| Dosgenin is obtained through Rhizoma Dioscoreae Zingiberensis, which is the raw material. More than 300 kinds of steroids medicines are made from it, which is called’Medical Gold’. The wastewater produced in this process is called’the king of wastewater’because of its large quantity, high concentration and strong acidity. Diosgenin production process is to turmeric shattered after fermentation, all of the slurry use the method of acid hydrolysis, filtration and washing, remaining slag and waste liquid.diosgenin production wastewater mainly consists of acid hydrolysis, wash ginger rinse water filtered water, spent wash.diosgenin manufacturing wastewater belongs to the highly difficult degradable industrial wastewater, high acidity, salinity and organic pollutants concentration. According to data shows, diosgenin manufacturing wastewater is mainly contains sugars, organic acids and short chain alcohol, aldehyde, and inorganic salts, curcumin and other substances. The main organic materials are:methanol, ethanol, acetic acid, aldehyde and other volatile substance. Aldehyde including furfural and its derivatives, due to turmeric and sugar cane bagasse, peanut shells, sorghum pole, oat hulls and corn cob same agricultural products, contain carbohydrates pentosan, under the action of an acid, pentosan first depolymerization into aldopentose further dehydration from furfural.Furfural is a heterocyclic compound containing a five-carbon ring, furan, and the pentose dehydration, to inhibit the growth of microorganisms or toxic effects. Because the molecular structure of it contains a furan ring, less susceptible to damage metabolic processes, showing difficult biodegradability. Furfural was found to be within the diosgenin wastewater dozens of organic pollutants into the highest concentration, and furfural subsequent biological wastewater treatment system has a great microbial inhibition. Furfural and its derivatives in the wastewater, for subsequent biological treatment systems have a certain toxicity microorganisms. Furfural concentration is too high to restrain the growth of microorganisms or even toxic effects. Thus, in wastewater treatment containing a higher concentration of furfural, the traditional activated sludge process has been extremely limited. Meanwhile, the high concentration of furfural high saponin wastewater COD is a great contribution. Microbial treatment technology in terms of refractory organic wastewater treatment has a good application, good effect, low cost, high efficiency; environmental protection has made a great contribution. Furfural is considered to be a pesticide, is harmful to animals mainly in irritation of the respiratory system, nervous system, liver, spleen and kidneys, blood system and so on. Because of its wide participants in industry, in various fields of national economy along with the growing use of lead into the environment, the total amount increasing, the risk of damage to the environment and ecology is also gradually increasing.To reduce the use of microorganisms furfural treatment of mixed wastewater effectively, not only can reduce the COD of diosgenin wastewater, while reducing furfural and its derivatives for the inhibition of microbial growth and subsequent development of biochemical systems, improve processing efficiency biodegradable, for diosgenin wastewater discharge standards has important significance.microbes in the subsequent biochemical treatment system has certain toxicity. Highly furfural concentration can restrain microbial growth even with poison effect. As a result, in contains a high concentration of furfural wastewater treatment, the traditional activated sludge process is great limited. Meanwhile, a high concentration of furfural of diosgenin wastewater is a great contribution to high COD. Microbial biological treatment for degradation-resistant wastewater has good application, low cost, high efficiency, has made a tremendous contribution in the field of environmental protection.Furfural is a five carbon heterocyclic compounds,containing an aldehyde group and a furan ring. It is considered an insecticide. With the growing use in various fields of national economy,lead to the total content increasing, the environmental and ecological damage is also gradually increasing.Using microbes which can effectively reduce the furfural to dispose diosgenin wastewater, not only can reduce the COD of diosgenin wastewater,but also can reduce the furfural and its derivatives on subsequent inhibition of microbial growth in biological systems.1. Isolation and identification of furfural degradation strainsFrom the biochemical treatment of diosgenin wastewater system in sewage sludge with furfural as sole carbon source, screened three strains to a certain tolerance to furfural and aerobic bacteria effective degradation of high concentration of furfural, analysis of morphological observation, physiological and biochemical characteristics and utilization, comprehensive use of Biolog bacterial identification system analysis, combined with the analysis of 16S rDNA sequencing and a variety of construction phylogenetic trees means a combination of the three strains of bacteria were identified to study. The three strains were named as DS1, DS3 and DS4, wherein DS1 colonies were round or approximately round, soft texture, no pigment, opaque, slightly shiny, with culture time