Lactobacillus paracasei for promoting dissolution of low-molecular-weight araboxylan of barley and application of lactobacillus paracasei

Abstract

The invention discloses a lactobacillus paracasei for promoting dissolution of barley low-molecular-weight arabinoxylan and application of the lactobacillus paracasei, the lactobacillus paracasei Pro1 has the Tibetan number of GDMCC No: 64957, the lactobacillus paracasei can promote dissolution of water-soluble arabinoxylan (WEAX) in barley bran (the dissolution improvement rate is 287%), and the dissolved WEAX has the characteristic of low molecular weight (reduced from 168150 to 6038); the lactobacillus paracasei Pro1 encodes a rich carbohydrate metabolic enzyme system and can improve the activity of xylanase in a barley bran fermentation system; compared with the non-fermented WEAX, the WEAX obtained by fermenting the lactobacillus paracasei Pro1 has better solubility, water holding capacity, swelling property, oil holding capacity, emulsibility, foamability and free radical scavenging capacity. The lactobacillus paracasei Pro1 can be used for preparing barley low-molecular-weight WEAX, and the obtained WEAX is remarkably improved in the aspects of processing characteristics, biological functions and the like and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of functional microorganisms, and particularly relates to a Lactobacillus paracasei strain that promotes the dissolution of low-molecular-weight arabinoxylan from barley and an application thereof. Background Art

[0002] Arabinoxylan (AX) is a complex dietary fiber found in grasses. AX consists of a main chain skeleton of β-D-pyranose residues, with several α-L-arabinofuranosyl substituents connected by C(O)-2, C(O)-3 or C(O)-2,3 bonds, and contains a certain amount of ferulic acid groups. AX has a variety of health benefits, including regulating the body's metabolic level and reducing the incidence of chronic diseases.

[0003] Barley (Hordeum vulgare L.) is rich in dietary fiber, polyphenols, vitamins and other bioactive substances. It is a whole grain food raw material with great development potential and application prospects. AX is present in barley bran at a high content, accounting for about 20% of the dry weight of bran. AX in barley can be further divided into water-soluble arabinoxylan (WEAX) and insoluble arabinoxylan (WUAX). The physiological functions and processing characteristics of AX are closely related to its structural characteristics. Studies have shown that WEAX has stronger physiological functions and processing characteristics than WUAX. Among them, low molecular weight WEAX is more easily utilized by the body and microbial communities than high molecular weight WEAX, and its biological activity is most prominent.

[0004] Microbial fermentation is a common biotransformation method with the advantages of low cost, controllability, and clear transformation pathways. In recent years, microbial fermentation technology has been increasingly used in the development and utilization of bioactive substances in barley. Microbial strains play a decisive role in whether the food fermentation process can be carried out efficiently. However, there is currently a lack of relevant strains and fermentation technologies that can effectively improve the low molecular weight WEAX of barley. Lactobacillus paracasei is a Gram-positive lactic acid bacterium. The National Health Commission issued the "List of Bacteria that Can Be Used in Food" in 2022, which includes all strains of Lactobacillus paracasei. Therefore, as a safe food-grade microorganism, Lactobacillus paracasei has broad application prospects in the food industry. Studies have shown that Lactobacillus paracasei can be used for solid-state fermentation of wheat bran, and significantly reduced the pH value of fermented wheat bran and increased the levels of lactic acid, acetic acid, and butyric acid in the fermentation broth (DOI: 10.1021 / acs.jafc.4c02423). However, there are no reports on the effect of Lactobacillus paracasei fermentation on barley WEAX. Summary of the invention

[0005] In view of the above-mentioned problem of bioconversion of water-soluble arabinoxylan (WEAX) in barley, especially low molecular weight WEAX, the present invention provides a strain of Lactobacillus paracasei that promotes the dissolution of low molecular weight WEAX in barley and its application. The specific technical scheme is as follows:

[0006] Firstly, the present invention provides a strain of Lactobacillus paracasei which can promote the dissolution of low molecular weight WEAX of barley. The strain is named Lactobacillus paracasei Pro1 and its deposit number is GDMCC No: 64957.

[0007] The aforementioned Lactobacillus paracasei can form obvious colonies with a diameter of 0.5 to 2 mm when cultured at 37°C in an aerobic or anaerobic environment for 36 hours. The colonies are round in shape from the front and convex in shape from the side, with neat edges, creamy white, opaque, moist and smooth surface, and do not produce pigment.

