Trehalose-rich yeast extract

Abstract

To provide a method for producing a trehalose-containing composition that can be used as an additive in food and beverages, and to provide uses of the trehalose-containing composition as an additive in cosmetic, pharmaceutical, food or beverage products.SOLUTION: Provided is a method for preparing a trehalose-rich yeast extract comprising a trehalose content of at least 15% (w / w) based on dry matter, the method comprising: (a) fermenting yeast cells in a suitable medium; (b) subjecting the yeast cells to abiotic stress; (c) subjecting the yeast cells to a temperature of at least 70°C to inactivate yeast enzymes; (d) incubating the yeast cells with a least one peptidase enzyme; (e) removing non-soluble cell components after peptidase treatment; and (f) obtaining the trehalose-rich yeast extract.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for preparing a trehalose-rich yeast extract, the method comprising the step of enzymatically disrupting yeast cells by using one or more proteases. The present invention further relates to a novel trehalose-rich yeast extract obtainable by the method of the present invention. The novel trehalose-rich yeast extract comprises trehalose in an amount of at least 15% (w / w) on a dry matter basis. The present invention also relates to the use of the novel trehalose-rich yeast extract as an additive in cosmetic, pharmaceutical, food or beverage products. [Background technology]

[0002] Trehalose, a non-reducing disaccharide of glucose, is found in many organisms, including plants, insects, bacteria and yeast. Trehalose acts as a storage carbohydrate and also as a protectant against various forms of stress. Among other things, trehalose has a stabilizing effect on plasma membranes, increasing the resistance of cells to desiccation, dehydration, temperature changes and high temperatures.

[0003] Although trehalose is only about half as sweet as sucrose, it is often used as a food and beverage additive due to its advantageous properties. Trehalose is an antioxidant and acts as a natural preservative, thereby extending the shelf life of foods and beverages. Apart from that, trehalose helps keep foods moist, maintains texture and flavor, reduces bitterness, and masks off-notes. For these reasons, trehalose is widely used in the industry as an additive to enhance the quality of foods and beverages.

[0004] Various processes for producing trehalose have been described in the prior art. For example, processes for extracting trehalose from yeast have been described, which involve the accumulation of trehalose in yeast cells and subsequent extraction of the sugar with H2SO4 or ethanol. Such extraction processes have been described in Koch & Koch (1925); Stewart et al. (1950); Yoshikawa et al. (1994); Steiner & Cori (1935); Chuanbin et al. (1998); Kanji & Yumi (1992). Unfortunately, these processes are not only time-consuming, laborious and expensive, but also involve low trehalose yields. Furthermore, the environmental burden of these processes is high, since sugar extraction involves the use of solvents or acids. For these reasons, trehalose is currently commonly prepared from corn starch using a combination of the enzymes α-1,4-D-glucan phosphorylase and trehalose phosphorylase. However, although these processes are more environmentally friendly, they are still laborious and expensive, resulting in high costs.

[0005] Therefore, there is a need for new methods for producing trehalose-containing compositions that can be used as additives in foods and beverages. The trehalose-containing compositions should be producible in a technically uncomplicated and inexpensive manner without the use of potentially hazardous substances. In particular, the use of organic solvents should be avoided. Summary of the Invention

[0006] Trehalose, also known as α-D-glucopyranosyl-[1,1]-α-D-glucopyranoside, is a non-reducing disaccharide that is widely distributed in nature. Trehalose is commonly used in chewing gum because it is more stable than sucrose under acidic conditions. Although its sweetening capacity is lower compared to sucrose, trehalose is much preferred in foods due to its lower effect on blood glucose levels after ingestion. The structural formula of trehalose is shown below: [ka]

[0007] On the one hand, the invention is based on the insight that a composition comprising a trehalose-rich yeast extract having a trehalose content of at least 15% (w / w) based on dry matter is a particularly advantageous product for many applications, and on the other hand, the invention is based on the finding that such an extract can be easily prepared in a reproducible manner by the method defined herein below.

