CN114774483A - Method for synthesizing PHA (polyhydroxyalkanoate) by taking blue algae and byproduct acetic acid as substrates and application of PHA - Google Patents
Method for synthesizing PHA (polyhydroxyalkanoate) by taking blue algae and byproduct acetic acid as substrates and application of PHA Download PDFInfo
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Abstract
The invention discloses a method for synthesizing PHA (polyhydroxyalkanoate) by taking blue algae and byproduct acetic acid as substrates and application thereof. The invention can realize the aim of high-efficiency PHA production, reasonably utilizes organic wastes, avoids environmental pollution, greatly reduces the PHA production cost and has industrial application prospect.
Description
Technical Field
The invention relates to a method for synthesizing PHA (polyhydroxyalkanoate) by taking blue-green algae and byproduct acetic acid as substrates and application thereof, belonging to the fields of environmental engineering and organic waste resource treatment.
Background
Polyhydroxyalkanoate (PHA) is a substance having material characteristics similar to those of general plastics and excellent biocompatibility and degradability. At present, the commonly used various plastic products are derived from petroleum, so that the raw materials of the plastic products are lack of sustainability, and the plastic products also cause serious environmental problems after being discarded. Therefore, the PHA is used for replacing plastic products, which has very important significance for circular economy, environment and sustainable development. However, the commercial production process of PHA generally requires the use of non-toxic pure high-value chemicals such as glucose, sodium acetate, etc. as carbon sources, which results in higher production cost and thus the product PHA lacks price competitiveness compared to common plastics derived from fossil fuels. Therefore, more research has been conducted in recent years to shift the raw materials for PHA synthesis to lower carbon sources, such as various organic wastes.
In addition, large quantities of algal biomass are periodically cleaned from the water and disposed of. Therefore, if the blue-green algae waste can be used as a carbon source raw material for synthesizing the PHA, the production cost of the PHA can be remarkably reduced, although the cost for synthesizing the PHA by using the blue-green algae waste as the raw material is very low, the technical process still faces a small challenge. Because the nitrogen content in the blue algae waste is high, if the blue algae waste is used as the only carbon source raw material to synthesize PHA, the carbon-nitrogen ratio in the substrate is very low, so that the inhibition on fermentation microorganisms is caused, and the PHA production efficiency is reduced finally.
Acrylic acid is an important chemical basic raw material and is widely applied to the fields of buildings, environmental protection, sanitary products and the like at present. Acetic acid, a by-product, is a major by-product present in the acrylic acid production process with an estimated annual national yield of over 7 million tons. Therefore, the byproduct acetic acid is a very easily obtained chemical production byproduct, has low cost and higher carbon content, and is a suitable choice for improving the carbon-nitrogen ratio in the PHA synthesis carbon source substrate. However, the by-produced acetic acid contains not less than 80% acetic acid, but also not less than 5% acrylic acid and other substances such as acrolein, formaldehyde, methyl isobutyl ketone, etc. in different proportions, which may have a serious inhibitory effect on the fermentative microorganisms in the PHA synthesis process.
Disclosure of Invention
In order to solve the problems, the invention adopts a new method for synthesizing PHA by taking blue algae and byproduct acetic acid as mixed substrates, pre-treats the byproduct acetic acid in advance to remove toxic impurities such as acrylic acid and the like in the byproduct acetic acid, realizes an innovative process mode for changing two waste pollutants into high value-added resources, is low-carbon and environment-friendly, provides a new path for synthesizing PHA, further reduces the synthesis cost by optimizing a fermentation process, and is suitable for industrial mass production.
The method comprises the following specific steps:
(1) performing alkali treatment on the blue algae waste, and centrifuging and performing suction filtration to obtain a blue algae solution;
(2) performing electro-Fenton pretreatment on the byproduct acetic acid;
(3) mixing the pretreated by-product acetic acid, the blue algae liquid and the aerobic sludge for co-fermentation;
(4) after fermentation is finished, centrifuging the fermentation liquor, and measuring the dry cell weight and PHA;
in one embodiment of the present invention, the treatment method of the byproduct acetic acid is electro-Fenton method, which is performed in an electrolytic cell reactor, and hydrogen peroxide and ferrous ions react to generate hydroxyl radicals with strong oxidizing property, so as to remove toxic impurities such as acrylic acid (acrylic acid content is reduced by 99.7%, and acetic acid is reduced by only 0.46%), thereby completing the pretreatment of the byproduct acetic acid.
