A biotransformation method for improving diosgenin in yam and its application

Abstract

The present invention discloses a bioconversion method for increasing diosgenin in Chinese yam and its application, relating to the field of microbial fermentation technology. The bioconversion method comprises the following steps: S1, adding water to crushed Chinese yam, adding glucose, and mixing in a boiling water bath for extraction; S2, inoculating Lactobacillus plantarum P9 at a 1-5% inoculum after sterilization for shaker fermentation culture, the fermentation culture conditions being 100-200 rpm, 35-38°C, and fermenting for 24-48 hours. After the fermentation is completed, sterilization is performed to obtain a probiotic fermented Chinese yam product; the deposit number of the Lactobacillus plantarum P9 is CGMCC No. 16401. The bioconversion method of the present invention can increase the diosgenin content, total flavonoid content, and total polysaccharide content in the probiotic Chinese yam product, and has high antioxidant activity.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial fermentation, and in particular to a bioconversion method for improving diosgenin in yam and an application thereof. Background Art

[0002] Chinese yam (Dioscorea opposita), a traditional crop with both medicinal and edible properties, is rich in active ingredients such as polysaccharides, saponins, mucins, and trace elements. In addition to its nutritional value, it also possesses medicinal benefits such as antioxidant, anti-inflammatory, anti-aging, liver protection, and gastrointestinal regulation. However, yam's high starch content and sticky texture make it susceptible to browning during processing. Currently, yam is primarily consumed through high-temperature processing, such as frying and stewing, which can easily degrade its active ingredients and reduce its health benefits. The lack of suitable processing technology has severely hampered the development of high-value-added yam products.

[0003] Microbial fermentation technology is widely used in the field of deep processing of medicine and food due to its green and efficient characteristics. It can degrade yam macromolecules through the metabolism of strains, increase the content of soluble components and generate new functional factors (such as short-chain fatty acids, extracellular polysaccharides, etc.), thereby enhancing the nutritional value and functional properties of the product.

[0004] Chinese patent CN107896921A discloses a Tremella fuciformis biotransformation composition of maca and Chinese yam and its production method. The production method comprises the following steps: (a) adding maca powder, Chinese yam powder, and soybean powder to cold water and stirring, then heating and sterilizing to obtain a seed culture medium solution; (b) cooling the seed culture medium solution obtained in step (a), inoculating Tremella fuciformis, and stirring and culturing for several days to obtain Tremella fuciformis seed culture liquid; (c) stirring maca powder, Chinese yam powder, and soybean powder to obtain a solid material; mixing the solid material with water and sterilizing it at high temperature to obtain a Tremella fuciformis liquid fermentation medium; (d) inoculating and fermenting: cooling the Tremella fuciformis liquid fermentation medium obtained in step (c), inoculating the Tremella fuciformis seed culture liquid obtained in step (b), mixing the two, and then loading them into a fermentation tank or fermentation tank for fermentation to obtain a Tremella fuciformis fermentation composition of maca and Chinese yam. The composition obtained by the production method of the invention has the functions of improving pulmonary fibrosis function and anti-fatigue. However, this preparation method cannot increase the diosgenin content.

[0005] Diosgenin, commonly known as saponin, is found in yam primarily as diosgenin, bound to glycosides. It is the primary saponin component of yam. Diosgenin exhibits desensitizing, anti-inflammatory, lipid-lowering, antioxidant, anti-tumor, hepatoprotective, and antiviral properties, and is attracting increasing attention in the development of yam-based products.

