A strain of Enterococcus faecium and its application in the biotransformation of flaxseed lignans

Abstract

The present invention discloses a strain of Enterococcus faecium and its application in the biotransformation of flaxseed lignans. This strain is named Enterococcus faecium ZB26, which was deposited on June 14, 2022 at the Guangdong Provincial Culture Collection Center of Microorganisms, Building 59, No. 100 Compound, Xianlie Middle Road, Yuexiu District, Guangzhou City, Guangdong Province, with the deposit number GDMCC No. 62548. This strain is a facultative anaerobe screened from fermented soy products. When inoculated into a medium supplemented with flaxseed lignan extract, it can convert SDG into END and intermediate metabolites such as SMG, SECO, demethylated SECO, demethyldehydroxy SECO, and DHENL. The conversion rate of SDG is over 90%, the production rate of SECO is over 80%, and mammalian lignan END is produced. This strain can also use fresh milk as a medium for SDG conversion to enhance food nutrition, and has good application prospects in the development of functional foods.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbiology, and particularly relates to a strain of Enterococcus faecium and its application in the biotransformation of secoisolariciresinol in flaxseed Background Art

[0002] Flax is an important oilseed crop. The by-product cake and meal remaining after oil pressing contains most of the nutrients and active ingredients of flaxseed. Due to limited processing technology level, it has not been well developed and utilized, and is generally used as animal feed, resulting in waste of flaxseed cake and meal resources.

[0003] Secoisolariciresinol (SECO) exists in the seed coat of flaxseed and is a polyphenolic phytoestrogen compound. After flaxseed is oil pressed, secoisolariciresinol remains in the flaxseed cake and meal. Secoisolariciresinol diglucoside (SDG) is the most important lignan in flaxseed and generally exists in flaxseed in the form of its glycoside. The bioavailability of SDG is low, and it needs to undergo a series of reactions such as deglycosylation, demethylation, and dehydroxylation under the action of the human intestinal flora to be transformed into mammalian lignans enterodiol (END) and enterolactone (ENL) and enter the blood to exert its physiological functions. Research shows that the structures of both END and ENL are similar to those of endogenous estrogens such as estradiol, and both have estrogenic and anti-estrogenic activities, as well as strong antioxidant and anti-cancer activities. Among them, the in vitro antioxidant ability of END is about 4 times that of SDG, which can prevent colon cancer, breast cancer, prostate cancer, inhibit diseases such as diabetes, and is beneficial to human health.

[0004] Since the bioavailability of SDG is affected by the health status and differences of the human intestinal flora, using microorganisms, especially probiotics, to biotransform SDG into mammalian lignans in vitro is an effective way to improve the bioavailability of SDG. It has been reported that Bifidobacterium and Lactobacillus can transform SDG to produce low levels of END and / or ENL under strictly anaerobic conditions and can be applied to lignan-enriched foods. Using these strains for transformation requires the use of strictly anaerobic equipment, which greatly increases the difficulty of industrial application, and the transformation efficiency needs to be improved. Summary of the Invention

[0005] The first object of the present invention is to overcome the disadvantages and deficiencies of the prior art and provide a strain of Enterococcus faecium. This strain is a lactic acid bacteria strain from traditional fermented soy products in China. The strain can ferment SDG in the extract of flaxseed lignans in liquid state to obtain multiple SDG conversion intermediate metabolites such as mammalian lignan END, SECO, secoisolariciresinol monoglucoside (SMG), demethylated SECO, demethylated dehydroxy SECO, and 2,3-bis(3,4-dihydroxybenzyl)butyrolactone (DHENL), etc., realizing multi-step conversion. Under facultative anaerobic conditions, the SDG conversion rate reaches more than 90% and the SECO production rate reaches more than 80%. At the same time, this strain has the ability to efficiently convert SDG into END, overcomes the strict anaerobic conditions in the reported conversion conditions, improves the bioavailability of lignans, reduces its dependence on the intestinal flora, has potential application value in the development of functional foods, has the potential for industrialization, and can provide more direct bioactive nutrients for consumers with poor gastrointestinal flora status or taking antibiotics.

[0006] Another object of the present invention is to provide the application of the above-mentioned Enterococcus faecium in the biotransformation of flaxseed lignans.

