Sequential fermentation of wheat straw and fruit-vegetable discards to produce circular feed in support of sustainable dairy production

• P. ostreatus and T. versicolor reduced lignin content by 33-55% in wheat straw • Lignin reduction was inhibited when mixing wheat straw with fruit/vegetables • Subsequent ensiling with fruit/vegetables generated lactic acids, reduced pH to 3.5 • Double-fermented feed showed similar in vitro digestibility as standard dairy diet • The integrated bioprocessing can produce novel alternative feeds for dairy farming Developing novel circular feed from plant-based biomass unfit for direct human consumption is imperative to mitigate environmental degradation. In this study, we tested a sequential fermentation strategy to treat wheat straw (WS) and preserve fresh fruit and vegetable (FFV) discards in making circular feed for ruminants. First, ground wheat straw (particle size less than 20 mm) moisturized (moisture content 70-80% by weight) by pure water and by FFV were treated with feed grade fungal strains Tramates versicolor (TV) and Pleurotus ostreatus (PO) at 28 °C for six weeks. Fungal treated mixture resulted in reduced lignin content by 35-55% and decreased lignin-to-cellulose ratio. Each fungal treated biomass was then mixed with additional FFV and anaerobically fermented at 28 °C for 16 days. Organic acids (over 80% was lactic acid) accounted for 9-10% dry matter of the substrates and lowered pH from 5 to about 3.5, which is adequate for preservation of the fermented feed. In vitro dry matter digestibility was not different between the standard diet and sustainability-plus diets that contained 10% or 25% of the double-fermented circular feed materials. Fungal fermentation coupled with bacteria-based ensiling of under-valued or wasted biomass can produce novel feeds to support sustainable dairy farming.