TWI652852B - Plant extract for enhancement of efficiency of microbial fuel cell - Google Patents

Abstract

A plant extract added to a microbial fuel cell to increase its electricity production efficiency, and the extract may be a Chinese herbal extract, such as: honeysuckle extract, clove extract, ephedra extract, dried ginger extract, etc., or It is a tea extract, such as: green tea extract, Pu'er tea extract, and eosin extract, which are measured by cyclic voltammetry to have a stable redox peak and a reversible stable change trend. These extracts not only have antioxidant activity, but also have an electron shuttle effect, and can be used for green circulation applications.

Description

Plant extract added to microbial fuel cells to increase their electrical production efficiency

The present invention relates to green energy, and more particularly to a plant extract added to a microbial fuel cell to increase its power production efficiency.

Due to the poor nature of natural resources, Taiwan has long relied on the shortcomings of foreign energy and related resources input in industrial development. Therefore, how to effectively recycle resources and find local renewable energy sources is an urgent task. In fact, based on the concept of green sustainable development, although Taiwan only accounts for 0.025% of the world's total land area, according to the relevant investigation report of the Ministry of Science and Technology of Taiwan and the Central Research Institute and the Council of Agriculture, the microbial diversity of Taiwan's native species is shown. It can enrich up to 2.5% of the world and has great application development potential. Therefore, based on the principle of not introducing alien species and not reducing the ecological burden of the species, this study selected the natural ecology of East Taiwan as the main field, and selected the native functional microorganisms from the natural environment ecology to carry out various greens. Research assessment of sustainable resource recycling. In recent years, it has been found that in the process of industrial dyeing and finishing wastewater treatment, it is also possible to recover electricity at the same time, and to discover a number of purely electrochemically active bacteria, which can be used to achieve such simultaneous dye wastewater treatment and recycling. The efficacy has a considerable development potential for the future application of dyeing and finishing wastewater treatment performance improvement.

Among them, Microbial Fuel Cell (MFC) is another representative of emerging alternative biomass energy in recent years. Moreover, most of the current MFC research considers the combination of microbial power generation and wastewater treatment for energy recovery and reuse, which is more in line with the green sustainable design of the "cradle to cradle". Furthermore, since the microbial treatment of dyeing and finishing wastewater is mostly operated under anaerobic conditions, previous studies have pointed out that under the catalysis of intracellular azo-reductase, the azo bond in the azo dye is cleaved, and the decolorized metabolic aromatic amine is produced. Intermediates (Chen et al., 2010; Hsueh et al., 2008), such aromatic amine intermediates are more capable of undergoing further hydroxylation and ring-opening reactions under aerobic conditions. Degradation can effectively treat the dyeing and finishing wastewater completely, so as to minimize the environmental pollution. In the study, it is more speculated that the decolorizing metabolic intermediates are likely to have the ability to act as a transporting intermediary (Chen et al., 2012). Some studies have also mentioned that such intermediates may also have the potential to improve the efficiency of microbial decolorization. This study will investigate the effects of such aromatic amine intermediates on MFC in order to understand the likely outcomes of MFC handling of dyeing and finishing wastewater.

It has been suggested in the literature that the antioxidant function and the electron shuttle ability of chemical substances may be electrochemical properties related to electron transfer. Moreover, it has been found in previous studies that the dye microbial decolorizing metabolite has the ability to promote decolorization and microbial production of electrons, but chemical dyes may be microbiologically toxic and have no ecologically friendly application concerns. Therefore, based on the consideration of environmental friendliness, it is indeed a very important research topic in the current green environment microbial technology to screen out components with natural effervescent properties from natural edible plants. Furthermore, the literature indicates that Chinese herbal medicines (eg, cloves, honeysuckle) contain polyphenols and flavonoid antioxidants, which are electrochemically active. The literature also pointed out that the tea containing catechins in electrochemical analysis studies may also have the electron shuttle characteristics of redox peaks, so it is reasonable to suspect that the pigments rich in natural Chinese herbal medicines may also be the chromophores for electron transfer, and There are nutrients needed by the human body or may have rich medicinal effects. For example, common Chinese herbal medicines such as Lonicera japonica and Syzygium aromaticum are considered to be health-promoting due to their rich natural polyphenol flavonoids. Phytochemicals, mainly due to their (1) excellent antioxidant activity, antiviral, anticancer, anti-inflammatory properties, and (2) excellent free radical scavenging ability. Therefore, it is reasonable to conclude that this electrochemical property can be used to simultaneously enhance microbial power generation and decolorization efficiency, so the feasibility of applying dye wastewater treatment will also be inferred.

