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Scientists have demonstrated a creative solution to plastic pollution, one of our most pressing environmental problems. Plastic was embedded with spores of plastic-eating bacteria that are activated when dumped in landfill, biodegrading 90% of the material in five months. Weirder still, this actually made the plastic tougher and stronger during use. Plastic is a strong, versatile material, but the same properties that make it useful also make it hard to dispose of. It famously takes decades or centuries to degrade, so huge amounts of plastic waste are clogging up landfill and oceans. Intriguingly, it seems like nature is adapting, as it so often does. In recent years scientists discovered bacteria that have evolved the ability to break down plastic, isolated the enzymes that do it, and even ramped up their efficiency. This could potentially make for more efficient recycling centers where plastic is treated with enzymes and bacteria. But what about plastic that doesn't make it to these facilities? Thermoplastic polyurethane (TPU) is a tough type of plastic commonly used to make things like shoes, sporting goods, phone cases and car parts, but can't currently be recycled. So for the new study, the team investigated a new potential method to dispose of TPU - embedding spores of the plastic-eating bacteria Bacillus subtilis right into the plastic itself. Ideally, you'd be able to use the plastic products as normal, without them breaking down too early, and only when they were dumped in landfill or natural environments would they start biodegrading. The first problem to overcome is that the high heat used to produce plastic would kill off most bacterial spores. So the researchers genetically engineered the microbes to withstand that heat, and found that 96 to 100% of the edited bacteria survived at the plastic processing temperature of 135 °C (275 °F), compared to just 20% of unedited bugs. Next, they tested how well the bacteria would break down the plastic, a process that's triggered by nutrients and moisture in the soil. At concentrations of up to 1% of the plastic's weight, the bacteria broke down over 90% of the material within five months of being buried in compost.
Han Sol Kim It's easy to assume that giving plastic its own Achille's heel will only make it weaker during use, but it turns out the opposite is true. Plastic made with the spores was found to be up to 37% tougher and had up to 30% higher tensile strength than regular TPU, with the team hypothesizing that the spores act as a reinforcing filler. The researchers say that this technique, which is potentially scalable, could open up a new way to dispose of unrecyclable TPUs, while making them tougher and stronger during use. Combine it with a few other methods and we might make some progress towards tackling the plastic pollution problem. The research was published in the journal Nature Communications. Source: University of California, San Diego via Scimex