Biotransformation method for improving yam diosgenin and application of biotransformation method

Abstract

The invention discloses a biotransformation method for improving yam diosgenin and application of the biotransformation method, and relates to the technical field of microbial fermentation. The biotransformation method comprises the following steps: S1, crushing Chinese yam, adding water, adding glucose, uniformly mixing in a boiling water bath, and extracting; s2, after sterilization, lactobacillus plantarum P9 is inoculated according to the inoculation amount of 1-5% for shaking table fermentation culture, the fermentation culture conditions are 100-200 rpm and 35-38 DEG C, fermentation is conducted for 24-48 h, sterilization is conducted after fermentation is finished, and the probiotic fermented Chinese yam product is obtained. The preservation number of the lactobacillus plantarum P9 is CGMCC (China General Microbiological Culture Collection Center) No.16401. According to the biotransformation method, the diosgenin content, the total flavone content and the total polysaccharide content in the probiotic Chinese yam product can be increased, and the probiotic Chinese yam product has high antioxidant activity.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial fermentation, and particularly relates to a method for improving the biotransformation of diosgenin in Chinese yam and its application. Background Art

[0002] Chinese yam (Dioscorea Opposita), as a traditional crop with both medicinal and edible properties, is rich in active ingredients such as polysaccharides, saponins, mucoproteins, and trace elements. In addition to its rich nutritional value, it also has medicinal values such as antioxidant, anti-inflammatory, anti-aging, liver protection, and gastrointestinal regulation. However, the high starch content and viscous texture of Chinese yam lead to easy browning during processing. At present, the main edible methods of Chinese yam are high-temperature methods such as frying and stewing, which easily cause the decomposition of active ingredients and reduce their health care value. Due to the lack of suitable processing technology, the development of high-value-added products of Chinese yam is severely restricted.

[0003] Microbial fermentation technology has been widely used in the deep processing field of traditional crops with both medicinal and edible properties due to its green and efficient characteristics. It can degrade macromolecular substances in Chinese yam through the metabolic action of strains, increase the content of soluble components, and generate new functional factors (such as short-chain fatty acids, exopolysaccharides, etc.), thereby enhancing the nutritional value and functional characteristics of products.

[0004] Chinese Patent CN107896921A discloses a Tremella fuciformis biotransformation composition of maca and Chinese yam and its manufacturing method. The manufacturing method includes the following steps: (a) Stir maca powder, Chinese yam powder, and soybean powder with cold water, and then heat and sterilize to obtain a seed culture medium solution; (b) Cool the seed culture medium solution obtained in step (a), inoculate Tremella fuciformis, and stir and culture for several days to obtain a Tremella fuciformis seed culture solution; (c) Stir maca powder, Chinese yam powder, and soybean powder evenly to obtain a solid material; mix the solid material with water evenly, and sterilize at high temperature to obtain a culture medium for liquid fermentation of Tremella fuciformis; (d) Inoculate and ferment: Cool the culture medium for liquid fermentation of Tremella fuciformis obtained in step (c), inoculate the Tremella fuciformis seed culture solution obtained in step (b), mix the two evenly, and then load them into a fermentation tank or fermenter for fermentation to obtain a Tremella fuciformis fermentation composition of maca and Chinese yam. The composition obtained by the production method of this invention has functions such as improving pulmonary fibrosis function and anti-fatigue. However, this preparation method cannot increase the content of diosgenin.

[0005] Diosgenin, commonly known as sapogenin, mostly exists in Chinese yam in the form of dioscin, combined with glycosides. It is the main saponin component in Chinese yam. Diosgenin has effects such as desensitization, anti-inflammatory, lipid-lowering, antioxidant, anti-tumor, liver protection, and antiviral, and has received increasing attention in the development of Chinese yam products.

[0006] Chinese Patent CN105996022A discloses a method for simultaneously transforming Chinese yam with Cordyceps fungus to produce functional foods. The preparation method uses Chinese yam and rice, wheat, corn, sorghum, etc. as solid substrates, and Cordyceps fungus as the starting strain, and is prepared through processes such as test tube scale-up culture, liquid shake flask culture, seed tank scale-up culture, solid fermentation culture, drying, pulverization, and packaging; the functional food contains 2 - 20 mg / g dry substrate of saponins, 10 - 100 mg / g dry substrate of Cordyceps polysaccharide, and 1 - 20 mg / g dry substrate of cordycepin, and has effects such as regulating blood lipid, blood sugar, and blood pressure, anti-radiation, and inhibiting tumors; the active ingredients saponins, Cordyceps polysaccharide, and cordycepin can be extracted from the functional food and used to produce tablets, capsules, and other drugs or functional foods for treating reducing blood lipid, blood sugar, and blood pressure, anti-radiation, and inhibiting tumors.

