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 capacity to reduce other compounds.
Also referred to as tremalose.
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.
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 plants, and sea algae. Within the fungus family, it is prevalent in some mushrooms such as shiitake (Lentinula edodes), maitake (Grifola fondosa), nameko (Pholiota nameko), and Judas's ear (Auricularia auricula-judae) which can contain 1% to 17% percent of trehalose in dry weight form (thus it is also referred to as mushroom sugar). Trehalose can also be found in such microorganisms as baker's yeast and wine yeast, and it is metabolized by a number of bacteria, including Streptococcus mutans, the common oral bacteria responsible for dental plaque.
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 (sometimes called the resurrection plant) which grows in desert and mountainous areas, may be cracked and dried out but will turn green again and revive after a rain, because of the function of trehalose. It is also said that the reason dried shiitake mushrooms spring back into shape so well in water is because they contain trehalose.
The two prevalent theories as to how trehalose works within the organism in the state of cryptobiosis are the vitrification theory, a state that prevents ice formation, or the water displacement theory, whereby water is replaced by trehalose, although it is possible that a combination of the two theories are at work.
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.
In 1994, Hayashibara, a saccharified starch maker in Okayama prefecture discovered 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.
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, plant activation, antibacterial sheets, and nutrients for larvae.