Trained bacteria convert bio-wastes into plastic

Delft University of Technology researcher Jean-Paul Meijnen has 'trained' bacteria to convert all the main sugars in vegetable, fruit and garden waste efficiently into high-quality environmentally friendly products such as bioplastics.

Photo: bacteria in training. B-BasicThere is considerable interest in bioplastics nowadays. The technical problems associated with turning potato peel into sunglasses, or cane sugar into car bumpers, have already been solved. The current methods, however, are not very efficient: only a small percentage of the sugars can be converted into valuable products. By adapting the eating pattern of bacteria and subsequently training them, Meijnen has succeeded in converting sugars in processable materials, so that no bio-waste is wasted.

Basis for bioplastics
The favoured raw materials for such processes are biological wastes left over from food production. Lignocellulose, the complex combination of lignin and cellulose present in the stalks and leaves of plants that gives them their rigidity, is such a material. Hydrolysis of lignocellulose breaks down the long sugar chains that form the backbone of this material, releasing the individual sugar molecules.

These sugar molecules can be further processed by bacteria and other micro-organisms to form chemicals that can be used as the basis for bioplastics. The fruit of the plant, such as maize, can be consumed as food, while the unused waste such as lignocellulose forms the raw material for bioplastics.

Cutting the price of the process
"Unfortunately, the production of plastics from bio-wastes is still quite an expensive process, because the waste material is not fully utilized," explains Jean-Paul Meijnen. (It should be noted here that we are talking about agricultural bio-wastes in this context, not the garden waste recycled by households.) The pre-treatment of these bio-wastes leads to the production of various types of sugars such as glucose, xylose and arabinose.

These three together make up about eighty per cent of the sugars in bio-waste.