[0007] At present, the systematic screening and adaptability evaluation research on probiotics specialized for Chinese yam fermentation are still relatively scarce, and no method for using Lactobacillus plantarum to improve the biotransformation of diosgenin in Chinese yam has been retrieved. Summary of the Invention

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

[0009] To achieve the above object of the invention, the technical solution of the present invention is as follows: On the one hand, the present invention provides a method for improving the biotransformation of diosgenin in Chinese yam, comprising the following steps: S1. After pulverizing Chinese yam, add water, add glucose, mix well and extract in a boiling water bath; S2. After sterilization, inoculate Lactobacillus plantarum P9 at an inoculation amount of 1 - 5% and perform shake flask fermentation culture. The conditions for fermentation culture are 100 - 200 rpm, 35 - 38 °C, and ferment for 24 - 48 h. After fermentation, sterilize to obtain the probiotic-fermented Chinese yam product; The preservation number of the Lactobacillus plantarum P9 is CGMCC No. 16401.

[0010] Specifically, the biotransformation method further includes a pretreatment step of Lactobacillus plantarum P9, specifically: after activating Lactobacillus plantarum P9 with MRS medium, centrifuge at 4000 - 6000 rpm for 3 - 6 min, and resuspend with physiological saline to adjust the viable count of Lactobacillus plantarum P9 to (8 - 10) × 10 8 CFU / mL.

[0011] Further, the pretreatment step of Lactobacillus plantarum P9 is: after activating Lactobacillus plantarum P9 with MRS medium for 2 generations, centrifuge at 5000 rpm for 3 min, and resuspend with physiological saline to adjust the viable count of Lactobacillus plantarum P9 to (8 - 10) × 108 CFU / mL.

[0012] Specifically, the Chinese yam after being crushed in step S1 is sieved through a 60-mesh sieve.

[0013] Specifically, the material-liquid ratio of Chinese yam to water in step S1 is (5 - 8) g / 100 mL; Further, the material-liquid ratio of Chinese yam to water in step S1 is 6 g / 100 mL.

[0014] Specifically, the addition amount of glucose in step S1 is 1 - 5%; Further, the addition amount of glucose in step S1 is 1 - 3%; Still further, the addition amount of glucose in step S1 is 1.5%.

[0015] Specifically, the extraction time in step S1 is 0.5 - 2 h; Further, the extraction time in step S1 is 1 h.

[0016] Specifically, the viable count of Lactobacillus plantarum P9 in step S2 is (8 - 10) × 10 8 CFU / mL.

[0017] Specifically, the sterilization conditions in step S2 are 105°C - 110°C, and the sterilization time is 10 - 20 min; Further, the sterilization conditions in step S2 are 105°C, and the sterilization time is 15 min.

[0018] Specifically, the inoculation amount in step S2 is 1 - 5 (v / v)%.

[0019] According to some embodiments of the present invention, the inoculation amount can be 1 (v / v)%, 2 (v / v)%, 3 (v / v)%, 4 (v / v)%, 5 (v / v)%.

[0020] Further, the inoculation amount in step S2 is 2 (v / v)%, 3 (v / v)% or 4 (v / v)%.

[0021] Further, the inoculation amount in step S2 is 3 (v / v)%.

[0022] Further, the fermentation culture conditions in step S2 are 150 rpm, 37°C, and ferment for 48 h.

[0023] Specifically, the sterilization conditions after fermentation in step S2 are sterilize at 90 - 100°C for 5 - 10 min; Further, the sterilization conditions after fermentation in step S2 are sterilize at 95°C for 5 min.

[0024] On the other hand, the present invention provides a probiotic-fermented yam product prepared by the above-mentioned biotransformation method.

[0025] Specifically, the probiotic-fermented yam product has a relatively high content of diosgenin, total flavonoids, and total polysaccharides.

[0026] Specifically, the probiotic-fermented yam product can improve antioxidant activity.

[0027] On the other hand, the present invention provides the application of the above-mentioned probiotic-fermented yam product in the preparation of an antioxidant product.

[0028] Specifically, the product includes foods and drugs.

