Solid State Fermentation
Post-consumer textiles remain a significant challenge to incorporate into a circular economy. The most widely used and often most affordable fabrics combine both an organic fiber (e.g. cotton) with a synthetic fiber (e.g. polyester). Such blends confound traditional mechanical and chemical recycling techniques, often unable to recover both fiber types.
The ubiquity of post-consumer textile and garment waste provides a widely available, low cost, highly standardized feedstock material. In addition to being a dense source of carbon, common fibers such as nylon possess a higher density of nitrogen than the agricultural waste used in biomanufacturing.
Fungi, particularly macrofungi like culinary mushrooms, innately produce a wide range of enzymes that breakdown organic matter into a wide range of high value products. Such fungi-based solid state fermentation platforms are industrial workhorses, producing a diversity of food, medicine and materials from waste.
Expanding the range of materials on which mushrooms grow will both lower cost and increase revenue to mushroom farmers, increasing both food and nutrition security in both cities and and food insecure states like Hawai'i:
What we're doing about it
In order to tackle the abundance of blended textile waste, we're developing co-cultures: a symbiosis between mushroom and microbe. There is an organism that eats nearly every material, but no organism alone eats every material. Mushrooms, like the widely cultivated oyster mushroom (Pleurotus ostreatus), are widely known to selectively grow on cotton textiles, but struggles to digest polyester. In contrast, a range of newly discovered microbes effectively breakdown polyester (e.g. polyethylene terephthalate). Growing together, these mushroom-microbe partnerships divide and conquer, forming a comprehensive process to efficiently transform waste into higher value products.
P. ostreatus, like many white-rot fungi, express a cocktail of extracellular enzymes that break down lignin, cellulose and hemicellulose, the main components of woody-biomass. Bacteria, on the other hand, produce a diversity of carboxyl ester hydrolases that attack the ester-linkage in PET fibres. They also produce a range of peptide hydrolases that cleave the peptide bonds found in proteins (e.g.silk, wool) and synthetic, nitrogenous polymers (e.g. nylon).
While fungi-bacteria symbioses are ubiquitous in nature, selecting for and balancing their interactions requires a wide, high-throughput search to pair the right microbe(s) with the right mushroom.
Our ongoing work looks for the right combination of mushroom + microbe, under the optimal conditions, to encompass the ever growing material diversity and complexity of post-consumer textile waste.