Plant lactobacillus YTM3 and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and relates to a plant lactobacillus YTM3 strain and application thereof. The lactobacillus plantarum YTM3 disclosed by the invention is preserved in the China General Microbiological Culture Collection Center on June 5, 2024, and the preservation number of the lactobacillus plantarum YTM3 is CGMCC (China General Microbiological Culture Collection Center) No.30867. The lactobacillus plantarum YTM3 disclosed by the invention has the advantages that the lactobacillus plantarum YTM3 is preserved in the China General Microbiological Culture Collection Center on June 5, 2024; the preservation address is No.3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The lactobacillus plantarum YTM3 is screened from naturally-fermented physalis alkekengi and has high adaptability, and the optimum growth temperature range of the lactobacillus plantarum YTM3 is 19-34 DEG C. The fermented physalis alkekengi prepared by using the strain has low environmental requirements, is suitable for sweet potato starch production, and can effectively play a role in both indoor and outdoor environments during sweet potato starch production (October to November). The fermented physalis alkekengi provided by the invention shows good flocculation activity and stability in the precipitation process of the sweet potato starch, can significantly improve the whiteness of the starch and the content of resistant starch, improves the quality and yield of the sweet potato starch, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and in particular relates to a strain of Lactobacillus plantarum YTM3 and an application thereof. Background Art

[0002] Sweet potato starch is an important raw material for industrial and food processing. It is currently produced mainly through the acid paste method and cyclone separation method. The acid paste method uses the acid paste formed by natural fermentation to promote the rapid aggregation and sedimentation of starch particles through its flocculation activity, and separates from impurities, thereby improving the purity and yield of starch. The acid paste method is particularly suitable for vermicelli processing. The vermicelli produced has high transparency and excellent processing performance. It is the preferred process for starch special for vermicelli.

[0003] However, the production process of the sour starch method relies on natural fermentation, which is affected by factors such as season, climate and operating experience, resulting in unstable sour starch quality, affecting the production efficiency and product quality of starch. At the same time, the existing process mainly focuses on improving starch purity and separation efficiency, and there is insufficient research on optimizing the content of resistant starch in starch. Resistant starch is widely used in the field of functional foods due to its functions of regulating intestinal flora and lowering blood sugar, but the resistant starch content in the sweet potato starch produced by the existing sour starch method is low and difficult to meet market demand. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a strain of Lactobacillus plantarum YTM3 and its application. The strain has an optimal growth temperature range of 19-34°C. The fermented sorrel prepared by the strain can adapt to the environmental temperature of the sweet potato starch preparation season (October to November) and effectively play the role of precipitating starch. The fermented sorrel provided by the present invention exhibits good flocculation activity in the precipitation process of sweet potato starch, and can significantly improve the whiteness of starch and the content of resistant starch.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a strain of Lactobacillus plantarum YTM3, whose classification name is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Committee on June 5, 2024, with the deposit number CGMCC No.30867; the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0006] Its 16S rDNA sequence (as shown in SEQ ID No.1) is as follows:

[0007] In a second aspect, the present invention further provides a bacterial agent comprising the above-mentioned Lactobacillus plantarum YTM3 and a biologically acceptable microbial agent carrier and / or auxiliary material.

[0008] In a third aspect, the present invention also provides a fermentation product of the above-mentioned Lactobacillus plantarum YTM3 strain, wherein the fermentation product is obtained by fermentation of the above-mentioned Lactobacillus plantarum YTM3 strain or a microbial combination comprising the above-mentioned Lactobacillus plantarum YTM3 strain.

[0009] The fermentation products include but are not limited to the bacteria of Lactobacillus plantarum YTM3, sterile fermentation broth, bacteria-containing fermentation broth and fermentation supernatant.

[0010] Preferably, the fermentation product is sweet potato fermented soursop; the sweet potato fermented soursop is obtained by fermenting sweet potato juice culture medium with the plant lactobacillus YTM3 strain, the pH value is 4.8-5.2, and the content of the plant lactobacillus YTM3 is greater than 5.23×10 9 CFU / mL.

[0011] The sweet potato juice culture medium involved in the present invention is a nutrient culture medium with sweet potato juice extracted during the sweet potato processing as the main component. According to different application requirements, the sweet potato juice culture medium can be additionally supplemented with nitrogen sources, carbon sources, inorganic salts and trace elements to optimize its nutritional composition, thereby meeting the requirements of different microbial culture or fermentation processes.

[0012] The components of the sweet potato juice culture medium for auxiliary starch extraction include 80%-90% sweet potato juice, 0.5%-2% carbon source, 0.3%-0.5% nitrogen source, 0.3%-1% inorganic salt, and pH 6.0. It may also include 0.1%-0.5% enzyme source; the enzyme includes but is not limited to α-amylase or glucoamylase. The formula ratio can be further optimized through experiments according to process requirements.

