Method for producing carotenoid
Technical Field
The invention belongs to the field of biotechnology, and particularly relates to a method for producing carotenoid.
Background
Carotenoids are fat-soluble pigments, most of which are insoluble in water, soluble in organic solvents and yellow, orange or red polyene compounds, and become important natural pigments due to wide distribution, various structures and more functions. It is present in both plants, animals and microorganisms. The carotenoid has various biological effects due to the structural characteristics, and researches show that the carotenoid can have the effects of preventing and treating heart diseases, cancers, cataract and several human chronic diseases and other biological activity effects. In addition, carotenoid as an excellent food additive and a nutritional supplement for improving human nutrition, its excellent quality and effect have long been recognized by various countries in the world and are known as the most promising antioxidant. Carotenoids have long been favored by people because of their good application prospects and excellent functions.
The chemically synthesized carotene is difficult to be absorbed by human bodies, has low physiological activity, can be synthesized into intermediate products harmful to the human bodies, is not easy to separate, has certain toxic or side effect, and is not popularized and used on a large scale. Naturally occurring carotene has no toxic or side effect and is more and more valued by people. At present, the sources of natural carotenoids are mainly extracted from plants and microbial fermentation. The plant extract is obtained by extracting carotenoid from carotenoid-rich plant such as carrot. The microbial fermentation extraction refers to the production of carotenoid by the fermentation of microorganisms such as Blakeslea trispora, seaweed of Dunaliella, yeast and the like. Chinese invention patent CN102702777A discloses a method for extracting carotenoid from plant material by enzymatic hydrolysis, firstly homogenizing fresh plant material and water by a homogenizer, and crushing by an ultrasonic crusher; adding cellulase, pectinase and surfactant for enzymolysis, adding diatomite into the enzymolysis liquid, filtering, and vacuum drying the filtrate to obtain carotenoid; the method has the defects of more raw materials consumption, high cost, larger influence of the raw materials and the like. Since the process for extracting carotenoids from natural plants is complicated and has low yield and is greatly influenced by raw materials, the production of carotenoids by microbial fermentation has become a research hotspot. For example, chinese patent CN104805168A discloses a method for producing carotenoids by fermentation using photosynthetic bacteria, wherein the yield of carotenoids is significantly increased by adjusting the culture conditions to be micro-aerobic. Some researches have also been conducted on mixed strain fermentation, such as "research on producing carotenoids by mixed solid fermentation of yam skins, science and technology in food industry in 2014", which adopts mixed solid fermentation of neurospora crassa and lactobacillus plantarum to produce carotenoids, wherein the solid fermentation time is 60 hours, the yield is less than 200ug/g of culture, and the yield is relatively low. The present natural carotene is high in price which is twice as high as chemicals and relatively high in cost due to the limitation of the content of carotenoid from plant sources, and the microbial fermentation method has the defects of low yield and high culture cost.
Disclosure of Invention
The invention aims to solve the defects of carotenoid production in the prior art and the like, and provides a method for producing carotenoid.
The invention is realized by the following technical scheme:
a process for producing carotenoids, which comprises the steps of:
centrifuging the composite microorganism culture, removing the supernatant, collecting thalli, adding acetone, performing ultrasonic wall breaking, standing for 30min, centrifuging, collecting the supernatant and precipitate, adding acetone with the same volume into the precipitate, performing ultrasonic treatment, and collecting the supernatant; mixing the two supernatants, evaporating to dry at low temperature with rotary evaporator, dissolving the residue with diethyl ether, adding KOH methanol solution, standing for 10-30min, adding NaCl solution to allow the solvent to separate, collecting the upper diethyl ether phase, and evaporating to dry to obtain carotenoid product.
