CN114774483B - Method for synthesizing PHA by using blue algae and byproduct acetic acid as substrates and application thereof - Google Patents
Method for synthesizing PHA by using blue algae and byproduct acetic acid as substrates and application thereof Download PDFInfo
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Abstract
The invention discloses a method for synthesizing PHA by using blue algae and byproduct acetic acid as substrates and application thereof. The invention can realize the goal of producing PHA with high efficiency, and has the advantages of reasonably utilizing organic waste, avoiding environmental pollution, greatly reducing the production cost of PHA and having industrial application prospect.
Description
Technical Field
The invention relates to a method for synthesizing PHA by taking blue algae and byproduct acetic acid as substrates and application thereof, belonging to the fields of environmental engineering and organic waste recycling treatment.
Background
Polyhydroxyalkanoate (PHA) is a substance having material characteristics similar to those of general plastics and excellent biocompatibility and degradability. The source of various plastic products commonly used at present is petroleum, and the raw materials of the plastic products lack of sustainability, and serious environmental problems are caused after the plastic products are discarded. Therefore, the use of PHA instead of plastic products has great significance for recycling economy, environment and sustainable development. However, in the commercial production process of PHA, nontoxic and pure high-value chemicals such as glucose, sodium acetate and the like are generally required to be used as carbon sources, so that the production cost is high, and the PHA product lacks price competitiveness compared with common plastics from fossil fuel sources. More recent studies have therefore shifted the raw materials for synthesizing PHA to low-cost carbon sources, such as various types of organic wastes.
In addition, a large amount of algal biomass needs to be cleaned and removed from the water body periodically and subjected to subsequent treatment. Therefore, if blue algae waste can be used as a carbon source raw material for synthesizing PHA, the production cost of PHA can be remarkably reduced, and although the cost for synthesizing PHA by using blue algae waste as a raw material is very low, the technical process still faces a small challenge. Because the nitrogen content in blue algae waste is high, if the blue algae waste is used as the only carbon source raw material to synthesize the PHA, the carbon nitrogen ratio in the substrate is very low, so that the fermentation microorganism is inhibited, and finally the PHA production efficiency is reduced.
Acrylic acid is an important chemical basic raw material and is widely applied to the fields of construction, environmental protection, sanitary products and the like at present. As a major byproduct present in the production process of acrylic acid, acetic acid as a byproduct is estimated to be produced in annual quantities exceeding 7 ten thousand tons nationally. Therefore, the byproduct acetic acid is a chemical production byproduct which is very easy to obtain, has low cost and higher carbon content, and is a proper choice for improving the carbon-nitrogen ratio in the PHA synthetic carbon source substrate. However, the byproduct acetic acid contains not less than 80% of acetic acid, but also more than 5% of acrylic acid and other substances such as acrolein, formaldehyde, methyl isobutyl ketone in different proportions, which may have serious inhibitory effects on fermenting microorganisms in the PHA synthesis process.
Disclosure of Invention
In order to solve the problems, the invention adopts a novel method for synthesizing the PHA by taking blue algae and byproduct acetic acid as mixed substrates, pre-treats the byproduct acetic acid in advance, removes toxic impurities such as acrylic acid and the like in the byproduct acetic acid, realizes an innovative process mode of changing two waste pollutants into high value-added resources, is low-carbon and environment-friendly, provides a novel path for synthesizing the 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 blue algae waste, and obtaining blue algae liquid after centrifugation and suction filtration;
(2) Electro Fenton pretreatment is carried out on the byproduct acetic acid;
(3) Mixing the pretreated byproduct acetic acid, blue algae liquid and aerobic sludge for co-fermentation;
(4) After fermentation, centrifuging the fermentation liquor, and measuring the dry weight and PHA of cells;
in one embodiment of the invention, the treatment method of the byproduct acetic acid is an electro-Fenton method, and is carried out in an electrolytic cell reactor, and hydroxyl free radicals with strong oxidability are generated by the reaction of hydrogen peroxide and ferrous ions, so that toxic impurities such as acrylic acid and the like are removed (the content of the acrylic acid is reduced by 99.7 percent, and the content of the acetic acid is reduced by only 0.46 percent), and the pretreatment of the byproduct acetic acid is completed.
In one embodiment of the present invention, the by-product acetic acid is prepared by diluting 2.5ml of the by-product acetic acid sample with distilled water to 250ml, and adding 0.775g of anhydrous sodium sulfate and 6.25ul of hydrogen peroxide to adjust the pH to 4.
In one embodiment of the present invention, the anode required for the electro-Fenton method is an iron plate, and the cathode is a carbon plate.
In one embodiment of the invention, the electro-Fenton method reaction is operated for 3 hours, aeration is continuously carried out, and the current is constantly controlled to be 0.5A.
In one embodiment of the present invention, the pH is controlled to 12 when the cyanobacteria waste is subjected to alkali treatment.
