Scientists Eye Bacterial Biodegradation As Way To Recycle Plastic

Researchers may be on the brink of a solution to the more than 300 million tons of plastic produce each year worldwide.

More plastic has been produced over the last decade than during the entire last century. Mechanical and chemical recycling have so far been the default responses to dealing with plastic. However, such methods can be energy intensive and can impair the integrity of polymer molecules before items are shipped to manufacturing companies for alternative uses.

Thus, researchers from Ben-Gurion University of the Negev in Israel are looking into biodegradation by bacteria, which could be a simpler and more environmentally friendly way to break down and recycle PET (polyethylene terephthalate), the most common type of plastic in food and beverage packaging and textile products.

BGN Technologies, the technology company of Ben-Gurion University, signed a research collaboration agreement with Portuguese company Ecoibéria in November as part of a one-year project to study and demonstrate the effectiveness of bacterial biodegradation of PET.

The results of the joint study may streamline the cumbersome plastic recycling process used today, which involves plastic being collected from recycling bins before being ground into small chips and melted into sheets of raw material and fibers.

20 years of research

“Our research dealt with the decomposition of various polymers of plastics,” said Professor Ariel Kushmaro of BGU’s department of biotechnology engineering, who is working on the project with lead researcher and 20-year veteran of recycling research, Professor Alex Sivan.

“We started from the understanding that biodegradation is derived from the microorganism’s requirement for an energy and carbon source,” Kushmaro said. “For that, they break down organic matter — carbon chains, like sugars and even proteins. We thought because plastic, polyethylene and PET were also made up of carbon chains, we would prepare a kind of ‘enrichment culture’ — soil that was contaminated over the years with plastic or PET with its original bacterial population.”

The obvious obstacle is that polyethylene is considered a non-biodegradable substance due to its highly stable carbon-carbon bonds. Therefore, its bacterial decomposition must be manually facilitated in a laboratory.

“Along with the bacteria, we added the material that we wanted them to break down and let them work for a few weeks. After several attempts, we saw a microorganism that grows and utilizes polyethylene as a carbon and energy source. These are the bacteria that can handle the polymers,” Kushmaro said. 

“We understood that in order for the bacteria to biodegrade the carbon bonds in the plastic polymers, it had to be grown in a carbon-free environment, so that the bacteria had no other choice but to consume the only available carbon in the plastic to survive,” the scientist said. “Of course, for the purpose of the process, it is not enough to just supply the bacteria with carbon chains. We had to give them all kinds of additives, like sources of nitrogen and phosphorus to make it easier for them to perform decomposition.”

Kushmaro, Sivan and their research team have discovered several types of bacteria capable of successfully biodegrading polyethylene microplastics in soil samples.

“We showed that within 30 days, 10 to 20 percent of the soil’s weight was lost just through the decomposition activity performed by the bacteria, which emitted carbon dioxide in the process of respiration,” Kushmaro said.

Ecoibéria, which specializes in recycling PET bottles, recognized the potential of the research and approached BGN Technologies for a collaboration, which will involve laboratory tests to determine how the bacteria can break down PET and if the intermediate byproducts can be separated and used as raw materials for the plastic industry.

If so, there will be another round of investment in the pilot. If the pilot is ultimately successful, then it will take at least two to three years of additional research before this technology can be applied in an industry setting.

More efficient, better quality

“Today, if you want to recycle efficiently, you have to separate water bottles from milk bottles and shampoo containers and more. The need to separate all types of plastic from each other is what makes the process so complex,” Dr. Noam van der Hal, who researches microplastics at the University of Haifa, said. “In fact, it is very difficult to recycle plastic products to the same quality level and properties they had originally. Today, instead of recycling a bottle back into a bottle, we recycle it into a playground floor, a bench or building material. Therefore, it is not recycling in the full sense of the word.”

The product obtained through biological decomposition is the original raw material, according to Kushmaro.

“What we are trying to produce together with Ecoibéria is a process where the same PET chips will break down into the source materials so that the product can be sold in its original raw material form,” Kushmaro said. “The idea is that microorganisms or enzymes will break down the molecular polymer chains in order to extract the clean raw materials from the mixture and reproduce the PET as conventional industry practices would.”

The researcher added that biodegradation is much cheaper than thermal or chemical processes of recycling, giving it a competitive edge in the raw materials market.

“They are looking at holistic solutions that can improve recycling,” Kushmaro said. “This is also related to environmental trends in the European market, where there is encouragement to invest in ‘green’ projects that will reduce environmental pollution. Our research is part of this welcome trend.”

Scientists Eye Bacterial Biodegradation As Way To Recycle Plastic appeared first on ISRAEL21c.

(Edited by Carlin Becker and David Martosko)