Specifically, the method comprises the following steps:
centrifuging the composite microorganism culture at 8000rpm and 4 deg.C for 20min, discarding the supernatant, collecting thallus, and mixing the thallus according to the volume ratio of 1kg thallus: adding 1-1.5L of acetone, ultrasonically breaking the wall, wherein the ultrasonic power is 300W, the ultrasonic time is 10s each time, the intermittent time is 10s, the total ultrasonic time is 30min, standing for 30min, centrifuging at 5000rpm for 5min, collecting the supernatant and the precipitate, adding acetone with the same volume into the precipitate, ultrasonically treating for 15min, ultrasonically breaking the wall, wherein the ultrasonic power is 300W, the ultrasonic time is 10s each time, the intermittent time is 10s, centrifuging at 5000rpm for 3min, and collecting the supernatant; mixing the two supernatants, evaporating to dryness at low temperature by using a rotary evaporator, dissolving the residue with diethyl ether, adding a fifth volume of 30% KOH methanol solution, standing for 10-30min, adding 5% NaCl solution to stratify the solvent, collecting the upper diethyl ether phase, and evaporating the diethyl ether phase to dryness to obtain the carotenoid product.
Specifically, the complex microorganism culture comprises bacillus subtilis, rhodopseudomonas capsulata and rhodotorula glutinis.
Further, the composite microorganism culture is prepared according to the following steps:
step 1) firstly, crushing rice straws to 1-5cm, and then carrying out steam explosion pretreatment;
step 2), sieving the rice straws subjected to steam explosion treatment by a 50-mesh sieve, collecting undersize products, and mixing the undersize products with the vinasse according to the ratio of 3: 1 to obtain a mixture, adding the mixture into water which accounts for 2-3 times of the weight of the mixture, heating to 60-70 ℃, stirring for 60-90min at 100rpm under the condition of heat preservation, then heating to 121 ℃, preserving heat for 3-5min, and naturally cooling to room temperature to obtain a culture solution;
step 3) inoculating the bacillus subtilis seed solution into a photosynthetic culture fermentation tank containing the culture solution according to the inoculation amount of 5-7% for culture for 24-36h, and then inoculating the rhodopseudomonas capsulata seed solution and the rhodotorula glutinis seed solution, wherein the inoculation amounts are 8-10%; continuously culturing for 24-36h to obtain the composite microorganism culture.
Preferably, the first and second electrodes are formed of a metal,
the steam explosion pretreatment conditions are as follows: the pressure is 1.5-1.8MPa, and the retention time is 5-10 min.
Preferably, the first and second electrodes are formed of a metal,
the culture conditions are as follows: the temperature is 30 ℃, the dissolved oxygen concentration is 1-3mg/L, and the illumination intensity is 2000-3000 lux.
Preferably, the first and second electrodes are formed of a metal,
the preparation method of the bacillus subtilis seed solution comprises the following steps: inoculating bacillus subtilis to an LB solid culture medium for culture to obtain a single colony; and selecting a single colony, inoculating the single colony on an LB liquid culture medium, and culturing to obtain a bacillus subtilis seed solution.
Preferably, the first and second electrodes are formed of a metal,
the preparation method of the rhodopseudomonas capsulata seed solution comprises the following steps: and (3) streaking and inoculating the rhodopseudomonas capsulata to a beef extract peptone agar culture medium for culture, then selecting colonies, and inoculating the colonies to a liquid seed culture medium for seed culture to obtain a rhodopseudomonas capsulata seed solution.
Preferably, the first and second electrodes are formed of a metal,
the liquid seed culture medium comprises the following components: 3g/L of glucose, 2g/L of yeast extract, 0.5g/L of ammonium chloride, 0.1g/L of monopotassium phosphate, 0.1g/L of magnesium sulfate heptahydrate and 0.01g/L of ferrous sulfate heptahydrate.
Preferably, the first and second electrodes are formed of a metal,
the preparation method of the Rhodotorula glutinis strain seed liquid comprises the following steps: inoculating rhodotorula glutinis to a YPDA solid culture medium for culture to obtain a single colony; and (3) selecting a single colony, inoculating the single colony to a YPD liquid culture medium for culture, and culturing at 30 ℃ for 24 hours to obtain Rhodotorula glutinis strain seed liquid.