[0007] In order to achieve the above-mentioned invention objects, the present invention adopts the following technical solutions:

[0008] A strain of Enterococcus faecium, named Enterococcus faecium ZB26, was deposited on June 14, 2022 at the Guangdong Provincial Microbial Culture Collection Center (GDMCC), Building 59, No. 100 Yard, Xianlie Middle Road, Yuexiu District, Guangzhou City, Guangdong Province, and the deposit number is: GDMCC No. 62548.

[0009] A biological bacterium agent with the activity of biotransforming flaxseed lignans, comprising the bacterial cells or culture solution of the above-mentioned Enterococcus faecium.

[0010] Further, the culture solution of the Enterococcus faecium is prepared by the following method: The Enterococcus faecium is streaked and isolated on an LB plate, and a single colony is picked and inoculated into an LB broth medium for culturing for 18±2 h to obtain the culture solution.

[0011] The application of the above-mentioned Enterococcus faecium or biological bacterium agent in the biotransformation of flaxseed lignans.

[0012] Further, the application is the application in the deglucosylation, demethylation and / or dehydroxylation transformation of flaxseed lignans.

[0013] Furthermore, the application is one or more of the following applications:

[0014] (1) Convert secoisolariciresinol diglucoside (SDG) to secoisolariciresinol (SECO);

[0015] (2) Convert secoisolariciresinol diglucoside (SDG) to demethylsecoisolariciresinol;

[0016] (3) Convert secoisolariciresinol diglucoside (SDG) to demethyldehydroxysecoisolariciresinol;

[0017] (4) Convert secoisolariciresinol diglucoside (SDG) to secoisolariciresinol monoglucoside (SMG);

[0018] (5) Convert secoisolariciresinol diglucoside (SDG) to dihydroxyenterolactone (DHENL);

[0019] (6) Convert secoisolariciresinol diglucoside (SDG) to enterodiol (END).

[0020] Furthermore, the application is as follows: Add secoisolariciresinol diglucoside (SDG) to the culture medium, inoculate the culture solution of the Enterococcus faecium, control the initial pH at 7 - 9, culture at a temperature of 30 - 37 °C for 1 - 5 days, and obtain secoisolariciresinol (SECO), demethylsecoisolariciresinol, demethyldehydroxysecoisolariciresinol, secoisolariciresinol monoglucoside (SMG), dihydroxyenterolactone (DHENL) and / or enterodiol (END) from the culture solution.

[0021] The culture medium is preferably any one of LB, BHI, and MRS sugar-free broth.

[0022] The initial concentration of secoisolariciresinol diglucoside (SDG) in the culture medium is 0.125 - 0.5 mmol / L.

[0023] In the above application, the culture is carried out in a facultative anaerobic manner.

[0024] The application of the above Enterococcus faecium or biological agent in the preparation of nutritionally fortified foods.

[0025] Furthermore, the foods include but are not limited to milk.

[0026] Furthermore, the application is as follows: Add secoisolariciresinol diglucoside (SDG) to the food, inoculate the culture solution of the Enterococcus faecium, and culture at a temperature of 30 ± 0.5 °C for 3 ± 0.5 days to obtain a lignan-fortified food.

[0027] Furthermore, the content of secoisolariciresinol diglucoside (SDG) in the food is 0.125 - 0.5 mmol / L.

[0028] The Enterococcus faecium ZB26 described in the present invention was screened from fermented soy products.

[0029] When the Enterococcus faecium ZB26 described in the present invention is inoculated into a sugar-free LB liquid medium supplemented with secoisolariciresinol diglucoside (SDG) extract, it can convert SDG into enterodiol (END) and intermediate metabolites such as secoisolariciresinol monoglucoside (SMG), secoisolariciresinol (SECO), demethylsecoisolariciresinol, demethyldehydroxysecoisolariciresinol, and dehydrodiconiferyl alcohol 9-O-β-D-glucopyranoside (DHENL).

[0030] When the Enterococcus faecium ZB26 described in the present invention is cultured in a sugar-free LB / BHI / MRS liquid medium supplemented with secoisolariciresinol diglucoside (SDG) extract, the conversion rate of SDG reaches over 90%, the production rate of SECO reaches over 80%, and mammalian lignan END is produced.

[0031] Using fresh milk as the medium and secoisolariciresinol diglucoside (SDG) extract as the substrate, the Enterococcus faecium ZB26 described in the present invention catalyzes the conversion of SDG into SECO, and the conversion rate of SDG reaches 10%-20%.

