Antifreeze proteins from a polar diatom to protect frozen bread rolls from freezer burn

Bremerhaven, 20 March 2012, The polar diatom Fragilariopsis cylindrus thrives where many other forms of life would succumb – namely in the sea ice of the Arctic and Antarctic. Its survival is guaranteed by an antifreeze protein, which the alga releases into its environment. Biologists from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have now succeeded in decoding the genetic plan of this natural antifreeze agent and in bioengineering the protein. In a joint project with food researchers from ttz Bremerhaven, investigations will now be conducted to determine whether the algal antifreeze can also protect frozen bread rolls from the destructive force of ice crystals.

The polar diatom Fragilariopsis cylindrus has chosen one of the most extreme habitats on earth to live in: the sea ice of the polar regions. It populates the small brine channels and pockets that are formed when sea water turns to ice. The water in these tiny cavities cools down to minus 20 degrees Celsius in extreme cases and is then almost seven times as salty as normal sea water. The algae are virtually resilient to frost and brines, however. They protect themselves by producing a so-called antifreeze protein, which they release to their surroundings. “At the start of our investigations we knew that there were various naturally occurring antifreeze proteins, which also have quite different functions. In fish, for example, they reduce the freezing point of blood. In plants they ensure that, if ice does form, the individual, small crystals do not expand, avoiding mechanical damage of the tissue“, says Dr. Maddalena Bayer-Giraldi, biologist at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.

The scientist is investigating how organisms live in the ice, and during her research has recently discovered that the antifreeze protein of Fragilariopsis cylindrus did not belong in any of the known protein groups. “It has emerged that the antifreeze protein of this polar diatom belongs to a new group of antifreeze proteins. Whilst it also slightly reduces the freezing point of water, far more striking are its properties inhibiting the expansion of ice crystals and altering the microstructure, the texture of the ice. We assume that the ice properties are changed, preventing the brine from being washed out of the ice cover. It stays in the channels and pockets, which thus hardly freeze up completely. They become smaller but still serve as habitat for the algae“, explains Maddalena Bayer-Giraldi.

Her research results have attracted the interest of scientists and experts in the food industry, because they constitute novel approaches for the development of new antifreeze agents. “Antifreeze proteins are of relevance to all those applications in which ice can cause damage, such as in the manufacture of paints or surfaces which should remain ice-free“, explains the biologist.

The Technologietransferzentrum (ttz) Bremerhaven is interested in Maddalena Bayer-Giraldi's research. Its Institute for Food Technology and Biotechnology is looking for new antifreeze methods to deep freeze bakery products. So far unbaked bread rolls and loaves have demonstrated distinct losses in quality due to freezing. Ice crystals produced when water freezes in the dough destroy both the structure and cohesive properties of the dough and of the yeast cells. This is why bakery products lose up to 20 per cent of their volume during defrosting. The surface of the product also dries out. Together the biologists and food researchers are looking to find a way to introduce the antifreeze protein from the polar diatom, such that crystallisation during deep freezing can be controlled.

Maddalena Bayer-Giraldi concentrates on two core issues here. “I am interested in how the protein interacts with the ice and how it influences its structure. For example, we do not yet know the concentration of the antifreeze protein required for these processes or which freezing conditions are optimal. These questions are decisive, however, for the industrial use of the protein and for understanding the ecology within the sea ice“, says the biologists. The baking and freeze tests by the food experts will then be developed from her findings.

This project is supported by the Allianz Industrie Forschung (AiF) and the Forschungskreis der Ernährungsindustrie e.V.. It is therefore an example of the transfer potential of fundamental research results obtained at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association for industrial applications.

Information for editors:

The title of the original publication is:

M. Bayer-Giraldi, I. Weikusat, H. Besir, G. Dieckmann (2011): Characterization of an antifreeze protein from the polar diatom Fragilariopsis cylindrus and its relevance in sea ice, Cryobiology 63 (201) 210-219, doi:10.1016/j.cryobiol.2011.08.006

Your contact partners in the Alfred Wegener Institute are Maddalena Bayer-Giraldi (Tel: 0471 4831-1996; E-Mail: Maddalena.Bayer(at)awi.de) and Sina Löschke in the Communication and Media Department (Tel: 0471 4831-2008; E-Mail: Sina.Loeschke(at)awi.de).

The Alfred Wegener Institute conducts research in the Arctic and Antarctic and in the high and mid-latitude oceans. The Institute coordinates German polar research and provides important infrastructure such as the research ice breaker Polarstern and research stations in the Arctic and Antarctic to the national and international scientific world. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.