[0006] Chinese patent CN105996022A discloses a method for producing functional foods by simultaneously transforming Chinese yam with cordyceps. The method uses Chinese yam and rice, wheat, corn, sorghum, etc. as a solid matrix, and uses cordyceps as the starting strain. The preparation process is sequentially carried out through test tube expansion culture, liquid shake flask culture, seed tank expansion culture, solid fermentation culture, drying, crushing, and packaging. The functional food contains 2-20 mg / g dry matrix of saponins, 10-100 mg / g dry matrix of cordyceps polysaccharides, and 1-20 mg / g dry matrix of cordycepin, and has the effects of regulating blood lipids, blood sugar, and blood pressure, providing radiation protection, and inhibiting tumors. The active ingredients of saponins, cordyceps polysaccharides, and cordycepin in the functional food can be extracted and used to produce tablets or capsules or other drugs or functional foods for lowering blood lipids, blood sugar, and blood pressure, providing radiation protection, and inhibiting tumors.

[0007] At present, there is still a lack of research on the systematic screening and adaptability evaluation of probiotics specifically for yam fermentation, and no method has been retrieved to use Lactobacillus plantarum to improve the biotransformation of diosgenin in yam. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for improving the biotransformation of diosgenin in yam and its application.

[0009] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0010] In one aspect, the present invention provides a method for improving the bioconversion of diosgenin in yam, comprising the following steps:

[0011] S1. After crushing the Chinese yam, add water and glucose, mix well and extract in a boiling water bath;

[0012] S2, after sterilization, inoculate Lactobacillus plantarum P9 at an inoculum size of 1-5% for shaker fermentation culture, the fermentation culture conditions are 100-200 rpm, 35-38 ° C, fermentation for 24-48 hours, and sterilize after the fermentation to obtain a probiotic fermented yam product;

[0013] The deposit number of the Lactobacillus plantarum P9 is CGMCC No. 16401.

[0014] Specifically, the biotransformation method further includes a Lactobacillus plantarum P9 pretreatment step, specifically: after activating Lactobacillus plantarum P9 with MRS culture medium, centrifuging at 4000-6000 rpm for 3-6 minutes, and resuspending with physiological saline to adjust the viable cell count of Lactobacillus plantarum P9 to (8-10)×10 8 CFU / mL.

[0015] Furthermore, the pretreatment step of Lactobacillus plantarum P9 is as follows: after activating Lactobacillus plantarum P9 for 2 generations with MRS medium, centrifuging at 5000 rpm for 3 minutes, and resuspending with physiological saline to adjust the viable count of Lactobacillus plantarum P9 to (8-10)×10 8 CFU / mL.

[0016] Specifically, in step S1, the yam is crushed and then passed through a 60-mesh sieve.

[0017] Specifically, in step S1, the material-liquid ratio of Chinese yam to water is (5-8) g / 100 mL;

[0018] Furthermore, in step S1, the material-liquid ratio of Chinese yam to water is 6 g / 100 mL.

[0019] Specifically, the amount of glucose added in step S1 is 1-5%;

[0020] Furthermore, the amount of glucose added in step S1 is 1-3%;

[0021] Furthermore, the amount of glucose added in step S1 is 1.5%.

[0022] Specifically, the extraction time in step S1 is 0.5-2h;

[0023] Furthermore, the time extracted in step S1 is 1 hour.

[0024] Specifically, the viable count of Lactobacillus plantarum P9 in step S2 is (8-10)×10 8 CFU / mL.

[0025] Specifically, the sterilization condition of step S2 is 105°C-110°C, and the sterilization time is 10-20 minutes;

[0026] Furthermore, the sterilization condition of step S2 is 105° C., and the sterilization time is 15 minutes.

[0027] Specifically, the inoculation amount described in step S2 is 1-5 (v / v)%.

[0028] According to some embodiments of the present invention, the inoculation amount may be 1 (v / v)%, 2 (v / v)%, 3 (v / v)%, 4 (v / v)%, or 5 (v / v)%.

[0029] Furthermore, the inoculation amount in step S2 is 2 (v / v)%, 3 (v / v)% or 4 (v / v)%.

[0030] Furthermore, the inoculation amount described in step S2 is 3 (v / v)%.

[0031] Furthermore, the fermentation culture conditions in step S2 are 150 rpm, 37° C., and fermentation for 48 hours.