[0008] Thus, in a first aspect, the present invention provides a method for preparing a trehalose-rich yeast extract containing a trehalose content of at least 15% (w / w) based on dry matter, comprising the steps of: (a) fermenting yeast cells in a suitable medium; (b) exposing the yeast cells to an abiotic stress; (c) exposing the yeast cells to a temperature of at least 70° C. to inactivate the yeast enzymes; (d) incubating the yeast cells with at least one protease or peptidase enzyme; (e) removing insoluble cellular components after peptidase treatment; (f) obtaining a trehalose-enriched yeast extract; The present invention relates to a method comprising the steps of:

[0009] In the first step of the above method, yeast cells are fermented in a suitable medium. Culture media and methods for fermenting yeast are well known in the art and are commercially available from various manufacturers. Suitable media include, for example, the YPD medium from Sigma Aldrich (Taufkirchen, Germany). Many other culture media are commercially available from various manufacturers.

[0010] Yeast cells can be cultured under standard conditions known in the art. For example, cells can typically be cultured in flasks at a temperature of 25-35°C. Cultivation can be continued with stirring until a predetermined cell density is reached. Cell density is preferably measured by optical density at 600 nm (OD600). It is preferred to culture the cells to an OD600 of 0.8-1.0 before exposing the cells to abiotic stress.

[0011] The type of yeast that can be used in the method of the present invention is not particularly limited. Suitable yeast cells include, for example, yeasts belonging to the genus Saccharomyces, such as S. cerevisiae, S. chevalieri, S. boulardii, S. bayanus, S. italicus, S. delbrueckii, S. rosei, S. microellipsodes, S. carlsbergensis, S. c. arlsbergensis, S. bisporus, S. fermentati, S. rouxii or S. uvarum; yeasts belonging to the genus Schizosaccharomyces, for example S. japonicus, S. kambucha, S. octosporus or S. pombe; yeasts belonging to the genus Hansenula, for example S. bisporus, S. fermentati, S. rouxii or S. uvarum; Yeasts, such as H.wingei, H.arni, H.henricii, H.americana, H.canadiensis, H.capsulata or H.polymorpha; yeasts belonging to the genus Candida, such as C.albicans, C.utilis, C.boidinii, C.stearyl alcohol, C.salt ... yeasts belonging to the genus Pichia, such as P. pastoris, P. kluyveri, P. polymorpha, P. barkeri, P. cactophila, P.yeasts belonging to the genus Kluyveromyces, such as K. marxianus; and yeasts belonging to the genus Torulopsis, such as T. bovina or T. glabrata.

[0012] In a preferred embodiment, the yeast cells fermented in step (a) of the above process belong to the genus Saccharomyces. In one particularly preferred embodiment, the yeast cells belong to the species S. cerevisiae.

[0013] If the extract obtained from the above method is intended for use in food, the cells can be washed with alkaline buffer, such as sodium hydroxide buffer, after step (a) or (b) in some cases. Such washing steps are useful for reducing the taste of the yeast extract obtained from the process. If the method of the present invention includes a washing step with alkaline buffer, the method includes at least one subsequent washing step with water to ensure that residual alkaline buffer is removed. For example, if yeast cells are washed with a certain amount of alkaline buffer, they are then washed with two times the amount of water.

[0014] After reaching a sufficient cell density (usually an OD600 of 1.0), the yeast cells are exposed to an abiotic stress in step (b) of the method. Abiotic stress may include incubating the cells at high or low temperatures, adding potentially toxic compounds such as ethanol, or applying high osmolarity conditions to the medium, such as high salt or sugar concentrations. In one particularly preferred embodiment, the abiotic stress of step (b) is applied by incubating the cells at high temperatures. This can be achieved by increasing the culture temperature at the end of the fermentation period. In preferred embodiments, the culture temperature is increased by 5°C or more, 10°C or more, or 15°C or more.

[0015] In a particularly preferred embodiment, the yeast cells are cultured in step (a) of the above method at a temperature between 25°C and 35°C until a desired density is reached, and then the temperature of the yeast culture is increased by 10°C to a stress temperature of between 35°C and 45°C. In an even more preferred embodiment, the yeast cells are cultured in step (a) of the above method at a temperature of about 30°C, and then shifted to a stress temperature of 40°C. The elevated stress temperature is maintained for at least 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, 210 minutes, 240 minutes, 270 minutes, or 300 minutes. In one embodiment, the stress temperature is 40° or higher and is maintained for 240 minutes or more during the above method steps.