[0008] The aforementioned Lactobacillus paracasei strain encodes 301 carbohydrate metabolism-related genes, including 64 glycoside hydrolase genes and 42 glycosyltransferase genes.

[0009] The aforementioned Lactobacillus paracasei is cultured in MRS medium at 37°C under aerobic or anaerobic conditions for 16 hours to reach the end of the logarithmic phase.

[0010] Secondly, the present invention provides an application of the aforementioned Lactobacillus paracasei, which can be used specifically for barley bran fermentation, can improve the xylanase activity in the fermented barley bran liquid, can increase the dissolution amount of WEAX in the barley bran, and can reduce the molecular weight of WEAX, and improve the solubility, water holding capacity, swelling capacity, oil holding capacity, emulsification, foaming property and free radical scavenging ability of WEAX

[0011] As a preferred technical solution, the application of the aforementioned Lactobacillus paracasei comprises the following steps:

[0012] 1) separating the barley bran to remove the palea husk, sieving, and sterilizing by ultraviolet light for later use;

[0013] 2) culturing the frozen Lactobacillus paracasei Pro1 to the logarithmic phase, removing the supernatant by centrifugation, and resuspending the culture solution with physiological saline for later use;

[0014] 3) mixing the bacterial liquid prepared in step 2) with the barley bran prepared in step 1) and distilled water in a certain proportion to form a fermentation material for fermentation;

[0015] 4) fermenting the fermented material mixed in step 3) in a shaking table at 31° C. and 220 rpm for 24 hours to obtain fermented barley bran;

[0016] 5) After the fermentation is completed, the fermented barley bran is sterilized in a water bath, cooled and centrifuged to obtain the fermented barley bran liquid.

[0017] As a further preferred technical solution, in step 2), the specific preparation method of the bacterial solution is: inoculate the frozen Lactobacillus paracasei Pro1 into MRS medium, and culture it anaerobically at 37°C to the end of the logarithmic phase so that the number of viable bacteria reaches 3×10 9 CFU / mL. Centrifuge at 8000rpm for 10min to obtain the bacteria, and resuspend them in distilled water to obtain the bacterial solution.

[0018] As a further preferred technical solution, in step 3), the bacterial liquid, barley bran and distilled water are mixed in a ratio of volume: mass: volume of 1:4:28.

[0019] As a further preferred technical solution, in step 5), the barley bran fermentation product is processed by heating the fermented barley bran in a water bath at 85° C. for 15 minutes, cooling to room temperature, and centrifuging at 8000 rpm for 15 minutes to obtain fermented barley bran liquid.

[0020] The above application of Lactobacillus paracasei, compared with the unfermented barley bran supernatant, in the fermented barley bran liquid:

[0021] Xylanase activity increased by 153%;

[0022] The dissolution improvement rate of WEAX was 287%;

[0023] The molecular weight of WEAX decreased from 168150 to 6038;

[0024] The solubility improvement of WEAX was 18%;

[0025] WEAX water holding capacity increase rate is 50%;

[0026] The WEAX swelling improvement rate is 19%;

[0027] WEAX oil retention increased by 36%.

[0028] The beneficial effects of the present invention are:

[0029] 1) The Lactobacillus paracasei Pro1 of the present invention can promote the dissolution of WEAX in barley bran (the dissolution amount improvement rate is 287%), and the dissolved WEAX has a low molecular weight characteristic (reduced from 168150 to 6038). Lactobacillus paracasei Pro1 encodes a rich carbohydrate metabolism enzyme system and can improve the enzymatic activity of xylanase in the barley bran fermentation system. Compared with unfermented WEAX, the WEAX obtained by fermentation of Lactobacillus paracasei Pro1 has better solubility, water retention, swelling, oil retention, emulsification, foaming and free radical scavenging ability. The Lactobacillus paracasei Pro1 can be used to prepare low-molecular-weight WEAX of barley, and the obtained WEAX is significantly improved in processing characteristics, biological functions, etc., and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the colony morphology of Lactobacillus paracasei Pro1 of the present invention;

[0031] Figure 2 COG functional classification diagram of the gene function annotation of Lactobacillus paracasei Pro1 of the present invention;

[0032] Figure 3 It is a functional classification of carbohydrate active enzymes of Lactobacillus paracasei Pro1 of the present invention and a statistical diagram of the corresponding gene quantity.