[0032] Specifically, the sterilization condition after fermentation in step S2 is 90-100°C for 5-10 minutes;

[0033] Furthermore, the sterilization condition after fermentation in step S2 is 95° C. for 5 minutes.

[0034] In another aspect, the present invention provides a probiotic fermented yam product prepared by the above-mentioned biotransformation method.

[0035] Specifically, the probiotic fermented yam product has high diosgenin content, total flavonoid content, and total polysaccharide content.

[0036] Specifically, the probiotic fermented yam product can improve antioxidant activity.

[0037] In another aspect, the present invention provides use of the above-mentioned probiotic fermented yam product in the preparation of antioxidant products.

[0038] Specifically, the products include food and medicine.

[0039] Furthermore, the food also includes auxiliary materials acceptable to food.

[0040] Furthermore, the food-acceptable excipients are selected from one or more of α-cyclodextrin, γ-cyclodextrin and dextrin, vitamin C, vitamin E, erythritol, D-mannitol, fumaric acid, glycerol, pectin, potassium alginate, sodium alginate, talc, sodium pyrophosphate, polydextrose, carrageenan, sodium ascorbate, ascorbyl palmitate, L-malic acid, maltitol, gelatin, xylitol, citric acid, potassium citrate, sodium citrate, citric acid fatty acid glyceride, agar, lactic acid, sodium lactate, sorbic acid and its potassium salt, sorbitol, acid red, calcium carbonate, sodium carbonate, sodium bicarbonate, beet red, oxidized starch, ethanol, sodium acetate, stearic acid, calcium stearate, and magnesium stearate.

[0041] Furthermore, the medicine also includes pharmaceutically acceptable excipients.

[0042] Furthermore, the pharmaceutically acceptable excipients include but are not limited to excipients, buffers, emulsifiers, stabilizers, diluents, adhesives, preservatives, lubricants, pH regulators, cryoprotectants, flavoring agents, and fillers.

[0043] Specifically, the application of the product is to improve the DPPH clearance rate.

[0044] The beneficial effects of the present invention are:

[0045] (1) The present invention takes yam fermentation strains as the research object, and screens out functional strains suitable for yam fermentation by analyzing the contents of total polysaccharides, total flavonoids and diosgenin, as well as indicators such as antioxidant properties, providing a theoretical basis and technical support for the deep processing of yam.

[0046] (2) The product prepared by the biotransformation method of the present invention has a high content of diosgenin, total flavonoids, and total polysaccharides, and has high antioxidant activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Figure 3 Effects of different preparation methods on diosgenin content. Letters (a, b, c, d) indicate significant differences. There were significant differences between groups with different letters and P < 0.05.

[0048] Figure 2 The results of different preparation methods on the content of total flavonoids are shown in Table 1. “*” indicates a significant difference compared with the blank control group (P < 0.05), and “**” indicates a very significant difference compared with the blank control group (P < 0.01).

[0049] Figure 3 The results of different preparation methods on the total polysaccharide content are shown in Table 2. “**” indicates that there is a significant difference compared with the blank control group (P<0.01).

[0050] Figure 4 IC50 values ​​of samples in different groups, "*" indicates significant difference compared with the blank control group (P<0.05), and "**" indicates extremely significant difference compared with the blank control group (P<0.01). DETAILED DESCRIPTION

[0051] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further illustrated below in conjunction with specific examples, but the following examples are only preferred embodiments of the present invention, not all. Based on the examples in the implementation manner, other embodiments obtained by those skilled in the art without making creative work are all within the scope of protection of the present invention. In the following examples, unless otherwise specified, the operating methods used are all conventional operating methods, the equipment used are all conventional equipment, and the equipment and materials used in each embodiment are all the same.

[0052] In the present invention, the deposition number of Lactobacillus plantarum P9 is CGMCC No. 16401, the deposition number of Lactobacillus plantarum HCS03-001 is CGMCC No. 16258, the deposition number of Lactobacillus plantarum N13 is CGMCC No. 5495, the deposition number of Lactobacillus plantarum Lp-06 is CGMCC No. 29665, the deposition number of Lactobacillus paracasei YMC1069 is CGMCC No. 18676, and the deposition number of Lactobacillus rhamnosus LR519 is CGMCC No. 15969.

