Origin and development of fungal communities in an engineered biofilter

Microbial communities underpin the performance of biofilters used for treating pollutants, but community ‘seeding’ and development is not well understood, particularly for fungi. Fungi have unique biocatalytic potential in biofilters, and identifying their inoculum sources and community succession can inform design and management strategies to improve biofilter operation. Our goal was to track fungal community development in a full-scale woodchip biofilter treating air exhaust from a swine barn facility. We sequenced fungal ITS-1 amplicons 1) from potential inoculum sources (fresh wood chip media; manure from pits below pig housing) and 2) from wood chip biofilms at the inlet and outlet of the biofilter, sampling annually over 3 years. Inlet and outlet fungal communities were distinct at the outset, but became increasingly similar by year 3. A shift from Basidiomycetes and yeasts to Ascomycetes and molds was associated with a loss of richness as the community became dominated by fungi that originated from the manure exhaust. Notably, dominant taxa were pig skin dermatophytes, likely seeded continuously from within the barn. These patterns differ from those in natural wood decomposition studies, and the results suggest that hygiene within the barn will affect the performance of biofilters located outside of the barn, an aspect of biofilter management that has not been exploited. These ‘upstream’ inoculum effects may complicate management, however, our results identify several candidate fungi and an avenue for increasing inoculum potential on a continuous basis that might be valuable for seeding biofilters, improving control, and reduce lag-times during biofilter development.