In one embodiment of the invention, working solution is required to be prepared for the by-product acetic acid, and the specific preparation method comprises the steps of taking 2.5ml of an original by-product acetic acid sample, diluting the sample to 250ml with distilled water, adding 0.775g of anhydrous sodium sulfate and 6.25ul of hydrogen peroxide, and adjusting the pH to be 4.
In one embodiment of the present invention, the anode used in the electro-Fenton method is an iron plate, and the cathode used in the electro-Fenton method is a carbon plate.
In one embodiment of the present invention, the electro-Fenton process is performed for 3 hours, aeration is continued, and the current is constantly controlled to 0.5A.
In one embodiment of the present invention, the pH of the cyanobacteria waste is controlled to 12 during the alkali treatment.
In one embodiment of the invention, after alkali treatment of the blue algae waste, the centrifugation rate is 5000r/min, and the centrifugation time is 15 minutes.
In one embodiment of the invention, the volume of fermentation liquor of four groups (by-product acetic acid after electrochemical treatment and alkali-added pretreated blue algae liquor are mixed according to the proportion of 1:1, 1:2, 1:3 and 1: 4) is controlled to be 300ml, the dissolved chemical oxygen demand (SCOD) is controlled to be 3000mg/l, 75ml of aerobic sludge with the same volume is respectively added into each group for mixed fermentation to synthesize PHA, the fermentation time is 0-72 hours, and the rotation speed is 100-400 r/min.
Preferably, the by-product acetic acid and the alkali pretreated blue algae liquid are mixed and fermented according to the ratio of 1:3, the fermentation time is 24 hours, and the rotation speed is 200 r/min.
In one embodiment of the present invention, the set fermentation condition temperature is 37 ℃.
A third object of the present invention is to provide an application of the above method in the industrial synthesis of PHA.
The invention has the beneficial effects that:
(1) the method adopts the electro-Fenton method, efficiently finishes the pretreatment of the byproduct acetic acid, further removes toxic impurities such as acrylic acid and the like, reduces the acrylic acid content by 99.7 percent and only reduces the acetic acid by 0.46 percent, and lays a foundation for the comprehensive utilization of the subsequent byproduct acetic acid in the synthesis of PHA.
(2) After the pretreatment of the byproduct acetic acid is finished, the byproduct acetic acid and the blue algae liquid are used as the co-fermentation substrate, so that the problem of too low carbon-nitrogen ratio of the fermentation substrate can be obviously improved, and the synthesis efficiency of PHA is improved. Preferably, the electrochemically treated by-product acetic acid (acetic acid concentration: 95.61%) and the alkali-pretreated cyanobacteria solution (SCOD concentration: 12800mg/L) were mixed and fermented at a ratio of 1:3 (SCOD 3000mg/L was obtained by diluting the pre-treated by-product acetic acid and cyanobacteria mixed fermentation broth), the fermentation time was 24 hours, the stirring speed was 200r/min, and the dry weight of the synthesized PHA was increased by 69.1% as compared with the control reactor without the by-product acetic acid. Compared with a byproduct acetic acid control group without any pretreatment, the synthesized PHA dry weight of the byproduct acetic acid group subjected to electrochemical pretreatment is increased by 109.8%.
(3) The current problems associated with the commercial production of PHA are relatively high costs, making the product PHA less price competitive relative to common plastics of fossil fuel origin. The blue algae and the byproduct acetic acid are organic wastes, which poses serious threats to water environment and drinking water safety. The invention realizes an innovative process mode of changing two waste pollutants into high value-added resources for the first time, realizes the aim of efficiently producing PHA, greatly reduces the production cost of PHA while reasonably utilizing organic wastes and avoiding environmental pollution, and produces products and services which are greatly beneficial to the environment, the society and the public.
