A method for purifying selenium and reducing cadmium in oysters

Abstract

The present application belongs to the technical field of heavy metal purification method in oyster, and discloses a biological purification method for Hong Kong oyster to reduce cadmium and enrich selenium, which comprises four steps of temporary oyster culture, nano-selenium solution preparation, cadmium stress treatment and nano-selenium feeding. The method can significantly reduce the cadmium content in oysters and increase the selenium content by using nano-selenium under specific conditions, and has no adverse effects on oysters. The method only needs to add a specific concentration of nano-selenium solution in the aquaculture water body; the cadmium reduction effect is significant: after 14 days of nano-selenium feeding treatment, the cadmium content in oysters is significantly reduced; the selenium enrichment effect is obvious: the selenium content in oysters is significantly increased after treatment; the safety is high: the physiological indexes of oysters return to normal level after treatment; the operation is simple: a new technical scheme is provided for the safe production of oyster products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal purification in oysters, more specifically, it relates to a Hong Kong oyster cadmium reduction and selenium enrichment biological purification method. BACKGROUND

[0002] With the aggravation of environmental pollution, the accumulation of heavy metal cadmium (Cd) in the food chain has become the focus of public health concern. Oysters, as a typical representative of cadmium accumulation in marine organisms, not only affect food safety, but also may affect human health through the food chain. Hong Kong oyster (Crassostrea hongkongensis) is the main economic shellfish cultured in the coastal areas of South China, mainly living in the junction of salt and fresh water, and has been long-term polluted by cadmium.

[0003] Selenium is a world-recognized element that can improve human immunity and anti-tumor function, and is an indispensable trace element for the human body. Since selenium cannot be synthesized in the human body, human selenium supplementation mainly depends on the intake of selenium-rich foods. At present, inorganic selenium or organic selenium is mainly used for feeding in the treatment of cadmium reduction and selenium enrichment in aquatic products, but these methods have the following technical defects: the treatment effect is not ideal, the absorption efficiency is low, the conversion efficiency is not high, and the safety has hidden dangers. As a new type of selenium source, nano selenium (SeNPs) has the following advantages: ultra-small particle size and extremely large surface area, as well as unique morphological characteristics; functions such as resistance to bacteria, inhibition of tumors, and improvement of immunity; high bioavailability and safety.

[0004] Studies have shown that SeNPs, due to its nanoscale particle size (usually tens to hundreds of nanometers), can easily pass through the cell wall and reach the plasma membrane. At the same time, due to its high specific surface area, the contact area with the cytoplasm is increased, and the absorption efficiency is improved. SeNPs enter the biological cytoplasm through aquaporin, and this transport method without energy and specific transport enzymes has a higher transport rate, with an absorption rate about 1.7 times that of conventional selenium (Se(IV) and Se(VI)).

[0005] In the field of agriculture, SeNPs have been widely used in rice, pepper, Chinese cabbage, melon, strawberry and other crops for selenium supplementation, not only significantly increasing the selenium content in the edible parts of crops, but also playing an important role in enhancing the stress resistance of crops. However, the application of SeNPs in the treatment of cadmium reduction and selenium enrichment in aquatic products is still in its infancy, and it is urgent to develop a safe and efficient method for oyster cadmium reduction and selenium enrichment. SUMMARY

[0006] In order to make up for the shortcomings in the prior art, the present application provides a Hong Kong oyster cadmium reduction and selenium enrichment biological purification method.

[0007] The second object of the present application is to provide the use of the above method in the reduction of cadmium and enrichment of selenium in Crassostrea hongkongensis.

[0008] The object of the present application is achieved by the following technical solutions.

[0009] The present application discloses a biological purification method for reducing cadmium and enriching selenium in Crassostrea hongkongensis, which comprises the following steps: S1, temporary cultivation of oysters; S2, preparation of a nano-selenium solution; S3, cadmium stress treatment; and S4, nano-selenium feeding.