[0053] Example 1

[0054] After Lactobacillus plantarum P9 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0055] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 3% (v / v) inoculum, and an unfermented control group was set up. The mixture was shaken thoroughly and fermented in a shaker incubator at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0056] Example 2

[0057] After Lactobacillus plantarum P9 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 9 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0058] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Pure water was added at a material-liquid ratio of 6 g / 100 mL, and 1.5% glucose was added. After stirring, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 2% (v / v) inoculum. An unfermented control group was also set up. After shaking, the mixture was placed in a shaker incubator and fermented at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0059] Example 3

[0060] After Lactobacillus plantarum P9 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 8 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0061] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Pure water was added at a material-liquid ratio of 6 g / 100 mL, and 1.5% glucose was added. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 4% (v / v) inoculum. An unfermented control group was also set up. After shaking, the mixture was placed in a shaker incubator and fermented at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0062] Comparative Example 1

[0063] After Lactobacillus plantarum HCS03-001 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0064] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 3% (v / v) inoculum, and an unfermented control group was set up. The mixture was shaken thoroughly and fermented in a shaker incubator at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0065] Comparative Example 2

[0066] After Lactobacillus plantarum N13 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0067] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the mixture was inoculated with each strain at a 3% (v / v) inoculum. An unfermented control group was also established. After shaking, the mixture was placed in a shaker incubator and fermented at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0068] Comparative Example 3

[0069] After Lactobacillus plantarum Lp-06 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0070] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 3% (v / v) inoculum, and an unfermented control group was set up. The mixture was shaken thoroughly and fermented in a shaker incubator at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0071] Comparative Example 4

[0072] After the Lactobacillus paracasei YMC1069 glycerol tube was activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0073] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 3% (v / v) inoculum, and an unfermented control group was set up. The mixture was shaken thoroughly and fermented in a shaker incubator at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0074] Comparative Example 5

[0075] After Lactobacillus rhamnosus LR519 glycerol tubes were activated for 2 generations with MRS medium, centrifuged at 5000 rpm for 3 min, the bacterial sludge was washed twice with sterile saline, and resuspended with sterile saline. The viable bacterial count of the strain was adjusted to 10 × 10 after counting with a hemocytometer. 8 CFU / mL, set aside.

[0076] The yam slices were crushed in a grinder and passed through a 60-mesh sieve. Purified water was added at a material-liquid ratio of 6 g / 100 mL, followed by 1.5% glucose. After stirring thoroughly, the mixture was extracted in a boiling water bath for 1 hour. After replenishing the water content, the mixture was sterilized at 105°C for 15 minutes. After cooling, the strain was inoculated at a 3% (v / v) inoculum, and an unfermented control group was set up. The mixture was shaken thoroughly and fermented in a shaker incubator at 150 rpm and 37°C for 48 hours. After fermentation, the mixture was sterilized at 95°C for 5 minutes to obtain the probiotic-fermented yam sample.

[0077] Experimental Example 1

[0078] 1. Detection method:

[0079] 1.1 Diosgenin Assay Method: Diosgenin standard solution was dissolved in methanol to prepare a 0.28 g / L standard solution. The solution was analyzed on an Agilent 1260 HPLC using a Zorbax SB-C18 (5 μm, 4.6 × 250 mm) column with a mobile phase of methanol:water (90:10) at a flow rate of 1.0 mL / min, a column temperature of 30°C, and DAD detection at a wavelength of 210 nm. The injection volume was 10 μL. A 10 g sample was extracted three times with 10 mL of chloroform. The combined chloroform extracts were evaporated to dryness, and the residue was dissolved in methanol to a final volume of 10 mL. The solution was filtered through a 0.22 μm filter and the diosgenin content in the sample was calculated based on the standard curve.

