Method for researching smelly ability of drinking water reservoir smelly actinomycetes under different exogenous environment conditions

Abstract

The invention belongs to the technical field of odor prevention and treatment of drinking water reservoirs, and provides a method for researching the odor-causing capability of odor-causing actinomycetes of drinking water reservoirs under different exogenous environment conditions aiming at the technical problem that the influence of different environmental factors on the odor-causing capability of actinomycetes is not clear at present. The method comprises the following steps: purifying and separating two streptomyces strains with relatively high drinking water reservoir olfactory production capability; the growth curve of the drinking water reservoir sediment-water interface sniffing actinomycetes is explored on the basis of the separated streptomyces strains; the smelly ability of the actinomycetes in different growth states is clarified, so that the growth and smelly production characteristics of the streptomyces smelly of the drinking water reservoir under different exogenous environment conditions are determined, and a direction is provided for controlling the smelly of the drinking water reservoir in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of odor prevention and control in drinking water reservoirs, and particularly relates to a research method for the odor-causing ability of odor-causing actinomycetes in drinking water reservoirs under different exogenous environmental conditions. Background Art

[0002] The unpleasant odor of drinking water sources is intolerable to consumers worldwide and has thus become a major concern in the drinking water industry. The odors of drinking water mainly include earthy moldy smell, fishy smell, septic tank smell, grassy smell, and chemical smell. Among the odor problems in 80% of water sources, the earthy moldy smell accounts for 41%. Lakes and reservoirs show a more significant earthy moldy smell, and 2-methylisoborneol (2-MIB) and geosmin (GSM) compounds are the two main secondary metabolites causing the earthy moldy smell in lake and reservoir water bodies. 2-MIB and GSM compounds are mainly formed by cyanobacteria, actinomycetes, myxobacteria, fungi, etc. During the non-algal bloom period, the odor problem mainly comes from the odor production of actinomycetes. However, currently, more research focuses on algal odor production, and actinomycete odor production has not been fully studied.

[0003] Actinomycetes are common soil inhabitants and also exist in many aquatic environments, from fresh water to salt water, and are widely present in the environment. Actinomycetes have strong biosynthetic ability and biological activity, and the actinomycetes input into drinking water reservoirs by runoff still retain strong growth and odor-producing activity in water. Streptomyces is the main contributor to the known odor production of actinomycetes and is often isolated from water bodies and sediments. Streptomyces antibioticus LJH21, Streptomyces sp. ZEU13, and Streptomyces sp. PQK19 are all isolated Streptomyces odor-causing strains. 2-MIB and GSM are found as secondary metabolites of Streptomyces, causing panic about drinking water safety. As an important producer of actinomycete odor - Streptomyces, it is of great significance to explore its growth and odor-producing factors.

[0004] Environmental substances can affect microbial growth and the production of 2-MIB and GSM, such as nutrients, dissolved oxygen, and temperature. Higher concentrations of 2-MIB and GSM are usually related to a lower TN:TP ratio. Ammonia nitrogen is the form with the lowest nitrogen content in aquatic systems, and its biological absorption efficiency is faster than that of nitrate nitrogen. Thermal stratification is a common feature of drinking water reservoirs in summer. The decrease in the dissolved oxygen concentration at the sediment-water interface causes the sediment to float, becoming another important reason for the production of odor substances in drinking water reservoirs. In the absence of nutrient limitations, temperature is the most important factor affecting growth and metabolism-induced odor. When the biomass is the lowest, studies have shown that the secondary metabolite production, that is, the odor concentration value, is the highest at 15°C. At higher temperatures, studies have shown that the growth of Streptomyces increases and the overall odor production corresponding to it increases. However, the effects of different environmental factors on the odor-causing ability of actinomycetes are not very clear at present. Therefore, exploring the external environmental factors causing odor in actinomycetes is an important support for controlling the odor in drinking water reservoirs. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a research method for the odor-causing ability of odor-causing actinomycetes in drinking water reservoirs under different external environmental conditions.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A research method for the odor-causing ability of odor-causing actinomycetes in drinking water reservoirs under different external environmental conditions, including the following steps:

