Trehalose

Trehalose, also known as mycose, is a natural alpha-linked disaccharide formed by an α, α-1, 1-glucoside bond between two α-glucose units. In 1832 Wiggers discovered trehalose in rye and in 1859 Berthelot isolated it from trehala manna (manna) made by weevils, and named it trehalose. It can be synthesised by fungi, plants, and invertebrate animals. It is implicated in anhydrobiosis — the ability of plants and animals to withstand prolonged periods of desiccation. It has high water retention capabilities and is used in food and cosmetics. The sugar is thought to form a gel phase as cells dehydrate, which prevents disruption of internal cell organelles by effectively splinting them in position. Rehydration then allows normal cellular activity to be resumed without the major, lethal damage that would normally follow a dehydration/reyhdration cycle. Trehalose has the added advantage of being an antioxidant. Extracting trehalose used to be a difficult and costly process, but, recently, the Hayashibara company (Okayama, Japan) confirmed an inexpensive extraction technology from starch for mass production. Trehalose is now being used for a broad spectrum of applications, as mentioned above.

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Structure

Trehalose is a disaccharide formed by a 1, 1-glucoside bond between two α-glucose units. Because trehalose is formed by the bonding of two reducing groups, it has no reducibility.

Chemical properties

Trehalose was first isolated from ergot of rye. Emil Fischer first described the trehalose-hydrolyzing enzyme in yeast. Trehalose is a non-reducing sugar formed from two glucose units joined by a 1-1 alpha bond giving it the name of α-D-glucopyranosyl-(1→1)-α-D-glucopyranoside. The bonding makes trehalose very resistant to acid hydrolysis, and therefore stable in solution at high temperatures even under acidic conditions. The bonding also keeps non-reducing sugars in closed-ring form, such that the aldehyde or ketone end-groups do not bind to the lysine or arginine residues of proteins (a process called glycation). Trehalose is broken down by the enzyme trehalase into glucose. Trehalose has about 45% the sweetness of sucrose. Trehalose is less soluble than sucrose, except at high temperatures (>80 °C). Trehalose forms a rhomboid crystal as the dihydrate, and has 90% of the calorific content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the dihydrate. Anhydrous forms of trehalose can show interesting physical properties when heat-treated.

Biological properties

Trehalose can be found in nature, animals, plants, and microorganisms. In animals, trehalose is prevalent in shrimp, and also in insects, including grasshoppers, locusts, butterflies, and bees, in which blood-sugar is trehalose. The trehalose is then broken down into glucose by the catabolic enzyme trehalase for use. Trehalose is also present in the nutrition exchange liquid of hornets and their larvae.

In plants, the presence of trehalose is seen in sunflower seeds, selaginella mosses, and sea algae. Within the fungus family, it is prevalent in some mushrooms such as shitake, maitake (grifola fondosa), nameko (pholiota nameko), and Judas's ear (A. auricularia-judae) contain 1% to 17% percent of trehalose in dry weight form, and is also referred to as mushroom sugar. Trehalose can also be found in such microorganisms as baker's yeast and wine yeast.

When tardigrades (water bears) dry out, the glucose in their bodies changes to trehalose when they enter a state called cryptobiosis - a state wherein they appear dead. However, when they receive water, they revive and return to their metabolic state. It is also thought that the reason the larva of sleeping chironomid (polypedihum vanderplanki) and artemia (sea monkeys, brine shrimp) are able to withstand dehydration is because they store trehalose within their cells.

Even within the plant kingdom, selaginella mosses that grow in desert and mountainous areas, although they may be cracked and dried out, will turn green again and revive after a rain, because of the function of trehalose; it is called the resurrection plant. It is also said that the reason dried shitake mushrooms spring back into shape so well in water is because they contain trehalose.

