Preparation method of soil conditioning type compound fertilizer based on chitin waste

Abstract

The invention discloses a preparation method of a soil conditioning type compound fertilizer based on chitin waste, and belongs to the technical field of soil fertilizer preparation. The method comprises the following steps: cleaning and drying shrimp and crab shells, and crushing to obtain chitin powder; mixing lactic acid or malic acid, glycerol, choline chloride and urea according to a specific mass ratio to prepare a chitin activating solution; under a mild condition, the chitin powder is activated by using the activating solution to obtain an activated chitin material; mixing the materials with humic acid, a mineral conditioner and a nitrogen-phosphorus-potassium basic chemical fertilizer according to a determined ratio, and granulating; a protective agent solution containing trehalose and bentonite is mixed with a functional microbial agent, the mixture is sprayed on the surfaces of fertilizer particles, and a finished product is obtained after low-temperature drying. According to the method, recycling of chitin waste is achieved through a green process, the obtained product can synergistically improve the soil structure, adjust the pH value and maintain the microbial activity, and the method is suitable for improvement of degraded soil.

Description

Technical Field

[0001] This invention belongs to the field of soil fertilizer preparation technology, specifically relating to a method for preparing a soil conditioning compound fertilizer based on chitin waste. Background Technology

[0002] In modern agricultural production systems, the long-term and excessive application of chemical fertilizers has led to a series of soil health problems. These problems are mainly manifested in the deterioration of soil physical structure, resulting in compaction; a continuous decline in soil organic matter content; and soil acidification due to the loss of basic ions. Simultaneously, the activity and diversity of beneficial microorganisms in the soil are suppressed, weakening ecosystem functions. On the other hand, the coastal seafood processing industry generates huge quantities of solid waste such as shrimp and crab shells, whose main component is chitin. Currently, most of this waste is discarded or simply landfilled, not only consuming land resources but also potentially burdening the environment during its natural decomposition process, essentially representing a waste of biomass resources.

[0003] Existing technologies for the agricultural application of chitin waste primarily focus on converting it into chitosan. A typical industrial method involves a prolonged deacetylation reaction at temperatures above 80°C using a high-concentration sodium hydroxide solution. This method has significant drawbacks: the chemical reaction is violent, requiring substantial energy consumption; the use of highly corrosive alkaline solutions poses high safety risks and generates difficult-to-treat alkaline wastewater, resulting in significant environmental costs; and the excessively harsh treatment conditions may damage the natural molecular structure and biological activity of chitin. These factors limit the application of this technology in large-scale, low-cost agricultural product manufacturing.

[0004] Furthermore, current soil amendment products on the market are not sufficiently integrated with fertilizers, and their functions are relatively singular. For example, some products are mainly composed of lime, focusing on rapidly neutralizing soil acidity; others are primarily composed of water-retaining minerals, mainly improving the soil's physical water-holding capacity; and there are various microbial agents aimed at regulating the rhizosphere microecology. However, simply mixing these functions often fails to achieve the desired results. Functional microorganisms struggle to survive in the high-salt environment of chemical fertilizers, and ordinary carriers cannot provide effective protection; different conditioning components lack synergistic design, potentially affecting each other's effectiveness. Therefore, developing a feasible compound fertilizer production technology that organically combines waste resource recovery, soil conditioning, nutrient supply, and microbial activity is a practical need in the agricultural and environmental fields. This invention aims to provide a new solution to this need. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a soil conditioning compound fertilizer based on chitin waste.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a soil conditioning compound fertilizer based on chitin waste includes the following steps:

[0008] S1. Chitin powder preparation: Shrimp or crab shells are washed, dried and then crushed to obtain chitin powder with a particle size of 60-100 mesh.

[0009] S2. Preparation of activation solution: Lactic acid or malic acid as the first component, glycerol as the second component, and a third component consisting of choline chloride and urea are mixed in a mass ratio of (3-5):(2-4):2 and stirred at 60-80℃ and 200-500 rpm for 30-60 minutes to form a homogeneous chitin activation solution; the mass ratio of choline chloride to urea in the third component is 1:1.

[0010] S3. Activation reaction: The chitin powder obtained in step S1 and the chitin activation solution obtained in step S2 are mixed at a mass ratio of 1:3-1:5. The mixture is reacted at 70-85℃, normal pressure and 100-300rpm for 2-4 hours. After the reaction, the solid and liquid are separated by centrifugation or filtration. The solid is then washed and dried to obtain the activated chitin material.

