TW202216985A - Method for culturing microalgae - Google Patents

Abstract

A method for culturing microalgae is used to accelerate the growth rate of microalgae cells. The microalgae cells are cultured in a luminous environment for 12-120 hours. The luminous environment consists of a visible light with an irradiance ranging from 20,000 to 30,000 mW/m ²and an ultraviolet A light with an irradiance ranging from 50 to 350 mW/m ².

Description

Microalgae cultivation method

The present invention relates to a method for culturing algae, in particular to a method for culturing microalgae.

Microalgae generally refer to single-celled algae with a cell size of about 1-10 μm, which are invisible to the naked eye, but have very large biomass and are widely distributed, and can be found in seawater, freshwater or moist soil. In the past, traditional biomass energy was mostly converted into fuel by using food such as soybeans and corn. However, due to the food pressure brought about by the population explosion, the practice of extracting oil from such food crops has always caused a controversy of "grabbing with the people". , Since the growth rate of microalgae cells is faster than that of ordinary plants, and the oil content of oil-producing microalgae cells can reach 20 to 50% of the weight of microalgae cells, or even as high as 80%, the oil-producing microalgae cells are used for The production efficiency of biodiesel can reach more than 100 times that of soybean, so microalgae has become one of the materials of biomass energy.

Furthermore, the nutritional value of microalgae is extremely high, containing more than 65% of vegetable protein, of which the proportion of essential amino acids in the human body is as high as 50%, and it also contains calcium, phosphorus, iron and other mineral elements, and is richer in β- Carotene, pantothenic acid, folic acid, biotin and A, B group, C and E and other vitamins, its vitamin B12, iron content is higher than liver, calcium content is higher than milk, so it has become a health food recognized by governments , functional food or dietary supplements. In addition, microalgae can also be used as aquatic food and animal feed additives. In addition to reducing the disease rate of animals and improving the survival rate of animals, they can also improve the color of aquatic products or egg yolks, and increase the by-products of aquatic and terrestrial organisms. commercial value.

To sum up, if the microalgal cell culture environment can be adjusted to promote the rapid growth of microalgal cells, it will not only help improve the production efficiency of biomass energy, but also help human health and dietary environment.

In order to solve the above problems, the purpose of the present invention is to provide a method for culturing microalgae, which can improve the growth efficiency of microalgae.

The microalgae culture method of the present invention is to culture the microalgae cells in a light environment for 12-120 hours; wherein, the light environment can be a visible light with an irradiance of 20,000-30,000 mW/m ² and 50-350 It is composed of a UV light A of mW/m ² .

Accordingly, the microalgae culture method of the present invention provides the microalgae cells with a slight growth stress by including visible light and ultraviolet light A with a specific illuminance, and promotes the rapid growth of the microalgae cells, which is the effect of the present invention.

In the microalgae cultivation method of the present invention, the irradiance of the visible light may preferably be 23,000-24,000 mW/m ² , and the irradiance of the ultraviolet light A may preferably be 310-330 mW/m ² . In this way, by adjusting the ratio of the irradiance of visible light and ultraviolet light A, the growth rate of microalgae cells can be increased.

In the method for culturing microalgae of the present invention, wherein, the visible light may preferably include red light with an irradiance percentage of 10-25%, orange light with 7-20%, yellow light with 5-15%, and yellow light with 25-45%. Green light, 2-10% blue light, 7-20% indigo light and 8-25% violet light. In this way, the growth rate of microalgae cells can be increased by adjusting the ratio of the irradiance of each wavelength band in the visible light.