[0013] Optionally, the components of the sweet potato juice culture medium are 5 g yeast extract powder, 2 g dipotassium hydrogen phosphate, 21 g glucose, 5 g anhydrous sodium acetate, and 1000 mL sweet potato juice, pH 6.0.

[0014] The sweet potato juice involved in the present invention is obtained by processing sweet potato raw materials and extracting soluble substances therein. The processing method for extracting the soluble substances can be juice extraction or heating extraction.

[0015] Specifically, the present invention provides a method for preparing sweet potato juice, comprising the following steps: adding sweet potato pieces into distilled water, wherein the solid-liquid ratio (g:L) of the sweet potato pieces to the distilled water is 1:5, heating and boiling for 20-30 min, and filtering with a 120-mesh sieve to obtain the sweet potato juice.

[0016] In a fourth aspect, the present invention further provides a method for preparing sweet potato fermented physalis, comprising the following steps: The activated Lactobacillus plantarum YTM3 was inoculated into the sweet potato juice medium. Based on the volume of the sweet potato juice medium, the inoculation amount of live Lactobacillus plantarum YTM3 was 2.62×10 8 -5.23×10 8 CFU / mL, 19-34℃, culture for 20-24 h until the content of Lactobacillus plantarum YTM3 is greater than 5.23×10 9 CFU / mL, and obtained the sweet potato fermented Physalis.

[0017] Preferably, the inoculation amount of the live bacteria of Lactobacillus plantarum YTM3 is 4.0×10 8 -5.23×10 8 CFU / mL, 25℃, cultured for 24 h, and obtained the fermented sweet potato pulp.

[0018] The activated Lactobacillus plantarum YTM3 bacterial slurry or the bacterial suspension or culture medium containing the activated Lactobacillus plantarum YTM3 can be used to inoculate the sweet potato juice culture medium.

[0019] Optionally, the bacterial suspension after centrifugation of the sweet potato fermented sour pulp is used for the production of the next batch of sweet potato fermented sour pulp.

[0020] In some embodiments, the method for preparing a sweet potato fermented soursop provided by the present invention further includes one or more steps of preparing sweet potato juice, preparing sweet potato juice culture medium, activating Lactobacillus plantarum YTM3, and expanding culture.

[0021] Specifically, the present invention provides a method for preparing sweet potato fermented physalis, comprising the following steps: (1) picking a single colony of Lactobacillus plantarum YTM3 or a frozen strain of Lactobacillus plantarum YTM3, inoculating it into 100-150 mL of sweet potato juice medium, and culturing it at 25-28° C. for 24 h to obtain an activated bacterial solution; (2) inoculating the activated bacterial solution into the sweet potato juice culture medium at an inoculation rate of 5-10%, and fermenting at 25° C. for 24 h to obtain a seed culture solution; the concentration of Lactobacillus plantarum YTM3 in the seed culture solution was 2.62×10 9 -5.23×10 9 CFU / mL; (3) The seed culture medium was inoculated into the sweet potato juice medium at a 10% inoculation rate and fermented at 25°C for 24 h to obtain the fermented sweet potato pulp.

[0022] In a fifth aspect, the present invention also provides the use of the above-mentioned Lactobacillus plantarum YTM3, bacterial agent, sweet potato fermented sorrel and the sweet potato fermented sorrel prepared by the above-mentioned preparation method in the preparation of sweet potato starch.

[0023] Preferably, the method is used in the preparation of sweet potato starch to accelerate the separation and sedimentation of impurities such as starch and protein.

[0024] In a sixth aspect, the present invention also provides a method for preparing sweet potato starch with high resistant starch, comprising the following steps: (1) Preparation of sweet potato slurry: Washed potato pieces are added with clean water and put into a grinder for slurrying, wherein the mass volume ratio of potato pieces to clean water is 1:1-1.5, and the sweet potato residue is removed by filtration to obtain sweet potato slurry.

[0025] (2) precipitation: the sweet potato slurry prepared in step (1) is allowed to settle for 6-8 hours, the bottom layer is starch precipitate, the upper aqueous solution is discharged, and impurities on the surface of the starch precipitate are washed with clean water, and the obtained crude starch is mixed with clean water, the volume of water added is the same as the volume of water added in step (1), to obtain a crude starch slurry; (3) Fermentation: The above-mentioned sweet potato fermented soursop or the sweet potato fermented soursop prepared by the above-mentioned preparation method is inoculated into the crude starch slurry obtained in step (2) at an inoculum amount of 5-10%, stirred and adjusted to a pH value of 5.0-6.0, and fermented at a temperature range of 19-34° C. for 12-14 h.

[0026] (4) Ultrasonic treatment: The ultrasonic power is 120-200 W, the ultrasonic frequency is 40-60 KHz, the ultrasonic treatment time is 40-60 min, and then the fermentation is continued for 12-14 h.