[0033] Figure 4 The effect of Lactobacillus paracasei Pro1 of the present invention on the WEAX content in the supernatant of fermented barley bran;

[0034] Figure 5 The effect of the xylanase activity in the supernatant of barley bran fermented by Lactobacillus paracasei Pro1 of the present invention;

[0035] Figure 6 The effect of Lactobacillus paracasei Pro1 of the present invention on the solubility of WEAX in barley bran;

[0036] Figure 7 The effect of Lactobacillus paracasei Pro1 of the present invention on the water holding capacity of WEAX in barley bran;

[0037] Figure 8 The effect of Lactobacillus paracasei Pro1 of the present invention on the swelling property of WEAX in barley bran;

[0038] Fig. 9 The effect of Lactobacillus paracasei Pro1 of the present invention on the oil retention of WEAX in barley bran;

[0039] Fig.10 The effect of Lactobacillus paracasei Pro1 of the present invention on the free radical scavenging ability of WEAX in barley bran;

[0040] Note: * indicates that Pro1 has significant difference compared with the control group (p<0.05).

[0041] a, b indicate that the groups represented by different letters have significant differences (p<0.05).

[0042] Control is the supernatant of unfermented barley bran, Pro1 is the supernatant of fermented barley bran, FAX is the water-soluble arabinoxylan in fermented barley bran, and RAX is the water-soluble arabinoxylan in unfermented barley bran. Three parallel samples were prepared for each sample for detection and statistical analysis. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0044] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0045] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0046] Example 1

[0047] The present embodiment provides a strain of Lactobacillus paracasei Pro1, which was deposited on August 5, 2024 in the Guangdong Provincial Microbiological Culture Collection Center, located at the 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, Guangdong Institute of Microbiology, with a deposit number of GDMCC No: 64957.

[0048] The Lactobacillus paracasei Pro1 described in this embodiment has the following biological characteristics:

[0049] (1) Bacterial characteristics: Gram-positive, non-spore-forming, non-motile bacteria.

[0050] (2) Colony characteristics: After 36 hours of aerobic or anaerobic culture, distinct colonies are formed, with a diameter of 0.5 to 2 mm, a round shape on the front, a protruding shape on the side, neat edges, creamy white, opaque, moist and smooth surface, and no pigment. See Appendix Figure 1 .

[0051] (3) Growth characteristics: The cells reached the late logarithmic phase after being cultured in MRS medium at 37°C under aerobic or anaerobic conditions for about 16 h.

[0052] The Lactobacillus paracasei Pro1 belongs to the genus Lactobacillus. The "List of Bacteria Species that Can Be Used in Food" issued by the National Health Commission of the People's Republic of China on August 18, 2022 approved the genus Lactobacillus as a species of bacteria that can be used in food.

[0053] Based on the whole genome sequencing results, gene function annotation of Lactobacillus paracasei Pro1 was performed. Figure 2 And attached Figure 3 The results showed that Lactobacillus paracasei Pro1 had 301 carbohydrate metabolism-related genes, including 64 glycoside hydrolases and 42 glycosyltransferases. The above results showed that Lactobacillus paracasei Pro1 had the potential to hydrolyze and promote the dissolution of AX.

[0054] Example 2

[0055] In this example, the Lactobacillus paracasei Pro1 described in Example 1 was used to ferment the fermented barley bran to prepare the fermented barley bran liquid. The details are as follows:

[0056] The barley bran is passed through a 30-mesh sieve, the husk is separated and removed, and then passed through an 80-mesh sieve to obtain the barley bran, which is then sterilized by ultraviolet light.

[0057] The frozen Lactobacillus paracasei Pro1 was inoculated into MRS medium and cultured anaerobically at 37°C for 12 h. It was then subcultured in MRS medium for 12 h. The bacterial solution was centrifuged at 8000 rpm for 10 min, the supernatant was removed, and the bacteria were resuspended in physiological saline to a viable count of 3 × 10 9 CFU / mL. The obtained bacterial suspension was mixed with barley bran and distilled water in a ratio of 1:4:28 (v / w / v). Fermented at 31°C, 220rpm shaker for 24h. After fermentation, sterilized in a water bath at 85°C for 15min, cooled at room temperature, and centrifuged at 8000r / min for 15min to obtain fermented barley bran liquid.

