Application of macadamia nut green peel in preparing antibacterial agent

Abstract

The present invention discloses an application of macadamia nut green peel in the preparation of an antibacterial agent, belonging to the technical field of antibacterial agent application. The present invention discovers for the first time that macadamia nut green peel has an antibacterial effect. The preparation method of the antibacterial agent comprises the following steps: cleaning the macadamia nut green peel, drying, crushing, and sieving; collecting the powder on the sieve; adding distilled water and conducting a hydrothermal reaction; filtering after the reaction; and collecting the filtrate. The obtained filtrate is the antibacterial agent. The antibacterial agent prepared from macadamia nut green peel can effectively inhibit Escherichia coli and Staphylococcus aureus. The present invention provides a new approach for the resource utilization of macadamia nut green peel.

Description

Technical Field

[0001] The invention discloses an application of macadamia nut green peel in preparing an antibacterial agent, belonging to the technical field of antibacterial agent application. Background Art

[0002] Macadamia nuts (Macadamia integrifolia), also known as macadamia nuts, are internationally acclaimed for their nutritious, delicate texture, and delicious flavor. They were introduced to China in the 1970s. Currently, my country is the world's largest producer of macadamia nuts. As of 2023, Yunnan Province had a cultivated area of ​​3.79 million mu (approximately 1.77 million hectares), accounting for 81.77% of the national total and 49.22% of the global total, ranking first worldwide. The macadamia nut fruit primarily consists of three parts: the green peel, shell, and kernel. The green peel accounts for 45% to 60% of the fresh fruit's mass. Consequently, a significant amount of green peel byproduct is generated during postharvest handling and primary processing, the vast majority of which is discarded, resulting in a significant waste of resources. Therefore, research on the comprehensive utilization of the green peel of macadamia nuts is of great practical significance for conserving resources and improving industrial efficiency.

[0003] At present, there are very few research reports using macadamia nut green peel as the main raw material, and there are few related papers and patents. The research mainly focuses on the preparation of antioxidants or organic fertilizers, such as "A macadamia nut green peel antioxidant and its preparation method (Invention Publication 202010380213.7)"; "A toner with macadamia nut protein peptide and green peel extract as active ingredients and its preparation method (Invention Publication 201810608248.4)"; "A preparation method of green peel organic fertilizer, preparation method of organic-inorganic compound fertilizer and application (Invention Publication 202311185241.3)" and other patents. It can be seen that there is still a large gap in the development and utilization of macadamia nut green peel antibacterial agents. Summary of the Invention

[0004] In order to make more effective use of macadamia nut green peel, the purpose of the present invention is to provide a use of macadamia nut green peel in the preparation of an antibacterial agent.

[0005] Preferably, the preparation method of the antibacterial agent comprises the following steps:

[0006] (1) Wash the green peel of macadamia nuts, dry it, crush it, sieve it, and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel.

[0007] (2) The macadamia nut green peel coarse powder is mixed with distilled water, ultrasonically treated and then subjected to hydrothermal reaction. After the hydrothermal reaction is completed, the filtrate collected by suction filtration is the antibacterial agent.

[0008] Preferably, the mesh size of the sieve used for sieving in step (1) is 100-200 mesh.

[0009] Preferably, in step (2), the solid-to-liquid ratio of the macadamia nut green peel coarse powder to distilled water is 1:10 to 30, expressed in g:mL.

[0010] Preferably, the hydrothermal reaction in step (2) is carried out at 140-220° C. for 6-24 hours.

[0011] Beneficial effects of the present invention

[0012] (1) The present invention has discovered a new use of macadamia nut green peel for the first time, providing a new method for resource utilization of macadamia nut green peel.

[0013] (3) The maximum antibacterial rate of the macadamia nut green peel prepared by the method of the present invention against Escherichia coli reached 90.2%, and the antibacterial rate against Staphylococcus aureus reached 44.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the antibacterial effect of the antibacterial agent prepared in Example 1 against Escherichia coli.

[0015] Figure 2 The antibacterial effect of the filter residue obtained in Example 1 on Escherichia coli.

[0016] Figure 3 Comparative Example 2 shows the antibacterial effect of the antibacterial agent against Escherichia coli.

[0017] Figure 4 The figure shows the antibacterial effect of the filter residue obtained in the comparative example on Escherichia coli.

[0018] Figure 5 This is the antibacterial effect of the antibacterial agent prepared in Comparative Example 3 on Escherichia coli.

