Can Mushrooms Eat Plastic? What We're Researching

Before The Sole Connection was a farm, it was a question I couldn't stop thinking about: could fungi actually break down plastic?

I first ran into the research on fungal plastic degradation years ago, but it became a real, hands-on project during COVID, while I was working for a plastics manufacturer. I started experimenting with different oyster mushroom strains against different polymers on the side — informally at first, then with an actual protocol. That work became the seed for what's now a longer-term goal alongside the farm: fungal remediation research, done properly, with real controls and real documentation.

Here's what that research has actually looked like so far — and where it's honest to say it stands today.

Starting with the strains

Not every oyster mushroom behaves the same way. I tested several strains against a few different engineering plastics — UHMW polyethylene, Delrin (acetal), and PET, chosen because they're common, durable industrial polymers, not the easy-to-degrade plastics you'd expect to break down on their own — and found that two strains, Pleurotus ostreatus and Pleurotus pulmonarius, consistently outperformed the others. Other oyster strains I tried were noticeably less effective. That strain-level difference turned out to matter a lot for everything that came after, because it meant the next experiment needed real controls to isolate what was actually

happening.

The experiment: putting fungi under oxygen stress with plastic as the only long-term food source

The core question I wanted to answer wasn't just "can fungi survive near plastic" — it was whether they could actually be using it as a resource. So I designed a selection experiment around white rot fungi (the group Pleurotus belongs to) under cyclic oxygen restriction, with four groups running in parallel:

- The experimental group: sealed in low-oxygen containers, with one of the three test polymers (UHMW, Delrin, or PET) as the main long-term substrate. Each culture got a small seed of familiar nutritive substrate — about 600 mg of leaf matter, coffee grounds, and sawdust, roughly two weeks' worth of growth — and a brief weekly reoxygenation window (30 minutes of ambient air).

- Control 1 (unsealed/aerobic): same seed substrate, normal oxygen, no restriction.

- Control 2 (starvation): sealed and oxygen-restricted like the experimental group, but with no seed substrate at all.

- Control 3 (no polymer): sealed, oxygen-restricted, and seeded identically to the

experimental group — but with no polymer present.

That third control is the important one. It's identical to the experimental group in every way except one variable: whether polymer was present.

What happened

All three control groups died off months before the experimental group did. The starvation control and the no-polymer control in particular are the telling comparison: both had the same oxygen restriction, and the no-polymer group even had the same starter nutrients as the experimental group — but without plastic present, it perished months earlier.

Three strains in the polymer group, by contrast, remained viable for 18 to 26 months — far longer than the roughly two weeks of growth that 600 mg of starter substrate could realistically sustain on its own. Since the no-polymer control was otherwise identical and died months earlier, the presence of polymer is the one variable that explains the difference in survival time.

That result strongly implicates the fungi utilizing the plastic itself under oxygen stress.

Survival time wasn't the only thing I observed. On the polymer segments themselves, I found visible striations exactly where the mycelium had been in contact — physical marking on the plastic's surface that lined up with where the fungus grew across it.

I want to be precise about what all of this does and doesn't prove. Extended survival in the presence of polymer, combined with visible surface striations at points of mycelial contact, is strong circumstantial evidence of polymer utilization — but it isn't, by itself, proof of enzymatic degradation. Confirming that would require mass-loss measurements and analysis of breakdown products, which I haven't run yet. That's the honest next step, not a claim I'm making today.

What I did take from those surviving cultures: I selected the three strains that made it through 18–26 months of oxygen-restricted, plastic-as-primary-substrate conditions for ongoing strain-development work. Whatever let them survive that long is worth understanding and building on.

Beyond plastic: heavy metals

Plastic degradation isn't the only remediation work I've run. I also designed and ran a fungal heavy-metal uptake and immobilization experiment — testing whether fungi could pull heavy metal contaminants out of a growing medium and hold onto them in their own tissue rather than letting them stay mobile in the environment.

That one has a piece of outside validation the polymer study doesn't yet have: the results were independently verified by a third-party NRCS (Natural Resources Conservation Service) contractor.

Where this is headed: training fungi for specific contaminants

The long-term direction of this work is what I think of as environmental conditioning — running white rot fungi through multiple generations, selecting for strains that express more of the specific ligninolytic enzymes (laccases, peroxidases) that matter for breaking down persistent contaminants. In plain terms: instead of hoping a wild strain happens to be good at this, deliberately breeding and selecting fungi that get better at it, generation over generation, the same way any breeding program works toward a trait.

That program is ongoing.

Why this lives next to a farm, not instead of one

I'll be straightforward about where things stand: this research doesn't currently have dedicated funding. It's running in parallel to a working mushroom and tincture farm, on the time and resources that are left over after the farm's own demands are met — which is exactly why building The Sole Connection's tincture business into something with real, dependable cash flow matters so much to me beyond just paying the bills. The plan has always been for the farm and the tincture line to be the economic engine that eventually makes this research possible to do

properly, not as a side project squeezed into whatever time is left.

I'm not there yet. But the survival data, the NRCS-verified heavy-metals work, and an ongoing strain-selection program are real, and they're the foundation I'm building from.