[0027] (5) The precipitated product obtained in step (4) is washed, precipitated, powdered and dried to obtain finished starch.

[0028] Optionally, the specific operation of step (5) is as follows: the upper aqueous solution of the product obtained in step (4) is discharged, and then the yellow powder on the surface of the starch is removed, and the surface impurities are washed with clean water, and then the mixture is added with twice the amount of clean water, and then stirred evenly, and allowed to stand for 8-12 hours to allow it to completely precipitate, and the supernatant and yellow powder are removed, and the mud and sand on the bottom are washed away, and the starch is dried or sun-dried after dehydration (or hanging filtration) to a moisture content of less than 14% to obtain the finished starch.

[0029] Preferably, the fermented sweet potato pulp in step (3) is inoculated into the crude starch slurry obtained in step (2) at an inoculum rate of 10%, stirred and adjusted to a pH of 5.0, and fermented for 12 h at a temperature range of 25-28°C.

[0030] Preferably, in step (4), the ultrasonic power is 180 W, the ultrasonic frequency is 50 kHz, and the ultrasonic treatment time is 50 min and then the fermentation is continued for 12 h.

[0031] In a seventh aspect, the present invention also provides sweet potato starch prepared according to any one of the above-mentioned preparation methods.

[0032] The present invention discloses the following technical effects: 1. The plant lactobacillus YTM3 provided by the present invention is derived from naturally fermented soya bean, and can effectively inhibit the growth of harmful microorganisms in the process of preparing fermented soya bean, reduce pollution and improve the safety of sweet potato fermented soya bean. At the same time, the plant lactobacillus YTM3 has an optimal growth temperature range of 19-34°C, which is more adaptable to the temperature during the production of sweet potato starch than other lactic acid bacteria in naturally fermented soya bean. The strain can reduce the strict requirements on the ambient temperature during the production of sweet potato fermented soya bean and sweet potato starch, simplify the production process, reduce the production cost, and has a wide range of application potential.

[0033] 2. The sweet potato fermented pulp prepared by Lactobacillus plantarum YTM3 showed good flocculation activity and starch sedimentation effect during the precipitation process of sweet potato starch, which can significantly improve the whiteness of starch. The whiteness of the prepared sweet potato starch can reach 84.6%.

[0034] 3. The sweet potato starch preparation method provided by the present invention increases the resistant starch content in the sweet potato starch through the combined action of sweet potato fermentation soy sauce of Lactobacillus plantarum YTM3 and ultrasonic treatment. The acidic substances in the sweet potato fermentation soy sauce can cause protein precipitation, and the starch is no longer protected by the protein, while inducing starch rearrangement and crystallization, and promoting molecular reorganization and crystal stabilization in combination with the mechanical and thermal effects of ultrasound, thereby significantly increasing the resistant starch content of the sweet potato starch. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The colony morphology and Gram staining of Lactobacillus plantarum YTM3 strain; (A is the colony morphology; B is the Gram staining picture) Figure 2 is the bacterial concentration of Lactobacillus plantarum YTM3 strain when grown at different temperatures for 24 h. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The strains used in the following examples of the present invention are derived from the following: The YTM3 strain of Lactobacillus plantarum was deposited in the General Microbiology Center of China National Microbiological Culture Collection on June 5, 2024, and its deposit number is CGMCC No.30867; the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0038] The culture medium used in the following examples of the present invention is as follows: MRS medium composition: 5 g beef extract, 20 g glucose, 5 g soy peptone, 5 g yeast extract, 20 g lactose, 10 g calcium carbonate, 20 g agar, 1 L water. Add 15 g agar powder to the solid medium, add the above ingredients to distilled water, heat to dissolve, adjust pH to 6.0, and sterilize at 121℃ for 20 min after packaging.

[0039] Sweet potato juice medium composition: 5 g yeast extract powder, 2 g potassium dihydrogen phosphate, 21 g glucose, 5 g anhydrous sodium acetate, 1000 mL sweet potato juice. Adjust pH to 6.0 and sterilize at 115℃ for 15 min.

[0040] The naturally fermented Physalis used in the following embodiments of the present invention is naturally fermented Physalis made from sweet potato starch from a farmer in Fuyang City, Anhui Province.

[0041] Unless otherwise specified, other reagents and materials in the examples of the present invention are commercially available.

[0042] The detection method involved in the following embodiments of the present invention is: The starch whiteness is tested according to the method provided in the national standard GB / T 22427.6-2008 "Determination of Starch Whiteness".

[0043] Resistant starch content determination method: The Megazyme resistant starch kit method was used according to AOAC method 2002.02. The sample was incubated with α-amylase and amyloglucosidase (AMG) in a shaking water bath at 37°C for 16 hours, and non-resistant starch was hydrolyzed into D-glucose. After the incubation, ethanol was added to terminate the reaction and the resistant starch was collected by centrifugation.