In order to make the above-mentioned and other objects, features and advantages of the present invention more obvious and easy to understand, the preferred embodiments of the present invention are exemplified below, and are described in detail as follows in conjunction with the accompanying drawings:

The “visible light” mentioned in the present invention refers to electromagnetic radiation visible to human eyes, the wavelength range of which is between 381 and 780 nm, and can be divided into red, orange, yellow and green according to the wavelength from long to short. Indigo violet and other 7 bands, among which, the wavelength range of red light is between 621 and 780 nm, the wavelength range of orange light is between 591 and 620 nm, and the wavelength range of yellow light is between 571 and 590 nm. , the wavelength range of green light is between 496-570 nm, the wavelength range of blue light is between 476-495 nm, the wavelength range of indigo light is between 451-475 nm, and the wavelength range of violet light is between 381- 450 nm; and, the "ultraviolet light (UV light)" in the present invention refers to electromagnetic waves with a wavelength range between 10 and 380 nm, wherein the wavelength range closest to visible light is Called "ultraviolet A light, UVA light", the wavelength is about 315-380 nm, which can penetrate into the dermis layer of human skin and cause sunburn, which is a common knowledge in the technical field to which the present invention belongs. It can be understood by the reader, so it will not be repeated here.

A method for culturing microalgae according to an embodiment of the present invention is to culture the microalgal cells in a lighted environment, and the lighted environment composed of visible light and ultraviolet light A is used to accelerate the growth of the microalgae cells.

Specifically, the lighting environment can be composed of visible light with an irradiance of 20,000-30,000 mW/m ² and an ultraviolet light A with an irradiance of 50-350 mW/m ² (approximately equivalent to 6,000-9,500 lux of visible light). and ultraviolet light of 15-105 lux); preferably, the irradiance of the visible light can be 23,000-24,000 mW/m ² , and the irradiance of the ultraviolet light A can be 310-330 mW/m ² , so by The ratio of the irradiance of visible light to UV light A increases the growth rate of microalgal cells.

For example, microalgal cells can be cultured in a culture tank made of poly(methyl methacrylate) (PMMA), and the culture tank can be filled with the culture medium shown in Table 1, The trace element solution shown in Table 2 and the chelating solution shown in Table 3, and a visible light source and an ultraviolet A light source are arranged outside the culture tank, so that the lighting environment can be formed in the culture tank. In this embodiment, the thickness of the culture tank is about 5 mm, the total irradiance of the visible light source disposed outside the culture tank is 22,000～32,000 mW/m ² , and the total irradiance of the ultraviolet light source A is 75～32,000 mW/m 2 . 950 mW/m ² , so that the lighting environment can be formed in the culture tank; however, those with ordinary knowledge in the art can adjust the total amount of the visible light source and the ultraviolet A light source according to the material and thickness of the culture tank used. The irradiance is not limited here.

Formulation of culture medium for culturing microalgal cells Element added amount Sodium nitrate (NaNO ₃ ) 0.85000 g Magnesium sulfate (magnesium sulfate, MgSO ₄ ‧7H ₂ O) 0.24650 g Calcium chloride (CaCl ₂ ‧2H ₂ O) 0.01470 g Potassium dihydrogen phosphate (potassium dihydrogen phosphate, KH ₂ PO ₄ ) 0.02722 g Potassium hydrogen phosphate (potassium hydrogen phosphate, K ₂ HPO ₄ ) 0.20904 g trace element solution 1 mL Chelating solution 1 mL Make up to 1 L with water

Formulation of trace element solutions for culturing microalgal cells Element added amount Zinc sulfate (ZnSO ₄ ‧7H ₂ O) 2.87540 g Manganese sulfate (manganese(II) sulfate, MnSO ₄ ‧7H ₂ O) 1.69020g Boric acid (boric acid, H ₃ BO ₃ ) 0.61840 g Cobalt(II) chloride (CoCl ₂ ‧6H ₂ O) 2.37940 g Sodium manganate (Na ₂ MoO ₄ ‧2H ₂ O) 0.24200 g Copper(II) sulfate (CuSO ₄ ‧5H ₂ O) 0.02500 g Ethylenediaminetetraacetic acid (EDTA) 3.72250 g Make up to 1 L with water

Formulation of chelating solution for culturing microalgal cells Element added amount Ferrous sulfate (iron(II) sulfate, FeSO ₄ ‧7H ₂ O) 3.48000 g Ethylenediaminetetraacetic acid (EDTA) 4.66000 g Make up to 1 L with water

In addition, different visible light compositions will also affect the growth of microalgae cells, so it is preferable to make the visible light include 10-25% of red light, 7-20% of orange light, 5-15% of light in terms of irradiance percentage Yellow light, 25-45% green light, 2-10% blue light, 7-20% indigo light and 8-25% violet light.

