In a world first, researchers have successfully produced 100% bio-based adipic acid, a raw material for polyamide 66, from sugars derived from inedible biomass.
Researchers at Japan-based Toray Industries, working in collaboration with the National Institute of Advanced Industrial Science and Technology, and RIKEN, Japan’s largest comprehensive research institution, employed a proprietary synthesis technique combining the company’s microbial fermentation technology with a chemical purification technology that made use of separation membranes to achieve this result.
Toray has developed a process for producing sugars from crop residues and other inedible plant resources. The company was the first in the world to discover microorganisms that produce an adipic acid intermediate from sugars. Genetic engineering technology is employed to enhance the production efficiency of the microorganisms, boosting production of the intermediate synthesised by these microorganisms more than 1,000-fold since the initial discovery, whilst dramatically improving synthesis efficiency.
Microfiltration, ultrafiltration, and nanofiltration membranes separate and remove unwanted components in microbial fermentation broth. Toray uses reverse osmosis separation membranes to concentrate the intermediate in the purification process. This approach is more energy efficient than other methods that do not use these membranes, such as concentration by evaporation.
The company has now started to scale up its capabilities in this area and will start by testing the polymerisation of PA66 and developing production technology. This will be followed by market research, prior to further steps towards commercialising applications for this bio-based adipic acid in around 2030.
PA 66 has been used for many years in fibres, resins, and other applications due to its exceptionally durable, strong, and rigid properties. Adipic acid is one of the two monomers needed to produce PA 66. During the production of conventional , petroleum-based adipic acid, a greenhouse gas called dinitrogen monoxide is generated. The bio-adipic acid production technique is free of dinitrogen monoxide emissions, and is therefore expected to help combat global warming.