[0029] Furthermore, the food also includes excipients acceptable in the food.

[0030] Still further, the excipients acceptable in the food 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, ponceau 4R, calcium carbonate, sodium carbonate, sodium bicarbonate, betanin, oxidized starch, ethanol, sodium acetate, stearic acid, calcium stearate, and magnesium stearate.

[0031] Furthermore, the drug also includes pharmaceutically acceptable excipients.

[0032] Still further, the pharmaceutically acceptable excipients include, but are not limited to, excipients, buffers, emulsifiers, stabilizers, diluents, binders, preservatives, lubricants, pH regulators, cryoprotectants, flavoring agents, and fillers.

[0033] Specifically, the application route of the product is to improve the DPPH scavenging rate.

[0034] The beneficial effects of the present invention are as follows: (1) Taking the yam-fermenting strains as the research object, by analyzing the contents of total polysaccharides, total flavonoids, diosgenin, and antioxidant characteristics and other indicators, functional strains suitable for yam fermentation are screened out, providing a theoretical basis and technical support for the deep processing of yams.

[0035] (2) The product prepared by the biotransformation method of the present invention has a relatively high content of diosgenin, total flavonoids, and total polysaccharides, and has relatively high antioxidant activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Effects of different preparation methods on the content of diosgenin. The letters (a, b, c, d) are significant difference markers, and there are significant differences between groups with different letters and P < 0.05.

[0037] Figure 2 Effects of different preparation methods on the total flavonoid content. "*" indicates a significant difference compared with the blank control group (P < 0.05), and "**" indicates a highly significant difference compared with the blank control group (P < 0.01).

[0038] Figure 3 Effects of different preparation methods on the total polysaccharide content. "**" indicates a highly significant difference compared with the blank control group (P < 0.01).

[0039] Figure 4 IC50 values of samples in different groups. "*" indicates a significant difference compared with the blank control group (P < 0.05), and "**" indicates a highly significant difference compared with the blank control group (P < 0.01). Detailed implementation manners

[0040] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the following specific embodiments are used to further clarify the present invention. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present invention. In the following embodiments, unless otherwise specified, the used operation methods are all conventional operation methods, the used equipment is all conventional equipment, and the equipment materials used in each embodiment are the same.

[0041] In the present invention, the preservation number of Lactobacillus plantarum P9 is CGMCC No. 16401, the preservation number of Lactobacillus plantarum HCS03-001 is CGMCC No.16258, the preservation number of Lactobacillus plantarum N13 is CGMCC No.5495, the preservation number of Lactobacillus plantarum Lp-06 is CGMCC No. 29665, the preservation number of Lactobacillus paracasei YMC1069 is CGMCC No.18676, and the preservation number of Lactobacillus rhamnosus LR519 is CGMCC No. 15969.

[0042] Example 1 After the glycerol tube of Lactobacillus plantarum P9 was activated for 2 generations with MRS medium, it was centrifuged at 5000 rpm for 3 min. After the bacterial sludge was washed twice with sterile physiological saline, it was resuspended with sterile physiological saline. After counting with a hemocytometer, the viable count of the strain was adjusted to 10×10 8 CFU / mL for standby.

[0043] The Chinese yam slices were pulverized by a pulverizer and then passed through a 60-mesh sieve. Pure water was added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose was added, and after stirring evenly, the mixture was extracted in a boiling water bath for 1 h. After making up the water, it was sterilized at 105 °C for 15 min. After cooling, the strain was inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group was set up. After shaking well, it was placed in a shaking incubator and cultured at 150 rpm and 37 °C for 48 h. After the fermentation was completed, it was sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0044] Example 2 After the glycerol tube of Lactobacillus plantarum P9 was activated with MRS medium for 2 generations, it was centrifuged at 5000 rpm for 3 min. The bacterial sludge was washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable count of the strain was adjusted to 9×10 8 CFU / mL for standby.

[0045] The Chinese yam slices were pulverized by a pulverizer and then passed through a 60-mesh sieve. Pure water was added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose was added, and after stirring evenly, the mixture was extracted in a boiling water bath for 1 h. After making up the water, it was sterilized at 105 °C for 15 min. After cooling, the strain was inoculated at an inoculation amount of 2% (v / v). At the same time, an unfermented control group was set up. After shaking well, it was placed in a shaking incubator and cultured at 150 rpm and 37 °C for 48 h. After the fermentation was completed, it was sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0046] Example 3 After the glycerol tube of Lactobacillus plantarum P9 was activated with MRS medium for 2 generations, it was centrifuged at 5000 rpm for 3 min. The bacterial sludge was washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable count of the strain was adjusted to 8×10 8 CFU / mL for standby.