It is to be noted that the main object of the present invention is to provide a plant extract which is added to a microbial fuel cell to increase its electricity production efficiency.

In order to attain the foregoing object, the present invention provides a plant extract added to a microbial fuel cell to increase its power production efficiency, which is obtained by taking a predetermined weight of a plant sample, chopped and ground, and then placed a predetermined volume and concentration of the extractant, soaked for a certain period of time, then concentrated under reduced pressure and filtered by air, and obtained by the cyclic voltammetry test of the plant extract, the mean number of electron transfer (equivalent number) Of electron transfer, nc) is greater than 0.04, wherein nc=57mV/|Epa-Epc|, Epa: oxidation peak potential Epc: reduction peak potential.

In one embodiment, the plant extract is selected from the group consisting of Lonicera japonica extract, Eriobotrya japonica extract, Polyporus umbellatus extract, Ephedra sinica extract, Syzygium aromaticum extract, Citrus reticulate extract, Schizonepeta tenuifolia extract, green tea ( Camellia sinensis (L.) Kuntze ) extract, and Camellia assamica (Mast.) Chang extract , and blush ( Camelliaboreali-yunnanica ) extract.

The added Chinese herbal medicines or tea extracts not only have antioxidant activity, but also have the effect of electronic shuttle, and can also be used for green circulation applications.

Fig. 1 is a comparison diagram of cyclic voltammetry of various Chinese herbal extracts before decolorization of microorganisms according to a preferred embodiment of the present invention.

Fig. 2 is a diagram showing changes in the cyclic voltammogram of various Chinese herbal extracts in 100 cycles according to a preferred embodiment of the present invention.

Figure 3 is a graph showing cyclic voltammogram changes of dried tangerine peel extract at different doses in a preferred embodiment of the present invention.

Figure 4 is a graph comparing the cyclic voltammograms of clove extracts in different pH environments according to a preferred embodiment of the present invention.

Figure 5 is a graph showing the power density of a Chinese herbal medicine extract added to a microbial fuel cell in a preferred embodiment of the present invention.

Figure 6 is an AC impedance diagram of a Chinese herbal medicine extract added to a microbial fuel cell in accordance with a preferred embodiment of the present invention.

Figure 7 is a graph comparing the cyclic voltammetry of green tea water extract and wine extract in a preferred embodiment of the present invention.

Figure 8 is a graph comparing the dose response curves of DPPH free radicals at different concentrations for 30 minutes at different concentrations of the tea extract in accordance with a preferred embodiment of the present invention.

The present invention mainly provides a plant extract which can be added to a microbial fuel cell to increase the power generation efficiency of the microbial fuel cell. Wherein, the microbial fuel cell can be a single cathode micro-fuel cell (single-chamber MFCs, SC-MFCs) or a poly(methyl methacrylate) (PMMA) tank. Self-assembled into a dual-slot microbial fuel cell. The culture medium of the microbial fuel cell is a liquid LB medium (Luria-Bertani broth medium), and the composition thereof contains 10 g L ^-1 tryptone, 5 g L ^-1 yeast extract and 10 g L ^-1 of chlorination. Sodium (NaCl), pH 7.0 ± 0.2.