[0080] 1.2 Determination of total flavonoids content

[0081] Rutin was used as a standard. Dissolve it in 60% ethanol to prepare a 200 mg / L stock solution. This solution was then diluted to prepare standard solutions of varying concentrations. 10 mL of each standard solution was placed in a 25 mL stoppered colorimetric tube. 1 mL of sodium nitrite solution (50 g / L) was added, shaken, and allowed to stand for 6 minutes. 1.5 mL of aluminum nitrate solution (100 g / L) was added, shaken, and allowed to stand for 6 minutes. 4 mL of sodium hydroxide solution (200 g / L) was added, and the solution was brought to volume with water. The solution was shaken, and allowed to stand for 15 minutes. Using a 1 cm cuvette, the absorbance was measured at 510 nm using a reagent blank as the zero point. A standard curve was constructed using absorbance values ​​corresponding to content. After centrifugation, 10 mL of the supernatant was placed in a 25 mL stoppered colorimetric tube. The assay procedure was the same as for the rutin standard. The absorbance was measured at 510 nm, and the total flavonoid content of the sample was calculated based on the standard curve.

[0082] 1.3 Determination of total polysaccharide content

[0083] Accurately weigh 1 g of glucose (at constant weight at 105°C) into a 1 L volumetric flask to prepare a 1 g / L stock solution. Continue diluting to prepare standard solutions of varying concentrations. Pipette 1 mL of each standard solution into a centrifuge tube. Add 1 mL of 5% phenol solution and 5 mL of concentrated sulfuric acid, respectively. Let stand for 10 minutes. Shake well, then incubate in a 30°C water bath for 20 minutes. Measure the absorbance at 490 nm. Construct a standard curve using glucose concentration as the horizontal axis and absorbance as the vertical axis. Centrifuge the sample to remove the precipitate. Add 95% ethanol to a concentration of 80%. Let stand at 4°C overnight. Centrifuge and remove the supernatant. Rinse the precipitate three times with 80% ethanol and dissolve in 1 mL of water. Follow the same assay steps as for the glucose standard solution. Measure the absorbance at 490 nm and calculate the total polysaccharide content of the sample based on the standard curve.

[0084] 1.4 DPPH free radical scavenging activity assay

[0085] Each group of fermented yam samples was centrifuged at 10,000 rpm for 10 minutes. The supernatant was lyophilized and then reconstituted with purified water to prepare samples of different concentrations (10 g / L, 20 g / L, 30 g / L, 40 g / L, and 50 g / L). 1 mg of DPPH was weighed and thoroughly dissolved in 95% ethanol. The absorbance was adjusted to approximately 1.0 and stored at 4°C in the dark until use. To a 96-well plate, 50 μL of sample and 50 μL of DPPH solution were added to form the assay group, recorded as Ai. 50 μL of sample of varying concentrations and 95% ethanol were added to form the sample control, recorded as Aj. 50 μL of DPPH solution and 50 μL of deionized water were added to form the blank control, recorded as A0. Each group was repeated three times. After each group was fully reacted in the dark for 30 minutes, the absorbance of each group was measured at 517 nm and recorded. The DPPH radical scavenging rate was calculated according to the following formula:

[0086] DPPH free radical scavenging rate (%) = [1- (Ai-Aj) / A0] × 100%.

[0087] 2 Experimental Results

[0088] 2.1 Effects of different preparation methods on diosgenin content

[0089] The results are as follows Figure 1 As shown, from Figure 1 It can be seen that the content of diosgenin was not detected in the non-fermented control group, while the content of diosgenin could be detected in the examples and the comparative examples, and the content of diosgenin in the examples was significantly higher than that in the comparative examples, among which the content of diosgenin in Example 1 was the highest.

[0090] 2.2 Effects of different preparation methods on total flavonoid content

[0091] The results are as follows Figure 2 As shown, from Figure 2 It can be seen that after fermentation with different strains, the total flavonoid content is increased to a certain extent, and the embodiment group is better than the control group; among them, the most significant increase in total flavonoid content is in Example 1, with a total flavonoid content of 0.208 g / L, which is 38.42% higher than that of the control group.