[0058] Example 3

[0059] This example investigates the effect of Lactobacillus paracasei Pro1 on the WEAX content in fermented barley bran liquid. The WEAX content in the fermentation supernatant was determined by the phloroglucinol method, and unfermented barley bran liquid was used as a control.

[0060] The preparation method of unfermented barley bran liquid is as follows: barley bran and distilled water are mixed in a ratio of 1:7 (w / v), shaken on a shaker at 31°C and 220 rpm for 24 hours, sterilized and cooled, and centrifuged at 8000 rpm for 15 minutes to obtain unfermented barley bran liquid for later use.

[0061] The specific detection methods are as follows:

[0062] Respectively draw 2mL of the fermented barley bran liquid and the unfermented barley bran liquid in Example 2 in a test tube, respectively add 10mL of reaction solution (2g phloroglucinol, 10mL anhydrous ethanol, 110mL glacial acetic acid, 2mL concentrated hydrochloric acid, 1mL glucose solution with a concentration of 17.5g / L, prepared and used), mix well and boil in a water bath for 25min, and cool immediately after the reaction ends. Determine the absorbance at a wavelength of 552nm and 510nm, and make the difference between the two. Accurately draw 0.00mL, 0.25mL, 0.50mL, 0.75mL, 1.00mL, 1.25mL, and 1.50mL of 1mg / mL xylose standard solution in a test tube, respectively, and the operating steps are the same as above. After measuring the absorbance, a standard curve of WEAX content can be drawn.

[0063] The experimental results are as attached Figure 4 As shown, the WEAX content in the fermented barley bran supernatant (0.46 mg / mL) was significantly higher than that in the unfermented barley bran supernatant (1.32 mg / mL), and the WEAX dissolution rate was increased to 287% of the original.

[0064] Example 4

[0065] This example investigates the effect of Lactobacillus paracasei Pro1 on the molecular weight of WEAX in barley bran. Unfermented barley bran liquid was used as a control sample. The preparation method of unfermented barley bran liquid was the same as that of Example 3.

[0066] In the present embodiment, the extraction method of WEAX in barley bran is as follows:

[0067] ① Weigh 100 g of the fermented barley bran in Example 2, add distilled water at a ratio of 1:10 (w / v), reflux with 85% ethanol for 2 h, cool at room temperature, centrifuge at 8000 rpm for 15 min, discard the supernatant, and dry the bran.

[0068] ② Weigh 100g of dried and fermented barley bran, add distilled water at a ratio of 1:10 (w / v), extract in a hot water bath at 85℃ for 2h, cool at room temperature, centrifuge at 8000rpm for 15min, collect the supernatant, repeat three times, and combine the supernatants.

[0069] ③Take 1000mL of supernatant, adjust pH to 6.5, add 20μL / g of thermostable α-amylase (2100U / g), react in 95℃ water bath for 2h, and cool at room temperature. Adjust pH to 4.3, add 1μL / g saccharifying enzyme (100000U / mL), react in 60℃ water bath for 1h, and cool at room temperature. Adjust pH to 6.7, add 15mg / g protease (2000U / mg), react in 60℃ water bath for 1h, boil for 20min to kill enzyme, cool at room temperature, centrifuge at 8000rpm for 15min, and retain supernatant.

[0070] ④ Appropriately concentrate 1000mL of supernatant, slowly add 95% ethanol (final ethanol concentration is 80%), and stir thoroughly. Stand at 4℃ overnight, centrifuge at 8000rpm for 15min, and collect the precipitate. Wash the precipitate three times with anhydrous ethanol and acetone respectively, re-dissolve the precipitate with distilled water, centrifuge at 8000rpm for 15min after sufficient dissolution, and discard the precipitate.

[0071] ⑤ Place the reconstituted WEAX extract in a 12 kDa dialysis bag and place it in a 4°C refrigerator for 72 hours, replacing distilled water every 12 hours. Freeze-dry the extract in the dialysis bag to obtain barley bran WEAX.

[0072] The WEAX molecular weight determination method is as follows:

[0073] Accurately weigh 1 g of WEAX sample, prepare a 1.0 mg / mL solution with the mobile phase (0.1 M sodium nitrate solution), filter it with a 0.22 μm filter membrane and inject it into an injection vial. Use high performance gel filtration chromatography (HPGFC) to analyze the molecular weight and distribution, gyration radius and intrinsic viscosity of the polysaccharide sample.