[0008] S1. Obtain water samples from drinking water reservoirs;

[0009] S2. Filter the water samples through a filter membrane, and place the filtered filter mesh in a solid medium for continuous cultivation for 7 days. Use the plate streaking method to repeat the purification cultivation in the solid medium 7 times to obtain pure actinomycetes, and identify and isolate two strains of Streptomyces with strong odor production;

[0010] S3. Conduct oscillation experiments on the two strains of Streptomyces using ultrapure water respectively, simulate the environmental conditions of drinking water reservoirs, cultivate the Streptomyces for 10 days, then detect the physical and chemical indexes of the water body, and analyze the influence of the physical and chemical properties of the water body on the growth and odor production of Streptomyces through the detection results of the physical and chemical indexes;

[0011] S4. Add different types of nitrogen sources and carbon sources to ultrapure water respectively, detect the total cell number of Streptomyces, the absorbance values at 590 nm and 750 nm, and the concentrations of 2-MIB and GSM every 24 hours, and analyze the influence of nutrients on the growth and odor production of Streptomyces through the detection results;

[0012] S5. Combine the analysis results of steps S3 and S4 to clarify the odor-causing ability of odor-causing actinomycetes in drinking water reservoirs under different external environmental conditions.

[0013] Preferably, in step S1, the water sample is sourced from the drinking water in the drinking water reservoir at a depth of 7 m.

[0014] Preferably, in step S2, the two Streptomyces strains are Strepotomyces albogriseolus and Strepotomyces tendae.

[0015] Preferably, in step S3, the environmental conditions of the drinking water reservoir are as follows:

[0016] The initial TP concentration is 0.02 mg / L, the initial carbon source concentration is 4 mg / L, the initial permanganate index is 4 mg / L, the rotation speed is 160 rpm, the culture temperature is: 5 °C, 15 °C, 25 °C, the dissolved oxygen concentration is: 0 mg / L, 4 mg / L, 8 mg / L, and the TN concentration is: 1 mg / L, 2 mg / L, and 4 mg / L.

[0017] Preferably, in step S3, the physical and chemical indexes of the water body are TN, permanganate index, pH, and TP.

[0018] Preferably, in step S4, the types of nitrogen sources are KNO3, NaNO2, NH4Cl, and tryptone.

[0019] Preferably, in step S4, the types of carbon sources are starch, amino acids, and glucose.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The research method provided by the present invention determines that the DO = 8 mg / L + 25 °C + NH4 + -N triple can maximize the 2-MIB production through environmental combination optimization design, while the DO = 0 mg / L + NO3 - -N combination will block the synthesis of 2-MIB;

[0022] (2) Through the research on the dual-factor synergistic mechanism, the present invention discovers that temperature-dissolved oxygen has a synergistic regulatory effect on the metabolism of Streptomyces, and high temperature and high oxygen activate NH4 + -N assimilation, while low temperature and low oxygen induce denitrification inhibition;

[0023] (3) By developing a SEM-GLM combined model, the present invention quantifies the core driving factors of nitrogen source types and realizes accurate prediction of odor risk;

[0024] (4) The research of the present invention clarifies the two-way effects of ammonia nitrogen promoting odor production and nitrate nitrogen inhibiting odor production, and establishes a dynamic regulation strategy based on the weight distribution of environmental factors. Description of the Drawings

[0025] Figure 1 Results of the effects of different carbon sources on the concentration of 2-MIB produced by two Streptomyces strains: (a) is starch; (b) is amino acid; (c) is glucose;

[0026] Figure 2 Cell growth curves of two Streptomyces strains under different carbon sources: (a) is starch; (b) is amino acid; (c) is glucose;

[0027] Figure 3 Results of the effects of different temperatures and dissolved oxygen on the odor produced by Streptomyces strains: (a) is the difference trend graph of 2-MIB production at different temperatures (5℃ / 15℃ / 25℃) and dissolved oxygen (0mg / L / 4mg / L / 8mg / L); (b) is the survival probability graph of odor events occurring under different temperature and dissolved oxygen conditions; (c) is the scatter plot of grouped fitting curves of different temperatures and dissolved oxygen changing with time;

