Sequential cultivation of oyster and shiitake mushrooms on willow enhances biomass degradability

Abstract Natural or man-made catastrophes, such as asteroid strikes, super-volcano eruptions, or nuclear war, could create environments with low sunlight and temperatures, severely disrupting agriculture and requiring alternative food and energy sources. Lignocellulosic biomass, rich in cellulose, offers potential as an energy source for human survival. Biological agents can effectively break down this biomass and increase the efficiency of enzymatic conversion of cellulose to glucose, a biofuel precursor. In this study, we asked whether single or sequential inoculation with two white-rot fungi, oyster ( Pleurotus ostreatus ) and shiitake ( Lentinula edodes ) mushrooms, could be used to pretreat willow ( Salix spp.) biomass to increase saccharification efficiency without any supplements at 15 °C, mimicking a post-catastrophic environment. To answer this question, mushroom-pretreated biomass was incubated with the Cellic CTec2 enzyme to produce glucose. Overall, the cellulose [44–60% w/w; dry basis (db)] and lignin content (21 to 25%; db) of the pretreated willow did not change compared to untreated willow. However, sequential inoculation of oyster and shiitake, regardless of the inoculation order, enhanced saccharification efficiency yielding more glucose (28–31%) compared to untreated willow (14%) after enzymatic treatment. Based on our data, one kilogram of willow, after undergoing sequential fungal inoculations and enzymatic treatment, would yield 311 g of glucose suitable for biofuel or food production. Additionally, the mushroom fruiting bodies derived from willow provide 12%, 13%, and 2% of the daily carbohydrate, protein, and fat requirements, respectively, for a moderately active person. To achieve a balanced macronutrient supply, additional sources such as single-cell microorganisms, edible insects, and small-scale ruminants can be incorporated.