[0019] Figure 6 The antibacterial effect of the filter residue obtained in Comparative Example 3 on Escherichia coli.

[0020] Figure 7 The antibacterial effect of untreated macadamia nut green peel powder on Escherichia coli.

[0021] Figure 8 The antibacterial effect of the antibacterial agent prepared in Example 1 on Staphylococcus aureus.

[0022] Figure 9 The antibacterial effect of the filter residue obtained in Example 1 on Staphylococcus aureus.

[0023] Figure 10 The antibacterial effect of the antibacterial agent prepared in Comparative Example 2 on Staphylococcus aureus.

[0024] Figure 11 The figure shows the antibacterial effect of the filter residue obtained in the comparative example on Staphylococcus aureus.

[0025] Figure 12 The antibacterial effect of the antibacterial agent prepared in Comparative Example 3 on Staphylococcus aureus.

[0026] Figure 13 The antibacterial effect of the filter residue obtained in Comparative Example 3 on Staphylococcus aureus.

[0027] Figure 14 The antibacterial effect of untreated macadamia nut peel powder against Staphylococcus aureus. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0029] Example 1

[0030] A method for preparing an antibacterial agent using macadamia nut green peels, comprising the following steps

[0031] (1) Wash the green peel of macadamia nuts, dry it in an oven, and grind it into powder in a grinder. Then, pass it through a 200-mesh sieve and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel.

[0032] (2) 1.0 g of macadamia nut green peel coarse powder was placed in a small beaker containing 10 mL of distilled water to obtain a suspension. The suspension was ultrasonicated at room temperature for 20 min and then hydrothermally reacted at 180 °C for 12 h. The suspension was naturally cooled to room temperature and the filtrate obtained by filtration was the antibacterial agent. The filter residue was retained for later use.

[0033] Example 2

[0034] A method for preparing an antibacterial agent using macadamia nut green peels, comprising the following steps

[0035] (1) Wash the green peel of macadamia nuts, dry it in an oven, and grind it into powder in a grinder. Then, pass it through a 150-mesh sieve and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel.

[0036] (2) 1.0 g of macadamia nut green peel coarse powder was placed in a small beaker containing 20 mL of distilled water to obtain a suspension. The suspension was ultrasonicated at room temperature for 20 min and then subjected to hydrothermal reaction at 140 °C for 24 h. The suspension was naturally cooled to room temperature and the filtrate obtained by filtration was the antibacterial agent. The filter residue was retained for later use.

[0037] Example 3

[0038] A method for preparing an antibacterial agent using macadamia nut green peels, comprising the following steps

[0039] (1) Wash the green peel of macadamia nuts, dry it in an oven, and grind it into powder in a grinder. Then, pass it through a 100-mesh sieve and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel.

[0040] (2) 1.0 g of macadamia nut green peel coarse powder was placed in a small beaker containing 30 mL of distilled water to obtain a suspension. The suspension was subjected to ultrasonic treatment at room temperature for 20 min and then hydrothermally reacted at 220 °C for 6 hours. The suspension was naturally cooled to room temperature and the filtrate obtained by filtration was the antibacterial agent. The filter residue was retained for later use.

[0041] Comparative Example 1

[0042] For comparison, the only difference between this comparative example and Example 1 is that the macadamia nut green peel antibacterial agent is prepared using the undersize powder, comprising the following steps:

[0043] (1) Wash the green peel of macadamia nuts, dry it in an oven, and grind it into powder in a grinder. Then, sieve it through a 200-mesh sieve and collect the powder under the sieve to obtain the fine powder of macadamia nut green peel.

[0044] (2) 1.0 g of macadamia nut green peel fine powder was placed in a small beaker containing 10 mL of distilled water to obtain a suspension. The suspension was ultrasonicated at room temperature for 20 min and then subjected to hydrothermal reaction at 180 °C for 12 h. The suspension was naturally cooled to room temperature and the filtrate obtained by filtration was the antibacterial agent. The filter residue was retained for later use.

[0045] Comparative Example 2

[0046] As a comparison, the difference between this comparative example and Example 1 is that the antibacterial agent is prepared by a common immersion method, including the following steps:

[0047] (1) Wash the green peel of macadamia nuts, dry it in an oven, and grind it into powder in a grinder. Then, pass it through a 200-mesh sieve and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel.