The plant extract provided by the invention can be mainly divided into a Chinese herbal extract and a tea extract, as described below:

1. Chinese herbal extracts:

In the present invention, the inventors selected dozens of common Chinese herbal medicines such as Lonicera japonica , Syzygium aromatic um, Ephedra sinica , Zingiber officinale , and Pueraria montana . The preparation step of the extract is firstly pulverized with fresh 2.5 g, dissolved in 50 mL of 50% ethanol solution (wine extract), soaked for 30 minutes, and then concentrated under reduced pressure at 65 ° C for 2 hours to be pumped. The gas was filtered, and the drug extract was taken, and then quantified to 50 mL with deionized water.

Cyclic voltammetry

The aforementioned extract will be subjected to cyclic voltammetry to determine its electrochemical condition. The cyclic voltammetry comprises the steps of: aerating the herbal juice with nitrogen for 15 minutes, then scanning 1.5V to -1.5V at a rate of 10 mV ‧ s ^-1 . Since the Chinese herbal medicine is a complex mixture of multiple complexes, it is observed whether there is a stable redox peak in six scans, and then the sample with this characteristic is subjected to cyclic voltammetry for 100 cycles to observe the reversible stable change trend of the peak with time. .

After testing by cyclic voltammetry, many Chinese herbal medicines have been found to have redox peaks before they are biologically treated (Fig. 1), and the electrochemistry of electron transfer quantification is estimated based on the detection values of redox peaks of various Chinese herbal medicines. For a comparison of features, please refer to the table below.

n ^c : equivalent number of electron transfer

n ^c =57mV/|E _pa -E _pc |, E _pa : oxidation peak potential E _pc : reduction peak potential

Overall, the extract can be used to add to the MFC when the number of electron transfer (n ^c ) values is greater than 0.04. According to Table 1, the herbal extracts according to the foregoing characteristics include: Lonicera japonica extract, Citrus reticulate , Pueraria montana extract, Eriobotrya japonica extract, and swine fever ( Polyporus umbellatus extract, Ephedra sinica extract, Syzygium aromaticum extract, Citrus reticulate extract, Schizonepeta tenuifolia extract.

In order to understand whether the electron shuttle ability of the redox peak is only reversible and stable in characteristics, it can be seen through a hundred cycles of scanning (Fig. 2) that as the number of cyclic voltammetry scans increases, the redox peak gradually It is declining, even at the initial declining most significant, and there is almost no change after the 80th lap, which means that the redox process may partially generate irreversible chemical species accumulation. Electrochemical The attenuation of the learning characteristics may actually represent the result that the antioxidant activity may predominate. The characteristics of the electronic shuttle are due to the catalytic properties, so it will gradually exhibit stable and reversible performance characteristics in hundreds of scans, and it also represents a higher electronic shuttle. Application feasibility of the feature. From the above comparison, the less obvious Chinese herbal medicine samples were deduced, and it is speculated that the electronic shuttle components may still have relative stability, which may increase the dye degradation and microbial production. Due to the nature of natural Chinese herbal medicines, Chinese herbal medicine waste, not just organic compost, is likely to be applied to wastewater treatment and refining applications in food preservation or medical energy biotechnology, followed by microbial decolorization to compare The difference in the degree of energy extraction between them defines the efficiency of engineering applications.

Pre-strain culture and bleaching

In addition, these extracts will further compare the difference in biochemical characteristics of the microorganisms before and after decolorization. The invention adopts a self-selected decolorizing strain Shewanella haliotis WLP72, Aeromonas sp NIU01, and adds a culture solution (25 g/L) prepared by sterilizing LB medium, and then separately added the strain into the culture solution, and performs two activations for 12 hours. Culture before shake flask to facilitate subsequent dye decolorization. In order to test whether the natural plant decolorizing metabolite has the ability to promote decolorization, take 1 ml of the activated strain and 50 ml of the selected colored plant juice, and add 50 ml, twice the LB (1:1 V: V) dilution. After shaking flask culture, the flask was incubated at 30 ° C and 125 rpm for 12 hours, and then decolorized for more than 20 hr. The cell density and dye concentration were measured at different times, and the growth and decolorization efficiency were estimated from the time curve. .