[0028] Figure 4 Results of the effects of different nutrient elements, nitrogen source concentrations, and types on odor production by Streptomyces strains: (a) is the SHAP model of the contribution degree of nutrient elements to 2-MIB under glucose, amino acid, and starch conditions. The bar graph and the honeybee swarm graph represent mean(|SHAP value|) and SHAP values respectively; (b) is the circular grouped cloud and rain graph of odor differences for different nitrogen source types; (c) is the numerical bubble graph of odor differences for two Streptomyces strains under different nitrogen source concentrations and types; (d) is the correlation analysis graph of odor substances and nutrient element concentrations;

[0029] Figure 5 Utilization rates of carbon sources by two Streptomyces strains cultured with different carbon sources and nitrogen sources: (a) is the circular heat map of the utilization rates of six carbon sources over time; (b) is the cloud and rain graph of the total utilization rates of six carbon sources;

[0030] Figure 6 Results of the comprehensive factor analysis of the concentration of 2-MIB produced by Streptomyces strains: (a) is the circular graph of the contribution degree ranking obtained from the structural equation SEM model and the SEM structural equation graph of different environmental factors, cell numbers, and -MIB production; (b) is the graph of the contribution degree ranking of environmental factors and cell numbers to the production of 2-MIB by Streptomyces strains analyzed by the generalized linear GLM model and the model prediction accuracy test graph. Specific implementation manners

[0031] Next, in combination with the Figures 1 to 6 embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] The present invention provides a research method for the odor-causing ability of actinomycetes in a drinking water reservoir under different external environmental conditions, including the following steps:

[0033] S1. Obtain the water sample of the drinking water reservoir; specifically, the water sample is from the drinking water at a depth of 7 m in the drinking water reservoir.

[0034] S2. Filter the water sample through a filter membrane, and place the filtered filter mesh in a solid medium for continuous culture for 7 days. Use the streak plate method to repeat the purification culture in the solid medium 7 times to obtain pure actinomycetes. Two strains of streptomycetes with strong odor production are identified and isolated: the two strains of streptomycetes are Strepotomyces albogriseolus and Strepotomycestendae respectively.

[0035] S3. Conduct oscillation experiments on the two strains of streptomycetes with ultrapure water respectively, simulate the environmental conditions of the drinking water reservoir, culture the streptomycetes for 10 days, and then detect the physical and chemical indexes of the water body. The physical and chemical indexes of the water body are TN, permanganate index, pH, and TP, and analyze the influence of the physical and chemical properties of the water body on the growth and odor production of streptomycetes through the detection results of the physical and chemical indexes.

[0036] In the present invention, the simulated environmental conditions of the drinking water reservoir are as follows:

[0037] The initial TP concentration is 0.02 mg / L, the initial carbon source concentration is 4 mg / L, the initial permanganate index is 4 mg / L, the rotation speed is 160 rpm, the culture temperature is: 5°C, 15°C, 25°C, the dissolved oxygen concentration is: 0 mg / L, 4 mg / L, 8 mg / L, and the TN concentration is: 1 mg / L, 2 mg / L, and 4 mg / L.

[0038] S4. Add different types of nitrogen sources and carbon sources to the ultrapure water respectively. The specific types of nitrogen sources are KNO3, NaNO2, NH4Cl, and tryptone, and the specific types of carbon sources are starch, amino acids, and glucose. Detect the total cell number of streptomycetes, the absorbance values at 590 nm and 750 nm, and the concentrations of 2-MIB and GSM every 24 h, and analyze the influence of nutrients on the growth and odor production of streptomycetes through the detection results.

[0039] S5. Combine the analysis results of step S3 and step S4 to clarify the odor-causing ability of the odor-causing actinomycetes in the drinking water reservoir under different external environmental conditions.

[0040] The following describes in detail the research method for the odor-causing ability of the odor-causing actinomycetes in the drinking water reservoir provided by the present invention through specific examples.