[0032] The present invention has the following advantages and effects compared with the prior art:

[0033] 1. The Enterococcus faecium ZB26 of the present invention is derived from traditional Chinese fermented soy products, has the ability to tolerate high temperature, salt, and bile, has no hemolytic property, and is a facultative anaerobic lactic acid bacterium, which is convenient for production and use.

[0034] 2. The liquid fermentation method for converting SDG of the present invention has the ability to efficiently convert SDG in secoisolariciresinol diglucoside (SDG) extract, and realizes the conversion of a single strain from SDG to mammalian lignan END.

[0035] 3. In the liquid fermentation method for converting SDG of the present invention, in an LB / BHI / MRS sugar-free broth, when the SDG concentration is 0.125 - 0.5 mmol / L, the initial pH is 7 - 9, the culture temperature is 30 - 37°C, and facultative anaerobic culture is carried out for 1 - 5 days, the conversion rate of SDG reaches 90% and above, it can be efficiently converted into SECO, and mammalian lignan END can be produced. The production rate of SECO reaches over 80%, and the production rate of END is 0.66% - 3.91%.

[0036] 4. The Enterococcus faecium ZB26 of the present invention has the ability to convert the main component SDG in the flaxseed lignan extract into mammalian lignans END, as well as intermediate metabolites such as SMG, SECO, demethylated SECO, demethylated dehydroxylated SECO, and DHENL, thereby obtaining a flaxseed lignan product with high bioavailability.

[0037] 5. The present invention uses fresh milk as a medium, adds flaxseed lignan extract, inoculates Enterococcus faecium ZB26 for fermentation, and cultivates at 30 °C for 3 days at an SDG concentration of 0.05 - 0.5 mmol / L to obtain a lignan-enriched fermented food, and the SDG conversion rate reaches about 10 - 20%. Description of the Drawings

[0038] Figure 1 It is a graph showing the observation result of the growth morphology of Enterococcus faecium ZB26 on an LB plate.

[0039] Figure 2 It is a graph showing the observation result of the morphology of Enterococcus faecium ZB26 under a microscope.

[0040] Figure 3 It is a graph showing the hemolytic assay result of Enterococcus faecium ZB26 on a blood plate.

[0041] Figure 4 It is a liquid chromatography graph of the conversion of SDG by Enterococcus faecium ZB26 in liquid fermentation in Example 3.

[0042] Figure 5 It is a liquid chromatography graph of the conversion of SDG by Enterococcus faecium ZB26 in fresh milk in Example 2.

[0043] Figure 6 It is a graph of qualitative analysis of the conversion of SDG by Enterococcus faecium ZB26 in liquid fermentation by LC-HRMSMS in Example 5. Detailed Embodiments

[0044] The present invention will be further described in detail below with reference to the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0045] The specific operation of the liquid phase detection method involved in the following embodiments is as follows:

[0046] Chromatographic column: Titank C18 5u organic silica hybrid chromatographic column (250*4.6mm); Mobile phase: Phase A is ultrapure water containing 0.1% glacial acetic acid, and Phase D is chromatographic grade acetonitrile; Detection wavelength: 280nm; Elution gradient: At 0 min, the proportion of Phase D is 10%, within 20 min, the proportion of Phase D linearly increases to 20%, from 20 - 50 min, the proportion of Phase D increases to 80%, and is balanced at 80% until 55 min, the proportion of Phase D drops to 10%, and is balanced at 10% until 60 min; Flow rate: 0.5 mL / min; Column temperature: 30 °C; Injection volume: 10 μL.

[0047] The liquid phase conditions of the liquid chromatography - mass spectrometry detection method are the same as the above - mentioned liquid chromatography detection method, and the time - of - flight high - resolution mass spectrometry SCIEXX500RQTOF is selected.

[0048] Example 1: Isolation and identification of Enterococcus faecium ZB26

[0049] Weigh 10 g of the by - product flaxseed cake remaining after oil extraction from crushed flaxseeds, add 2 times the weight of mashed fermented soy products, add 20 times the volume of sterile physiological saline, and culture at 37 °C for 3 weeks to obtain a mixed fermentation culture solution. Screen for lignan - converting bacteria from the mixed fermentation culture solution. The above fermentation culture solution is separated and screened using a sugar - free LB plate supplemented with SDG polymer, and single colonies are obtained by repeated streaking separation and microscopic examination.