[0011] S4. Material mixing: By weight percentage, 15%-30% of the activated chitin material, 10%-20% of humic acid, 10%-25% of mineral conditioner (preferably containing attapulgite and active calcium-based material) and 35%-55% of nitrogen, phosphorus and potassium basic fertilizer are uniformly mixed to obtain a mixture.

[0012] S5. Granulation and Microbial Loading: The mixture obtained in step S4 is granulated to obtain fertilizer granules; a functional microbial agent suspension and a protective agent solution are mixed at a volume ratio of 1:1 and sprayed onto the surface of the fertilizer granules; the functional microbial agent is selected from Bacillus subtilis, Bacillus amyloliquefaciens, or other beneficial agricultural Bacillus species, and its suspension viable cell concentration is [missing information]. The protective agent solution is an aqueous solution containing 2% trehalose and 5% bentonite by mass.

[0013] S6. Post-processing: The fertilizer granules processed in step S5 are dried at a temperature not exceeding 40°C until the moisture content is ≤5%, and then sieved to obtain the soil conditioning compound fertilizer.

[0014] Furthermore, in step S4, the mineral conditioning agent comprises attapulgite clay and calcined oyster shell powder, wherein the calcined oyster shell powder is obtained by grinding oyster shells after calcining them at 800-900℃ for 2-3 hours.

[0015] Furthermore, in step S5, the granulation is completed using a disc granulator, and a 5% polyvinyl alcohol solution is sprayed as a binder during the granulation process.

[0016] Furthermore, in step S5, the spraying is performed using a pressure spraying device with a spraying pressure of 0.1-0.3 MPa.

[0017] Furthermore, in step S3, the stirring speed is 100-300 rpm, and the stirring duration is consistent with the reaction time.

[0018] Furthermore, in step S3, the drying conditions are drying at 50-70°C to constant weight.

[0019] Furthermore, in step S1, the drying process involves drying at 70-90°C to a constant weight.

[0020] Furthermore, in step S6, the particle size of the finished fertilizer after sieving is 2-4 mm.

[0021] Furthermore, in step S4, the weight ratio of the attapulgite clay to the calcined oyster shell powder is 1.5:1.

[0022] Further, in step S5, the composite bacterial agent suspension is prepared by mixing Bacillus subtilis suspension and gelatinous Bacillus suspension at a 1:1 volume ratio, and the total viable bacteria concentration after mixing is [missing information]. .

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This method provides a more environmentally friendly approach to the treatment of chitin waste. It uses a composite solution composed of lactic acid or malic acid, glycerol, choline chloride, and urea as the activation medium. These substances are biodegradable or environmentally compatible compounds. The entire reaction process is completed under moderate temperature conditions, without the need for strong acids or bases, and produces virtually no harmful chemical wastewater, reducing environmental pressure, energy consumption, and production hazards, thus better meeting the requirements of green production.

[0025] 2. This method enables the functional modification of chitin under mild conditions. Under the action of a composite activating solution with a specific ratio, chitin undergoes partial deacetylation, while its surface active groups, such as amino and hydroxyl groups, are exposed and enhanced. The resulting activated chitin material not only retains its soil-improving ability, but its enhanced functional group properties also improve its adsorption and fixation capacity for certain heavy metal ions in the soil, and it can itself serve as a slowly released organic nitrogen source.

[0026] 3. This method constructs a multifunctional soil conditioning and nutrient system. This system combines activated chitin with humic acid and specific mineral conditioners. The synergistic effect of activated chitin and humic acid promotes soil aggregate formation and organic matter replenishment. Among the mineral conditioners, attapulgite enhances the composite's adsorption capacity and water and fertilizer retention ability; while oyster shell powder, calcined at specific high temperatures, is transformed into active calcium, which slowly dissolves in the soil, providing stable and sustained acidity neutralization and calcium nutrition, avoiding drastic short-term pH changes. This conditioning system, combined with conventional nitrogen, phosphorus, and potassium fertilizers, achieves a balance between organic and inorganic nutrients, helping to improve nutrient retention and utilization efficiency in the soil.