[0041] Example 1

[0042] I. Materials and Methods

[0043] 1.1 Research Area and Strain Isolation

[0044] The research area is from Yuzi Gully Reservoir in Xi'an, China (34°27′52″N, 108°54′19″E), which is an important drinking water source area in Xi'an. 3 L of water samples were taken from the bottom layer (depth 7 m) of the drinking water reservoir and stored at 4°C. 1 L of water sample was filtered through a 0.22 μm polycarbonate membrane in triplicate, and then the filtered polycarbonate membrane was placed in No. 1 Gao's solid medium containing potassium dichromate and continuously cultured for 7 days. The pure actinomycetes were obtained by repeating the purification culture in the medium 7 times using the streak plate method. Two strains of Streptomyces with strong odor production were purified and isolated by biomolecular methods, namely Strepotomyces albogriseolus (abbreviated as Sa) and Strepotomyces tendae (abbreviated as St).

[0045] 1.2 Physical-Chemical Parameters of Water Quality

[0046] In the experiment, 250 mL of simulated reservoir water was prepared with ultrapure water. The initial total phosphorus (TP) concentration was fixed at 0.02 mg / L, and three experimental systems with TN:TP ratios of 50:1, 100:1, and 200:1 were constructed by setting the total nitrogen (TN) concentration gradient (1 mg / L, 2 mg / L, 4 mg / L). Two strains of Streptomyces, Strepotomyces albogriseolus and Strepotomyces tendae, were inoculated and cultured with shaking at an inoculation amount of 1%. The radial oscillation mode was set, the rotation speed was 160 rpm, and the amplitude was 3 cm to simulate the water flow shear force in the reservoir. The culture temperatures were set at 5°C, 15°C, and 25°C to cover the water temperatures in different periods of the reservoir, and the dissolved oxygen concentrations were set at 0 mg / L (anaerobic), 4 mg / L (medium oxygen), and 8 mg / L (aerobic) to conduct nine orthogonal environmental gradients under different conditions. The experimental period was 10 days, and the permanganate index (COD Mn ) was maintained at 4 mg / L during this period. After the culture ended, TN, COD Mn , pH, TP and other indicators were measured according to the Hygienic Standard for Drinking Water (GB 5749-2022), and the growth characteristics of Streptomyces and the regular changes of 2-MIB were analyzed synchronously.

[0047] 1.3 Growth and Metabolic Activity

[0048] The experiment used a standardized Biolog ECO plate (Biolog, CA, USA) system to evaluate the metabolic characteristics of strains: ultra-pure water was used as the basal medium, and a test system containing four nitrogen sources (KNO3, NaNO2, NH4Cl, tryptone) and three types of carbon sources (amino acids, glucose, starch) was prepared. Specifically, the nitrogen source settings covered inorganic salts (KNO3 / NaNO2 / NH4Cl) and organic nitrogen (tryptone), and the carbon sources were grouped into amino acids, glucose, and starch. By inoculating samples into the wells of the ECO plate pre-loaded with different substrates, a response map of microorganisms to the nutrient matrix was established to systematically analyze the functional differentiation mechanism of Streptomyces albogriseolus and Streptomyces tendae in carbon-nitrogen co-metabolism. The total cell number of the strains in the shake flask was detected using a flow cytometer and the stain SYBR Green I (10 μL / mL, Invitrogen, USA) every 24 h. The absorbance values of the streptomyces strains were detected at 590 nm and 750 nm using a Biology automatic microbial identifier (BIOLOG, Hayward, CA, USA).

[0049] 1.4, Odor compounds

[0050] Samples were taken daily and stored in glass bottles with gaskets for the determination of 2-MIB and GSM concentrations in the water body. Odor compounds were immediately detected by headspace solid-phase microextraction (SPME) combined with GC-MS (Agilent 8890, Agilent Tech., USA). The 2-MIB standard was Supelco CRM47523, and the GSM standard was Supelco CRM47522. The limits of quantification (LOQ) for 2-MIB and GSM were both 1 ng / L.