[0074] Chromatographic analysis conditions: mobile phase is 0.1M sodium nitrate solution, flow rate is controlled at 0.9mL / min; column and detector temperature are both 45.0±0.5℃. Chromatographic column: Ultrahydrogel TM Linear 300mm×7.8mmid×2. Instrument Waters1525 high performance liquid chromatograph (equipped with 2414 differential refractometer and Empower3 workstation). The experimental results are shown in Table 1.

[0075] Table 1. Molecular weights of RAX and FAX

[0076]

[0077] As can be seen from Table 1, the molecular weight of water-soluble arabinoxylan (RAX) in unfermented barley bran is 168150, and the molecular weight of water-soluble arabinoxylan (FAX) in fermented barley bran is 6038. Fermentation with Lactobacillus paracasei Pro1 reduced the molecular weight of WEAX in barley bran by 27 times compared with that before fermentation.

[0078] Example 5

[0079] This example investigates the effect of Lactobacillus paracasei Pro1 on the xylanase activity in barley bran fermentation liquid. Unfermented barley bran liquid was used as a control sample. The preparation method of unfermented barley bran liquid was the same as that of Example 3.

[0080] In this example, the xylanase activity was determined according to the method of GB / T 23874-2009. The specific method is as follows:

[0081] ① Take 4 mL of acetic acid-sodium acetate buffer solution, add 5 mL of DNS reagent, and heat in a boiling water bath for 5 min. Cool to room temperature with tap water, and dilute to 25 mL with distilled water to prepare a standard blank sample.

[0082] 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL and 7 mL of xylose solution were respectively taken and the volume was made up to 100 mL with acetic acid-sodium acetate buffer solution to prepare xylose standard solutions with concentrations of 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL and 0.7 mg / mL.

[0083] ② Take 2mL of the above concentration series of xylose standard solution and add it to a graduated test tube, then add 2mL of acetic acid-sodium acetate buffer and 5mL of DNS reagent. Electromagnetic oscillation for 3-5s, and heat in a boiling water bath for 5min. Cool to room temperature with tap water, and then dilute to 25mL with distilled water. Use the standard blank sample as a reference to adjust to zero, and measure the absorbance value at 540nm, recorded as A. Draw a standard curve with xylose concentration as the Y axis and A value as the X axis.

[0084] ③Pipette 10mL of xylan solution and equilibrate at 37℃ for 20min. Pipette 10mL of appropriately diluted barley bran fermentation broth and equilibrate at 37℃ for 10min. Add 2mL of the above enzyme solution to a graduated test tube, then add 5mL of DNS reagent and oscillate electromagnetically for 3-5s. Add 2mL of xylan solution, keep warm at 37℃ for 30min, and heat in a boiling water bath for 5min. Cool to room temperature with tap water, add water to make up to 25mL, and oscillate electromagnetically for 3-5s. Use the standard blank sample as the blank control and measure the absorbance AB at 540nm.

[0085] ④ Take 2mL of fermented barley bran liquid with an enzyme activity of 0.04U / mL-0.10U / mL and unfermented barley bran liquid (both have been equilibrated at 37°C), add them to a graduated test tube, then add 2mL of xylan solution (equilibrated at 37°C), electromagnetically oscillate for 3-5s, and keep warm at 37°C for 30min. Add 5mL of DNS reagent and electromagnetically oscillate for 3-5s to terminate the enzymatic reaction. Heat in a boiling water bath for 5min, cool to room temperature with tap water, add distilled water to make up to 25mL, and electromagnetically oscillate for 3-5s. Use the standard blank sample as the blank control and measure the absorbance A at 540nm. E .

[0086] The activity of xylanase in the fermentation broth was calculated according to the following formula:

[0087]

[0088] Where:

[0089] X D is the activity of xylanase in the diluted enzyme solution, U / mL; A E is the absorbance of barley bran fermentation liquid; A B is the absorbance of the enzyme blank sample; K is the slope of the standard curve; C0 is the intercept of the standard curve; M is the molar mass of xylose (150.2 g / mol); t is the enzymatic reaction time.