[0044] Example 1 This embodiment provides a strain of Lactobacillus plantarum YTM3, which is isolated from naturally fermented sweet potato and fermented Physalis.

[0045] 1. Screening of lactic acid bacteria 1.1 Isolation and purification of lactic acid bacteria Take 10 mL of naturally fermented sweet potato fermented sour pulp (from a farmer in Fuyang City, Anhui Province) and mix it in 90 mL of sterile saline to prepare a gradient dilution sample suspension, with the gradient being 10 -1 , 10-2 , 10 -3 , 10 -4 . Take 100 μL of each gradient dilution sample suspension and evenly spread it on MRS agar medium, culture it at 30℃ for 48 h, and when the colony grows to a suitable size, streak it for separation and purification. Repeat several times until a single colony is obtained. A total of 44 strains were isolated and purified. The purified strains were numbered YTM1-44 and stored in a -80℃ refrigerator.

[0046] 1.2 Screening of efficient starch flocculation and sedimentation bacteria Each strain numbered YTM1-44 was activated, rejuvenated, inoculated and expanded to obtain pure bacterial fermentation liquid. Each strain was cultured to the stable stage and the concentration of the bacterial liquid was controlled at 1.2×10 9 CFU / mL.

[0047] Prepare 15 g / L starch slurry with distilled water and sweet potato starch. Take 2 mL of pure bacterial solution of No. YTM1-44 and add it to 48 mL of 15 g / L starch emulsion, stir rapidly for 1 min, then stir slowly for 3 min, and then let it stand for 10 min. Take the clear liquid at the 40 mL mark and measure the OD on a UV-visible spectrophotometer. 600 This is the treated sample, recorded as A2; another sample is treated with an uninoculated blank culture medium instead of bacterial solution in starch emulsion and the same operation is performed as a blank control. The measured absorbance is recorded as A1. Calculate the flocculation rate of each strain on starch slurry. The calculation formula of flocculation rate is as follows: Flocculation rate (%) = (A1-A2) / A1×100%; Among them, A1 represents the OD of the control supernatant 600 , A2 represents the OD of the treated supernatant 600 .

[0048] Taking the flocculation rate as an indicator, the strain with the highest flocculation and sedimentation starch activity was selected and named YTM3.

[0049] 2. Identification of Lactobacillus plantarum YTM3 strain 2.1 Colony and bacterial morphology of YTM3 strain Colony morphology of the strain: milky yellow, round, with neat edges, opaque, smooth and shiny surface, slightly raised, and a colony diameter of 2-3 mm; see Figure 1 -A; Microscopic morphology of bacteria: Gram-positive bacteria, bacterial size (0.7-1.2 μm) × (1.4-2.4 μm), cells are oval or short rod-shaped, arranged in chains after cell division, no spores, no movement; see for details Figure 1 -B.

[0050] The strain was initially identified as Lactobacillus plantarum ( Lactiplantibacillus plantarum ).

[0051] 2.2 Molecular biological identification of YTM3 strain The strains obtained by screening were streaked onto MRS medium and cultured at 30°C for 48 h. The cells were collected and sent to Rongxu Biotechnology (Shanghai) Co., Ltd. for 16S rDNA sequencing. The 16S rDNA sequence of strain YTM3 was compared on the Genbank website, and the results were consistent with those of Lactobacillus plantarum ( Lactiplantibacillus plantarum )The similarity reaches 99.72%.

[0052] In summary, combined with 16S rDNA sequence analysis and physiological and biochemical identification results, the YTM3 strain was identified as Lactobacillus plantarum (Lactiplantibacillus plantarum ) strain and named it Lactobacillus plantarum YTM3.

[0053] The plant lactobacillus YTM3 strain was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on June 5, 2024, and its deposit number is CGMCC No.30867; the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0054] 3. Growth characteristics of Lactobacillus plantarum YTM3 The screened Lactobacillus plantarum YTM3 was cultured at different temperatures, and its bacterial concentration at 24 h at different temperatures was determined.

[0055] The selected single colony of Lactobacillus plantarum YTM3 was inoculated into 100 mL MRS liquid medium and cultured at 19, 22, 25, 28, 31, 34 and 37 °C at 150 rpm for 24 h, and then the OD was measured. 600 , and calculate the corresponding plant lactobacillus YTM3 bacterial concentration in the culture medium, and plot the bacterial concentration against the corresponding culture temperature to obtain the curve of the optimum growth temperature of plant lactobacillus YTM3, see Figure 2 .

[0056] As shown in the figure, the bacterial concentration of the bacteria can exceed 1×10 9 CFU / mL, and the optimum growth temperature is 25° C. It can be seen that the Lactobacillus plantarum YTM3 provided by the present invention can adapt to the indoor or outdoor temperature during the sweet potato starch production period (October to November). Example 2 This embodiment provides a Lactobacillus plantarum YTM3 liquid inoculum, which is composed of Lactobacillus plantarum YTM3 and sweet potato juice culture medium, and is specifically prepared by the following steps: (1) Streak Lactobacillus plantarum YTM3 onto MRS plates and culture at 25°C for 24 h.