growth, surface is red; the DS3 colonies were circular or nearly circular, opaque, black and white or yellowish, with incubation time growth, the middle part of the surface of the single colony will gradually form a wrinkled white mould. DS4 colonies were round, opaque, light yellow, smooth surface, edge smooth. Of the three strains were Gram staining, scanning electron microscope and plate culture, showed that the three strains are rod-shaped bacteria, including strains DS1 and DS3 were gram positive bacteria, strain DS4 was gram negative bacteria. The 16S rDNA sequences of three strains DS1, DS3, DS4 to submit Genbank registration, registration number were:HM773424, KJ641588 and KJ641589. By constructing phylogenetic tree of the three strains were identified as Bacillus cereus, Bacillus subtilis and Stenotrophomonas maltophilia. At the same time on the growth characteristics of the three strains of furfural and tolerance to carry on the research analysis. Respectively on three strains of bacteria in adding furfural and furfural is carried out under the condition of not adding the growth curve experiment,. When the culture medium of furfural, growth rates of three strains of the lag phase increased obviously slowed down. After adding 1000 mg L-1 furfural, lag phase DS1 by about 4h is extended to 8h; the induction period of DS3 by about 4h is extended to 6h; the induction period of DS4 is extended to 12h from about 4h. Compared to the other two, the strain DS3 showed better tolerance and degradation rate of furfural. Preliminary studies showed that the three strains, with furfural as the sole carbon source strains on its tolerance 4000 mg L’1, 6000 mg L-1 and 2000 mg L-1, respectively, much better than the other strains of the existing literature reports. The three strains of the optimum growth pH were 7,8,9; the optimum growth substrate concentration is 1000 mg L-1,2000 mg L-1 and 2000 mg L-1.2.Study on the factors of effect on the degradation of furfuralAs the most effected and tolerant among the three strains, Bacillus Subtilis DS3 is selected as the object of study. After 7 days of growth,17%～30% of the furural could be degraded by strain DS3.The article studied on the different environmental factors to the degradation effect of strain DS3 under the liquid culture conditions. In the single factor experiment, the optimum degrading-pH value of strain DS3 is 8, and the degradation rate could reach 29.77% at the 7th day. Strain DS3 effected best on the degradation of furfural, when the pH value was too low or too high, strain DS3 didn’t show some good affection to furfual, and the degradation rate reduced accordingly. The optimum initial substrate concentration of degradation by strain DS3 is 4000 mg L-1, and the degradation rate increased with increasing substrate concentration. The optimum inoculums of strain DS3 is 10%, and increasing the amount of inoculums could increase the furfural degradation rate to a certain extent at the same time. By using Box-Behnken method on the response surface analysis of furfural degradaion factor, substrate concentration and inoculation rate of degradation were more significant. After further analysis and calculation, as predicted, the furfural degradation reaches up to the maximum value when conditions are:pH 8.73,4000mg L-1 and furfural concentration inoculation is 10%, degradation ratio reaches 37.26%, under this condition, response prediction value is 99.1%. In fact, with the optimized conditions, the furfural degradation ratio by the strain DS3 gets a small scale promotion, measured as 36.91%.3. The reason of furfural degrading product and metabolic pathwayDetermined by Fourier transform infrared analysis of degradation products and the presence of substrate while aldehyde or ketone, methylene and primary alcohols. Compared with non-plus species of furfural solution, DS3 role of degradation products and degradation products after 3d 7d after the group of the same species, suggesting that 3-7 days, degradation products may not translate into functional groups but on the number of occurrence cumulative. Microbial degradation of furfural may have occurred in the aldehyde, by conversion of the aldehyde group to achieve lower microbial inhibition effect. GCMS after further testing, strain DS3 furfural degradation metabolites detected in alcohol, as well as due furoin and 3-hydroxy-2-butanone. No degradation products exist furoate, the oxidative metabolic pathways that alcohol and reported in the literature is inconsistent. Bacillus subtilis DS3 degradation of furfural aldehyde also mainly through the completion of the original. Speculate furfural alcohol dehydrogenase may be responsible for the catalytic reduction reaction of alcohol. Speculated acetoin is DS3 furfural as carbon substrates catabolism. Furfural pyruvate generated through glycolysis pathway, and then enter the citric acid cycle decomposition of NADH generated during the TCA cycle into the respiratory chain, ATP produced by oxidative phosphorylation; NADPH formed by another part of furfural pentose phosphate pathway, and provide important precursors for the synthesis of fatty acids, cholesterol and so on. The excess acetyl-CoA by pyruvate then into the overflow metabolism to produce 3-hydroxy-2-butanone. H2O and CO2 come out in this process. Inference Furoin arises benzoin condensation reaction occurs under the