revealed balanced essential amino acid distributions for human consumption, confirming that future food court by-products are viable substrates for sustainable fungal protein production in a circular economy.