[0057] (2) Pick a single colony of Lactobacillus plantarum YTM3 on the MRS plate and inoculate it into the sweet potato juice medium for seed culture at 25°C and 200 rpm for 24 h.

[0058] (3) After the seed culture is completed, the inoculum size is 10% and transferred to the sweet potato juice medium. The culture is carried out at 25°C and 200 rpm for 24 h to obtain the liquid inoculum of Lactobacillus plantarum YTM3.

[0059] The test showed that the number of viable bacteria of the bacterial agent Lactobacillus plantarum YTM3 was 6×10 9 CFU / mL.

[0060] Example 3 The present embodiment provides a Lactobacillus plantarum YTM3 powder, which is composed of Lactobacillus plantarum YTM3, xylooligosaccharides and skimmed milk powder, and is specifically prepared by the following steps: (1) Preparation of protective agent: Dissolve xylooligosaccharides and skimmed milk powder in water and mix well to make the mass percentage concentration of xylooligosaccharides in the obtained mixed solution 7% and the mass percentage concentration of skimmed milk powder 12%.

[0061] (2) Streak Lactobacillus plantarum YTM3 onto MRS plates and culture at 25°C for 24 h.

[0062] (3) Pick a single colony of Lactobacillus plantarum YTM3 on the MRS plate and inoculate it into MRS liquid culture medium. Culture it at 25°C and 200 rpm for 24 h. After activation culture for two generations, obtain the Lactobacillus plantarum YTM3 culture medium.

[0063] (4) The culture medium of Lactobacillus plantarum YTM3 was centrifuged at 6000 rpm / min for 10 min at 4°C to collect the bacterial sludge, which was then washed twice with 0.85% saline. The obtained bacterial sludge was added to the protective agent to prepare a bacterial suspension, and the volume was adjusted so that the bacterial concentration reached 1×10 9 -1×10 10 CFU / mL, and prepared into Lactobacillus plantarum YTM3 powder by freeze-drying process. The freeze-drying parameters were -80℃, vacuum degree 1.0 pa, and freezing time 24 h.

[0064] The test showed that the number of viable bacteria in the inoculant was 2×10 8 CFU / g.

[0065] Example 4 This embodiment provides a fermented sour milk that can be used to precipitate sweet potato starch milk, and the preparation method thereof is as follows.

[0066] (1) Pick a single colony of Lactobacillus plantarum YTM3 or a frozen strain of Lactobacillus plantarum YTM3, inoculate it into 100 mL of sweet potato juice medium, and ferment it at 25°C for 24 hours to obtain an activated bacterial solution; (2) Inoculate the activated bacterial solution into the sweet potato juice medium at a 10% inoculation rate and ferment at 25°C for 24 h to obtain the seed culture solution; (3) The seed culture medium was inoculated into the sweet potato juice medium at an inoculum rate of 10% and fermented at 25°C for 24 h to obtain the sweet potato fermented sour pulp for settling the sweet potato starch emulsion.

[0067] The pH of the fermented sweet potato pulp was 5.0, and the concentration of Lactobacillus plantarum YTM3 was 5.23×10 9 CFU / mL.

[0068] The number of coliform bacteria in the sweet potato fermented soursop and the naturally fermented soursop of this embodiment was detected with reference to GB 4789.3-2016 "National Food Safety Standard Food Microbiology Test Coliform Group Count", and the results are shown in Table 1. The results show that the sweet potato fermented soursop in the present invention is pure bacterial fermentation, without contamination by pathogenic bacteria such as miscellaneous bacteria, and can improve the edible safety of starch products.

[0069] Table 1 The number of coliform bacteria in different fermented physalis

[0070] Example 5 This embodiment provides a fermented sour milk that can be used to precipitate sweet potato starch milk, and the preparation method thereof is as follows.

[0071] (1) Take 0.5 mL of frozen Lactobacillus plantarum YTM3 strain and inoculate it into 150 mL of sweet potato juice medium. After culturing at 25°C and 150 rpm for 24 h, an activated bacterial solution is obtained. (2) Inoculate the activated bacterial solution into the sweet potato juice medium at a 10% inoculation rate, and culture at 30°C and 150 rpm for 30 h to obtain the seed culture solution; (3) The seed culture solution was inoculated into the sweet potato juice medium at an inoculum rate of 10% and fermented at 30°C for 30 h to obtain the sweet potato fermented sour pulp for settling the sweet potato starch emulsion.

[0072] The pH of the fermented sweet potato pulp was 5.2, and the concentration of Lactobacillus plantarum YTM3 was 6.5×10 9 CFU / mL.