Toxicity test

It is well known that drugs are above the threshold concentration and below the physiologically acceptable concentration, and are "poisonous" at too high a concentration. Although Chinese herbal medicine is rich in natural antioxidants, it may have antibacterial properties. Ingredients, with the increase of the concentration of Chinese herbal medicine, the efficacy of the electronic shuttle is improved, but the ability to inhibit bacteria is also increased. The antibacterial ability may also be caused by its biosuppressive toxicity. Therefore, it is necessary to find the best bacteria to withstand. The electron shuttle dose condition was therefore tested for biosuppression toxicity to observe changes in growth.

It can be seen from the growth curve (data not listed) that as the concentration of cloves increases, the maximum value of bacterial growth saturated cells decreases, and when the dose is higher than 6 gL ^-1 , the concentration of the cells cannot grow with time. Increase or even decrease. It is speculated that the bacteria cannot withstand toxicity and have been inhibited. At 0 hours, the concentration increased with increasing clove concentration, which was significantly affected by the color of the clove extract and its impurities, so there was a significant difference from the value of no added clove. Subsequent biorespiration devices or BOD/COD are used as biodegradability indicators to define their toxic effects.

Dose effect

Even if the Chinese herbal medicine may contain a chemical with a redox peak, the dose must still be higher than the threshold to effectively display the bioelectrochemical property, otherwise the peak value will not be revealed. Therefore, the dose analysis of each Chinese herbal medicine is discussed here (Fig. 3). As can be seen from Fig. 3, the tangerine peel has a significant redox peak at high doses (greater than 40gL ^-1 ). If it is lower than its threshold, its redox peak is not easy to observe or even disappear. To make it effective to discover the efficacy of the electronic shuttle, it is necessary to increase the dose above its threshold to have an effect. Therefore, in addition to considering the effective species of Chinese herbal medicine, the dosage conditions are also necessary conditions to function as a fusiform shuttle. However, Chinese herbal medicine is not only a drug, but it may still have a negative effect on the organism when it is too high. Therefore, it is necessary to carry out subsequent toxicity assessment to facilitate the optimization evaluation analysis.

pH effect

pH may affect the ability of antioxidants (ie polyphenols) to scavenge free radicals, and The pH value will cause a significant change in the redox peak of cyclic voltammetry. Therefore, it is necessary to consider whether the effects of Chinese herbal medicines are evaluated under different pH values. It is pointed out from Fig. 4 that the extract of Chinese herbal medicine is mostly acidic, although this characteristic is beneficial to the digestion and absorption of the gastrointestinal tract of the organism, but it does not seem to favor the electrochemical performance. In particular, in the case of cloves, the untreated pH of the extract is about 3.63, thus adversely operating the pH neutral neutral acid conditions of the microbial fuel cell. When the antioxidant component is close to neutral alkaline, its redox peak changes to significant. If it is added to MFCs, the effective pH regulation will enhance its redox ability and its applicability will be improved. In one embodiment, the plant extract has a pH between 4.76 and 7.25.

Microbial battery - AC impedance and polarization curve

In order to evaluate the efficiency of battery power generation, linear power voltammetry (LSV) was used to measure the power density (P) and current density (I) of the MFC, and a corresponding value was recorded using a multimeter. Power density (P) and current density (I) were calculated by the formulas P=V2/(A×R) and I=V/(A×R), respectively. Electrochemical impedance spectroscopy (EIS) (HIOKI 3522-50, Japan) measuring. The EIS uses the two-pole MFCs anode as the working electrode and the cathode as the reference electrode and the auxiliary electrode. The stable voltage, the disturbance amplitude is 10.0 mV, and the frequency range is 104~5×10 ^-2 Hz. The intercept of the EIS curve and the x-axis is the actual impedance (Z _re ), which can be used as the electrolyte resistance (R _ele ); and the curve projection of the curve in the impedance diagram after the intersection of the x-axis The length is the sum of the reaction kinetic resistance and the diffusion resistance (R _kin +R _diff ). The sum of the three values is the internal resistance of the battery Rin(R _elec +R _kin +R _diff ), using Nyquist Graph software (Zview 2.6b, Jiehan Tech) collects data and analyzes and estimates electrochemical properties.