[0092] 2.3 Effects of different preparation methods on total polysaccharide content

[0093] The results are as follows Figure 3 As shown, from Figure 3It can be seen that after fermentation with different strains, the total polysaccharide content increased to a certain extent, and the example group was superior to the comparative example group; among them, the most significant increase in total polysaccharide content was in Example 2, with a total polysaccharide content of 2.241 g / L, an increase of 79.25% over the blank control group. On the one hand, probiotic fermentation can degrade large molecular weight polysaccharides into smaller molecular weight polysaccharides, thereby converting some insoluble or bound polysaccharides in the original yam into water-soluble polysaccharides. On the other hand, probiotic growth also produces extracellular polysaccharides, which significantly increases the polysaccharide content in the fermentation broth.

[0094] 2.4 Effects of different preparation methods on antioxidant activity

[0095] DPPH is a stable free radical with a single electron. When encountering a substance with antioxidant ability, the single electron of DPPH is paired. The higher the scavenging activity, the stronger the antioxidant ability of the substance, which can provide electrons or hydrogen atoms to stabilize free radicals and prevent the oxidation reaction caused by free radicals. As can be seen from Table 1, the scavenging activity of the embodiment group on DPPH is better than that of the comparative example group; among them, the scavenging activity of Example 1 on DPPH is the highest. In the antioxidant experiment, the scavenging rate of free radicals in the system was fitted by samples of different concentrations, and the concentration required to scaveng 50% of the free radicals in the system was obtained. The lower the IC50 value, the better the antioxidant activity. Figure 4 It can be seen from Table 1 that the IC50 in the embodiment is lower than that in the comparative example. Figure 4 The results showed that the antioxidant activity of the examples was better than that of the comparative examples.

[0096] Table 1 DPPH scavenging rate of different samples (%)

[0097]

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for improving the biotransformation of diosgenin in yam, characterized in that: The following steps are involved: S1. After crushing the Chinese yam, add water and glucose, mix well and extract in a boiling water bath; S2, after sterilization, inoculate Lactobacillus plantarum P9 at an inoculum size of 1-5% for shaker fermentation culture, the fermentation culture conditions are 100-200 rpm, 35-38 ° C, fermentation for 24-48 hours, and sterilize after the fermentation to obtain a probiotic fermented yam product; The deposit number of the Lactobacillus plantarum P9 is CGMCC No. 16401.

2. The bioconversion method according to claim 1, characterized in that The biotransformation method further includes a pretreatment step of Lactobacillus plantarum P9, wherein the pretreatment step comprises activating Lactobacillus plantarum P9 with MRS culture medium, centrifuging at 4000-6000 rpm for 3-6 minutes, and resuspending with physiological saline to adjust the viable count of Lactobacillus plantarum P9 to 8×10 8 -10×10 8 CFU / mL.

3. The bioconversion method according to claim 1, characterized in that In step S1, the material-liquid ratio of yam to water is 5-8:100, in g:mL; and the amount of glucose added is 1-5%.

4. The bioconversion method according to claim 3, characterized in that In step S1, the material-liquid ratio of Chinese yam to water is 6:100, the unit is g:mL, and the amount of glucose added is 1.5%.

5. The bioconversion method according to claim 1, characterized in that The extraction time in step S1 is 0.5-2 h.

6. The bioconversion method according to claim 1, characterized in that The inoculum size described in step S2 is 2-4%.

7. The bioconversion method according to claim 1, characterized in that The fermentation conditions in step S2 are 150 rpm, 37° C., and fermentation for 48 h.

8. A probiotic fermented yam product prepared by the biotransformation method according to any one of claims 1 to 7.

9. Use of the probiotic fermented yam product according to claim 8 in the preparation of antioxidant products.

10. The use according to claim 9, characterized in that The products include food and medicine.

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