[0090] The experimental results are as attached Figure 5 As shown, the xylanase activity in the fermented barley bran supernatant (63.91 U / mL) was significantly higher than that in the unfermented barley bran supernatant (25.27 U / mL), with an increase rate of 153%. Combined with the gene function annotation results, the dissolution effect of Lactobacillus paracasei Pro1 on low molecular weight WEAX can be achieved through the xylanase it encodes.

[0091] Example 6

[0092] This example investigates the effect of Lactobacillus paracasei Pro1 on the solubility of WEAX. Unfermented barley bran liquid was used as a control sample. The preparation method of unfermented barley bran liquid was the same as that of Example 3.

[0093] The solubility of WEAX in this example was determined as follows:

[0094] Weigh 1 g of FAX and RAX respectively, dissolve them in 100 mL of distilled water, place them in a water bath at 80°C for 5 min to fully dissolve them, cool them to room temperature, centrifuge them at 5000 rpm, take the supernatant and dry them in an oven at 105°C to constant weight, and calculate according to the following formula:

[0095] Solubility (%) = W0 / W1×100

[0096] Where: W0 is the dry weight of the supernatant / g, W1 is the sample weight / g.

[0097] The experimental results are as attached Figure 6 As shown, fermentation with Lactobacillus paracasei Pro1 can significantly increase the solubility of WEAX in barley bran, and the solubility of WEAX increases from 54.1% to 63.9%, with an increase rate of 18%.

[0098] Example 7

[0099] This example is to investigate the effect of Lactobacillus paracasei Pro1 on the water holding capacity of WEAX. Unfermented barley bran liquid was used as a control sample. The preparation method of unfermented barley bran liquid was the same as that of Example 3.

[0100] The water holding capacity of WEAX in this embodiment is determined as follows:

[0101] Weigh 0.5 g of FAX and RAX respectively, add 20 mL of distilled water to dissolve them, let stand at room temperature for 24 h, centrifuge at 8000 rpm for 10 min, and calculate the water holding capacity according to the following formula:

[0102] Water holding capacity (g / g) = (W1-W0) / W0

[0103] Where: W0 is the mass of the sample before water absorption / g, W1 is the mass of the sample after water absorption / g.

[0104] The experimental results are as attached Figure 7 The results showed that fermentation with Lactobacillus paracasei Pro1 could significantly increase the water holding capacity of WEAX in barley bran from 3.37 g / g to 5.07 g / g, with an increase rate of 50%.

[0105] Example 8

[0106] This example investigates the effect of Lactobacillus paracasei Pro1 on the swelling property of WEAX. Unfermented barley bran liquid is used as a control sample. The preparation method of unfermented barley bran liquid is the same as that of Example 3.

[0107] The swelling property of WEAX in this example is determined as follows:

[0108] Weigh 2.5 g of FAX and RAX respectively into a 100 mL measuring cylinder, add 50 mL of distilled water, tap the wall of the measuring cylinder to eliminate air bubbles, let it stand at room temperature for 24 hours, read the volume of the polysaccharide solution, and calculate the swelling according to the following formula:

[0109] Swelling (mL / g) = (V1-V0) / W

[0110] Where: V0 is the sample volume before water absorption / mL, V1 is the sample volume after water absorption / mL, and W is the sample mass / g.

[0111] The experimental results are as attached Figure 8 As shown, fermentation with Lactobacillus paracasei Pro1 can significantly improve the swelling capacity of WEAX in barley bran, and the swelling capacity of WEAX is increased from 1.66 mL / g to 1.98 mL / g, with an increase rate of 19%.

[0112] Example 9

[0113] This example is to investigate the effect of Lactobacillus paracasei Pro1 on the oil holding capacity of WEAX. Unfermented barley bran liquid was used as a control sample. The preparation method of unfermented barley bran liquid was the same as that of Example 3.

[0114] The oil holding capacity of WEAX in this embodiment is determined as follows:

[0115] Weigh 0.1 g of FAX and RAX respectively, add 1 mL of food-grade blended oil, place at 4 °C for 1 h, centrifuge at 8000 rpm for 10 min, remove the upper layer of grease, and then use filter paper to remove the residual grease in the sample. Calculate the oil retention according to the following formula:

[0116] Oil retention (g / g) = (W1-W0) / W0

[0117] Where: W0 is the mass of the sample before oil absorption / g, W1 is the mass of the sample after oil absorption / g.