Figure 5 shows the change in power density of the Chinese herbal extracts added to the microbial fuel cell, and Figure 6 shows the change in the AC impedance of the Chinese herbal extracts added to the microbial fuel cell. As can be seen from the figure, the battery power density map is used to observe Add the orange peel extract and clove respectively to MFCs, which is produced by electric power to 18.21mWm ^{-2 -2} lifting 12.56mWm 15.22mWm ^-2 improve productivity and electrical efficiency of 45.0% and 21.2%. The following table shows the AC impedance comparison table for adding different Chinese herbal extracts to microbial fuel cells:

It can be seen from the table that after adding the Chinese herbal extract, the internal resistance of the battery decreases, which can be reduced from 621.74 Ω to 481.35 Ω and 593.30 Ω, with a decrease ratio of 22.6% and 4.57%. Therefore, it can be confirmed that the Chinese herbal medicine extract does have the effect of promoting the power generation of the electronic shuttle, but as mentioned above, the electronic shuttle effect of the Chinese herbal medicine belongs to a milder one. It is worth mentioning that the ratio of power density increase is not parallel with the ratio of internal resistance reduction. It may be because there are other impurities in the extract that do not have the effect of electron shuttle, which may be used as a growth or physiological metabolism matrix. As a result, the battery voltage rises and the internal resistance does not decrease relatively significantly.

Second, tea extracts:

The present invention first determines unused tea leaves for evaluation. First, different degrees of tea, such as: green tea ( Camellia sinensis (L.) Kuntze ), Puer tea ( Camellia assamica (Mast.) Chang ), blush ( Camelliaboreali-yunnanica ), first take fresh 2.5g chopped, Dissolve in 50mL of 50% ethanol solution (Ethanol extract) and 50mL of distilled water (Water extract) two extractants, soak for 30 minutes, then concentrate under reduced pressure at 65 ° C for 2 hours, pumping, take The extract was then quantified to 50 mL with deionized water for subsequent evaluation analysis.

Cyclic voltammetry

The tea extract was aerobically aerated with nitrogen for 15 minutes, then scanned 1.5V to -1.5V at a rate of 10mV. s ^-1 . Since the tea is a mixture of multiple compounds, it is observed whether there is a redox peak in six scans, and then the sample having this characteristic is subjected to cyclic voltammetry for 100 cycles to observe whether the peak has a reversible stable change tendency with time. Then compare the difference in electrochemical characteristics before and after decolorization of the microorganisms to facilitate comparative analysis.

Tea extraction method evaluation

Firstly, it is evaluated whether different extraction methods (water extraction and wine extraction) have an effect on the tea extraction effect, and which can extract a higher content of polyphenols in order to facilitate subsequent evaluation of electron transfer related evaluation. First, the water extract and the tea extract juice of the wine extract were subjected to cyclic voltammetry tests to confirm whether or not there is a redox peak which promotes electron transfer. According to the results of Figure 7, it is found that both water extraction and wine extraction have redox peaks that promote electron transfer, but the water extraction is obviously superior to the wine extraction, and has a significant redox peak. The reason may be water bath extraction energy. More hydrophilic phenolic molecules are extracted, and the phenolic structural formula contains -OH bonds, so it is easier to form a hydrogen bond and dissolve. Therefore, the solubility in water is high, and subsequent extraction is performed by water bath as a standard operating procedure.