Drawings
FIG. 1 is a graph showing a comparison of the acrylic acid content in by-produced acetic acid after pretreatment by the electro-Fenton method;
FIG. 2 is the effect of the mixed fermentation ratio of different by-product acetic acids and cyanobacteria liquid on the PHA synthesis effect;
FIG. 3 is a graph showing the effect of different fermentation times on the efficiency of PHA synthesis;
FIG. 4 is a graph showing the effect of different stirring speeds on the synthesis of PHA;
FIG. 5 is a graph showing the effect of pre-treatment by-product acetic acid and non-pre-treatment by-product acetic acid as co-fermentation substrates on PHA synthesis.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.
A by-produced raw acetic acid sample (main components: acetic acid 96.07%, methyl isobutyl ketone 0.62%, and acrylic acid 3.06%, total chemical oxygen demand 107500mg/L) was obtained from Taxing, Inc.
Example 1: by-product acetic acid pretreatment by electro-Fenton method
2.5ml of a by-produced acetic acid precursor sample was taken, diluted with distilled water to 250ml, and 0.775g of anhydrous sodium sulfate and 6.25ul of hydrogen peroxide were added to adjust the pH to 4. It was charged to an electro-Fenton reactor, the reaction run time was 3 hours, during which aeration was continued and the current was stabilized at 0.5A. The acrylic acid content of by-produced acetic acid was reduced by 99.7% as compared with the control group which had not been subjected to electro-fenton pretreatment (fig. 1).
Example 2: taking the pretreated by-product acetic acid and blue algae liquid as co-fermentation substrates to synthesize PHA
Firstly, alkali treatment is carried out on blue algae waste, the pH value is controlled to be 12, and blue algae liquid is obtained after centrifugation and suction filtration, wherein the centrifugation speed is 5000r/min, and the centrifugation time is 15 minutes.
And then mixing the pretreated by-product acetic acid, the blue algae liquid and the aerobic sludge for co-fermentation. After fermentation was complete, the fermentation broth was centrifuged to determine cell dry weight and PHA. In the fermentation process, the electrochemical-treated by-product acetic acid and the alkali-pretreated blue algae liquid are controlled to be mixed and fermented according to the proportion of 1:3, the fermentation time is 24 hours, the stirring speed is 200r/min, and compared with the control reaction without the by-product acetic acid, the dry weight of the synthesized PHA is increased by 69.1%.
Example 3: influence of mixed fermentation ratios of different by-product acetic acid and blue algae liquid on PHA synthesis
The mixing fermentation ratio of the electrochemically treated by-product acetic acid and the alkali pretreated cyanobacteria liquid was adjusted to 1:1, 1:2 and 1:4, and other conditions or parameters were the same as those in example 2. In comparison with example 2, the effect of synthesizing PHA was the best when the ratio of the by-produced acetic acid to the blue algae solution was 1:3 (the dry weight of PHA was 0.086g), and the dry weight of the synthesized PHA was increased by 62.8%, 55.8% and 67.4% respectively, as compared with the case where the ratio of the by-produced acetic acid to the mixed fermentation of the blue algae solution was 1:1, 1:2 and 1:4 (fig. 2).
Example 4: effect of different fermentation times on PHA Synthesis
The fermentation time of the mixed fermentation was adjusted to 48 hours and 72 hours, and other conditions or parameters were identical to those of example 2. In comparison with example 2, the effect of synthesizing PHA was the best when the fermentation time was 24 hours (dry weight of PHA was 0.086g), increasing the dry weight of synthesized PHA by 27.9% and 31.4% compared to 48 hours and 72 hours, respectively (fig. 3).
Example 5: effect of different stirring speeds on PHA Synthesis
The stirring speed was adjusted to 100, 300 and 400r/min, and the other conditions or parameters were in accordance with example 2. In comparison with example 2, the effect of synthesizing PHA is best when the stirring speed is 200r/min (PHA dry weight is 0.086g), increasing the dry weight of synthesized PHA by 19.8%, 12.8% and 24.4% respectively, compared to stirring speeds of 100, 300 and 400r/min (FIG. 4).