In one embodiment of the invention, after the blue algae waste is subjected to alkali treatment, the centrifugation speed is 5000r/min, and the centrifugation time is 15 minutes.
In one embodiment of the invention, four groups of fermentation liquid volumes (mixing the by-product acetic acid after electrochemical treatment and the blue algae liquid subjected to alkali adding pretreatment according to the proportion of 1:1, 1:2, 1:3 and 1:4) are controlled to be 300ml, the dissolved chemical oxygen demand (SCOD) is 3000mg/l, 75ml of equal-volume aerobic sludge is added to each group to perform mixed fermentation to synthesize PHA, the fermentation time is 0-72 hours, and the rotating speed is 100-400r/min.
Preferably, the byproduct acetic acid and the blue algae liquid pretreated by adding alkali are mixed and fermented according to the proportion of 1:3, the fermentation time is 24 hours, and the rotating speed is 200r/min.
In one embodiment of the invention, the fermentation set-point temperature is 37 ℃.
A third object of the present invention is to provide the use of the above-mentioned method for the industrial synthesis of PHA.
The invention has the beneficial effects that:
(1) The invention adopts the electro-Fenton method, efficiently completes pretreatment of byproduct acetic acid, further removes toxic impurities such as acrylic acid, reduces the content of acrylic acid by 99.7 percent, reduces acetic acid by only 0.46 percent, and lays a foundation for the subsequent comprehensive utilization of byproduct acetic acid in PHA synthesis.
(2) After the pretreatment of the byproduct acetic acid is finished, the byproduct acetic acid and blue algae liquid are used as co-fermentation substrates, so that the problem of too low carbon nitrogen ratio of the fermentation substrates can be obviously improved, and the synthesis efficiency of PHA is improved. As the optimization of the technical scheme, the by-product acetic acid (the concentration of acetic acid is 95.61%) after electrochemical treatment and the blue algae liquid (the concentration of SCOD is 12800 mg/L) after alkaline pretreatment are mixed and fermented according to the proportion of 1:3 (the mixed fermentation liquid of the pretreated by-product acetic acid and blue algae is diluted to make the SCOD be 3000 mg/L), the fermentation time is 24 hours, the stirring speed is 200r/min, and compared with a control reactor without the by-product acetic acid, the dry weight of the synthesized PHA is improved by 69.1%. Compared with the byproduct acetic acid control group without any pretreatment, the dry weight of the synthesized PHA of the byproduct acetic acid group subjected to electrochemical pretreatment is improved by 109.8 percent.
(3) At present, the commercial production of PHA generally has the problem of high cost, so that the PHA product lacks price competitiveness compared with common plastics of fossil fuel sources. Blue algae and byproduct acetic acid are organic wastes, and pose a serious threat to the safety of water environment and drinking water. The invention realizes the innovative process mode of changing two waste pollutants into high value-added resources for the first time, achieves the aim of producing PHA with high efficiency, reasonably utilizes organic wastes, avoids environmental pollution, greatly reduces the production cost of PHA, and produces products and services which are greatly beneficial to the environment, society and public.
Drawings
FIG. 1 is a comparison of acrylic acid content in acetic acid byproduct after pretreatment by electro-Fenton method;
FIG. 2 shows the effect of mixed fermentation ratios of different byproduct acetic acid and cyanobacteria liquid on PHA synthesis;
FIG. 3 is a graph showing the effect of different fermentation times on PHA synthesis;
FIG. 4 is a graph showing the effect of different stirring speeds on PHA synthesis;
FIG. 5 is an illustration of the effect of pretreated byproduct acetic acid and non-pretreated byproduct 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 better illustration of the invention, and should not be construed as limiting the invention.
A crude sample of byproduct acetic acid (the main components are 96.07% acetic acid, 0.62% methyl isobutyl ketone and 3.06% acrylic acid, and the total chemical oxygen demand is 107500 mg/L) is obtained from the Uygur chemical Co., ltd.
Example 1: pretreatment by-product acetic acid by electro Fenton method
A byproduct of acetic acid was taken as a sample of 2.5ml, diluted to 250ml with distilled water, and 0.775g of anhydrous sodium sulfate and 6.25ul of hydrogen peroxide were added thereto to adjust the pH to 4. This was added to the electro-Fenton reactor and the reaction was run for 3 hours, during which aeration was continued and the current was stabilized at 0.5A. The acrylic acid content of the by-product acetic acid was reduced by 99.7% compared to the control group without electro-Fenton pretreatment (FIG. 1).
Example 2: the pretreated byproduct acetic acid and blue algae liquid are used as co-fermentation substrates to synthesize PHA
Firstly, carrying out alkali treatment on blue algae waste, controlling the pH value at 12, and obtaining blue algae liquid after centrifugation and suction filtration, wherein the centrifugation speed is 5000r/min, and the centrifugation time is 15 minutes.