The strains specifically adopted in the embodiment of the invention are bacillus subtilis ATCC6633, rhodopseudomonas capsulata ATCC33762 and rhodotorula glutinis ATCC 32759. The preparation method of the seed liquid of the strain is not limited to the method described in the examples, and can be performed according to the conventional preparation method in the field.
Compared with the prior art, the invention has the advantages that the invention mainly comprises but is not limited to the following aspects:
the carotenoid product prepared by the method has high purity which reaches more than 94 percent, and the conversion yield reaches more than 90 percent.
In the extraction process, ultrasonic-assisted wall breaking extraction is adopted, so that the usage amount of an extraction reagent is reduced;
the steam explosion pretreatment can partially degrade the hemicellulose and the lignin, destroy the wrapping effect of the lignin and the hemicellulose on the cellulose, destroy the crystallization area of the cellulose, increase the porosity and the inner surface area of the raw material, and be more beneficial to the subsequent enzyme hydrolysis of the cellulose.
The invention carries out crushing and blasting treatment on agricultural waste straws, combines with vinasse, can provide normal growth conditions for bacillus subtilis, has relatively low raw materials and can reduce the enterprise cost;
under the stress condition of proper nutrient deficiency or hypoxia condition, more carotenoid and other substances can be produced in the bacterial cells, and then the slow proliferation of the bacterial strains is easily caused, so that the yield of the carotenoid, the proliferation of the bacterial cells and the culture cost need to be balanced in industrial production;
rhodopseudomonas capsulata and rhodotorula glutinis are strains for producing carotenoid, and the rhodotorula capsulata and the rhodotorula glutinis can be symbiotic and can utilize xylose as a fermentation substrate, but reducing sugar nutrients such as xylose in the straw treatment product are insufficient and are not beneficial to the growth of the strains; the method comprises the following steps of firstly, fermenting straws and vinasse by using bacillus subtilis, wherein the bacillus subtilis can produce cellulase and protease, a carbon source in a culture solution is mainly cellulose and lignin components, the bacillus subtilis can produce enzyme with high efficiency under the stress condition of relatively insufficient carbohydrate components, the cellulase can produce reducing sugar by using the cellulose as a substrate for rhodopseudomonas capsulata and rhodotorula glutinis, the rhodopseudomonas capsulata and the rhodotorula glutinis have a nutrition competition relationship, and a large amount of carotene substances can be produced intracellularly under the stress condition; the protease produced by the bacillus subtilis can also carry out enzymolysis on vinasse, and an enzymolysis product can be used as a nitrogen source; the three strains can be symbiotically coordinated in a culture system, and the proliferation of the strains and the generation of the carotenoids are promoted.
Drawings
FIG. 1: the influence of mixed culture time on the biomass of the thalli;
FIG. 2: effect of mixed culture time on carotenoid production.
Detailed Description
Those skilled in the art can modify the process parameters appropriately to achieve the desired results with reference to the disclosure herein. It is expressly intended that all such similar substitutes and modifications which would be obvious to one skilled in the art are deemed to be included in the invention. While the products and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations and modifications, or appropriate alterations and combinations, of the products and methods described herein may be made and utilized without departing from the spirit, scope, and spirit of the invention. For a further understanding of the present invention, reference will now be made in detail to the following examples.