[0047] The Chinese yam slices were pulverized by a pulverizer and then passed through a 60-mesh sieve. Pure water was added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose was added, and after stirring evenly, the mixture was extracted in a boiling water bath for 1 h. After making up the water, it was sterilized at 105 °C for 15 min. After cooling, the strain was inoculated at an inoculation amount of 4% (v / v). At the same time, an unfermented control group was set up. After shaking well, it was placed in a shaking incubator and cultured at 150 rpm and 37 °C for 48 h. After the fermentation was completed, it was sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0048] Comparative Example 1 After the Lactobacillus plantarum HCS03-001 was activated for 2 generations with MRS medium in a glycerol tube, it was centrifuged at 5000 rpm for 3 min. The bacterial sediment was washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable cell count of the strain was adjusted to 10×10 8 CFU / mL and reserved for use.

[0049] The Chinese yam slices were crushed with a pulverizer and passed through a 60-mesh sieve. Pure water was added according to the solid-liquid ratio of 6 g / 100 mL, 1.5% glucose was added, and after stirring evenly, it was extracted in a boiling water bath for 1 h. After making up the water, it was sterilized at 105°C for 15 min. After cooling, the strain was inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group was set up. After shaking well, it was placed in a shaking incubator and fermented at 150 rpm and 37°C for 48 h. After the fermentation was completed, it was sterilized at 95°C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0050] Comparative Example 2 After the Lactobacillus plantarum N13 was activated for 2 generations with MRS medium in a glycerol tube, it was centrifuged at 5000 rpm for 3 min. The bacterial sediment was washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable cell count of the strain was adjusted to 10×10 8 CFU / mL and reserved for use.

[0051] The Chinese yam slices were crushed with a pulverizer and passed through a 60-mesh sieve. Pure water was added according to the solid-liquid ratio of 6 g / 100 mL, 1.5% glucose was added, and after stirring evenly, it was extracted in a boiling water bath for 1 h. After making up the water, it was sterilized at 105°C for 15 min. After cooling, each strain was inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group was set up. After shaking well, it was placed in a shaking incubator and fermented at 150 rpm and 37°C for 48 h. After the fermentation was completed, it was sterilized at 95°C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0052] Comparative Example 3 After the Lactobacillus plantarum Lp-06 was activated for 2 generations with MRS medium in a glycerol tube, it was centrifuged at 5000 rpm for 3 min. The bacterial sediment was washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable cell count of the strain was adjusted to 10×10 8 CFU / mL and reserved for use.

[0053] The Chinese yam slices are pulverized by a pulverizer and then sieved through a 60-mesh sieve. Pure water is added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose is added, and after stirring evenly, it is extracted in a boiling water bath for 1 h. After making up the water, it is sterilized at 105 °C for 15 min. After cooling, the strain is inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group is set up. After shaking well, it is placed in a shaking incubator and fermented at 150 rpm and 37 °C for 48 h. After the fermentation is completed, it is sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0054] Comparative Example 4 After the glycerol tube of Lactobacillus paracasei YMC1069 is activated for 2 generations with MRS medium, it is centrifuged at 5000 rpm for 3 min. The bacterial sludge is washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable count of the strain is adjusted to 10×10 8 CFU / mL for standby.

[0055] The Chinese yam slices are pulverized by a pulverizer and then sieved through a 60-mesh sieve. Pure water is added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose is added, and after stirring evenly, it is extracted in a boiling water bath for 1 h. After making up the water, it is sterilized at 105 °C for 15 min. After cooling, the strain is inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group is set up. After shaking well, it is placed in a shaking incubator and fermented at ①②③④⑤⑥⑦⑧⑨⑩⑪⑫⑬⑭⑮⑯⑰⑱⑲⑳㉑㉒㉓㉔㉕㉖㉗㉘㉙㉚㉛㉜㉝㉞㉟㊱㊲㊳㊴㊵㊶㊷㊸㊹㊺㊻㊼㊽㊾㊿ 150 rpm and 37 °C for 48 h. After the fermentation is completed, it is sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0056] Comparative Example 5 After the glycerol tube of Lactobacillus rhamnosus LR519 is activated for 2 generations with MRS medium, it is centrifuged at 5000 rpm for 3 min. The bacterial sludge is washed twice with sterile normal saline and then resuspended with sterile normal saline. After counting with a hemocytometer, the viable count of the strain is adjusted to 10×10 8 CFU / mL for standby.