[0016] Then, in the next step (c), the yeast cells are exposed to a temperature of at least 70°C in order to inactivate the yeast enzymes that catalyze the degradation of the trehalose molecules accumulated in the cells. During this step, the temperature can be, for example, about 75°C, about 80°C, about 85°C, about 90°C, about 95°C, or higher. Incubation of the yeast cells at the enzyme inactivation temperature is preferably carried out for at least 10 minutes, at least 20 minutes, at least 30 minutes, at least 60 minutes or more. Incubation at a temperature of at least 70°C for at least 60 minutes is particularly preferred. In some embodiments, the enzyme inactivation temperature can be maintained for more than 60 minutes, for example, at least 90 minutes, 120 minutes, 150 minutes, 180 minutes, 210 minutes, 240 minutes, 270 minutes, or 300 minutes. Incubation at a temperature of at least 90°C for 1 to 4 hours is particularly preferred. Incubation at a temperature of at least 90°C for 2 to 3 hours is even more preferred.

[0017] After inactivation of the enzyme, the yeast cells are lysed in step (d) of the above method. For this purpose, the yeast cells obtained from step (c) of the above method are incubated with at least one peptidase enzyme effective to break down the cell wall of the yeast cells. As used herein, the term "peptidase" refers to a proteolytically active enzyme that catalyzes the degradation of proteins or peptides. The term is meant to include both peptidases and proteases.

[0018] Peptidases suitable for use in the method of the present invention include both endopeptidases and exopeptidases. As used herein, "endopeptidase" refers to any enzyme that can break down the internal peptide bond of a protein or peptide. In contrast, "exopeptidase" is an enzyme that can break down the peptide bond located at one of the termini of a protein or peptide.

[0019] In a preferred embodiment, the lysis in step (d) of the method comprises the use of at least one endopeptidase. In another preferred embodiment, the lysis in step (d) of the method comprises the use of at least one exopeptidase. In another preferred embodiment, the lysis in step (d) of the method comprises the use of at least one endopeptidase and at least one exopeptidase. For example, the lysis comprises the use of a mixture of endopeptidase and exopeptidase. For example, the lysis of yeast cells in step (d) of the method can be achieved by the addition of an enzyme mixture containing both endopeptidase and exopeptidase.

[0020] The peptidase enzymes used in the process of the present invention can be derived from different sources. For example, peptidases can be derived from fungal, plant, or animal sources. Examples of commercially available peptidases include Flavourzyme® (Novozymes A / S), ProteAX (Amano Enzyme Inc.), ProHydrolase (Deerland Enzymes Inc.), Sumizyme LPL-G (Shin Nihon Chemical CO.,LTD.), FlavorPro 795 MDP (Biocatalysts Ltd.), FoodPro Alkaline Protease (Danisco A / S), etc. Other enzymes provided by various manufacturers can also be used.

[0021] Preferably, the peptidase incubation is carried out at a dry matter content of about 4-20%, preferably about 6-18%, more preferably about 8-16%. The dry matter content of a composition such as a yeast cell culture can be determined according to standard procedures using commercially available equipment, for example a moisture analyzer (Mettler-Toledo GmbH, Giessen, Germany). Once the dry matter content of the starting yeast cell culture has been determined, it can be adjusted to a given value by diluting or concentrating the culture.

[0022] Depending on the peptidase selected for the degradation of yeast cell proteins, it may be necessary to adjust the appropriate pH of the mixture to provide optimal conditions for the enzymatic degradation of the proteins. Depending on the peptidase, step (d) can be carried out under conditions ranging from pH 3 to 10, preferably from pH 4 to 9.

[0023] The peptidase or mixture of peptidases can be added to the yeast cell suspension at a concentration of 0.1-5.0% (w / w) peptidase per total dry matter of the composition. Preferably, the concentration is 0.2-4.0% (w / w) peptidase per total dry matter of the composition, more preferably 0.3-3.0%, for example 2.0%. The yeast cells are incubated with the peptidase or mixture of peptidases under conditions that allow degradation of cell wall proteins. These conditions preferably include a temperature of about 30-65°C, more preferably about 40-60°C, for example 50-55°C.

