A fermentation method for red yeast rice with low citrinin content

Abstract

This invention belongs to the field of microbial fermentation technology and provides a fermentation method for red yeast rice with low citrinin content. Adding gastrodin to the rice fermentation culture medium can effectively reduce the citrinin content in red yeast rice without reducing pigment yield. The method is not only simple to operate and safe and reliable, but also has excellent and stable effects, and is expected to be used in industrial production.

Description

Technical Field

[0001] This invention belongs to the field of microbial fermentation technology, specifically relating to a fermentation method and application of red yeast rice with low citrinin content. Background Technology

[0002] Red yeast rice, a solid-state fermentation product of Monascus purpureus, has a long history of application in my country and is commonly known as Danqu, Chiqu, Hongqu, Hongmi, Fumi, etc. In my country, red yeast rice is not only used in the food processing industry for its antibacterial and preservative properties, color enhancement, and nutritional improvement in various foods such as meat, fish, and beans, resulting in a variety of well-known condiments and culinary delights; it is also used in the pharmaceutical and health care fields due to its anti-cancer and lipid-lowering effects.

[0003] However, during the fermentation process, red yeast rice often produces citrinin, a fungal toxin with teratogenic, carcinogenic, and nephrotoxic properties. The presence of citrinin has, to some extent, limited the promotion and application of red yeast rice and related products. Therefore, optimizing fermentation conditions to effectively reduce the citrinin content in red yeast rice without decreasing the yield of red yeast pigments is one of the research hotspots in this field.

[0004] Currently, reducing citrinin production can be achieved through three main approaches: First, strain screening and modification can be used to regulate the metabolism of red yeast rice strains at the molecular level, thereby reducing citrinin production or increasing color value during fermentation. Second, optimizing fermentation conditions can increase the production of functional substances such as pigments while reducing citrinin production. Third, adding exogenous additives can affect the metabolic pathways of red yeast rice, thereby reducing citrinin or increasing red yeast rice pigment. The first two methods suffer from operational difficulties and complex procedures, while the last method generally has limitations in reducing citrinin; for example, adding rutin, α-glucosylrutin, or troxerutin can only reduce citrinin by approximately 29-55%. Therefore, it is essential to find a novel active ingredient that can effectively reduce citrinin content without decreasing red yeast rice pigment production.

[0005] Gastrodin, a small-molecule phenolic glycoside, is the main active ingredient of the traditional Chinese medicine Gastrodia elata. It possesses anti-inflammatory and antioxidant properties, and also offers some protection against damaged myocardial cells. Gastrodin also exhibits good water solubility. Currently, there are no reports on the use of gastrodin in solid-state fermentation of Monascus purpureus to reduce the citrinin content in red yeast rice without affecting pigment yield. Summary of the Invention

[0006] The present invention provides a fermentation method for red yeast rice with low citrinin content. By adding gastrodin to the rice fermentation culture medium, the citrinin content in red yeast rice can be effectively reduced without reducing the yield of red yeast pigment.

[0007] This invention provides the following technical solutions:

[0008] This invention provides a method for fermenting red yeast rice that effectively reduces citrinin content without reducing the yield of red yeast pigment. The method includes: inoculating red yeast rice into a rice fermentation medium supplemented with gastrodin for fermentation. The red yeast pigment includes red, yellow, and orange pigments; the amount of gastrodin added is 0.02–0.1 g of gastrodin per 30 g of rice, preferably 0.02–0.04 g, with an optimal value of 0.04 g of gastrodin; the rice fermentation medium consists of rice; and the rice variety is japonica rice.

[0009] The fermentation method includes the following steps: First, a suspension of Monascus purpureus spores is prepared, then it is inoculated into a seed culture medium to obtain a seed liquid, and then the seed liquid is inoculated into a rice fermentation medium with added gastrodin to obtain a red yeast rice fermentation medium. Finally, the rice is allowed to ferment statically to obtain red yeast rice with low content of citrinin.

[0010] The present invention adds 0.04g of gastrodin to the rice in the red yeast rice fermentation medium, which reduces the content of citric acid in the red yeast rice by 78.95% compared with that without the addition of gastrodin, without affecting the yield of red yeast pigment.

[0011] The fermentation method for reducing the citrinin content in red yeast rice provided by this invention is not only simple to operate, but also safe and stable, and is expected to be used in industrial production. Attached Figure Description

[0012] Figure 1 The effect of adding gastrodin on the citrinin content in red yeast rice;

[0013] Figure 2 The effect of adding gastrodin on the content of red yeast rice pigment. Detailed Implementation

[0014] This invention provides a fermentation method for effectively reducing the citrinin content in red yeast rice without reducing pigment yield. The method includes: inoculating red yeast rice into a rice fermentation medium supplemented with gastrodin for fermentation. The amount of gastrodin added is 0.02–0.1 g per 30 g of rice, more preferably 0.02–0.04 g. By adding gastrodin during rice fermentation, the effect of gastrodin on the growth and metabolism of red yeast rice effectively inhibits the ability of red yeast rice to produce citrinin without reducing pigment yield.