[0051] II. Results and discussion

[0052] 2.1, Odorous substances

[0053] In this study, the synergistic regulatory mechanism of dissolved oxygen (DO), temperature (T), and nitrogen source (N) on 2-MIB biosynthesis was systematically analyzed through orthogonal experiments, and the results are as Figure 1 shown. The results of Figure 1 showed that in a high-oxygen environment with DO = 8 mg / L, temperature was the dominant factor: the 2-MIB yield of the NH4 + -N system (Sa-NH4Cl) was relatively high at 25°C, revealing that high temperature significantly activated the ammonium salt metabolic pathway; at 15°C, NO2 -The output of the system (St-NaNO2) increases, suggesting that low temperature induces the activity of nitrate reductase; while the concentrations of all systems are relatively low at 5°C, confirming the general inhibition of low temperature on microbial metabolism. When DO drops to 4 mg / L, the type of nitrogen source becomes the core regulatory factor. The NH4 + -N and NO3 - -N systems (Sa-NH4Cl / Sa-KNO3) both maintain high and stable output, but the output of the NO2 - -N and organic nitrogen systems significantly decays, indicating that there are functional limitations in the nitrate metabolism of St strains. Under anaerobic conditions (DO = 0 mg / L), the NH4 + -N system (Sa-NH4Cl) still maintains the stable synthesis of high-concentration 2-MIB, while the output of the NO3 - -N / NO2 - -N system decreases and the St-NH4Cl group shows violent fluctuations, confirming the inhibition of the anoxic environment on the nitrate metabolism pathway and the metabolic heterogeneity of the sludge microbial community. Based on the above rules, the process optimization suggestions are as follows: The ternary combination of DO = 8 mg / L + 25°C + NH4 + -N can maximize the 2-MIB output, while the combination of DO = 0 mg / L + NO3 - -N can effectively block its biosynthesis pathway.

[0054] 2.2 Growth status of Streptomyces and its impact on odor production

[0055] Figure 2It is shown that the utilization characteristics of the strains Streptomyces albogriseolus and Streptomyces tendae for different nitrogen sources exhibit significant temperature sensitivity and oxygen environment dependence. The Sa strain has a higher biomass at 25°C, indicating its mesophilic characteristics and the ability to preferentially utilize organic nitrogen sources; the biomass decreases significantly at low temperature (5°C), showing that the metabolic activity is inhibited by temperature. It is worth noting that the Sa strain has a better assimilation of ammonium salt (NH4Cl) in an environment with high dissolved oxygen (DO = 8 mg / L), but its ability to utilize nitrite (NaNO2) decreases significantly under low temperature or oxygen-rich conditions. On the contrary, the St strain has the best biomass for utilizing NaNO2 at low temperature (5°C) and oxygen-rich (DO = 8 mg / L), reflecting the synergistic effect of cold tolerance and nitrite oxidation ability; even under high temperature (25°C) and anoxic (DO = 0 mg / L) conditions, it still maintains a medium biomass, suggesting that it adapts to the low-oxygen environment through the denitrification pathway. There are temperature-dependent differences in the utilization of inorganic nitrogen sources by the two strains: the Sa strain utilizes NH4Cl more efficiently at high temperature, while the St strain has a better utilization rate of NH4Cl at 15°C than at 25°C; the metabolism of NaNO2 shows a differentiation that the St strain is better at low temperature and oxygen-rich conditions than the Sa strain which is inhibited at low temperature. For organic nitrogen sources, the biomass of the Sa strain is significantly higher than that of the St strain at high temperature, presumably closely related to its protease secretion ability. The dissolved oxygen level further regulates the metabolism of the two strains: high DO (8 mg / L) promotes ammonium salt assimilation in the Sa strain and nitrite oxidation in the St strain, while low DO (0 mg / L) triggers the denitrification metabolism in the St strain. This study reveals the complementary functional characteristics of the two strains - the Sa strain dominates the decomposition of ammonium salt and organic nitrogen under high temperature and aerobic conditions, and the St strain completes nitrite conversion and denitrification in a low-temperature oxygen-rich or anoxic environment. The temperature-oxygen environment coupling mechanism of their metabolic characteristics provides a theoretical basis for constructing a seasonally dynamically regulated composite denitrification system.

