Being able to produce artificial spider silk has long been a dream of many scientists, but all attempts have until now involved harsh chemicals and have resulted in fibers of limited use. Now, a team of researchers from the Swedish University of Agricultural Sciences and Karolinska Institutet has, step by step, developed a method that works.
Today they report that they can produce kilometer long threads that for the first time resemble real spider silk.Spider silk is an attractive material–it is well tolerated when implanted in tissues, it is light-weight but stronger than steel, and it is also biodegradable. However, spiders are difficult to keep in captivity and they spin small amounts of silk. Therefore, any large scale production must involve the use of artificial silk proteins and spinning processes. A biomimetic spinning process (that mimics nature) is probably the best way to manufacture fibers that resemble real spider silk. Until now, this has not been possible because of difficulties to obtain water soluble spider silk proteins from bacteria and other production systems, and therefore strong solvents has been used in previously described spinning processes.
Spider silk is made of proteins that are stored as an aqueous solution in the silk glands, before being spun into a fiber. Researcher Anna Rising and her colleagues Jan Johansson and Marlene Andersson at the Swedish University of Agricultural Sciences and at Karolinska Institutet have previously shown that there is an impressive pH gradient in the spider silk gland, and that this well-regulated pH gradient affects specific parts of the spider silk proteins and ensures that the fiber forms rapidly in a defined place of the silk production apparatus.
This knowledge has now been used to design an artificial spider silk protein that can be produced in large quantities in bacteria, which makes the production scalable and interesting from an industrial perspective.
“To our surprise, this artificial protein is as water soluble as the natural spider silk proteins, which means that it is possible to keep the proteins soluble at extreme concentrations”, says Anna Rising.
To mimic the spider silk gland, the research team constructed a simple but very efficient and biomimetic spinning apparatus in which they can spin kilometer-long fibers only by lowering the pH.
“This is the first successful example of biomimetic spider silk spinning. We have designed a process that recapitulates many of the complex molecular mechanisms of native silk spinning. In the future this may allow industrial production of artificial spider silk for biomaterial applications or for the manufacture of advanced textiles”, says Anna Rising.
Learn more: Spinning spider silk is now possible
Although its head office is located in Ultuna, Uppsala, the university has several campuses in different parts of Sweden, the other main facilities being Alnarp in Lomma Municipality, Skara, and Umeå. Unlike other state owned universities in Sweden, it is funded through the budget for the Ministry for Rural Affairs.
The university has four faculties: Faculty of Landscape planning, Horticulture and Agricultural Sciences, Faculty of Natural Resources and Agriculture Sciences, Faculty of Veterinary Medicine and Animal Science and Faculty of Forest Sciences. SLU had in 2012 3080 full-time staff, 3935 full-time students, 714 research students and 241 professors.
Microplastics are increasingly seen as an environmental problem of global proportions. While the focus to date has been on microplastics in the ocean and their effects on marine life, microplastics in soils have largely been overlooked. Researchers are concerned about the lack of knowledge regarding potential consequences of microplastics in agricultural landscapes from application of sewage sludge.
Microplastics are tiny plastic particles (1?m – 5 mm) which originates from degeneration of car tires, domestic goods, industrial processes and from degeneration of surfaces composed of, or coated with, plastics, i.e. artificial grass. Most of these particles originate in urban areas. In most developed regions, urban run-off water ends up in sewage treatment plants.
Sewage sludge is in principle waste, but it can also represent a resource in agriculture and horticulture. Fertilizer based on sludge contains valuable nutrients, but sustainable use requires that the levels of undesirable substances in the sludge is kept under control. Waste water treatment plants receive large amounts of microplastics emitted from households, industry and surface run-off in urban areas. Most of these microplastics accumulate in the sewage sludge.
Today, sludge from municipal sewage treatment plants is applied to agricultural areas as a supplement to traditional fertilizers. These applications are generally well regulated as sludge might contain hazardous substances of different sorts. Microplastics are however not currently on the regulatory agenda for the use of sludge in agriculture. The potential consequences for sustainability and food security have not been adequately analyzed.
These concerns have been expressed in an article recently published in the journal Environmental Science & Technology. The researchers behind the article are Luca Nizzetto and Sindre Langaas from the Norwegian Institute for Water Research (NIVA) and Martyn Futter from the Swedish University of Agricultural Sciences (SLU) in Uppsala.