Example 1
A process for producing carotenoids, which comprises the steps of:
centrifuging the composite microorganism culture at 8000rpm and 4 deg.C for 20min, discarding the supernatant, collecting thallus, and mixing the thallus according to the volume ratio of 1kg thallus: adding acetone into 1L of acetone, performing ultrasonic wall breaking, performing ultrasonic treatment at an ultrasonic power of 300W, an ultrasonic time of 10s each time, an intermittent time of 10s, a total ultrasonic time of 30min, standing for 30min, centrifuging at 5000rpm for 5min, collecting supernatant and precipitate, adding acetone with the same volume into the precipitate, performing ultrasonic treatment for 15min, performing ultrasonic treatment at an ultrasonic power of 300W, an ultrasonic time of 10s each time, an intermittent time of 10s, centrifuging at 5000rpm for 3min, and collecting supernatant; and combining the two supernatants, evaporating to dryness at low temperature by using a rotary evaporator, dissolving the residue by using diethyl ether with twice weight, adding a KOH methanol solution with the mass fraction of 30 percent accounting for one fifth volume of the dissolved substance, standing for 30min, adding a NaCl solution with the mass fraction of 5 percent to stratify the solvent, collecting an upper diethyl ether phase, and evaporating the diethyl ether phase to dryness to obtain the carotenoid product.
The compound microorganism culture is prepared according to the following steps:
1) firstly, crushing rice straws to 2cm, and then placing under the conditions of 1.5MPa of pressure and 10min of residence time for steam explosion pretreatment;
2) sieving the rice straws subjected to steam explosion treatment by a 50-mesh sieve, collecting undersize products, and mixing the undersize products with vinasse according to the weight ratio of 3: 1 to obtain a mixture, adding the mixture into water which accounts for 2 times of the weight of the mixture, heating to 60 ℃, stirring for 90min at 100rpm under the condition of heat preservation, then heating to 121 ℃, preserving heat for 5min, and naturally cooling to room temperature to obtain a culture solution;
3) inoculating the bacillus subtilis seed solution into a photosynthetic culture fermentation tank containing a culture solution according to the inoculation amount of 7 percent (volume ratio) for culture, wherein the temperature is 30 ℃, the dissolved oxygen concentration is 1mg/L, the illumination intensity is 2000lux, and the culture time is 36h, and then inoculating the rhodopseudomonas capsulata seed solution and the rhodotorula glutinis seed solution, wherein the inoculation amounts are 10 percent (volume ratio); and continuously culturing for 36h to obtain the composite microorganism culture.
The preparation method of the bacillus subtilis seed solution comprises the following steps: inoculating bacillus subtilis to an LB solid culture medium for culture to obtain a single colony; selecting single colony, inoculating to LB liquid culture medium, and culturing to obtain thallus concentration of 1 × 108cfu/ml of bacillus subtilis seed solution;
the rhodopseudomonas capsulataThe preparation method of the seed liquid comprises the following steps: inoculating Rhodopseudomonas capsulata to beef extract peptone agar medium for culturing, selecting colony, inoculating to liquid seed culture medium for seed culture to obtain thallus concentration of 3 × 108cfu/ml of rhodopseudomonas capsulata seed solution; the liquid seed culture medium comprises the following components: 3g/L of glucose, 2g/L of yeast extract, 0.5g/L of ammonium chloride, 0.1g/L of monopotassium phosphate, 0.1g/L of magnesium sulfate heptahydrate and 0.01g/L of ferrous sulfate heptahydrate;
the preparation method of the Rhodotorula glutinis strain seed liquid comprises the following steps: inoculating rhodotorula glutinis to a YPDA culture medium for culture to obtain a single colony; selecting single colony, inoculating to YPD liquid culture medium, culturing at 30 deg.C for 24 hr to obtain thallus concentration of 5 × 107cfu/ml Rhodotorula glutinis strain seed liquid.
Example 2
A process for producing carotenoids, which comprises the steps of:
centrifuging the composite microorganism culture at 8000rpm and 4 deg.C for 20min, discarding the supernatant, collecting thallus, and mixing the thallus according to the volume ratio of 1kg thallus: adding acetone into 1.5L of acetone, performing ultrasonic wall breaking, performing ultrasonic treatment at an ultrasonic power of 300W, performing ultrasonic treatment at an ultrasonic power of 10s each time, performing intermittent operation of 10s, performing total ultrasonic treatment for 30min, standing for 30min, centrifuging at 5000rpm for 5min, collecting supernatant and precipitate, adding acetone with the same volume into the precipitate, performing ultrasonic treatment for 15min at an ultrasonic power of 300W, performing ultrasonic treatment at an ultrasonic time of 10s each time, performing centrifugal operation at 5000rpm for 3min, and collecting supernatant; and combining the two supernatants, evaporating to dryness at low temperature by using a rotary evaporator, dissolving the residue by using ether, adding a KOH methanol solution with the mass fraction of 30% in one sixth volume, standing for 20min, adding a 5% NaCl solution to stratify the solvent, collecting an ether phase at the upper layer, and evaporating the ether phase to dryness to obtain the carotenoid product.