[0048] (2) Take 1.0 g of macadamia nut green peel coarse powder in a small beaker filled with 10 mL of distilled water to obtain a suspension. After stirring at room temperature for 48 hours, the filtrate obtained by suction filtration is the antibacterial agent, and the filter residue is retained for later use.

[0049] Test Example 1

[0050] The antibacterial agent prepared from Example 1 and Comparative Examples 1-2 and the retained filter residue were used to conduct an antibacterial test. All the antibacterial agents and filter residues of macadamia green peel to be tested were referred to as test samples.

[0051] The Gram-positive bacteria Staphylococcus aureus (S. aureus, CCTCC AB 91093) and Escherichia coli (E. coli, CCTCCAB 204033) were selected as experimental strains for antibacterial detection.

[0052] The preparation method of the culture medium used in the experiment is as follows:

[0053] LB agar medium: 5 g tryptone, 2.5 g yeast powder, 5 g sodium chloride, 500 mL distilled water, 7.5 g agar;

[0054] LB liquid medium: 5 g tryptone, 2.5 g yeast powder, 5 g sodium chloride, and 500 mL distilled water.

[0055] The specific test steps are as follows:

[0056] (1) Add the strain to sterile LB liquid medium and cultivate it to a concentration of 5×10 6 CFU / mL of bacterial suspension, when the concentration of cell suspension is greater than 5×10 6 CFU / mL, dilute with sterile water.

[0057] (2) 5 mg of the sample to be tested (the macadamia nut green peel antibacterial agent and filter residue prepared in all examples and comparative examples) was mixed with 10 mL of the diluted bacterial solution and placed in a sterile test tube to prepare a suspension. The suspension was incubated on a shaker at 37°C and 200 rpm for 30 min. 100 μL was then dropped into a culture dish containing LB agar medium. The bacterial solution was evenly spread on the culture medium using the spread plate method. The culture dish was placed in a constant temperature incubator and cultured for 18 to 24 h.

[0058] (3) After cultivation, the antibacterial rate of each sample was calculated using the colony counting method.

[0059] The calculation formula is as follows:

[0060] After testing, the antibacterial effects of the samples of all embodiments and comparative examples on Escherichia coli are as follows: Figures 1 to 6 As shown in the figure (A in all figures represents a blank control, and B represents an experimental group), it can be seen from the figure that the antibacterial effect of the antibacterial agent prepared by the method of the present invention on Escherichia coli is significantly better than that of the antibacterial agent prepared by other methods; the antibacterial effect of the samples to be tested in all embodiments and comparative examples on Escherichia coli is shown in FIG. Figures 8 to 13 As shown (in all figures, A represents the blank control and B represents the experimental group), it can be seen from the figure that the antibacterial agent prepared by the method of the present invention has a significantly better antibacterial effect on Staphylococcus aureus than the antibacterial agents prepared by other methods.

[0061] The antibacterial rates of the samples to be tested in Example 1 and Comparative Examples 1-2 were calculated and are shown in Table 1.

[0062] Table 1 Antibacterial rate of samples tested in Examples and Comparative Examples

[0063]

[0064] It can be more intuitively seen from Table 1 that the antibacterial agent prepared by the method of the present invention has the best antibacterial effect on Escherichia coli.

[0065] The antibacterial effects of the antibacterial agents prepared in Examples 2 and 3 were similar to those in Example 1.

[0066] Finally, the same method was used to test the antibacterial effect of macadamia nut green peel coarse powder, and it was found that the antibacterial effect was not good. Figure 7 and Figure 14 As shown, the antibacterial rate is almost 0%.

Claims

1. A use of macadamia nut green peel in the preparation of an antibacterial agent, characterized in that: The preparation method of the antibacterial agent comprises the following steps: (1) Wash the green peel of macadamia nuts, dry it, crush it, sieve it, and collect the powder on the sieve to obtain the coarse powder of macadamia nut green peel; (2) Mix the macadamia nut green peel coarse powder with distilled water, perform hydrothermal reaction after ultrasonic treatment, cool to room temperature after the hydrothermal reaction, and collect the filtrate by suction filtration to obtain the antibacterial agent; The mesh size of the sieve used for sieving in step (1) is 100-200 mesh; The hydrothermal reaction conditions in step (2) are 140-220° C. for 6-24 h.

2. The use according to claim 1, characterized in that: In step (2), the solid-liquid ratio of the macadamia nut green peel coarse powder to distilled water is 1:10-30, and the unit is g:mL.

Images