[0073] Example 6 This embodiment provides a method for fermenting Physalis to precipitate starch, and the preparation method thereof is as follows: (1) Material selection: Select fresh and disease-free sweet potatoes, and remove diseased pieces and stones.

[0074] (2) Cleaning: Place the selected sweet potatoes into a potato cage or screw conveyor type potato washing machine for cleaning.

[0075] (3) Preparation of sweet potato slurry: The washed potato pieces are put into a grinder for pulping. 1.5 tons of water is added for every ton of potato pieces. After pulping, the slurry is first coarsely filtered through an 80-mesh filter and then passed through a 120-160-mesh fine sieve to remove fine potato residues to obtain sweet potato slurry.

[0076] (4) Precipitation: The sweet potato slurry is allowed to settle for 6-8 h until the starch is precipitated to the bottom layer. The upper aqueous solution is discharged and impurities on the starch surface are washed off with clean water. The resulting crude starch is mixed with clean water. The volume of water added is the same as that in step (3) to obtain a crude starch slurry.

[0077] (5) Preparation of fermented sweet potato sour pulp: the preparation method is the same as that of Example 2 or Example 3.

[0078] (6) Fermentation: The fermented sweet potato slurry obtained in step (5) is inoculated into the crude starch slurry obtained in step (4) at an inoculum rate of 5%, stirred and the pH value is adjusted to 5.0, the fermentation temperature is controlled within the range of 19-34° C., and the fermentation is carried out for 14 h.

[0079] (7) Ultrasonic treatment: The ultrasonic power was 120w, the ultrasonic frequency was 40 kHz, and the ultrasonic treatment time was 40 min. After that, the fermentation was continued for 14 h.

[0080] (8) Cleaning, powdering and drying: The upper aqueous solution of the product obtained in step (7) is discharged, and then the yellow powder on the surface of the starch is removed. After the surface impurities are washed with clean water, the mixture is added with twice the amount of clean water, stirred evenly, and allowed to stand for 10 hours to allow it to settle completely. The supernatant and yellow powder are removed, and the mud and sand on the bottom are washed away. The starch is then dehydrated (or suspended and filtered) and then dried or sun-dried until the moisture content is below 14%, thereby obtaining the finished starch.

[0081] The whiteness of the sweet potato starch prepared according to the method is 83.9%, and the content of resistant starch is 12.04%.

[0082] Example 7 This embodiment provides a method for fermenting Physalis to precipitate starch, and the preparation method thereof is as follows: (1) Material selection: Select fresh and disease-free sweet potatoes, and remove diseased pieces and stones.

[0083] (2) Cleaning: Place the selected sweet potatoes into a potato cage or screw conveyor type potato washing machine for cleaning.

[0084] (3) Preparation of sweet potato slurry: The washed potato pieces are put into a grinder for pulping, and 1.0 ton of water is added for every ton of potato pieces. After the pulping is completed, the slurry is first coarsely filtered through an 80-mesh filter, and then passed through a 120-160-mesh fine sieve to remove fine potato residues to obtain sweet potato slurry.

[0085] (4) Precipitation: The sweet potato slurry is allowed to settle for 6-8 h until the starch is precipitated to the bottom layer. The upper aqueous solution is discharged and impurities on the starch surface are washed off with clean water. The resulting crude starch is mixed with clean water. The volume of water added is the same as that in step (3) to obtain a crude starch slurry.

[0086] (5) Preparation of fermented sweet potato sour pulp: the preparation method is the same as that of Example 2 or Example 3.

[0087] (6) Fermentation: The fermented sweet potato slurry obtained in step (5) is inoculated into the crude starch slurry obtained in step (4) at an inoculum rate of 10%, stirred and the pH value is adjusted to 6.0, the fermentation temperature is controlled within the range of 25-28° C., and the fermentation is carried out for 12 h.

[0088] (7) Ultrasonic treatment: The ultrasonic power was 200 W, the ultrasonic frequency was 60 kHz, and the ultrasonic treatment time was 60 min. After that, the fermentation was continued for 12 h.

[0089] (8) Cleaning, powdering and drying: The upper aqueous solution of the product obtained in step (7) is discharged, and then the yellow powder on the surface of the starch is removed. After the surface impurities are washed with clean water, the mixture is added with twice the amount of clean water, stirred evenly, and allowed to stand for 10 hours to allow it to settle completely. The supernatant and yellow powder are removed, and the mud and sand on the bottom are washed away. The starch is then dehydrated (or suspended and filtered) and then dried or sun-dried until the moisture content is below 14%, thereby obtaining the finished starch.

[0090] The whiteness of the sweet potato starch prepared according to the method is 84.6%, and the content of resistant starch is 12.54%.

[0091] Comparative Example 1 This comparative example provides a sweet potato starch prepared by a traditional natural fermentation method, and the preparation method thereof is as follows: (1) Material selection: Select fresh and disease-free sweet potatoes, and remove diseased pieces and stones.