[0057] The Chinese yam slices are pulverized by a pulverizer and then sieved through a 60-mesh sieve. Pure water is added for mixing according to a solid-liquid ratio of 6 g / 100 mL, 1.5% glucose is added, and after stirring evenly, it is extracted in a boiling water bath for 1 h. After making up the water, it is sterilized at 105 °C for 15 min. After cooling, the strain is inoculated at an inoculation amount of 3% (v / v). At the same time, an unfermented control group is set up. After shaking well, it is placed in a shaking incubator and fermented at 150 rpm and 37 °C for 48 h. After the fermentation is completed, it is sterilized at 95 °C for 5 min to obtain the probiotic-fermented Chinese yam sample.

[0058] Experimental Example 1 1 Detection method: 1.1 Detection method of diosgenin: The diosgenin standard was dissolved in methanol to prepare a standard solution with a concentration of 0.28 g / L. On an Agilent 1260 high-performance liquid chromatograph, a Zorbax SB-C18 (5μm, 4.6×250mm) chromatographic column was used. The mobile phase was methanol-water (90:10), the flow rate was 1.0 mL / min, the column temperature was 30°C, the detection wavelength of DAD was 210 nm, and the injection volume was 10 μL. Weigh 10 g of the sample, extract it 3 times with 10 ml of chloroform, combine the chloroform and evaporate to dryness. The residue was dissolved in methanol and diluted to 10 mL, filtered through a 0.22 μm filter membrane and then detected. The content of diosgenin in the sample was calculated according to the standard curve.

[0059] 1.2 Determination of total flavonoid content Using rutin as the standard, it was dissolved in 60% ethanol to prepare a stock solution of 200 mg / L, and then further diluted into standard solutions with different concentrations. Respectively, 10 mL of the standard solution was pipetted into 25 mL stoppered colorimetric tubes, 1 mL of sodium nitrite solution (50 g / L) was added, shaken well, and left for 6 min. Then 1.5 mL of aluminum nitrate solution (100 g / L) was added, shaken well, and left for 6 min. Next, 4 mL of sodium hydroxide solution (200 g / L) was added, and the volume was made up to the mark with water, shaken well, and left for 15 min. Using a 1 cm colorimetric cell, the reagent blank was used to adjust the zero point, and the absorbance was measured at a wavelength of 510 nm. A standard curve was plotted with the absorbance values corresponding to the contents. After centrifuging the sample, 10 mL of the supernatant was pipetted into a 25 mL stoppered colorimetric tube. The detection steps were the same as those for the rutin standard. After measuring the absorbance at 510 nm, the total flavonoid content of the sample was calculated according to the standard curve.

[0060] 1.3 Determination of total polysaccharide content Accurately weigh 1 g of glucose, which was dried to a constant weight at 105°C, into a 1 L volumetric flask to prepare a stock solution of 1 g / L, and then further diluted into standard solutions with different concentrations. Then, 1 mL of each standard solution was pipetted into centrifuge tubes, and then 1 mL of phenol solution (5%) and 5 mL of concentrated sulfuric acid were added respectively. Let it stand for 10 min, shake well, and then place it in a water bath at 30°C for 20 min. Measure the absorbance at 490 nm. A standard curve was made with the glucose concentration as the abscissa and the absorbance as the ordinate. The sample was first centrifuged to remove the precipitate, then 95% ethanol was added to make the ethanol concentration 80%, and it was left to stand overnight at 4°C. After centrifuging to remove the supernatant, the precipitate was washed 3 times with 80% ethanol solution and then dissolved in 1 mL of water. The detection steps were the same as those for the glucose standard solution. After measuring the absorbance at 490 nm, the total polysaccharide content of the sample was calculated according to the standard curve.

