Design, production, and characterization of artificial designer proteins as bio-based binders for wood and sand adhesives

Background

Formaldehyde-based resins are currently the main binders used in the wood and foundry industries, for example in the manufacture of chipboards or sand-casting molds. Despite their good technical properties, they are considered harmful to human health: formaldehyde is classified as carcinogenic and can be released both during production and over the life cycle of products. Accordingly, the EU has adopted strict emission limits under the REACH Regulation, which will become legally binding from 2026 [Raydan, Robles et. al, 2021].

In addition to health concerns, formaldehyde resins are also problematic as they are derived from finite fossil raw materials and their end products can only be recycled to a limited extent. This applies in particular to sand casting molds, as sand is the world’s most widely used resource after water and is increasingly subject to scarcity.

Proteins as binders

Proteins from animal and plant sources were already being used as adhesives long before industrialization. However, with the advent of inexpensive fossil-based resins, their use declined, not least because of their limited moisture resistance and variable adhesive properties.

Current research approaches are investigating not only proteins but also other bio-based binders, such as starch, cellulose, lignin, or tannins. Protein-based systems offer particular potential, but face the challenge that natural proteins are not primarily designed toward adhesive functions and often come from resources that compete with food production.

However, nature provides numerous examples of high-performance protein-based adhesives, such as those found in mussels, barnacles, spiders, and sandworms. This project draws inspiration from these biological models and transfers their functional principles to artificially developed, modular Designer Proteins (DPs) [Miserez, Mohammadi et. al, 2023].

Using modern genetic engineering methods, selected functional protein building blocks are combined and produced biotechnologically. The genetic blueprints are expressed in microorganisms such as Escherichia coli or Pichia pastoris, where residual and side streams can also be used as nutrient media. Following production, the proteins are purified and characterized for their biochemical and material properties.

Objective

The focus is on the development of sustainable, protein-based binders as an alternative to formaldehyde-based adhesives. The developed Designer Proteins are not only intended to compete with conventional formaldehyde resins, but also to replace them in the long term. The goal is a high-performance, bio-based binding agent system based on renewable resources that enables the complete recycling of wood and sand materials. The project thus contributes to the substitution of fossil-based adhesive systems and supports industrial partners in the transformation to more sustainable, regulatory-compliant, and circular production processes.

Literature:

Del Valle Raydan, N., Leroyer, L., Charrier, B., & Robles, E. (2021). Recent Advances on the Development of Protein-Based Adhesives for Wood Composite Materials—A Review. Molecules, 26(24), 7617. https://doi.org/10.3390/molecules26247617

Miserez, A., Yu, J., & Mohammadi, P. (2023). Protein-Based Biological Materials: molecular design and artificial production. Chemical Reviews, 123(5), 2049–2111. https://doi.org/10.1021/acs.chemrev.2c00621