[0118] The experimental results are as attached Fig. 9 As shown, fermentation with Lactobacillus paracasei Pro1 can significantly improve the oil holding capacity of WEAX in barley bran, and the oil holding capacity of WEAX is increased from 3.39 g / g to 4.61 g / g, with an increase rate of 36%.

[0119] Example 10

[0120] This example is to investigate the effect of Lactobacillus paracasei Pro1 on the emulsification of WEAX, with unfermented barley bran liquid as a control sample. The preparation method of unfermented barley bran liquid is the same as that of Example 3.

[0121] The emulsification and emulsion stability determination methods of WEAX in this example are as follows:

[0122] Prepare 0.25% (w / v), 0.5% (w / v), and 1% (w / v) RAX and FAX solutions respectively, homogenize at 3000r / min for 2min with a high-speed homogenizer, add 5mL of food-grade blending oil, mix evenly, homogenize for 1min, centrifuge at 5000rpm for 10min, read the volume of the emulsified layer, and calculate the emulsification capacity according to the following formula:

[0123] Emulsifying capacity (%) = V2 / V1×100

[0124] Where: V1 is the total liquid volume / mL, V2 is the emulsion layer volume / mL.

[0125] The emulsified sample was placed in a water bath at 80°C for 30 minutes, cooled for 15 minutes, and centrifuged at 5000 rpm for 5 minutes. The volume of the emulsion layer was recorded, and the emulsion stability was calculated according to the following formula:

[0126] Emulsion stability (%) = V2 / V1×100

[0127] Where: V1 is the original emulsion layer volume / mL, V2 is the emulsion layer volume / mL.

[0128] The experimental results are shown in Table 2.

[0129] Table 2. Emulsification and emulsion stability of RAX and FAX

[0130]

[0131] It can be seen from the results in Table 2 that at different sugar solution concentrations, Lactobacillus paracasei Pro1 can improve the emulsification of WEAX in barley bran.

[0132] Embodiment 11

[0133] This example is to investigate the effect of Lactobacillus paracasei Pro1 on the foaming property of WEAX, with unfermented barley bran liquid as a control sample. The preparation method of unfermented barley bran liquid is the same as that of Example 3.

[0134] The method for determining the foamability and bubble stability of WEAX in this embodiment is as follows:

[0135] 0.25% (w / v), 0.5% (w / v), and 1% (w / v) RAX and FAX solutions were prepared respectively, and 25 mL of RAX or FAX solution of different concentrations was taken into a 50 mL measuring cylinder and stirred at 12000 rpm for 2 min.

[0136] Record the foam volume at the beginning and after 30 minutes, and calculate according to the following formula:

[0137] Foaming capacity (%) = V2 / V1×100

[0138] Foam stability (%) = V3 / V2×100

[0139] Where: V1 is the initial solution volume / mL, V2 is the initial foam volume / mL, and V3 is the foam volume after 30 minutes / mL.

[0140] The experimental results are shown in Table 3.

[0141] Table 3. Foaming properties and foaming stability of RAX and FAX

[0142]

[0143] It can be seen from the results in Table 3 that, at different sugar solution concentrations, Lactobacillus paracasei Pro1 can improve the foaming property of WEAX in barley bran.

[0144] Example 12

[0145] This example investigates the effect of Lactobacillus paracasei Pro1 on the WEAX free radical scavenging ability. Unfermented barley bran liquid is used as a control sample. The preparation method of unfermented barley bran liquid is the same as that of Example 3.

[0146] The method for determining the free radical scavenging ability of WEAX in this embodiment is as follows:

[0147] (1) DPPH free radical scavenging activity

[0148] 2.0 mL of RAX or FAX solution with a concentration of 0.25 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 4 mg / mL was mixed with 2.0 mL of DPPH solution (0.1 mM). The mixture was placed in the dark at room temperature for 30 min, and the absorbance was measured at 517 nm. The scavenging effect of the antioxidant was calculated by the following formula:

[0149] Clearing effect (%) = {1-(A1-A2) / A3}*100%

[0150] Where: A1 is the absorbance of the test sample; A2 is the absorbance of the blank; A3 is the absorbance of the control.