[0061] 1.4 Detection of DPPH free radical scavenging activity Centrifuge the yam fermentation samples of each group at 10,000 rpm for 10 min, take the supernatant for freeze-drying, and then prepare samples with different concentrations (10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L) with pure water for standby. Weigh 1 mg of DPPH, dissolve it thoroughly with 95% ethanol, and adjust the absorbance value to about 1.0, and store it in the dark at 4 °C for standby. Add 50 μL of the sample and the DPPH solution to each well of a 96-well plate as the measurement group, recorded as Ai; add 50 μL of samples with different concentrations and 95% ethanol respectively as the sample control, recorded as Aj; add 50 μL of the DPPH solution and deionized water respectively as the blank control, recorded as A0, and repeat each group 3 times. After each group reacts fully in the dark for 30 min, measure the absorbance of each group at 517 nm and record it. Calculate the DPPH free radical scavenging rate according to the following formula: DPPH free radical scavenging rate (%) = [1 - (Ai - Aj) / A0] × 100%.

[0062] 2 Experimental results 2.1 Effects of different preparation methods on the content of diosgenin The results are as Figure 1 shown. It can be seen from Figure 1 that the content of diosgenin was not detected in the unfermented control group, while the content of diosgenin could be detected in the examples and 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.

[0063] 2.2 Effects of different preparation methods on the content of total flavonoids The results are as Figure 2 shown. It can be seen from Figure 2 that after fermentation with different strains, the content of total flavonoids has increased to a certain extent, and the example group is better than the comparative example group; among them, the most significant increase in the content of total flavonoids is in Example 1, and the content of total flavonoids is 0.208 g / L, which is 38.42% higher than that of the control group.

[0064] 2.3 Effects of different preparation methods on the content of total polysaccharides The results are as Figure 3 shown. It can be seen from Figure 3It can be seen that after fermentation with different strains, the total polysaccharide content has increased to a certain extent, and the experimental group is better than the control group; among them, the total polysaccharide content has increased most significantly in Example 2, with a total polysaccharide content of 2.241 g / L, which is 79.25% higher than that of the blank control group. On the one hand, probiotic fermentation can degrade large-molecular polysaccharides into smaller-molecular polysaccharides, thereby converting some insoluble or bound polysaccharides in the original yam into water-soluble polysaccharides. On the other hand, extracellular polysaccharides will also be produced during the growth of probiotics, resulting in a significant increase in the polysaccharide content in the fermentation broth.

[0065] 2.4 Influence of Different Preparation Methods on Antioxidant Activity DPPH is a stable free radical with a single electron. When it encounters 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 oxidation reactions initiated by free radicals. As can be seen from Table 1, the scavenging activity of the experimental group against DPPH is better than that of the control group; among them, the scavenging activity of Example 1 against DPPH is the highest. In the antioxidant experiment, by fitting the scavenging rate of free radicals in the system by samples with different concentrations, the concentration required to scavenge 50% of the free radicals in the system is obtained. The lower the IC50 value, the better the antioxidant activity. As Figure 4 can be seen, the IC50 in the examples is lower than that in the control group. Combining Table 1 and Figure 4 the results show that the antioxidant activity of the examples is better than that of the control group.

[0066] Table 1 Scavenging Rate of Different Samples against DPPH (%)

[0067] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for enhancing the biotransformation of diosgenin in Chinese yam, characterized in that, It includes the following steps: S1. After the Chinese yam is pulverized, water is added, glucose is added, and the mixture is extracted in a boiling water bath; S2. After sterilization, Lactobacillus plantarum P9 is inoculated according to an inoculation amount of 1-5% and subjected to shaking flask fermentation culture. The conditions for the fermentation culture are 100-200 rpm and 35-38 °C, and the fermentation is carried out for 24-48 h. After the fermentation is completed, sterilization is carried out to obtain the probiotic-fermented Chinese yam product; The preservation number of the Lactobacillus plantarum P9 is CGMCC No. 16401.

2. The bioconversion method according to claim 1, characterized in that, The described biotransformation method further includes a pretreatment step of Lactobacillus plantarum P9. The pretreatment step is to activate Lactobacillus plantarum P9 with MRS medium, centrifuge it at 4000 - 6000 rpm for 3 - 6 min, and resuspend it 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 Chinese yam to water is 5-8:100, with the unit of g:mL; the addition amount of glucose is 1-5%.

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

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

6. The bioconversion method according to claim 1, wherein In step S2, the inoculation amount is 2-4%.

7. The bioconversion method according to claim 1, wherein In step S2, the conditions for the fermentation culture are 150 rpm and 37 °C, and the fermentation is carried out for 48 h.

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

9. The application of the probiotic-fermented Chinese yam product according to claim 8 in the preparation of an antioxidant product.

10. The application according to claim 9, characterized in that, The product described above includes food and medicine.

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