[0027] 4. This method effectively solves the problem of maintaining the activity of functional microorganisms in compound fertilizers. A protective agent solution containing trehalose and bentonite is prepared, mixed with a specific microbial agent, and then sprayed onto the surface of fertilizer granules. Trehalose forms a protective layer around the microbial cells, mitigating damage caused by drying and osmotic pressure; bentonite acts as a physical adsorption carrier, reducing direct contact between the microorganisms and high concentrations of fertilizer salts. Combined with a low-temperature drying process not exceeding 40 degrees Celsius, this technique significantly improves the survival rate and stability of beneficial microorganisms in the finished fertilizer, ensuring the actual efficacy of the product after application to the soil.

[0028] 5. This method establishes a complete and highly operable production process. From raw material washing and crushing, activation solution preparation, mild activation reaction, multi-component material mixing, disc granulation, microbial spraying and loading, to final low-temperature drying and sieving, the entire process is clearly defined with precise parameters. The main equipment used is general-purpose, and the raw materials are widely available, making this technical solution feasible for stable industrial production. It provides a practical technical route for large-scale treatment of chitinous waste and the production of high-value-added soil conditioning products. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of a soil conditioning compound fertilizer based on chitin waste. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] Example 1

[0032] This embodiment provides a method for preparing a soil conditioning compound fertilizer based on chitin waste. Figure 1 The specific steps are as follows:

[0033] S1. Preparation of chitin powder: Collect shrimp shells of Litopenaeus vannamei, wash them with tap water to remove residual meat, and then place them in an electric heating drying oven to dry at 80℃ until constant weight. Use a high-speed pulverizer to pulverize the dried shrimp shells and pass them through an 80-mesh standard sieve to obtain chitin powder with a particle size of 60-100 mesh.

[0034] S2. Preparation of Activation Solution: Weigh 300g of lactic acid, 200g of glycerol, 100g of choline chloride, and 100g of urea. Place the above raw materials in a three-necked flask and put it in a 70℃ constant temperature oil bath. Turn on the mechanical stirrer, set the speed to 300 rpm, and stir continuously for 45 minutes to form a homogeneous chitin activation solution. Lactic acid is the first component, glycerol is the second component, and choline chloride and urea together are the third component, with a mass ratio of 3:2:2; the mass ratio of choline chloride to urea in the third component is 1:1.

[0035] S3. Activation Reaction: Weigh 100g of the chitin powder obtained in step S1 and add it together with 400g of the chitin activation solution obtained in step S2 into a reactor equipped with stirring and reflux condensation. Place the reactor in a 75℃ water bath and react for 3 hours at 200rpm under normal pressure and stirring conditions. After the reaction is complete, centrifuge the mixture to separate the solid and liquid phases, collect the solid, and wash it twice with deionized water. Dry the washed solid at 60℃ to constant weight to obtain activated chitin material.

[0036] S4. Material Mixing: Weigh the following raw materials by weight percentage: 25 kg of activated chitin material obtained in step S3, 15 kg of humic acid, 20 kg of attapulgite, 10 kg of calcined oyster shell powder, and 30 kg of nitrogen, phosphorus, and potassium basic fertilizer. The calcined oyster shell powder is obtained by grinding oyster shells after calcining at 900℃ for 2.5 hours. The nitrogen, phosphorus, and potassium basic fertilizer is a compound fertilizer with a total nutrient content of 45%. Put all the weighed materials into a mixer and mix them evenly to obtain a mixture.

[0037] S5. Granulation and Microbial Loading: The mixture is fed into a disc granulator for granulation. During granulation, a 5% polyvinyl alcohol solution is sprayed as a binder to obtain fertilizer granules with a particle size of 2-4 mm. A protective agent solution is prepared by mixing 2% trehalose and 5% bentonite in water. Separately, Bacillus subtilis powder is diluted with sterile water to prepare a viable bacterial concentration of [missing information]. The microbial agent suspension was prepared. The microbial agent suspension and the protective agent solution were mixed evenly at a volume ratio of 1:1. Using a pressure spraying device, the mixture was evenly sprayed onto the surface of the fertilizer granules at a spraying pressure of 0.2 MPa.

[0038] S6. Post-processing: Place the fertilizer granules loaded with microorganisms in an oven at 35℃ and dry them until the moisture content of the granules is ≤5%. After drying, the granules are sieved, and granules with a particle size of 2-4mm are selected as the finished product to obtain soil conditioning compound fertilizer A.

