Clothing made from biologically inspired super fibers - researchers have now come a step closer to this goal. In order to increase the hitherto lacking yield in the production of synthetic spider silk, they successfully used another bio-patent: By combining it with a sticky mussel foot protein, a new spider silk fusion material could be produced in large quantities. Fibers obtained from it are also particularly strong and tough. This could lead to a viable production opportunity for high-performance and sustainable textiles, say the scientists.
No synthetic fiber can compete with the spiders' patent, because their silk threads have an amazing combination of properties: They are extremely strong and tough, but still light and flexible. This material, which is based on protein structures, has great potential for humans. However, it is not possible to obtain it naturally in usable quantities. Unlike silkworms, spiders are not suitable for mass production of their threads. In order to make the material usable nonetheless, researchers have been working for some time on producing silk proteins biotechnologically. To do this, the genetic blueprint of the substance is inserted into bacteria so that they form the basic material for fiber production.
Bacteria produce spider silk
Basically, the team led by senior author Fuzhong Zhang from Washington University in St. Louis succeeded in obtaining recombinant spider silk in 2018. But so far, as is well known, this has not resulted in any spider silk products on the market. The reason for this is the lack of yield so far. This is due to the limited ability of bacteria to produce very long-chain proteins, explains Zhang: "The excellent mechanical properties of natural spider silk are based on particularly long and repetitive protein sequences. It has turned out to be extremely difficult to get bacteria to produce large numbers of such proteins,” says the scientist.
However, as he and his colleagues report, they have discovered a possible solution to the problem: They came up with the idea of having the bacteria produce smaller pieces of silk protein, which then link together. “We looked for proteins that can be fused with silk fragments to then promote molecular interaction. And indeed, we have found such proteins in the course of our work that we have already done on mussel foot proteins," says Zhang.
Mussels secrete these adhesive proteins to attach themselves to objects. Zhang and his team have already genetically engineered bacteria to produce these proteins. They can then be used, for example, as adhesives for biomedical applications. Within the scope of these investigations, it was shown that the mussel foot proteins also have a strong binding force among themselves. So the researchers came up with the idea of combining them with the spider silk proteins. Using genetic engineering methods, they actually succeeded in placing a piece of mussel foot protein at the end of a shortened silk protein sequence.
High yield and high performance
It has been confirmed that bacteria can form these relatively short spider silk fusion proteins comparatively effectively: The team found that the microbial production of the fusion silk produced eight times the yield of the previous recombinant silk proteins. As they then link together, the raw material for the production of new types of spider silk fibers is created. In this way, a remarkable eight grams of fiber material can be obtained from one liter of bacterial culture. But are these structures any good? Investigations and tests of the performance of these so-called btMSilk fibers showed that they even significantly outperform the earlier versions.
According to the team, this is a breakthrough in the production of synthetic spider silk that could pave the way for a new era of sustainable clothing production. Because higher yields are crucial if the bio-inspired silk is to be used in everyday applications. "Because our silk is made from simple raw materials using bacteria, it could provide a renewable and biodegradable replacement for petroleum-derived fibrous materials such as nylon and polyester," Zhang said.
Source: Washington University in St. Louis, professional article: Nature Communications, doi: 10.1038/s41467-023-37563-0