[0056] 2.3, Effects of Dissolved Oxygen and Temperature on Odor Production by Streptomyces

[0057] To explore the seasonal distribution of reservoir water temperature, the experimental temperatures were set at 5°C, 15°C, and 25°C. To explore the effect of the dissolved oxygen level in a drinking water reservoir on Streptomyces, the dissolved oxygen gradients were set at 0 mg / L, 4 mg / L, and 8 mg / L. A differential analysis was performed on the production of 2-MIB under different carbon sources, gradient dissolved oxygen, and temperature conditions, and the results are as Figure 3 shown, through Figure 3(a) It can be seen that the yield of 2-MIB is significant in all three groups of experiments at 25 °C, and the yield of 2-MIB is also relatively high under the condition of 5 °C in the glucose group; both dissolved oxygen concentrations of 0 mg / L and 8 mg / L can trigger relatively high 2-MIB concentrations, and the anaerobic condition of 0 mg / L also has a good effect on the yield of low-concentration 2-MIB. Extreme temperature and dissolved oxygen conditions can trigger high-concentration 2-MIB production. Through Figure 3 (b) It can be seen that the probability of odor events breaking out is most prominent at 25 °C and 8 mg / L. The aerobic condition of 8 mg / L has a more prominent odor outbreak probability compared to the high temperature condition of 25 °C. Curve fitting was performed on the 2-MIB concentration at different times and different temperature and dissolved oxygen concentrations, and the results are as Figure 3 (c) shown, through Figure 3 (c) It can be seen that within the 10-day growth cycle of Streptomyces, different temperatures have relatively little average impact on the yield of 2-MIB, and high 2-MIB concentration values all appear under the condition of 5 °C. Compared with the aerobic condition, the average yield of 2-MIB in the anaerobic condition is significantly increased, and a large number of high-concentration limit values appear under the anaerobic condition, thus increasing the average concentration under the anaerobic condition. The 2-MIB concentration in the aerobic condition is relatively mild, but there are also high 2-MIB values. The technical advantages of the present invention are reflected in: for the first time, revealing the two-way activation mechanism of the anaerobic / supersaturated dissolved oxygen environment on the odor-producing metabolism of Streptomyces, and constructing an odor warning system based on the temperature-dissolved oxygen interaction.

[0058] 2.4. Influence of Nutrient Elements on Odorous Substances

[0059] Based on the SHAP model analysis and multi-dimensional experimental results, the present invention reveals the key mechanism and optimization path of the synergistic regulation of 2-MIB odor production by Streptomyces by carbon and nitrogen sources. The specific results are as Figure 4 shown. Figure 4 (a) shows the influence of nutrient elements on the odor production of Streptomyces. The SHAP model predicts the contribution values of different environmental factors to the 2-MIB concentration. Through Figure 4 (a) It can be seen that the positive contribution value of nitrate nitrogen characteristics in the glucose group is the best, the ammonia nitrogen shows a slight positive contribution value, and the permanganate index and TP show negative benefit values for 2-MIB. In the amino acid group, the positive contribution values of ammonia nitrogen and nitrate nitrogen characteristics are relatively good, but the number of positive nitrate nitrogen characteristic points is small, and the positive contribution effect of ammonia nitrogen on 2-MIB is better. The contribution of the remaining environmental factors to 2-MIB is not significant. In the starch group, ammonia nitrogen and nitrate nitrogen show positive contribution values, and nitrate nitrogen has a more predictive contribution to 2-MIB than ammonia nitrogen, and TN shows a significant negative contribution value. The remaining environmental factors have no obvious positive or negative contribution values. Through comprehensive analysis, ammonia nitrogen and nitrate nitrogen have a good positive predictive effect on the 2-MIB produced by Streptomyces. The differences in 2-MIB odor under different combinations of carbon source and nitrogen source types are as Figure 4 (b) shown, throughFigure 4 (b) It can be seen that the combinations of starch and ammonia nitrogen, nitrite nitrogen and organic nitrogen sources show more obvious concentration differences. Under the three different types of carbon sources, the concentration differences of 2-MIB caused by the addition of ammonia nitrogen are relatively large. The influence of ammonia nitrogen on 2-MIB under different treatment conditions is more significant than that of other nitrogen source types. Figure 4 (c) shows the changes in 2-MIB concentration and the results of significant differences caused by the initial addition of different carbon sources. Through Figure 4 (c) It can be seen that for Strepotomyces albogriseolus, the ammonia nitrogen and nitrate nitrogen bubbles are larger, the P value is smaller and the results are more significant, and the change range of 2-MIB concentration is smaller than that of Strepotomyces tendae. For Strepotomyces tendae, the change range and result significance of nitrate nitrogen are better than those of other environmental factors. Figure 4 (d) shows the results of correlation analysis of different physicochemical factors, 2-MIB and GSM. Through Figure 4 (d) It can be seen that the 2-MIB concentration has a certain correlation with different physicochemical factors and a slight negative correlation with GSM. The results show that different physicochemical factors all play a promoting role in the process of odor generation. By analyzing the non-linear coupling mechanism between the carbon-nitrogen nutrient factor metabolic network and environmental factors, a 2-MIB prediction system based on the SHAP model is established for the first time, which has significant application value in the field of drinking water safety.