[0015] In this invention, the gastrodin is added simultaneously with the rice during the preparation of the rice fermentation culture medium, and then sterilized at high temperature for later use. As an optional embodiment, the gastrodin and rice are mixed in a specific ratio and then sterilized at 121°C for 20 minutes for later use.

[0016] In this invention, the rice fermentation culture medium comprises 30g of japonica rice.

[0017] The preferred composition of the culture medium is 30g of japonica rice and 0.04g of gastrodin.

[0018] The preferred method for fermenting red yeast rice provided by the present invention is as follows: first, a suspension of red yeast spores is prepared, then it is inoculated into a seed culture medium for cultivation, and then the seed liquid is inoculated into a rice fermentation culture medium with added gastrodin to obtain a red yeast rice fermentation culture medium, and then the red yeast rice is prepared by static fermentation.

[0019] As an optional implementation, the fermentation method of the present invention includes the following steps:

[0020] (1) Preparation of Monascus purpureus spore liquid

[0021] MPPY medium composition: 3% glucose, 0.05% KCl, 0.2% yeast extract, 0.3% NaNO3, with ultrapure water added to make 100mL of culture solution, which is then placed in a 250mL Erlenmeyer flask and sterilized at high temperature (121℃, 20min).

[0022] Monascus purpureus was inoculated into sterilized MPPY medium and incubated for two days in a constant-temperature shaking incubator at 30°C and 180 rpm. Then, 1 mL of the culture solution was evenly spread onto pre-prepared malt extract solid medium and incubated at 30°C for 7–12 days. Once the spores matured and turned deep red, they were washed with 0.9% physiological saline, filtered to remove impurities, and a spore suspension was obtained. The concentration of the spore suspension was calculated using microscopic counting. The remaining spore suspension was stored at -20°C.

[0023] (2) Preparation of Monascus seed liquid

[0024] The seed culture medium for Monascus purpureus has the following composition: 3% glucose, 0.3% NaNO3, 0.05% MgSO4·7H2O, 0.2% KH2PO4, and 0.05% KCl.

[0025] The prepared spore solution was diluted with sterile water to a concentration of 1.0 × 10⁻⁶. 7 -1.0×10 8 Spores per mL were collected and 1 mL of spore solution was transferred to a 250 mL Erlenmeyer flask containing seed culture medium. The flask was then incubated in a constant temperature shaking incubator (150–250 rpm, 28–32 °C) for two days.

[0026] (3) Fermented red yeast rice

[0027] The seed liquid obtained in the above steps was inoculated into rice fermentation medium containing gastrodin at an inoculation rate of 10% (v / v), and fermented at a constant temperature of 28°C for 7-11 days to obtain red yeast rice.

[0028] This invention provides red yeast rice prepared by the aforementioned solid-state fermentation method, which can achieve a low content of citric acid without affecting its pigment content.

[0029] The present invention also provides the application of the red yeast rice in the fields of food, brewing and medicinal health care, and it can be used as a raw material for preparing health care products, food coloring agents, preservatives, etc.

[0030] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0031] In a specific embodiment, the malt extract solid culture medium is prepared by adding 2% agar to the malt extract, sterilizing at 121°C for 20 minutes, pouring the mixture into plates promptly, and allowing it to cool before use.

[0032] Methods for detecting citric acid and red yeast rice pigment in red yeast rice: Red yeast rice is dried to constant weight, ground and passed through a 60-mesh sieve. 0.1g of red yeast rice is added to 1mL of high performance liquid chromatography grade methanol, mixed thoroughly, and sonicated for 0.5h. After centrifugation at 6000r / min for 10min, the supernatant is collected and filtered through a 0.45μm organic filter membrane to obtain the fermentation extract.

[0033] The red yeast rice is Monascus purpureus 30141.

[0034] Example 1

[0035] This embodiment provides a method for fermenting red yeast rice:

[0036] (1) Preparation of Monascus purpureus spore suspension

[0037] First, Monascus purpureus was inoculated into MPPY medium and cultured for 2 days. Then, 1 mL of the culture solution was spread onto a pre-prepared malt extract solid medium and cultured at 30°C for 8 days. After the spores matured, they were washed with 0.9% physiological saline. A small portion of the mixed spore solution was then taken for counting, and the rest was stored in a -20°C refrigerator.

[0038] (2) Red Monascus Seed Liquid

[0039] The spore solution obtained in the previous step was diluted with sterile water to a concentration of 1.0 × 10⁻⁶. 8 Take 1 mL of the culture medium per 1 mL sample and place it in a 250 mL Erlenmeyer flask. Incubate for two days in a constant temperature shaking incubator (150–250 rpm, 28–32 °C).

