Rational Design of Spider Silk Materials Genetically Fused with an Enzyme

• Published in: Advanced functional materials 2015-09, Vol.25 (33), p.5343-5352
• Main Authors: Jansson, Ronnie, Courtin, Christophe M., Sandgren, Mats, Hedhammar, My
• Format: Article
• Language: English
• Subjects: Araneae; Biofysik; Biophysics; Catalysis; enzyme immobilization; Enzymes; Fibers; gene fusion; Materialkemi; Materials Chemistry; protein-based materials; Proteins; recombinant spider silk; Self assembly; Silk; Spiders; Xylanase
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.201501833

Enzyme immobilization is an attractive route for achieving catalytically functional surfaces suitable for both continuous and repeated use. Herein, genetic engineering is used to combine the catalytic ability of a xylanase with the self‐assembly properties of recombinant spider silk, realizing silk materials with enzymatic activity. Under near‐physiological conditions, soluble xylanase‐silk fusion proteins assembled into fibers displaying catalytic activity. Also, a xylanase‐silk protein variant with the silk part miniaturized to contain only the C‐terminal domain of the silk protein formed fibers with catalytic activity. The repertoire of xylanase‐silk formats is further extended to include 2D surface coatings and 3D foams, also being catalytically active, showing the versatile range of possible silk materials. The stability of the xylanase‐silk materials is explored, demonstrating the possibility of storage, reuse, and cleaning with ethanol. Interestingly, fibers can also be stored dried with substantial residual activity after rehydration. Moreover, a continuous enzymatic reaction using xylanase‐silk is demonstrated, making enzymatic batch reactions not the sole possible implementation. The proof‐of‐concept for recombinantly produced enzyme‐silk, herein shown with a xylanase, implies that also other enzymes can be used in similar setups. It is envisioned that the concept of enzyme‐silk can find its applicability in, for example, multienzyme reaction systems or biosensors. Two recombinant spider silk modules, 4RepCT and CT, are genetically fused to the enzyme xylanase and produced as soluble enzyme‐silk fusion proteins. Self‐assembly is used to make enzyme‐silk materials in the form of fibers, 2D surface coatings and 3D foams, which all show retained enzymatic activity from the added xylanase domain. Activity is shown for batch and continuous enzymatic reactions.