[0050] Morphological characteristic analysis: As Figure 1 and Figure 2 shown, the colonies on the LB plate are white, round, opaque, with neat edges, smooth surface without wrinkles, and the microscopic cell morphology is spherical.

[0051] Physiological and biochemical analysis: The strain is a Gram - positive bacterium without spores, and can grow in 50 °C, 6.5% high - salt broth, and 40% bile broth, with the ability to tolerate high temperature, salt, and bile; As Figure 3 shown, there is no hemolysis phenomenon on the blood agar plate, and it does not have hemolytic property. The physiological and biochemical identification results are shown in Table 1.

[0052] Table 1. Physiological and biochemical identification results of the strain

[0053]

[0054] 16S rDNA analysis: The strain was inoculated into LB liquid medium and cultured for 16 - 18 h until the logarithmic phase, then a bacterial suspension was prepared. The genomic DNA of the strain was extracted according to the operation instructions of the TSINGKE Plant DNA Extraction Kit (Universal Type). The genomic DNA obtained was used as a template for PCR amplification of the 16S rDNA fragment, and the sequencing was completed by Beijing Tsingke Biotechnology Co., Ltd., Guangzhou Branch (the sequencing primers were 27F / 1492R). The obtained 16S rDNA sequence was subjected to Blast alignment in the Gene Bank database and had more than 99.9% homology with Enterococcus faecium strain HBUAS664649. Combining the morphological characteristics and the results of physiological and biochemical experiments, this strain was identified as Enterococcus faecium and named Enterococcus faecium ZB26.

[0055] 16S rDNA sequence:

[0056]

[0057] Example 2: Application of Enterococcus faecium ZB26 in converting SDG to produce mammalian lignans END and producing nutritionally enhanced foods

[0058] The above strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium and cultured for 18 h to obtain a seed solution. The above seed solution was inoculated into 5 mL of sugar-free LB broth supplemented with 0.125 mmol / L SDG, with an initial pH of 7.0, and cultured facultatively anaerobically at 37°C for 5 d. The supplemented SDG was flaxseed lignan extract containing 20% SDG (the supplementation amount was calculated according to the concentration of SDG in the medium being 0.125 mmol / L). The control was 5 mL of medium without SDG and 5 mL of non-inoculated medium containing SDG, cultured at 37°C. The product was centrifuged at 10,000 rpm for 10 min at 4°C, and the supernatant was detected for SDG, SMG, SECO, and END by HPLC; other metabolites were extracted with ethyl acetate and rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS. The SDG conversion rate reached 91.50%, the SECO production rate reached 83.59%, END was produced, and the production rate was 2.60%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethylated dehydroxylated SECO, and DHENL.

[0059] The above strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium and cultured for 18 h to obtain a seed solution. The above seed solution was inoculated into fresh milk supplemented with 0.5 mmol / L SDG and cultured at 30°C for 3 d. The supplemented SDG was flaxseed lignan extract containing 20% SDG. The product was extracted with acetonitrile-water and centrifuged at 13,000 rpm for 10 min at 4°C to obtain a supernatant, and the contents of SDG, SMG, and SECO in the product were analyzed by HPLC. The SDG conversion rate reached 12.55%.

[0060] Example 3: Application of Enterococcus faecium ZB26 in converting SDG to produce mammalian lignans END and producing nutritionally enhanced foods

[0061] The above-mentioned strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into 5 mL of sugar-free LB broth supplemented with 0.5 mmol / L SDG, with an initial pH of 7.0, and cultured facultatively anaerobically at 37 °C for 5 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The controls were 5 mL of medium without SDG and 5 mL of non-inoculated medium containing SDG, cultured at 37 °C. The product was centrifuged at 10,000 rpm for 10 min at 4 °C, and the supernatant was detected for SDG, SMG, SECO, and END by HPLC; other metabolites were extracted with ethyl acetate and rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS; the SDG conversion rate reached 90.73%, the SECO production rate reached 96.71%, END was produced, and the production rate was 3.91%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethyldehydroxy SECO, and DHENL.

[0062] The above-mentioned strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into fresh milk supplemented with 0.05 mmol / L SDG and cultured at 30 °C for 3 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The product was extracted with acetonitrile-water and centrifuged at 13,000 rpm for 10 min at 4 °C to obtain the supernatant, and the contents of SDG, SMG, and SECO in the product were analyzed by HPLC. The SDG conversion rate reached 17.35%.