The compound microorganism culture is prepared according to the following steps:
1) firstly, crushing rice straws to 5cm, and then placing under the conditions of 1.8MPa of pressure and 5min of residence time for steam explosion pretreatment;
2) sieving the rice straws subjected to steam explosion treatment by a 50-mesh sieve, collecting undersize products, and mixing the undersize products with vinasse according to the weight ratio of 3: 1 to obtain a mixture, adding the mixture into water which accounts for 3 times of the weight of the mixture, heating to 70 ℃, stirring for 80min at 100rpm under the condition of heat preservation, then heating to 121 ℃, preserving heat for 4min, and naturally cooling to room temperature to obtain a culture solution;
3) inoculating the bacillus subtilis seed solution into a photosynthetic culture fermentation tank containing a culture solution according to the inoculation amount of 6 percent (volume ratio) for culture, wherein the temperature is 30 ℃, the dissolved oxygen concentration is 2mg/L, the illumination intensity is 3000lux, the culture time is 24 hours, and then inoculating the rhodopseudomonas capsulata seed solution and the rhodotorula glutinis seed solution, wherein the inoculation amounts are 8 percent (volume ratio); and continuously culturing for 30h to obtain the composite microbial culture.
The preparation method of the bacillus subtilis seed solution comprises the following steps: inoculating bacillus subtilis to an LB solid culture medium for culture to obtain a single colony; selecting single colony, inoculating to LB liquid culture medium, and culturing to obtain thallus concentration of 2 × 108cfu/ml of bacillus subtilis seed solution;
the preparation method of the rhodopseudomonas capsulata seed solution comprises the following steps: inoculating Rhodopseudomonas capsulata to beef extract peptone agar medium for culturing, selecting colony, inoculating to liquid seed culture medium for seed culture to obtain thallus concentration of 3 × 108cfu/ml of rhodopseudomonas capsulata seed solution; the liquid seed culture medium comprises the following components: 3g/L of glucose, 2g/L of yeast extract, 0.5g/L of ammonium chloride, 0.1g/L of monopotassium phosphate, 0.1g/L of magnesium sulfate heptahydrate and 0.01g/L of ferrous sulfate heptahydrate;
the preparation method of the Rhodotorula glutinis strain seed liquid comprises the following steps: inoculating rhodotorula glutinis to a YPDA culture medium for culture to obtain a single colony; selecting single colony, inoculating to YPD liquid culture medium, culturing at 30 deg.C for 24 hr to obtain thallus concentration of 7 × 107cfu/ml Rhodotorula glutinis strain seed liquid.
Example 3
The changes of the main components of the rice straw by the blasting are shown in the table 1:
TABLE 1
Index (I)
|
Before blasting
|
After blasting
|
Hemicellulose and cellulose%
|
53.7
|
40.5
|
Lignin%
|
27.9
|
22.1
|
Oligo-xylose%
|
0
|
3.4 |
And (4) conclusion: the blasting causes the cell wall of the straw to be damaged, and part of hemicellulose and cellulose are degraded and dissolved out, so that the subsequent enzymolysis of cellulose by cellulase is facilitated; the crystallinity and polymerization degree of cellulose are reduced in the process of blasting pretreatment, and the hemicellulose is degraded into monosaccharide and oligosaccharide through self-hydrolysis and can be used as a carbon source of a strain.