[0010] Preferably, the biological purification method for reducing cadmium and enriching selenium in Crassostrea hongkongensis comprises the following steps:

[0011] S1, temporary cultivation of oysters: after the Crassostrea hongkongensis is cleaned, the water temperature is controlled at 28 DEG C, the salinity is controlled at 20±1 ‰, and the oysters are temporarily cultivated for 7 days; water is changed and the oysters are fed at a fixed time every day;

[0012] S2, preparation of a nano-selenium solution: a 0.2 g / L nano-selenium mother solution is prepared, and the solution needs to be mixed before use;

[0013] S3, cadmium stress treatment: after the temporary cultivation in step S1 is completed, a cadmium chloride solution is added to the cultivation water, so that the cadmium concentration in the water reaches 80 μg / L, and the cadmium stress treatment is started, and the stress treatment lasts for 7 days;

[0014] S4, nano-selenium feeding: after the cadmium stress treatment is completed, the same volume of the nano-selenium mother solution is added to the cultivation water every day, and the nano-selenium feeding lasts for 14 days.

[0015] More preferably, in the biological purification method for reducing cadmium and enriching selenium in Crassostrea hongkongensis, the final concentration of the nano-selenium solution in the cultivation water where the Crassostrea hongkongensis lives is 20 μg / L.

[0016] The present application also provides the use of the above method in the reduction of cadmium and enrichment of selenium in Crassostrea hongkongensis.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The present application discloses a biological purification method for reducing cadmium and enriching selenium in Crassostrea hongkongensis, which comprises the following steps: S1, temporary cultivation of oysters; S2, preparation of a nano-selenium solution; S3, cadmium stress treatment; and S4, nano-selenium feeding. The method can significantly reduce the cadmium content in the oysters and increase the selenium content in the oysters by using nano-selenium under specific conditions, and has no adverse effects on the oysters. The method only needs to add a nano-selenium solution with a specific concentration to the cultivation water; the cadmium reduction effect is significant: after 14 days of nano-selenium feeding treatment, the cadmium content in the oysters is significantly reduced; the selenium enrichment effect is significant: the selenium content in the oysters is significantly increased after the treatment; the safety is high: the physiological indicators of the oysters return to the normal level after the treatment; and the operation is simple: the method provides a new technical solution for the safe production of oyster products. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The fullness (%) of each treatment group of Hong Kong oysters is shown in the box plot. Among them, Cd0_Se0 is the control group, Cd80_Se0 is the cadmium stress group, Cd80_Se10 is the 10 μg / L nano selenium treatment group, and Cd80_Se20 is the 20 μg / L nano selenium treatment group. Each point in the figure represents a single sample data, the thick black line in the box plot represents the median, the box represents the interquartile range, and the different lowercase letters (a, b) above the box plot represent the significance of the difference between groups (P<0.05).

[0020] Figure 2 The changes of cadmium and selenium contents in different treatment groups of Hong Kong oysters are shown. The left side of the figure is the cadmium content (mg / kg), and the right side is the selenium content (mg / kg). Among them, Cd0_Se0 is the control group, Cd80_Se0 is the cadmium stress group, Cd80_Se10 is the 10 μg / L nano selenium treatment group, and Cd80_Se20 is the 20 μg / L nano selenium treatment group. Different lowercase letters (a, b, c) above the column chart represent the significance of the difference between groups (P<0.05), and the error line represents the standard error. DETAILED DESCRIPTION

[0021] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific drawings and examples. In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0022] Example 1

[0023] A Hong Kong oyster cadmium-reducing and selenium-enriching biological purification method comprises the following steps:

[0024] S1, oyster temporary cultivation: select Hong Kong oysters with good vitality and appropriate volume, wash to remove surface impurities, and then put them into 50L cuboid water tanks, add 30L seawater to each tank, and put 25 oysters into each tank. Control the water temperature at 28℃, the salinity at 20±1‰, and temporarily cultivate for 7 days. Replace the water and feed at fixed times every day.

[0025] S2, nano selenium solution preparation: weigh 1.961g of nano selenium, prepare 0.2g / L of nano selenium mother solution with 100mL of pure water, mix uniformly with an ultrasonic cleaning machine, and store at 4℃ after sub-packaging. Mix uniformly for 10min before use. Prepare and update every three days.

[0026] S3, cadmium stress treatment: after the temporary cultivation is completed, add cadmium chloride solution to the cultivation water to make the cadmium concentration in the water reach 80 μg / L, and the stress time is 7 days.

[0027] S4, nano selenium feeding: after the end of cadmium stress, daily addition of nano selenium mother solution (the final concentration of nano selenium 20 μg / L) to the aquaculture water, continuous feeding for 14 days.