action of cleavage of the enzyme substrate furfural in the cell. Strain DS3 furfural into low toxic substances, mainly converted to alcohol, and furfuryl benzoin and acetoin. From the biotransformation process putative substrate degradation, the furfural involved a variety of metabolic DS3 Bacillus subtilis cells, and the role of related enzymes are inseparable, and cells in the body’s energy levels are closely related.Due to the metabolic pathway metabolites Institute was more trace, and because of the time and conditions, no combination of nuclear magnetic resonance spectroscopy, isotope tracer techniques and identification methods and means of the standard controls such as metabolites of other possible intermediates for detailed in-depth The study, to be further detailed metabolic pathways perfect complement.From the biotransformation process putative substrate degradation, the furfural involved a variety of metabolic DS3 Bacillus subtilis cells, and the role of related enzymes are inseparable. Furfural degrading enzymes produced by the strain DS3 mainly located in the cell membrane, is for intracellular enzyme. With HPLC determination of enzyme degradation rate of furfural and whole cell SDS-PAGE electrophoresis, to determine the non-degrading enzyme inducible enzyme. Regardless of whether the substrate contains furfural, degrading enzymes can be synthesized and then play degradation. Synthesis and degradation by enzymes within the microbial cells only gene regulation, without inducing substance that is present in the environment of furfural. Furfural degrading enzyme compared to the cells themselves, in the degradation of the play, quickly and efficiently, at 8h, furfural residual concentration in the medium is 1379.79 mg L-1, i.e., the degradation rate was 31.01%; while the alcohol generated is maintained at 464.73 mg L-or so. Under degrading enzymes, alcohol is generated primarily within 0-6h occurs when more than 6h, the amount of alcohol is not cumulative; conversion of furfural alcohol may have ended, but for other substances (such as Furoin and 3- hydroxy-2-butanone) transformation is still underway, furfural involved in cell metabolism in response. Speculated to play a role in this process degrading enzyme system include alcohol dehydrogenase, a-acetolactate decarboxylase, lyase, NADH, etc.Due to the metabolic pathway metabolites Institute was more trace, and due to time constraints, no combination of UV-visible spectroscopy and nuclear magnetic resonance spectroscopy to identify the means and standard control technology and metabolites such as the detailed in-depth study of other possible intermediates. Detailed metabolic pathway remains to further improve the supplement.4. Study on characteristics of furfural degrading enzymeFrom the biotransformation process putative substrate degradation, the furfural involved a variety of metabolic DS3 Bacillus subtilis cells, and the role of related enzymes are inseparable. Furfural degrading enzymes produced by the strain DS3 mainly located in the cell membrane, is for intracellular enzyme. In SDS-PAGE electrophoresis of whole cell, determining a non-degrading enzyme inducible enzyme. Regardless of whether the substrate contains furfural, degrading enzymes can be synthesized and then play degradation. Synthesis and degradation by enzymes within the microbial cells only gene regulation, without inducing substance that is present in the environment of furfural. Furfural degrading enzyme compared to the cells themselves, in the degradation of the play, quickly and efficiently, at 8h, furfural residual concentration in the medium is 1379.79mg L-1, i.e., the degradation rate was 31.01%; while the alcohol generated is maintained at 464.73 mg L"1 or so. Under degrading enzymes, alcohol is generated primarily within 0-2h occurs when more than 2h, the amount of alcohol is not cumulative; conversion of furfural alcohol may have ended, but for other substances (such as Furoin and 3-hydroxy-2-butanone) transformation is still underway, furfural involved in cell metabolism in response. Furfural alcohol is the main biological degradation products. Degrading enzymes, crude enzyme solution contains not only the alcohol dehydrogenase, further comprising furfural into furfuryl benzoin and 3-hydroxy-2-butanone compound such other enzymes, in particular enzymes various metabolic reactions, but alcohol dehydrogenase plays a major role in the degradation process of furfural.5. The application of degrading bacteria in diosgenin wastewater treatmentThe strain DS3 is added into the diosgenin wastewater to degrade high concentrations of organic pollutants. Diosgenin wastewater contains large amounts of sulfate ions due to the sulfuric acid hydrolysis was used to hydrolysis raw materials in a diosgenin production process. The result show that the strain DS3 can withstand high concentrations of sulfuric acid ion, and a good growth characteristic was exhibit and in this condition that sulfate ion concentration reached 8000mg L-1. Within 72 hours, strain DS3 of saponin wastewater COD removal efficiency reached 50.71%, with the ability to remove the saponin good organic pollutants in wastewater.Strain DS3 has along with the tolerance of high concentrations of sulfate ions and degradation of furfural organic pollutants two properties, and has good practical value. |
PDF Full Text Request