[0151] (2) Total antioxidant (FRAP) capacity determination

[0152] The antioxidant capacity test was performed according to the instructions of the FRAP kit. 180 μL of FRAP working solution was added to a 96-well plate, followed by 5 μL of FeSO4 standard solution of each concentration or 5 μL of RAX or FAX solution of 0.25 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, and 4 mg / mL. The plates were incubated at 37°C for 5 min and the absorbance was measured at 595 nm. The concentrations of the FeSO4 standard solution were 150 μmol / mL, 300 μmol / mL, 600 μmol / mL, 900 μmol / mL, 1200 μmol / mL, and 1500 μmol / mL, and the results were expressed in mmol FeSO4 / g dry weight.

[0153] The experimental results are as attached Fig.10 As shown, under different sugar concentrations, the free radical scavenging ability of FAX was significantly higher than that of RAX, indicating that Lactobacillus paracasei Pro1 can be used to prepare WEAX with better free radical scavenging ability.

[0154] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be covered by the claims of the present invention.

Claims

1. A strain of Lactobacillus paracasei that promotes the dissolution of low molecular weight arabinoxylan from barley, characterized in that: The strain is named Lactobacillus paracasei Pro1, and its deposit number is GDMCC No: 64957.

2. Lactobacillus paracasei according to claim 1, characterized in that: The strain can form obvious colonies after 36 hours of aerobic or anaerobic culture at 37°C. The diameter is between 0.5-2mm, the front shape is round, the side shape is protruding, the edges are neat, creamy white, opaque, the surface is moist and smooth, and no pigment is produced.

3. Lactobacillus paracasei according to claim 1, characterized in that: The strain encodes 301 carbohydrate metabolism-related genes, including 64 glycoside hydrolase genes and 42 glycosyltransferase genes.

4. Lactobacillus paracasei according to claim 1, characterized in that: The strain was cultured in MRS medium at 37°C under aerobic or anaerobic conditions for 16 hours to reach the end of the logarithmic phase.

5. the application of any described Lactobacillus paracasei of claim 1-4, is characterized in that: It can be used for barley bran fermentation, can improve the activity of xylanase in the fermented barley bran liquid, can increase the dissolution amount of water-soluble arabinoxylan (WEAX) in barley bran, and reduce the molecular weight of WEAX, and improve the solubility, water retention, swelling, oil retention, emulsification, foaming and free radical scavenging ability of WEAX.

6. The use according to claim 5, characterized in that: The following steps are involved: 1) Separate the barley bran to remove the husk, sieve it, sterilize it by ultraviolet light, and set aside; 2) Cultivate the frozen Lactobacillus paracasei Pro1 to the logarithmic phase, remove the supernatant by centrifugation, and resuspend it in physiological saline to form a bacterial solution for later use; 3) mixing the bacterial liquid prepared in step 2) with the barley bran prepared in step 1) and distilled water in a certain proportion to form a fermentation material for fermentation; 4) fermenting the fermented material mixed in step 3) in a shaking table at 31° C. and 220 rpm for 24 hours to obtain fermented barley bran; 5) After fermentation, sterilize the fermented barley bran in a water bath, cool and centrifuge to obtain the fermented barley bran liquid.

7. The use according to claim 6, characterized in that: In step 2), the specific preparation method of the bacterial solution is: inoculate the frozen Lactobacillus paracasei Pro1 into MRS medium, and culture it anaerobically at 37°C until the end of the logarithmic phase, so that the number of viable bacteria reaches 3×10 9 CFU / mL; Centrifuge at 8000 rpm for 10 min to obtain bacterial cells, and resuspend them in distilled water to obtain bacterial liquid.

8. The use according to claim 6, characterized in that: The following steps are involved: In step 3), the bacterial liquid, barley bran and distilled water are mixed in a volume: mass: volume ratio of 1:4:

28.

9. The use according to claim 6, characterized in that: In step 5), the fermented barley bran product is processed by heating the fermented barley bran in a water bath at 85° C. for 15 minutes, cooling to room temperature, and centrifuging at 8000 rpm for 15 minutes to obtain the fermented barley bran liquid.

10. The use according to claim 5, characterized in that: Compared with the unfermented barley bran supernatant, the fermented barley bran liquid contained: The xylanase activity improvement rate was 153%; The dissolution improvement rate of WEAX was 287%; The molecular weight of WEAX decreased from 168150 to 6038; The solubility improvement rate of WEAX is 18%; WEAX water holding capacity improvement rate is 50%; The swelling improvement rate of WEAX is 19%; WEAX oil retention rate increased by 36%.

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