[0092] (2) Cleaning: Place the selected sweet potatoes into a potato cage or screw conveyor type potato washing machine for cleaning.

[0093] (3) Preparation of sweet potato slurry: The washed potato pieces are put into a grinder for pulping. 1.5 tons of water is added for every ton of potato pieces. After pulping, the slurry is first coarsely filtered through an 80-mesh filter and then passed through a 120-160-mesh fine sieve to remove fine potato residues to obtain sweet potato slurry.

[0094] (4) Precipitation: The sweet potato slurry is allowed to settle for 6-8 h until the starch is precipitated to the bottom layer. The upper aqueous solution is discharged and impurities on the starch surface are washed off with clean water. The resulting crude starch is mixed with clean water. The volume of water added is the same as that in step (3) to obtain a crude starch slurry.

[0095] (5) Fermentation: Inoculate the crude starch slurry obtained in step (4) with the naturally fermented sour pulp at an inoculum rate of 10%, stir and adjust the pH value to 6.0, control the fermentation temperature within the range of 25-28°C, and ferment for 24 h.

[0096] (6) Cleaning, powdering and drying: The upper aqueous solution of the product obtained in step (5) is discharged, and then the yellow powder on the surface of the starch is removed. After the surface impurities are washed with clean water, the mixture is added with twice the amount of clean water, stirred evenly, and allowed to stand for 10 hours to allow it to settle completely. The supernatant and yellow powder are removed, and the mud and sand on the bottom are washed away. The starch is then dehydrated (or suspended and filtered) and then dried or sun-dried until the moisture content is below 14%, thereby obtaining the finished starch.

[0097] The whiteness of the sweet potato starch prepared according to the method is 78.6%, and the content of resistant starch is 8.70%.

[0098] Verification Example 1 Take fresh sweet potatoes, remove impurities and rotten parts, cut into small pieces with a diameter of about 2 cm, add water at a ratio of 1:1.5 and slurry in a food processor, then use a 120-mesh sieve to filter out the sweet potato residue, mix the starch and water and retain them to obtain sweet potato slurry.

[0099] 1. Comparison of flocculation rate of sweet potato starch with different treatments Take three portions of 45 mL of sweet potato slurry in 50 mL centrifuge tubes, respectively, and mark them as slurry No. 1, slurry No. 2, and slurry No. 3. Add 10.00% of the total volume of clean water to slurry No. 1, add 10.00% of the total volume of naturally fermented acid slurry to slurry No. 2, and add 10.00% of the total volume of sweet potato fermented acid slurry (provided in Example 4) to slurry No. 3. Shake the three slurries up and down in a sealed state, then stand at room temperature for 4 h and 24 h, take the clear liquid at the 10 mL mark, and measure the OD on a UV-visible spectrophotometer. 600 The flocculation rate of sweet potato starch with different treatments was compared. The results are shown in Table 2.

[0100] Table 2 Comparison of flocculation rate of sweet potato starch in different treatments

[0101] The results show that the flocculation rate of the sweet potato starch of the fermented sweet potato pulp provided by the present invention at 4 h and 24 h is equivalent to that of the natural fermented sweet potato pulp, and is significantly higher than that of the natural sedimentation. At 24 h, the flocculation rate of the sweet potato starch of the fermented sweet potato pulp provided by the present invention is 15.33% higher than that of the natural sedimentation. This shows that the fermented sweet potato pulp provided by the present invention has an excellent flocculation effect under long-term standing conditions and can be applied to the precipitation of sweet potato starch.

[0102] 2. Comparison of whiteness and resistant starch content of sweet potato starch after different treatments Take 4 portions of 45 mL of sweet potato slurry in 50 mL centrifuge tubes and mark them as slurry No. 1, No. 2, No. 3 and No. 4. Add 10.00% of the volume of sweet potato slurry to slurry No. 1, add 10.00% of the volume of sweet potato slurry of naturally fermented Physalis to slurry No. 2, and add 10.00% of the volume of sweet potato slurry of fermented Physalis to slurries No. 3 and No. 4. After stirring, the slurries No. 1-3 were allowed to stand at room temperature for 24 h. After stirring, the slurry No. 4 was allowed to stand at room temperature for 12 h, and then subjected to ultrasonic treatment at 200 W and 40 KHz for 40 min, and then continued to ferment for 12 h. The starch in the slurries No. 1-4 sank freely, and then the supernatant and yellow powder layer were taken out, and clean water twice the volume of the remaining starch was added. After stirring, it was allowed to stand for 10 h. On the second day, the supernatant was drawn out, and then 2 times the clean water was added. After standing for 4 h, the supernatant was taken out and dried in a drying oven at 80.0 ° C. After the 4 portions of starch were dried to constant mass, starch samples No. 1, No. 2, No. 3 and No. 4 were obtained. The whiteness test and resistant starch content test were performed on the 4 starch samples, and the results are shown in Table 3.