The theories as to how trehalose works within the organism in the state of cryptobiosis are that of either the vitrification theory, a state that maintains limited molecular activity, or the water displacement theory, whereby water is replaced by trehalose^[2], or a combination of the two theories are at work.　 Trehalose is metabolized by a number of bacteria, including Streptococcus mutans, the common oral bacteria responsible for dental plaque.

The enzyme trehalase, a glycoside hydrolase, present but not abundant in most people, breaks trehalose into two glucose molecules, which can then be readily absorbed in the gut.

Trehalose is the major carbohydrate energy storage molecule used by insects for flight. One possible reason for this is that the double glycosidic linkage of trehalose, when acted upon by an insect trehalase, releases two molecules of glucose, which is required for the rapid energy requirements of flight. This is double the efficiency of glucose release from the storage polymer starch, for which cleavage of one glycosidic linkage releases only one glucose molecule.

Natural sources

• Trehala manna
• Locust
• Resurrection plant
• Fungi

Production

Trehalose is being manufactured through an extraction process from cultured yeast, but, since it costs several tens of thousands of yen for 1 kg, it is being used only in a portion of cosmetics and chemicals.

In 1994, Hayashibara, a saccharified starch maker in Okayama prefecture, succeeded in what was thought to be impossible, discovering a method of inexpensively mass-producing trehalose from starch. The following year, Hayashibara started marketing trehalose by activating two enzymes, the glucosyltrehalose-producing enzyme that changes the reducing terminal of starch into a trehalose structure, and the trehalose free enzyme that detaches this trehalose structure. As a result, a high-purity trehalose from starch can be mass-produced for a very low price.

Use

Trehalose has been accepted as a novel food ingredient under the GRAS terms in the U.S. and the EU. Trehalose has also found commercial application as a food ingredient. The uses for trehalose span a broad spectrum that cannot be found in other sugars, the primary one being its use in the processing of foods. Trehalose is used in a variety of processed foods such as dinners, western and Japanese confectionery, bread, vegetables side dishes, animal-derived deli foods, pouch-packed foods, frozen foods, and beverages, as well as foods for lunches, eating out, or prepared at home.　This use in such a wide range of products is due to the multi-faceted effects of trehalose's properties, such as its inherently mild sweet flavor, its preservative properties, which maintain the quality of the three main nutrients (carbohydrates, proteins, fats), its powerful water-retention properties that preserve the texture of foods by protecting them from drying out or freezing, its properties to suppress smells and tastes such as bitterness, stringency, harsh flavors, and the stench of raw foods, meats, and packaged foods, which when combined can potentially bring about promising results. However, less-soluble and less-sweet than sucrose, trehalose is seldom used as a direct replacement for conventional sweeteners, such as sucrose, regarded as the "gold standard." Technology for the production of trehalose was developed in Japan, where enzyme-based processes converts wheat and corn syrups to trehalose. It is also used as a protein-stabilizing agent in research ^[3]. It is particularly effective when combined with phosphate ions^[4]. Trehalose has also been used in at least one biopharmaceutical formulation, the monoclonal antibody trastuzumab, marketed as Herceptin.

Cosmetics： Capitalizing on trehalose's moisture-retaining capacity, it is used as a moisturizer in many basic toiletries such as bath oils and hair growth tonics.

Pharmaceuticals： Using trehalose's properties to preserve tissue and protein to full advantage, it is used in organ protection solutions for organ transplants.

Other： Other fields of use for trehalose span a broad spectrum including fabrics that have deodorization qualities and are compatible to Japan's official 'Cool Biz' attire, plant activation, antibacterial sheets, and nutrients for larvae.

Related research

After trehalose became readily available in mass quantities at a low price, all kinds of research involving trehalose accelerated rapidly. Research is being conducted, especially in the field of medicine, to achieve uses for trehalose in post-surgery adhesion suppressants, dry-eye treatments and the manufacturing of dry blood.

See also

Hayashibara (major manufacturer of trehalose)

• Biostasis
• Cryptobiosis
• Freeze drying
• Cryoprotectant

References