[0024] The reaction time depends on several factors, such as the cell density at the time of enzyme addition, the amount of enzyme added, and the incubation temperature. The incubation time can be from 30 minutes to 24 hours, but will usually be in the range of 1 to 12 hours, such as 2 to 8 hours, or most preferably 4 to 6 hours. Optimal conditions can be identified by one of skill in the art by routine experimentation.

[0025] After disruption of the yeast cells by peptidase treatment, the soluble fraction is separated from the insoluble fraction in step (e) of the above method. The insoluble fraction contains primarily cell wall components, organelles, and unlysed cells. Separation of the soluble fraction from the insoluble fraction can be performed by a variety of methods, including centrifugation, filtration, and other methods.

[0026] In a simple embodiment, the cell lysate containing the disrupted yeast cells, whether diluted or not, is centrifuged, for example at 2000-25000 g, to precipitate the insoluble material. The supernatant containing the soluble cell components, including the accumulated trehalose, is obtained and cooled, preferably below 20° C., until further use. Alternatively, the removal of the insoluble material can be performed by standard filtration using a filter material that retains said insoluble compounds. For example, dead-end filtration using a filter with a pore size of 3 μm or less can be performed. Cross-flow or tangential flow filtration is also possible to avoid clogging or fouling of the filter. In all cases, the filter pore size must be less than 3 μm to hold back the yeast cells and cell debris.

[0027] In step (f) of the above method, the yeast extract rich in trehalose is obtained and can be further processed, if necessary. For example, the yeast extract can be sterilized or dried. In one preferred embodiment, the aqueous extract is sterilized. Sterilization can be carried out by heat treatment, UV irradiation, or other common techniques. For example, sterilization can be achieved by filtering the aqueous phase through a filter with a pore size of 0.22 μm or less.

[0028] In certain preferred embodiments, the process of the present invention, i.e. the process defined above by steps (a)-(f), does not involve organic solvents such as ethanol or propanol, or acids such as sulfuric acid. In particular, the process of the present invention does not involve a trehalose extraction step utilising any organic solvent or acid.

[0029] In another preferred embodiment, the aqueous extract is dried. The drying of the extract can be carried out, for example, by freeze-drying or spray-drying. The principle of spray-drying is based on dispersing a solution into fine droplets, which are introduced into a stream of hot air. As the solvent evaporates from the substrate droplets, dry product clusters remain as a result. Standard spray-drying equipment can be used, such as the Mini Spray Dryer B-290 from Buechi Labortechnik GmbH (Essen, Germany) or the Mobile Minor™ spray dryer from GEA (Berlin, Germany).

[0030] Freeze drying or lyophilization is a process that removes moisture from a product to extend its shelf life. Freeze drying involves freezing the product and then reducing pressure to sublimate the frozen water within the material. Various methods can be applied to freezing the product. For example, freezing can be achieved by using a standard freezer or cooling bath. Cooling the product below the triple point ensures that sublimation occurs upon heating. Freezing is done rapidly to prevent the formation of large crystals that can damage the structure of the product being dried. As the frozen water sublimes, approximately 95% of the water in the product is removed. Most materials can be dried to a residual moisture of 1-5%. Standard freeze-drying equipment can be used, such as the Lyovac™ equipment from GEA (Berlin, Germany), the Gamma 2-20 Freeze Dryer LCM-1 from Christ (Osterode am Harz, Germany), or the Christ Martin™ Alpha 1-2 Lyophilisator from Fisher Scientific GmbH (Schwerte, Germany).

[0031] In another aspect, the present invention provides a trehalose-rich yeast extract obtainable by the above-mentioned process, i.e. comprising steps (a) to (f). The extract comprises a trehalose content of at least 15% (w / w), based on dry matter. Preferably, the trehalose content is at least 30%, at least 35%, at least 40% or at least 45% (w / w), based on dry matter. The extract is free of exogenously added sugars, in particular exogenously added trehalose. This means that the total amount of trehalose in the extract is derived from the yeast cells. The trehalose content is preferably measured by the "Trehalose Assay Kit" from Megazyme, Wicklow, Ireland.