[0028] Example 2

[0029] A Hong Kong oyster cadmium reduction selenium-rich biological purification method comprises the following steps:

[0030] S1, oyster temporary breeding: select good vitality, medium size Hong Kong oyster, wash off surface impurities, put into 50L cuboid water tank, add 30L seawater to each tank, put 25 oysters. Control water temperature 28℃, salinity 20±1‰, temporary breeding for 7 days. Replace water and feed at fixed time every day.

[0031] S2, nano selenium solution preparation: weigh 1.961g nano selenium, prepare 0.2g / L nano selenium mother solution with 100mL pure water, ultrasonic mixing with ultrasonic cleaning machine, store at 4℃ after sub-packaging. Mix for 10min before use. Prepare every three days.

[0032] S3, cadmium stress treatment: after temporary breeding, add cadmium chloride solution to the aquaculture water to make the cadmium concentration in the water reach 80μg / L, and the stress time is 7 days.

[0033] S4, nano selenium feeding: after the end of cadmium stress, daily addition of nano selenium mother solution (the final concentration of nano selenium 20 μg / L) to the aquaculture water, continuous feeding for 14 days.

[0034] Test example

[0035] 1, oyster fullness determination

[0036] Measure the total weight of oysters, dry the shell and tissue at 60℃ for 48 hours to constant weight, and weigh the dry shell and dry tissue weight respectively.

[0037] Calculate fullness: CI = dry tissue weight / (total oyster weight - dry shell weight).

[0038] As can be seen from Figure 1 , the fullness of the control group (Cd0_Se0) is the highest, showing normal growth state; the fullness of the cadmium stress group (Cd80_Se0) is significantly lower than that of the control group, indicating that cadmium stress has a significant inhibitory effect on oyster growth; the fullness of the 10 μg / L nano selenium treatment group (Cd80_Se10) is similar to that of the cadmium stress group, indicating that the treatment effect of this concentration is not obvious; the fullness of the 20 μg / L nano selenium treatment group (Cd80_Se20) is significantly higher than that of the cadmium stress group, close to the control group level, indicating that the nano selenium treatment at this concentration can effectively improve the negative impact of cadmium stress on oyster growth.

[0039] The figure proves that 20ug / L is the best treatment concentration, under which the inhibition of cadmium stress on the growth of Hong Kong oysters can be effectively alleviated.

[0040] 2. Heavy metal content determination: according to the method of GB 5009.268-2016, the concentrations of Se and Cd in dry soft tissues were determined by ICP-OES.

[0041] From Figure 2 It can be seen that cadmium stress significantly increases the content of cadmium in oysters, while nano-selenium treatment can significantly reduce the accumulation of cadmium in oysters, and the 20ug / L nano-selenium treatment group has the most significant effect of reducing cadmium. Selenium content: with the increase of nano-selenium treatment concentration, the selenium content in oysters gradually increases, and the 20ug / L nano-selenium treatment group has the most significant effect of selenium enrichment. The figure directly shows that the application of nano-selenium treatment can achieve the dual effect of reducing cadmium and enriching selenium in Hong Kong oysters.

[0042] Finally, it should be explained that the above examples are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application 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 application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for bioremediation of cadmium-reduced and selenium-enriched Hong Kong oysters, characterized in that, It comprises the following steps: S1, oyster temporary breeding: after Hong Kong oyster is cleaned, water temperature is controlled to 28 DEG C, salinity is 20+ / -1 ‰, and temporary breeding is carried out for 7 days; water is changed and feeding is carried out at fixed time every day; S2, nano selenium solution preparation: 0.2 g / L nano selenium mother solution is prepared, and mixing is required before use; S3, cadmium stress treatment: after Hong Kong oyster completes temporary breeding of step S1, cadmium chloride solution is added to the water body, so that the cadmium concentration in the water body reaches 80 μg / L, and cadmium stress starts, and the stress time is 7 days; S4, nano selenium feeding: after cadmium stress ends, the same volume of nano selenium mother solution is added to the water body every day, and continuous feeding is carried out for 14 days; the final concentration of the nano selenium solution in the water body where Hong Kong oyster lives is 20 μg / L.

2. The application of the method in claim 1 in the reduction of cadmium and the enrichment of selenium in Hong Kong oyster.

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