Kari Koivuranta and Jukka Niskanen of VTT have over the past couple of years identified microbial enzymes capable of not only breaking down and digesting different types of plastics, but also converting them into biodegradable materials such as fatty acids.
According to Koivuranta the research has focused mainly on the most common plastics in the world, polythene and polypropylene – partly because of their abundance in plastic waste and partly because their biotechnological recycling has not been researched as extensively as, for example, PET.
While the research has successfully identified enzymes capable of breaking down the plastics, the breakdown process remains slow due to the innate properties of the plastics and additives used to improve them.
“They are hard, durable and water-repellent, preventing the microbes and enzymes from getting into their surfaces,” he explained.
VTT is consequently looking into various pre-treatment methods that enhance the capability of enzymes to digest plastics. Oxidation, for example, improves the mixing of plastics in water and makes the process faster.
“Microbes can produce new materials from carbon sources, and this is already happening on an industrial scale. In the future, the carbon source could be plastic waste instead of sugars or wood, which we can use in other ways. Plastics also contain in general more carbon per gram compared to sugars,” told Niskanen.
The biotechnological recycling of plastics, though, is not expected to replace but rather complement existing recycling methods.
“So far, polyester has been used to biotechnologically produce comparable new polyesters, but there are no public examples of using plastic waste in general to produce biodegradable material. But this will be possible in the future: it may only be five to 10 years until we can use oil-based materials to make biodegradable and biocompatible materials,” envisioned Koivuranta.