[0032] In yet another embodiment, the present invention provides a trehalose-rich yeast extract comprising a trehalose content of at least 15%, at least 20%, at least 25% (w / w) based on dry matter. Preferably, the trehalose content is at least 30%, at least 35%, at least 40%, or at least 45% (w / w) based on dry matter. For example, the trehalose content can be at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, or at least 30% (w / w) based on dry matter. The protein content of the extract is at least 20%, at least 25%, at least 30%, or at least 40% (w / w) based on dry matter. The extract does not contain exogenously added sugars, in particular exogenously added trehalose. This means that all of the trehalose in the extract comes from the yeast cells.

[0033] The trehalose-rich yeast extract of the present invention preferably comprises an RNA content of 1-30% (w / w), for example 2-25% (w / w), 3-20% (w / w), 4-15% (w / w), 5-10% (w / w), or 6-8% (w / w), based on dry matter. The yeast extract of the present invention preferably further comprises NaCl in an amount of 0.1-5% (w / w), for example 0.2-4% (w / w), 0.5-2.5% (w / w), or 1-2% (w / w), based on dry matter. The fat content of the trehalose-rich yeast extract of the present invention is preferably 1-10% (w / w), for example 2-7% (w / w), or 3-5% (w / w), based on dry matter. The ash content of the yeast extract of the present invention is preferably 1 to 20% (w / w) based on dry matter, for example 3 to 15% (w / w), 5 to 10% (w / w), or 6 to 8% (w / w).

[0034] The trehalose-rich yeast extract is further characterized by a high protein content. The protein content of the extract is at least 20%, at least 25%, at least 30%, or at least 40% (w / w) based on dry matter. The protein content is preferably determined by the standard Kjeldahl method, for example by using a Kjeltec™ 8400 instrument (FOSS GmbH, Hamburg, Germany).

[0035] In a particular preferred embodiment, the trehalose-enriched yeast extract of the present invention comprises: (a) a trehalose content of at least 20%, more preferably at least 25% (w / w) on a dry matter basis; (b) a protein content of at least 20%, more preferably at least 25% (w / w), on a dry matter basis; (c) a fat content of 1-10% (w / w) on a dry matter basis; (d) RNA content of 1–30% (w / w) based on dry matter; Includes.

[0036] In yet another aspect, the present invention provides pharmaceutical compositions, cosmetic compositions, food or beverage products comprising the trehalose-rich yeast extract described herein, preferably such compositions and products do not contain trehalose from a source other than the trehalose-rich yeast extract.

[0037] Cosmetic compositions supplemented with the trehalose-rich yeast extract described herein may include syrups, such as cough syrups, and tablets.

[0038] Cosmetic compositions supplemented with the trehalose-rich yeast extract described herein may include skin care gels, lotions, or creams, in which trehalose may aid in the skin penetration of the composition.

[0039] The food or beverage products that can be added with trehalose-rich yeast extract are not particularly limited.In principle, all different types of food or beverage products can be optimized by adding trehalose-rich yeast extract as described elsewhere herein.Suitable foods that can be added with trehalose-rich yeast extract include, but are not limited to, dairy products (e.g., yogurt), baked goods (e.g., bread, biscuits), puddings, fruit preparations, tomato ketchup, sauces, condiments, ice cream, breakfast cereals, chocolates, candies, fruit or wine gums, confectionery, cakes, jams and jellies, chocolate or hazelnut spreads, etc.

[0040] Beverages to which the trehalose-rich yeast extract may be added include, but are not limited to, flavored waters, fruit punches, dairy beverages, such as yogurt drinks, buttermilk, kefir, fruit juices, lemonades, energy drinks and sports drinks, teas, such as iced tea, sweet tea, instant tea and ready-to-drink tea, coffees, such as iced coffee, flavored coffee, instant coffee and ready-to-drink coffee, soy beverages, dairy beverages, such as flavored dairy beverages (e.g., vanilla, chocolate, or strawberry flavors), sweetened powdered beverages, caffeinated or caffeine-free soft drinks, etc. In a particularly preferred embodiment, the product to which the trehalose-rich yeast extract is added is a dairy beverage, preferably a soy milk beverage.

[0041] The food or beverage product may contain additional ingredients that are frequently used in the field of food and nutrition technology. For example, the food or beverage product may contain other sweeteners such as glucose, maltose, sucrose, lactose, aspartame, saccharin, sucralose, or sugar alcohols. The composition may also contain vitamins or flavors, such as orange, vanilla, lemon, or strawberry flavors. Other common additives include colorants, emulsifiers, stabilizers, texturizers, preservatives, antioxidants, thickeners, etc.