[0063] Example 4: Application of Enterococcus faecium ZB26 in converting SDG to produce mammalian lignan END and producing nutritionally fortified foods

[0064] The above-mentioned strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into 5 mL of sugar-free LB broth supplemented with 0.5 mmol / L SDG, with an initial pH of 9.0, and cultured facultatively anaerobically at 30 °C for 5 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The controls were 5 mL of medium without SDG and 5 mL of non-inoculated medium containing SDG, cultured at 30 °C. The product was centrifuged at 10,000 rpm for 10 min at 4 °C, and the supernatant was detected for SDG, SMG, SECO, and END by HPLC; other metabolites were extracted with ethyl acetate and rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS; the SDG conversion rate reached 96.45%, the SECO production rate reached over 91.95%, END was produced, and the production rate was 1.17%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethyldehydroxy SECO, and DHENL.

[0065] The above strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above seed solution was inoculated into fresh milk supplemented with 0.15 mmol / L SDG, and cultured at 30 °C for 3 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The product was extracted with acetonitrile and water, centrifuged at 13000 rpm for 10 min at 4 °C to obtain the supernatant, and the contents of SDG, SMG and SECO in the product were analyzed by HPLC. The SDG conversion rate reached 13.51%.

[0066] Example 5: Application of Enterococcus faecium ZB26 in converting SDG to produce mammalian lignan END and producing nutritionally fortified foods

[0067] The above strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above seed solution was inoculated into 5 mL of sugar-free LB broth supplemented with 0.5 mmol / L SDG, with an initial pH of 8.0, and cultured at 30 °C under facultative anaerobic conditions for 1 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The control was 5 mL of a medium without SDG and 5 mL of a non-inoculated medium containing SDG, cultured at 30 °C. The product was centrifuged at 10000 rpm for 10 min at 4 °C, and the supernatant was detected for SDG, SMG, SECO and END by HPLC; other metabolites were extracted with ethyl acetate, rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS; the SDG conversion rate could reach 91.74%, the SECO production rate reached 94.89%, END was produced, and the production rate was 2.69%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethyldehydroxy SECO, and DHENL.

[0068] The above strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above seed solution was inoculated into fresh milk supplemented with 0.2 mmol / L SDG, and cultured at 30 °C for 3 d. The supplemented SDG was a flaxseed lignan extract containing 20% SDG. The product was extracted with acetonitrile and water, centrifuged at 13000 rpm for 10 min at 4 °C to obtain the supernatant, and the contents of SDG, SMG and SECO in the product were analyzed by HPLC. The SDG conversion rate reached 16.44%.

[0069] Example 6: Application of Enterococcus faecium ZB26 in converting SDG to produce mammalian lignan END and producing nutritionally fortified foods

[0070] The above-mentioned strain was streaked and isolated on a BHI plate, and a single colony was picked and inoculated into a BHI broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into 5 mL of sugar-free BHI broth supplemented with 0.25 mmol / L SDG, with an initial pH of 7.4, and cultured at 37 °C under facultative anaerobic conditions for 5 d. The supplemented SDG was an extract of flaxseed lignans containing 20% SDG. The controls were 5 mL of medium without SDG and 5 mL of non-inoculated medium containing SDG, cultured at 37 °C. The product was centrifuged at 10,000 rpm for 10 min at 4 °C, and the supernatant was detected for SDG, SMG, SECO, and END by HPLC; other metabolites were extracted with ethyl acetate, rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS; the SDG conversion rate could reach 92.75%, the SECO production rate could reach 84.57%, END was produced, and the production rate was 2.85%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethyldehydroxy SECO, and DHENL.

[0071] The above-mentioned strain was streaked and isolated on an LB plate, and a single colony was picked and inoculated into an LB broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into fresh milk supplemented with 0.25 mmol / L SDG and cultured at 30 °C for 3 d. The supplemented SDG was an extract of flaxseed lignans containing 20% SDG. The product was extracted with acetonitrile-water, centrifuged at 13,000 rpm for 10 min at 4 °C to obtain a supernatant, and the contents of SDG, SMG, and SECO in the product were analyzed by HPLC. The SDG conversion rate reached 20.41%.