And then mixing the pretreated byproduct acetic acid, blue algae liquid and aerobic sludge for co-fermentation. After the fermentation, the fermentation broth was centrifuged to determine the dry cell weight and PHA. In the fermentation process, the co-product acetic acid after electrochemical treatment and the blue algae liquid pretreated by adding alkali are controlled to carry out mixed fermentation 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 adding the co-product acetic acid, the dry weight of the synthesized PHA is improved by 69.1 percent.
Example 3: influence of mixed fermentation ratios of different byproduct acetic acid and blue algae liquid on PHA synthesis
The mixed fermentation ratio of the by-product acetic acid after electrochemical treatment and the blue algae liquid subjected to alkali addition pretreatment is adjusted to be 1:1, 1:2 and 1:4, and other conditions or parameters are consistent with example 2. In contrast to example 2, the effect of synthesizing PHA was optimal (PHA dry weight 0.086 g) when the ratio of by-product acetic acid to cyanobacteria liquid was 1:3, and the dry weight of synthesized PHA was increased by 62.8%, 55.8% and 67.4% respectively when the mixed fermentation ratio of by-product acetic acid to cyanobacteria liquid was 1:1, 1:2 and 1:4 (FIG. 2).
Example 4: effects 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 consistent with example 2. In contrast to example 2, the effect of synthesizing PHA was optimal (PHA dry weight 0.086 g) when the fermentation time was 24 hours, and the dry weight of the synthesized PHA was increased by 27.9% and 31.4% respectively compared to 48 hours and 72 hours of fermentation time (FIG. 3).
Example 5: influence of different stirring speeds on PHA synthesis
The stirring speeds were adjusted to 100, 300 and 400r/min, and other conditions or parameters were consistent with example 2. In contrast to example 2, the effect of the synthesized PHA was optimal (PHA dry weight 0.086 g) at a stirring speed of 200r/min, and the dry weight of the synthesized PHA was increased by 19.8%, 12.8% and 24.4% respectively, compared to stirring speeds of 100, 300 and 400r/min (FIG. 4).
Control example: influence of different treatments of byproduct acetic acid on synthesis of PHA
And respectively mixing the byproduct acetic acid subjected to electrochemical pretreatment and the byproduct acetic acid which is not subjected to any pretreatment with the blue algae liquid subjected to alkali pretreatment for fermentation, mixing the byproduct acetic acid with the blue algae liquid according to the proportion of 1:3, wherein the fermentation time is 24 hours, and the stirring rotating speed is 200r/min. The dry weight of the synthesized PHA in the electrochemically pretreated co-product acetic acid group was increased by 109.8% compared to the co-product acetic acid control group without any pretreatment (fig. 5).
While the invention has been described with reference to the preferred embodiments, it is not limited thereto, and 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 (6)
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 blue algae waste, and obtaining blue algae liquid after centrifugation and suction filtration;
(2) Electro Fenton pretreatment is carried out on the byproduct acetic acid;
(3) Mixing the pretreated byproduct acetic acid, blue algae liquid and aerobic sludge for co-fermentation;
(4) After fermentation is completed, centrifuging the fermentation liquor, measuring the dry weight of cells, and collecting PHA;
the electro-Fenton pretreatment method of the byproduct acetic acid comprises the following steps of carrying out in an electrolytic cell reactor, generating hydroxyl free radicals with strong oxidability by the reaction of hydrogen peroxide and ferrous ions, further removing toxic impurities, and completing pretreatment of the byproduct acetic acid;
preparing a working solution for pretreatment of the byproduct acetic acid, specifically, taking a byproduct acetic acid sample of 2.5-ml, diluting distilled water to 250-ml, adding 0.775-g anhydrous sodium sulfate and 6.25-ul hydrogen peroxide, and adjusting the pH to 4;
the reaction operation time of the electro-Fenton method is 3 hours, aeration is continuously carried out, and the current is constantly controlled at 0.5 and A;
and 3) mixing and fermenting the byproduct acetic acid and the blue algae liquid pretreated by adding alkali according to the proportion of 1:1-1:4, wherein the fermentation time is 24-72 hours, and the rotating speed is 100-400r/min.
2. The method of claim 1, wherein the electro-Fenton method anode is an iron plate and the cathode is a carbon plate.
3. The method according to any one of claims 1 to 2, wherein the pH is controlled to 12, the centrifugation rate is 5000r/min, and the centrifugation time is 15 minutes when the cyanobacterial waste is subjected to alkali treatment.
4. The method of claim 3, wherein the byproduct acetic acid in the step 3) and the blue algae liquid pretreated by adding alkali are mixed and fermented according to the proportion of 1:3, the fermentation time is 24 hours, and the rotating speed is 200r/min.
5. The method according to claim 4, wherein the temperature of the mixed fermentation in step 3) is 37 ℃.
6. Use of the method of claim 1 for the industrial synthesis of PHA.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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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| US7141400B2 (en) * | 2002-01-16 | 2006-11-28 | University Of Hawaii | Production of biodegradable thermoplastic materials from organic wastes |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| 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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