Pet food protein ingredient from solidstate fermentation of agricultural sidestreams using filamentous fungi

Abstract

The use of microbial fermentation to produce sustainable protein ingredients is an emerging research area. This thesis investigates the optimization of solid-state fermentation (SSF) using filamentous fungi on selected industrial side-streams to produce a protein-rich ingredient for dry dog food applications. Initial substrate screenings were conducted to identify suitable substrate ratios. Key fermentation parameters were then systematically evaluated using one-factor-at-a-time (OFAT) approach to determine their effects on fungal growth and nitrogen. A ratio of 70% solid-based substrate to 30% liquid-based substrate combined with an initial moisture content (MC) of 60% yielded favorable nitrogen values. The addition of a nitrogen supplement consisting of ammonium and nitrate at an inclusion level of 2% improved both fungal growth and nitrogen content. Fermentation times between 72 and 96 hours, as well as, scale-up from petri-dish to tray level showed promising results. The final protein product demonstrated an approximate 40% protein increase from low-value substrates to a high-value product. Nutritional characterization revealed an amino acid profile comparable towards soybean meal, although methionine levels remained lower than in fishmeal. Overall, protein content did not reach that of soybean meal and fishmeal. This study suggests a feasibility of fungal protein production via SSF, however additional refinement is required to improve its applicability.