[0060] 2.5 Carbon source utilization ability of Streptomyces

[0061] The present invention relates to the technical field of microbial culture, and specifically relates to the carbon source metabolic characteristics of Streptomyces strains and their applications in fermentation processes. Figure 5 shows the utilization ability of Strepotomyces albogriseolus and Strepotomyces tendae for 6 different types of carbon sources during a 10-day culture period and the total carbon source utilization ability under different conditions. These six types of carbon sources are monosaccharides, amino acids, esters, alcohols, amines and esters. Through Figure 5It can be seen that the two strains of Streptomyces have similar abilities to utilize carbon sources. Streptomyces albogriseolus has the highest utilization rates for amino acids and esters, while Streptomyces tendae has the highest utilization rate for esters. The two strains of Streptomyces show better utilization rates for various carbon sources in the glucose group compared to the starch and amino acid groups. In the starch group, the utilization rates of carbon sources are similar among inorganic nitrogen sources, with the worst utilization rate for carbon sources when nitrite nitrogen is added and the best utilization rate when tryptone is added. In the amino acid group, the utilization rate of carbon sources is worse when tryptone is added compared to when inorganic nitrogen sources are added. Streptomyces albogriseolus shows significant differences in the utilization of esters under different nitrogen sources. In the glucose group, the addition of ammonia nitrogen results in strong abilities for various carbon sources, while the addition of nitrate nitrogen leads to the lowest utilization rates of carbon sources for the two strains of Streptomyces. The utilization ability of carbon sources in the starch group is more stable than that in the other two groups, and there are multiple aggregation points for the utilization rates of carbon sources with different carbon and nitrogen sources. The total utilization rate of carbon sources by the two strains of Streptomyces is always higher when organic nitrogen sources are added compared to inorganic nitrogen sources. The technical advantages of the present invention are reflected in: for the first time, revealing the regulatory effect of organic nitrogen sources on the carbon source metabolic network of Streptomyces and establishing a quantitative correlation between nitrogen source types and specific carbon source metabolism.

[0062] 2.6, Comprehensive evaluation of environmental factors on odor production by Streptomyces