Electrochemical evaluation of microbial degradation of tea extract

Since the difference in the quality of the tea may be due to the degree of fermentation, it is evaluated whether the tea extract of various fermentation degrees has the characteristics of the electron shuttle after microbial transformation to promote electron transfer. The tea extract juice and the tea extract treated with the WLP72 Shewanella microorganism were first subjected to cyclic voltammetry to observe whether or not the redox peak size which promotes electron transfer was increased or increased. The results showed that the extracts after microbial treatment were superior to those without microbial treatment.

Tea extract - antioxidant capacity assessment

In order to determine the correlation between antioxidant and electron transfer, different concentrations (0.1, 0.5, ^1, 10, 50gL ^-1 ) of green tea and eosin extract were tested for the antioxidant capacity of DPPH free radicals, as shown in Figure 4. It can be seen that as the concentration of the tea extract increases, as the concentration of the polyphenol compound increases, the DPPH free radical scavenging efficiency also increases. Fig. 8 and Table 1 further indicate that the removal effect of EC50 is about 0.2~0.4g L-1 of tea leaves. It can be seen that the free radical scavenging effect of tea is quite effective when the B value is greater than 1. Moreover, the unoxidized tea (green tea) has better antioxidant capacity than fermented tea (blush) at any concentration. The dose response curve of Figure 8 also clearly indicates that green tea (curve on the right) has higher antioxidant activity. Elimination of activity (EC50: 0.203gL ^-1 (green tea) <0.408gL ^-1 (blush)), the response curve equations of the two are Y=6.74+2.51 logZ (green tea) Y=5.69+1.77 logZ (blush) And the result is also consistent with the expected anti-oxidation ability of the tea with strong redox spindle characteristics. The reason may be that the antioxidant is the process of electron transfer, and the tea with strong electronic shuttle characteristics is electronic. The transfer ability is also stronger, so there is a positive correlation between the two, indicating that the antioxidant activity of the polyphenol-rich compound does have electrochemical properties.

In summary, according to the research results of the present invention, it has been confirmed in the present study that various extracts of Chinese herbal medicines and tea leaves are electrochemically active, and have not only antioxidant activity, but also electronic shuttle action, and can also be used for green circulation applications.

The above embodiments are merely illustrative of the technology of the present invention and its effects, and are not intended to limit the present invention. Any person skilled in the art can modify and change the above embodiments without departing from the technical spirit and spirit of the present invention. Therefore, the scope of protection of the present invention should be as listed in the patent application scope mentioned later. .

Claims (4)

A plant extract for adding to a microbial fuel cell for improving the power generation efficiency of the microbial fuel cell, characterized in that the plant extract is obtained by taking a predetermined weight of a plant sample and chopping and grinding Thereafter, it is placed in a predetermined volume and concentration of the extractant, soaked for a certain period of time, and then concentrated under reduced pressure and filtered by air, and obtained by cyclic voltammetry after the plant extract is subjected to electron transfer. The number of electron transfer (n ^c ) is greater than 0.04, wherein n ^c =57 mV/|E _pa -E _pc |, E _pa : oxidation peak potential E _pc : reduction peak potential, wherein the plant extract is selected from Lonicera japonica extract, Citrus reticulate , Pueraria montana extract, Eriobotrya japonica extract, Polyporus umbellatus extract, Ephedra sinica extract , Syzygium aromaticum extract, Citrus reticulate extract, Schizonepeta tenuifolia extract, wherein the plant extract is dried tangerine peel ( Cit) Rus reticulate an extract having a dose greater than 40 g L ^-1 , wherein the plant extract is a Syzygium aromaticum extract at a dose of less than 6 g L ^-1 . The plant extract according to claim 1, wherein the plant extract has a pH between 4.76 and 7.25. The plant extract according to claim 1, wherein the extractant is selected from the group consisting of a 50% ethanol solution (Ethanol extract) and distilled water (Water extract). The plant extract according to claim 1, wherein the cyclic voltammetry is at a cycle potential of 1.5 V to -1.5 V at a rate of 10 mV. An s ^-1 cycle was applied to the plant extract to obtain the redox peaks.