It is worth noting that, since the growth of microalgae cells will be affected when the microalgae cells grow excessively, it is preferable to set a stirring element in the culture tank, so that the microalgae cells can be evenly distributed in the culture tank; Furthermore, the concentration of the microalgae cells in the culture tank should not be too high. When inoculated in the culture solution, the dry weight of the microalgae cells per liter of the culture solution is preferably about 0.75 g, and the average dry weight is about 0.75 g. At the temperature of 28 to 33 °C, the culture was continued for 12 to 120 hours. During the incubation period, air (about 0.5 L/min) was continuously injected with an air pump, so that the microalgae cells could be maintained in the log phase of growth for a long time. ).

In order to confirm that this microalgae culture method can indeed increase the growth rate of microalgae cells, Chlorella vulgaris Beij. strain #3001 was used as a model cell, and the following experiments were carried out:

(A) Spectral analysis results

In this experiment, a spectrometer (SRI-2000UV) was used to analyze the irradiance of the visible light source inside the culture tank (the analysis band was between 250 and 850 nm). (area under curve), which can be converted into red light (between 621 and 780 nm), orange light (between 591 and 620 nm), yellow light (between 571 and 590 nm), and green light (between 496 and 570 nm) The irradiance of blue light (between 476 and 495 nm), indigo light (between 451 and 475 nm) and violet light (between 381 and 450 nm) are about 3750, 2750, 2050, 7350, 1550 and 3400, respectively. and 2200 mW/m ² , it can be known that the visible light source inside the culture tank contains about 16.3% red light, 11.9% orange light, 8.9% yellow light, 31.9% green light, 6.7% irradiance percentage. 14.8% blue light, 14.8% indigo light and 9.5% violet light.

(B) Culture rate of microalgal cells

Next, the microalgal cells were cultured in each group of light environments as shown in Table 4, the culture medium was collected at different time points, and the absorbance at 660 nm wavelength was measured, and the relative time points of the microalgal cells in each group were shown Growth curve.

Table 4, the lighting environment of each group in this experiment group visible light UV light A B1 22,976 mW/m ² 0 mW/m ² B2 23,477 mW/m ² 320 mW/m ² B3 23,036 mW/m ² 525mW/ ^m2

Please refer to Figure 2, the microalgae cells cultured in the light environment of group B2, stimulated by a trace amount of ultraviolet light A, have a growth rate that is better than the growth rate of microalgae cells in the light environment of group B1; and , although the illumination environment of group B3 also includes ultraviolet light A, but because the illumination of ultraviolet light A is too high, the growth rate of microalgae cells is not good, which is slightly inferior to that of group B2.

To sum up, the microalgae culture method of the present invention provides microalgae cells with a slight growth stress by including visible light and ultraviolet light A with a specific illuminance, and promotes the rapid growth of microalgae cells, which is the effect of the present invention.

Although the present invention has been disclosed by the above-mentioned preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications relative to the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the patent application attached hereto.

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[Picture 1] In the test (A), the spectral analysis results of the visible light source. [Picture 2] In experiment (B), the growth curves of microalgal cells cultured in each group of light environments.

Claims (3)

A method for culturing microalgae, which comprises culturing microalgae cells in an illumination environment for 12-120 hours; wherein, the illumination environment consists of a visible light with an irradiance of 20,000-30,000 mW/m ² and a visible light of 50-350 mW/m ² is composed of a UV light A. The method for culturing microalgae according to claim 1, wherein the irradiance of the visible light is 23,000-24,000 mW/m ² of visible light, and the irradiance of the ultraviolet light A is 310-330 mW/m ² . The method for culturing microalgae as claimed in claim 1 or 2, wherein the visible light comprises red light with an irradiance percentage of 10-25%, orange light at 7-20%, yellow light at 5-15%, and yellow light at 25-45%. green light, 2-10% blue light, 7-20% indigo light and 8-25% violet light.

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