[0042] In a final aspect, the present invention relates to the use of the yeast extract described herein as an additive in a cosmetic, pharmaceutical, food or beverage product. [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 shows a schematic overview of a preferred embodiment for preparing a trehalose-enriched yeast extract powder according to the present invention and prepared in accordance with Example 1 herein below. EXAMPLES

[0044] The following examples are provided to illustrate the present invention. However, it should be understood that the scope of the present invention is not limited by the examples. Those skilled in the art will understand that some modifications can be made without departing from the scope of the present invention.

[0045] Example 1 : Preparation of trehalose-rich yeast extract S. cerevisiae strain ATCC204508 was grown overnight at 30°C in YPD medium (1% yeast extract, 2% peptone, 2% glucose). The following morning, fresh YPD medium was added to the yeast cells to obtain an OD600 of 0.1. The cells were cultured at 30°C until the OD600 reached 1.0. The exponentially growing yeast cell culture was then subjected to a heat shock by increasing the growth temperature from 30°C to 40°C for 4 hours. The yeast cells were harvested using a standard separator and washed twice with water.

[0046] In this way, a yeast cell substrate with about 18% dry matter and a trehalose concentration of about 9% (w / w) based on the dry matter was obtained. The yeast substrate was heated to 90°C for 1 h to inactivate the intrinsic yeast enzymes. Afterwards, a peptidase (Corolase 7089, AB Enzymes GmbH, Darmstadt, Germany) was added at a concentration of 0.5% (w / w) based on the dry matter yeast substrate. The dry matter content was determined using a moisture analyzer (Mettler-Toledo GmbH, Giessen, Germany).

[0047] The hydrolysis reaction was incubated at 55° C. for 3 hours with vigorous stirring. The pH was maintained at pH 7 using 10% sodium hydroxide solution. The hydrolyzed mixture was then separated using a standard laboratory centrifuge (10 min, 4700 g, room temperature, Heraeus Multifuge X3R, ThermoFisher Scientific). The solid pellet was removed to obtain the aqueous trehalose-rich yeast extract.

[0048] The aqueous phase was then sterilized by heating to 90°C for 30 min and spray dried using a Mini Spray Dryer B-290 from Büchi Labortechnik GmbH (Essen, Germany) at a constant input temperature of 133-136°C and an output temperature of 93±2°C to obtain a dried, powdered product. The trehalose content of the final powdered product was analyzed, resulting in a trehalose concentration of 25.3% (w / w) in the dry matter.

Claims

1. 1. A method for preparing a trehalose-rich yeast extract containing a trehalose content of at least 15% (w / w) on a dry matter basis, comprising the steps of: (a) fermenting yeast cells in a suitable medium and culturing the cells to an OD600 of 0.8-1.0; (b) exposing the yeast cells to a temperature of between 35°C and 45°C; (c) subjecting the yeast cells to a temperature of at least 70° C. to inactivate yeast enzymes; (d) incubating the yeast cells with at least one peptidase enzyme; (e) removing insoluble cellular components after peptidase treatment; (f) obtaining the trehalose-enriched yeast extract; Including, the peptidase treatment of step (d) comprises incubation with at least one endopeptidase and / or at least one exopeptidase; The method, wherein the cells are optionally washed with an alkaline buffer after step (a) or (b).

2. The method of claim 1 , wherein the yeast cell belongs to the genus Saccharomyces.

3. 3. The method of claim 1 or 2, wherein step (b) comprises culturing the yeast cells at a temperature of at least 40°C.

4. The method according to any one of claims 1 to 3, wherein the peptidase treatment in step (d) is carried out at a pH of 4 to 9.

5. 5. The method of claim 1, wherein removing insoluble cellular components after protease or peptidase treatment in step (e) comprises centrifugation.

6. The method of claim 1, wherein the alkaline buffer is a sodium hydroxide buffer.

7. 7. The method according to any one of claims 1 to 6, further comprising drying the trehalose-rich yeast extract obtained in step (f).

8. The method of claim 7, further comprising adding the trehalose-rich yeast extract to a pharmaceutical, cosmetic, food or beverage product.