[0063] The present invention reveals the key regulatory pathway of nitrogen metabolism on 2-MIB odor production by Streptomyces and the synergistic mechanism of environmental factors through the integrated analysis of structural equation model (SEM) and generalized linear model (GLM). The results are as Figure 6 shown. Figure 6 (a) shows the analysis results of the structural equation (SEM) model: the path coefficients of ammonia nitrogen (NH4 + ) and nitrate nitrogen (NO3 - ) for the 2-MIB generation reach 7.281 and 8.758 respectively (p < 0.05), which are significantly higher than those of other environmental factors (the path coefficients of temperature and dissolved oxygen < 0.5), confirming that the nitrogen source type is the core driving factor for 2-MIB biosynthesis. The permanganate index (COD Mn ) is significantly negatively correlated with cell density (path coefficient = -2022.169, p < 0.05), suggesting that the organic matter oxidation process may inhibit the metabolic activity of microorganisms. Figure 6(b) shows the evaluation results of the comprehensive factors affecting the odor production of two Streptomyces strains by the Generalized Linear Model (GLM). The GLM has a good fit, the residual distribution is concentrated, and the proportion of outliers is <5%, proving that the model has high reliability in predicting the contribution degree of 2-MIB odor. Nitrate nitrogen (4.71) and ammonia nitrogen (3.65) have a significant positive effect on the 2-MIB concentration, while TN and cell density show a stable negative regulation, which is highly consistent with the SEM conclusion. Through the combined analysis of SEM-GLM, the limitations of a single model are broken through, the quantitative regulation rights of the nitrogen metabolism pathway are clarified, ammonia nitrogen and nitrate nitrogen are locked as the key process regulation nodes, providing data support for optimizing the carbon-nitrogen ratio (C / N) and nitrogen source dosing strategy.

[0064] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A research method for the odor-causing ability of actinomycetes causing odor in a drinking water reservoir under different external environmental conditions, characterized in that, It includes the following steps: S1. Obtain water samples from a drinking water reservoir; S2. Filter the water samples through a filter membrane, place the filtered filter mesh in a solid medium for continuous culture for 7 days, and repeat the purification culture 7 times in the solid medium using the streak plate method to obtain pure actinomycetes, and identify and isolate two Streptomyces strains with strong odor production; S3. Conduct oscillation experiments on the two Streptomyces strains respectively using ultrapure water, simulate the environmental conditions of the drinking water reservoir, culture the Streptomyces strains for 10 days, then detect the physicochemical indexes of the water body, and analyze the influence of the physicochemical properties of the water body on the growth and odor production of the Streptomyces strains through the detection results of the physicochemical indexes; S4. Add different types of nitrogen sources and carbon sources to the ultrapure water respectively, detect the total cell number of the Streptomyces strains, the absorbance values at 590 nm and 750 nm, and the concentrations of 2-MIB and GSM every 24 hours, and analyze the influence of nutrients on the growth and odor production of the Streptomyces strains through the detection results; S5. Combine the analysis results of step S3 and step S4 to clarify the odor-causing ability of the odor-causing actinomycetes in the drinking water reservoir under different external environmental conditions.

2. The research method for the odor-causing ability of actinomycetes causing odor in drinking water reservoirs under different external environmental conditions according to claim 1, characterized in that, In step S1, the water samples are sourced from the drinking water at a depth of 7 m in the drinking water reservoir.

3. The research method for the odor-causing ability of actinomycetes causing odor in drinking water reservoirs under different external environmental conditions according to claim 1, characterized in that, In step S2, the two Streptomyces strains are Streptomyces albogriseolus and Streptomyces tendae respectively.

4. The research method for the odor-causing ability of actinomycetes causing odor in drinking water reservoirs under different external environmental conditions according to claim 1, characterized in that, In step S3, the environmental conditions of the drinking water reservoir are as follows: The initial TP concentration is 0.02 mg / L, the initial permanganate index is 4 mg / L, the rotation speed is 160 rpm, the culture temperatures are 5°C, 15°C, and 25°C, the dissolved oxygen concentrations are 0 mg / L, 4 mg / L, and 8 mg / L, and the TN concentrations are 1 mg / L, 2 mg / L, and 4 mg / L.

5. The research method for the odor-causing ability of actinomycetes causing odor in a drinking water reservoir under different external environmental conditions according to claim 1, characterized in that, In step S3, the physicochemical indexes of the water body are TN, permanganate index, pH, and TP.

6. The research method for the odor-causing ability of actinomycetes causing odor in a drinking water reservoir under different external environmental conditions according to claim 1, characterized in that, In step S4, the types of nitrogen sources are KNO3, NaNO2, NH4Cl, and tryptone.

7. The research method for the odor-causing ability of actinomycetes causing odor in drinking water reservoirs under different external environmental conditions according to claim 1, characterized in that, In step S4, the types of carbon sources are starch, amino acids, and glucose.

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