[0103] Table 3 Comparison of whiteness and resistant starch content of sweet potato starch after different treatments

[0104] The experimental results show that the whiteness of the natural sedimentation treatment is the lowest, the whiteness is improved after adding natural physalis, and the whiteness of the sweet potato fermented physalis treatment is the highest, indicating that the sweet potato fermented physalis provided by the present invention can more effectively remove impurities and improve starch whiteness. In terms of resistant starch content, the resistant starch in the sweet potato starch obtained by the sweet potato fermented physalis treatment and the sweet potato fermented physalis plus ultrasonic treatment is significantly higher than that of the other two groups, which may be related to the fact that the metabolites in the sweet potato fermented physalis (such as organic acids such as lactic acid) promote the reorganization of starch molecular structure and enhance the formation of resistant starch. At the same time, the fermented physalis decomposes proteins and impurities more thoroughly, which helps to release resistant starch precursors. Combined with the mechanical and thermal effects of ultrasound, it promotes molecular reorganization and crystal stabilization, thereby significantly improving the resistant starch content of sweet potato starch.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A strain of Lactobacillus plantarum YTM3, characterized in that Its classification name is Lactobacillus plantarum YTM3 ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Committee on June 5, 2024, with the deposit number CGMCC No.30867; the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

2. A bacterial agent, characterized in that The invention comprises the Lactobacillus plantarum YTM3 as claimed in claim 1 and a biologically acceptable microbial agent carrier and / or auxiliary material.

3. The fermentation product of the plant lactobacillus YTM3 strain according to claim 1, characterized in that: The fermentation product is obtained by fermenting the Lactobacillus plantarum YTM3 strain according to claim 1 or a microbial combination comprising the Lactobacillus plantarum YTM3 strain according to claim 1.

4. The fermentation product according to claim 3, characterized in that The fermentation product is sweet potato fermented soursop; the sweet potato fermented soursop is obtained by fermenting sweet potato juice culture medium with the plant lactobacillus YTM3 strain, the pH value is 4.8-5.2, and the content of the plant lactobacillus YTM3 is greater than 5.23×10 9 CFU / mL.

5. A method for preparing sweet potato fermented physalis, characterized in that: The method comprises the following steps: taking activated plant lactobacillus YTM3 and inoculating it into a sweet potato juice medium, wherein the inoculation amount of plant lactobacillus YTM3 live bacteria is 2.62×10 8 -5.23×10 8 CFU / mL, 19-34℃, culture for 20-30 h until the content of Lactobacillus plantarum YTM3 is greater than 5.23×10 9 CFU / mL, and obtained the sweet potato fermented Physalis.

6. Use of the plant lactobacillus YTM3 described in claim 1, the bacterial agent described in claim 2, the fermented sweet potato physalis described in claim 4, and the fermented sweet potato physalis prepared by the preparation method described in claim 5 in the preparation of sweet potato starch.

7. A method for preparing sweet potato starch with high resistant starch, characterized in that: The following steps are involved: (1) Preparation of sweet potato slurry: Washed potato pieces are added with clean water and put into a grinder for slurrying, wherein the mass volume ratio of potato pieces to clean water is 1:1-1.5, and the sweet potato residue is removed by filtration to obtain sweet potato slurry. (2) precipitation: the sweet potato slurry prepared in step (1) is allowed to settle for 6-8 hours, the bottom layer is starch precipitate, the upper aqueous solution is discharged, and impurities on the surface of the starch precipitate are washed with clean water, the obtained crude starch is mixed with clean water, and the volume of water added is the same as the volume of water added in step (1), to obtain a crude starch slurry; (3) Fermentation: The above-mentioned sweet potato fermented soursop or the sweet potato fermented soursop prepared by the above-mentioned preparation method is inoculated into the crude starch slurry obtained in step (2) at an inoculum amount of 5-10%, stirred and adjusted to a pH value of 5.0-6.0, and fermented at a temperature range of 19-34° C. for 12-14 h. (4) Ultrasonic treatment: The ultrasonic power is 120-200 W, the ultrasonic frequency is 40-60 kHz, the ultrasonic treatment time is 40-60 min, and then the fermentation is continued for 12-14 h. (5) The precipitated product obtained in step (4) is washed, precipitated, powdered and dried to obtain finished starch.

8. The preparation method according to claim 7, characterized in that: The fermented sweet potato pulp in step (3) is inoculated into the crude starch slurry obtained in step (2) at an inoculum amount of 10%, stirred and adjusted to a pH value of 5.0, and fermented for 12 hours at a temperature range of 25-28°C.

9. The preparation method according to claim 7, characterized in that: In step (4), the ultrasonic power is 180 W, the ultrasonic frequency is 50 kHz, and the ultrasonic treatment time is 50 min. After that, the fermentation is continued for 12 h.

10. The sweet potato starch prepared according to any one of claims 7 to 9.

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