– We have found figures from the Nordic countries suggesting that a large fraction of all the microplastics generated in Western societies tend to end up in the sludge in wastewater treatment plants, says Nizzetto. Via the sludge the particles are transferred to agricultural soils.
The amount of sewage sludge used as fertilizer varies greatly from country to country. In Europe and North America approximately 50 % of this sludge is reused as fertilizer on average. According to Statistics Norway, about two thirds of the sludge is reused in this manner.
– Our estimates suggest that between 110.000 and 730.000 tons of microplastics are transferred every year to agricultural soils in Europe and North America, comprehensively. This is more than the estimated total burden of microplastics currently present in ocean water.
These figures are of concern since the effects of microplastics accumulating in agricultural soils are unknown.
– We have very little knowledge on the effect of microplastics on soil organisms, and their impact on farm productivity and food safety is unknown.
Microplastics are tiny plastic particles which originates from household articles, industrial processes and degeneration of plastic products. (Photo: Oregon State University)
The first simulation of microplastic fate on land and rivers
In an earlier study from the same authors, and researchers of Oxford University, the first mathematical model describing the dynamics of microplastics’ fate in terrestrial environments and rivers was presented. Due to a lack of empirical data on microplastics emissions and concentrations in soils and the stream system, this study was conceived to provide a purely theoretical, nevertheless rigorous, assessment of microplastics circulation.
The model is called INCA Microplastics, and simulations have showed a strong influence of meteorological conditions and river characteristics and flows in controlling the export of microplastics from agricultural soils and their transport to the ocean. Application of sewage sludge to soils likely represent a considerable source of microplastics to the coastal and ocean environments. Similar predictions for the transport of microplastics in rivers were independently confirmed by a follow-up study by Besseling et al.
INCA Microplastics is an important tool for risk assessment and evaluating sludge management scenarios. It is the first model able to simulate microplastic applications to land, and the consequent fate of these materials in soils and surface waters.
Surprising knowledge gap
The consequences of transfers of microplastics from urban waste water to agricultural soil barely have been considered by researchers and authorities, particularly in lieu of the extended attention directed at microplastics in the ocean.
– Clearly further research is needed to get an overview of the problem – and to find solutions – so that the growing need in the community for recycling and so-called circular economy can be safeguarded, Luca Nizzetto says.
Discovery delivers high starch content, virtually no methane emissions
Rice serves as the staple food for more than half of the world’s population, but it’s also the one of the largest manmade sources of atmospheric methane, a potent greenhouse gas. Now, with the addition of a single gene, rice can be cultivated to emit virtually no methane from its paddies during growth. It also packs much more of the plant’s desired properties, such as starch for a richer food source and biomass for energy production, according to a study in Nature.
With their warm, waterlogged soils, rice paddies contribute up to 17 percent of global methane emissions, the equivalent of about 100 million tons each year. While this represents a much smaller percentage of overall greenhouse gases than carbon dioxide, methane is about 20 times more effective at trapping heat. SUSIBA2 rice, as the new strain is dubbed, is the first high-starch, low-methane rice that could offer a significant and sustainable solution.
Researchers created SUSIBA2 rice by introducing a single gene from barley into common rice, resulting in a plant that can better feed its grains, stems and leaves while starving off methane-producing microbes in the soil.
The results, which appear in the July 30 print edition of Nature and online, represent a culmination of more than a decade of work by researchers in three countries, including Christer Jansson, director of plant sciences at the Department of Energy’s Pacific Northwest National Laboratory and EMSL, DOE’s Environmental Molecular Sciences Laboratory. Jansson and colleagues hypothesized the concept while at the Swedish University of Agricultural Sciences and carried out ongoing studies at the university and with colleagues at China’s Fujian Academy of Agricultural Sciences and Hunan Agricultural University.
“The need to increase starch content and lower methane emissions from rice production is widely recognized, but the ability to do both simultaneously has eluded researchers,” Jansson said. “As the world’s population grows, so will rice production. And as the Earth warms, so will rice paddies, resulting in even more methane emissions. It’s an issue that must be addressed.”