[0072] Example 7: Application of Enterococcus faecium ZB26 in the conversion of SDG to produce mammalian lignan END

[0073] The above-mentioned strain was streaked and isolated on an MRS plate, and a single colony was picked and inoculated into an MRS broth medium for culturing for 18 h to obtain a seed solution. The above-mentioned seed solution was inoculated into 5 mL of sugar-free MRS broth supplemented with 0.5 mmol / L SDG, with an initial pH of 8.0, and cultured at 30 °C under facultative anaerobic conditions for 3 d. The supplemented SDG was an extract of flaxseed lignans containing 20% SDG. The controls were 5 mL of medium without SDG and 5 mL of non-inoculated medium containing SDG, cultured at 30 °C. The product was centrifuged at 10,000 rpm for 10 min at 4 °C, and the supernatant was detected for SDG, SMG, SECO, and END by HPLC; other metabolites were extracted with ethyl acetate, rotary evaporated to obtain a concentrate, dissolved in methanol, and detected by LC-HRMSMS; the SDG conversion rate could reach 93.38%, the SECO production rate could reach 83.95%, END was produced, and the production rate was 0.66%. The product also contained intermediate metabolites such as SMG, demethylated SECO, demethyldehydroxy SECO, and DHENL.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the described embodiments. Any other changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A strain of Enterococcus faecium, characterized in that: Named Enterococcus faecium ZB26, it was deposited on June 14, 2022 at the Guangdong Provincial Microbial Culture Collection Center, Building 59, No. 100 Yard, Xianlie Middle Road, Yuexiu District, Guangzhou City, Guangdong Province, with the deposit number: GDMCC No. 62548.

2. A biological bacterium agent with the activity of biotransforming secoisolariciresinol diglucoside, characterized in that: Containing the cells or culture broth of Enterococcus faecium described in claim 1.

3. The biological bactericide with secoisolariciresinol biotransformation activity according to claim 2, characterized in that: The culture broth of the Enterococcus faecium is prepared by the following method: Streak and isolate the Enterococcus faecium on an LB plate, pick a single colony and inoculate it into an LB broth medium and culture for 18±2 h to obtain the culture broth.

4. Application of the Enterococcus faecium described in claim 1 or the biological bactericide described in any one of claims 2-3 in the biotransformation of secoisolariciresinol.

5. The application according to claim 4, wherein: The application is for the application in the deglucosylation, demethylation and / or dehydroxylation transformation of secoisolariciresinol.

6. The application according to claim 5, characterized in that: The application is one or more of the following applications: (1) Transforming secoisolariciresinol diglucoside SDG to produce secoisolariciresinol SECO; (2) Transforming secoisolariciresinol diglucoside SDG to produce demethylated SECO; (3) Transforming secoisolariciresinol diglucoside SDG to produce demethylated and dehydroxylated SECO; (4) Transforming secoisolariciresinol diglucoside SDG to produce secoisolariciresinol monoglucoside SMG; (5) Transforming secoisolariciresinol diglucoside SDG to produce dihydroxyenterolactone DHENL; (6) Transforming secoisolariciresinol diglucoside SDG to produce enterodiol END.

7. The application according to claim 6, characterized in that: The application is: Add secoisolariciresinol diglucoside SDG to the medium, inoculate the culture broth of the Enterococcus faecium, control the initial pH to 7-9, culture at a temperature of 30-37 °C for 1-5 d, and obtain secoisolariciresinol SECO, demethylated SECO, demethylated and dehydroxylated SECO, secoisolariciresinol monoglucoside SMG, dihydroxyenterolactone DHENL and / or enterodiol END from the culture broth.

8. The application according to claim 7, characterized in that: The medium is any one of LB, BHI, and MRS sugar-free broth; The initial concentration of secoisolariciresinol diglucoside SDG in the medium is 0.125-0.5 mmol / L; In the application, the culture is carried out in a facultative anaerobic manner.

9. Application of the Enterococcus faecium described in claim 1 or the biological bactericide described in any one of claims 2-3 in the preparation of nutritionally fortified foods.

10. The application according to claim 9, characterized in that: The food is milk The application is: Add secoisolariciresinol diglucoside SDG to the food, inoculate the culture broth of the Enterococcus faecium, and culture at a temperature of 30±0.5 °C for 3±0.5 d to obtain a lignan-fortified food; The content of secoisolariciresinol diglucoside (SDG) in the described food is 0.125 - 0.5 mmol / L.

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