Comparative example: effect of different treatment modes of by-product acetic acid on PHA synthesis
Respectively mixing the byproduct acetic acid subjected to electrochemical pretreatment and the byproduct acetic acid not subjected to any pretreatment with the blue algae liquid subjected to alkali pretreatment for fermentation, wherein the byproduct acetic acid and the blue algae liquid are mixed according to the proportion of 1:3, the fermentation time is 24 hours, and the stirring speed is 200 r/min. The synthesized PHA dry weight of the electrochemically pretreated by-product acetic acid group was increased by 109.8% compared to the by-product acetic acid control group without any pretreatment (fig. 5).
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for synthesizing PHA by taking blue algae and byproduct acetic acid as mixed substrates comprises the following specific steps:
(1) performing alkali treatment on the blue algae waste, and centrifuging and performing suction filtration to obtain a blue algae solution;
(2) performing electro-Fenton pretreatment on the byproduct acetic acid;
(3) mixing the pretreated by-product acetic acid, the blue algae liquid and the aerobic sludge for co-fermentation;
(4) and after the fermentation is finished, centrifuging the fermentation liquor, measuring the dry weight of cells, and collecting PHA.
2. The method of claim 1, wherein the electro-Fenton pre-treatment of the by-produced acetic acid is performed in an electrolytic cell reactor by generating hydroxyl radicals having strong oxidizing property by reacting hydrogen peroxide with ferrous ions, thereby removing toxic impurities and completing the pre-treatment of the by-produced acetic acid.
3. The method according to claim 1 or 2, wherein the pretreatment of the by-produced acetic acid requires preparation of a working solution by taking 2.5ml of a sample of the by-produced acetic acid as a raw material, diluting the sample with distilled water to 250ml, adding 0.775g of anhydrous sodium sulfate and 6.25ul of hydrogen peroxide, and adjusting the pH to 4.
4. The method of claim 2, wherein the anode of electro-Fenton process is an iron plate and the cathode is a carbon plate.
5. The method of claim 3 or 4, wherein the electro-Fenton process is carried out for a reaction time of 3 hours with continuous aeration and a constant current of 0.5A.
6. The method of claims 1-2, wherein the blue algae waste is subjected to alkali treatment, the pH is controlled at 12, the centrifugation rate is 5000r/min, and the centrifugation time is 15 minutes.
7. The method as claimed in claim 6, wherein the byproduct acetic acid and the alkali-pretreated blue algae liquid in step 3) are mixed and fermented according to the ratio of 1:1-1:4, the fermentation time is 0-72 hours, and the rotation speed is 100-400 r/min.
8. The method of claim 7, wherein the byproduct acetic acid in step 3) and the alkali-pretreated blue algae liquid are mixed and fermented according to a ratio of 1:3, wherein the fermentation time is 24 hours, and the rotation speed is 200 r/min.
9. The method according to claim 8, wherein the temperature of the mixed fermentation in the step 3) is 37 ℃.
10. Use of the method of claim 1 for the industrial synthesis of PHA.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060088921A1 (en) * | 2002-01-16 | 2006-04-27 | Jian Yu | Production of biodegradable thermoplastic materials from organic wastes |
| CN101993896A (en) * | 2010-11-11 | 2011-03-30 | 江南大学 | Method for continuously producing hydrogen and polyhydroxyalkanoates by taking blue-green algae as substrate through coupling fermentation |
| CN110963637A (en) * | 2019-10-27 | 2020-04-07 | 平湖石化有限责任公司 | Biochemical treatment method for acrylic acid and ester production wastewater |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060088921A1 (en) * | 2002-01-16 | 2006-04-27 | Jian Yu | Production of biodegradable thermoplastic materials from organic wastes |
| CN101993896A (en) * | 2010-11-11 | 2011-03-30 | 江南大学 | Method for continuously producing hydrogen and polyhydroxyalkanoates by taking blue-green algae as substrate through coupling fermentation |
| CN110963637A (en) * | 2019-10-27 | 2020-04-07 | 平湖石化有限责任公司 | Biochemical treatment method for acrylic acid and ester production wastewater |
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