Example 4
Determination of biomass of bacteria and yield of carotenoid:
centrifuging the composite microorganism culture at 8000rpm and 4 deg.C for 20min, removing supernatant, and drying at 45 deg.C for about 36h to reach constant weight. Accurately weighing 0.5g of thallus, adding 2mL of 2mol/L hydrochloric acid, mixing uniformly, carrying out suction filtration, washing to be neutral, and taking filter residue for later use. Adding 10mL of acetone into filter residue, leaching for 30min at room temperature, twice, centrifuging filtrate, combining supernate obtained by twice centrifugation, adding acetone into the supernate obtained by twice centrifugation to fix the volume to 25 mL. Mixing ofThe absorbance was measured at 461nm using acetone as a blank. Carotenoid content (mg/g biomass) = (A) measured by carotenoid content methodλmax×D×V)/(1000×0.16×W)。
In the formula Aλmax-absorbance at the wavelength of maximum absorption of the carotenoid; v-amount of solvent used for extraction (mL); d-the dilution factor when determining the sample; w-cell weight (g); 0.16-molar extinction coefficient of carotenoid.
Setting a control group to verify the synergistic effect of each strain, wherein the control group 1: the preparation method is the same as that of the example 1 only by adopting the bacillus subtilis and the rhodopseudomonas capsulata and not adding the rhodotorula glutinis; control group 2: the preparation method is the same as that of example 1 only by using bacillus subtilis and rhodotorula glutinis without adding rhodopseudomonas capsulata. Specific detection results are shown in table 2:
TABLE 2
Group of
|
Dry weight g/L of biomass of thallus
|
Yield mg/g bacterial biomass of carotenoid
|
Example 1
|
12.7
|
2.08
|
Example 2
|
12.1
|
1.96
|
Control group 1
|
10.9
|
1.65
|
Control group 2
|
9.8
|
1.50 |
As shown in Table 2, in examples 1-2, the biomass and the carotenoid yields were higher than those of the control group 1-2, and the carotenoid yields were significantly higher than those of the control group 1-2. Wherein, the biomass dry weight of the thalli in the example 1 is 12.7g/L, which is 16.5 percent and 29.6 percent higher than that of the control groups 1 and 2 respectively; the yield of carotene was 2.08mg/g of bacterial biomass, which was 26.1% and 38.7% higher than those of control groups 1 and 2, respectively.
Example 5
The effect of the mixed culture time of the three strains on the biomass of the bacteria and the yield of the carotenoid.
Taking the method of example 1 as an example, different mixed culture time points, specifically 6, 12,18,24,30,36 and 42h, were set. As shown in the figure 1-2, the increase of the biomass of the thallus is obvious within 12 hours, but the yield of the carotenoid is maintained at a lower level, the biomass of the thallus and the yield of the carotenoid are obviously increased along with the increase of the culture time, and the increase of the biomass of the thallus is slowed after the culture time is 24 hours, probably because the culture components in the culture solution are reduced, the proliferation rate of the strain is reduced under the condition of nutrient deficiency and stress, but the yield of the carotenoid is continuously increased, the biomass of the thallus reaches the peak value when the strain is cultured for 36 hours, and then the biomass of the thallus is reduced, probably because the strain is dead, and correspondingly, the yield of the carotenoid is also reduced.
Example 6
The influence of the extraction method of example 1-2 of the present invention on purity and yield:
30kg of cells were obtained by drying each 100kg of the complex microbial culture, based on the water content of the complex microbial culture of 70%, and the theoretical values of the cucurbitacin content were 62.4g (example 1) and 58.8g (example 2).
The carotenoid product was weighed and the purity of the carotenoid in the product was determined spectrophotometrically. See table 3 for details:
TABLE 3
Group of
|
Product weight g
|
Purity%
|
Example 1
|
60.7
|
94.8
|
Example 2
|
56.9
|
94.3 |
As shown in Table 3, the carotenoid product of the invention has high purity, which reaches more than 94%, and the yield is respectively 92.2% (example 1) and 91.3% (example 2).
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.