[0040] (3) Red yeast rice fermentation

[0041] The seed culture prepared in the above steps was inoculated into rice fermentation medium containing gastrodin at an inoculation rate of 10% by volume. Then, 30% sterile water was added and fermented at a constant temperature of 28°C for 7 days to obtain red yeast rice.

[0042] The rice fermentation culture medium consists of 30g of japonica rice and 0.04g of gastrodin.

[0043] The preparation method is as follows: Gastrodin is evenly mixed with japonica rice in the fermentation culture medium, and then placed in a 250mL Erlenmeyer flask and sterilized at 121℃ for 20min.

[0044] Example 2

[0045] The only difference between this embodiment and Embodiment 1 is that the rice culture medium consists of 30g of japonica rice and 0.02g of gastrodin.

[0046] Comparative Example 1

[0047] The only difference between this comparative example and Example 1 is that the rice fermentation culture medium consists of 30g of japonica rice. The preparation method is as follows: accurately weigh 30g of japonica rice and place it in an Erlenmeyer flask.

[0048] Example 3

[0049] The only difference between this embodiment and Embodiment 1 is that:

[0050] (1) Preparation of Monascus purpureus spore suspension

[0051] Monascus purpureus was inoculated into MPPY medium and cultured in a constant temperature shaker (180 r / min, 30 ℃) for 50 h; 1 mL of culture solution was transferred to malt extract solid medium and cultured in a constant temperature (30 ℃) for 11 days; after the spores matured, the spores were washed off.

[0052] Example 4

[0053] The only difference between this embodiment and Embodiment 1 is that:

[0054] (2) Red Monascus Seed Liquid

[0055] Spore solution diluted to 1×10 7 After obtaining the spores per mL, take 1 mL of the spore solution and inoculate it into the seed culture medium. Incubate at 200 rpm and 32℃ for 50 h with constant shaking to obtain the red yeast seed solution.

[0056] Example 5

[0057] The only difference between this embodiment and Embodiment 1 is that:

[0058] (3) Red yeast rice fermentation

[0059] Take 15% (v / v) of the red yeast seed liquid obtained in step (2) and inoculate it into rice culture medium. Then ferment it in a constant temperature (30℃) incubator for 7 days to obtain red yeast rice.

[0060] Example 6

[0061] This embodiment uses the fermentation methods of Example 1, Example 2 and Comparative Example 1 to investigate the content of citrusin and red yeast rice pigment in the fermentation broth.

[0062] (1) Effects of adding gastrodin on the content of citrinin and red yeast rice in red yeast rice

[0063] Experimental group 1: Fermentation method of Example 1 was used;

[0064] Experimental group 2: The fermentation method of Example 2 was used;

[0065] Control group: Fermentation method of Comparative Example 1 was used.

[0066] The contents of citrinin and red yeast pigment in the fermentation broth of Monascus purpureus obtained from experimental groups 1-2 and the control group were detected, and the results are shown in the figure. Figures 1-2 .

[0067] Depend on Figure 1 It can be seen that the yield of citrinin was the highest in the control group, at 758.87 μg / g; the content of citrinin in experimental group 1 was 159.77 μg / g, which was 78.95% lower than that in the control group; and the content of citrinin in experimental group 2 was 227.43 μg / g, which was 70.03% lower than that in the control group.

[0068] Depend on Figure 2 It can be seen that the content of yellow pigment, red pigment and orange pigment in the control group and experimental groups 1-2 are basically the same.

[0069] This indicates that the addition of gastrodin can reduce the citrinin content in red yeast rice without affecting pigment yield.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fermentation method for red yeast rice with low citrinin production, characterized in that, Red yeast rice is prepared by inoculating red yeast rice into a rice fermentation medium supplemented with gastrodin and fermenting it. The fermentation method is used to reduce the citric acid in red yeast rice without affecting the red yeast pigment. In the rice fermentation culture medium, the amount of gastrodin added per 30 g of rice is 0.02~0.04 g.

2. The fermentation method according to claim 1, characterized in that, The red yeast rice pigments include yellow, red, and orange pigments.

3. The fermentation method according to claim 1, characterized in that, In the rice fermentation medium, the amount of gastrodin added per 30 g of rice is 0.04 g.

4. The fermentation method according to any one of claims 1 to 3, characterized in that, The rice fermentation culture medium consists of: japonica rice.

5. The fermentation method according to any one of claims 1 to 3, characterized in that, Includes the following steps: First, a suspension of Monascus purpureus spores is prepared, then inoculated into a seed culture medium to obtain a seed liquid. The seed liquid is then inoculated into a rice fermentation medium supplemented with gastrodin to obtain a red yeast rice fermentation medium. Finally, the rice is allowed to ferment statically to obtain red yeast rice.

6. Red yeast rice prepared by the fermentation method according to any one of claims 1 to 5.

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