[0039] Example 2

[0040] The main difference between this embodiment and Example 1 lies in the ratio of the activating solution and the selection of the mineral conditioning agent.

[0041] S1, Same as Example 1.

[0042] S2. Preparation of Activation Solution: Weigh 350g of malic acid, 150g of glycerol, 100g of choline chloride, and 100g of urea. Stir at 65℃ and 250rpm for 50 minutes to form a homogeneous activation solution. The mass ratio of the first component, the second component, and the third component is 3.5:2:2.

[0043] S3. Activation reaction: Chitosan powder and activation solution are mixed at a mass ratio of 1:3.5 and reacted at 80°C and 150 rpm for 3.5 hours. Subsequent treatment is the same as in Example 1.

[0044] S4. Material Mixing: Weigh the following materials by weight percentage: 20 kg activated chitin, 18 kg humic acid, 15 kg attapulgite, 12 kg calcined dolomite powder, and 35 kg nitrogen, phosphorus, and potassium basic fertilizer. The calcined dolomite powder is obtained by calcining dolomite at 850℃ for 3 hours. Mix thoroughly.

[0045] S5. Granulation and Microbial Loading: Granulation is the same as in Example 1. Bacillus amyloliquefaciens was selected as the inoculum, and the viable cell concentration of the inoculum suspension was [missing information]. Mix with a protective agent solution of the same formula at a volume ratio of 1:1 and then spray. The spraying pressure is 0.15 MPa.

[0046] S6. Post-processing: Same as in Example 1, to obtain finished fertilizer B.

[0047] Example 3

[0048] The main difference between this embodiment and Example 1 lies in the activation reaction conditions.

[0049] S1, Same as Example 1.

[0050] S2. Preparation of Activation Solution: Weigh 300g of lactic acid, 200g of glycerol, 100g of choline chloride, and 100g of urea. Stir at 75℃ and 400rpm for 30 minutes. The mass ratio of the three components is 3:2:2.

[0051] S3. Activation reaction: Chitosan powder and activation solution are mixed at a mass ratio of 1:5 and reacted at 85°C and 100 rpm for 2 hours. Subsequent treatment is the same as in Example 1.

[0052] S4. Material Mixing: Weigh the following by weight percentage: 30 kg of activated chitin material, 10 kg of humic acid, 25 kg of attapulgite clay, and 35 kg of nitrogen, phosphorus, and potassium basic fertilizer (omitting calcined oyster shell powder). Mix thoroughly.

[0053] S5. Granulation and Microbial Loading: Granulation is the same as in Example 1. The bacterial agent used is a compound agent of Bacillus subtilis and Bacillus mucilaginosus, maintaining a total viable cell concentration of [missing information]. The protective agent and spraying method are the same as in Example 1.

[0054] S6. Post-processing: Same as in Example 1, to obtain finished fertilizer C.

[0055] Comparative Example 1

[0056] This comparative example uses the strong alkali method commonly used in existing technologies to treat chitin and mixes the same components to make fertilizer.

[0057] S1. Preparation of chitin powder: Same as in Example 1.

[0058] S2. Chitosan preparation: 100g of chitin powder was mixed with 500mL of 40% sodium hydroxide solution and stirred in a 95℃ water bath for 4 hours. After the reaction, the mixture was centrifuged, washed with water until neutral, and dried to obtain chitosan.

[0059] S3. Material Mixing: Weigh the following by weight percentage: 25 kg of chitosan, 15 kg of humic acid, 20 kg of attapulgite, 10 kg of calcined oyster shell powder, and 30 kg of nitrogen, phosphorus, and potassium basic fertilizer. Mix thoroughly.

[0060] S4. Granulation: The mixture is bound with a 5% polyvinyl alcohol solution and granulated using a disc granulator.

[0061] S5. Post-treatment: Dry at 60℃ until moisture content ≤5%, then sieve to obtain finished fertilizer D. This comparative example does not undergo microbial loading.

[0062] Comparative Example 2

[0063] This comparative example aims to illustrate the impact of the absence of the specific protective agent system of this invention on microbial survival.

[0064] S1 to S4: Same as in Example 1, fertilizer granules without microorganisms were prepared.

[0065] S5, Microbial Loading: A suspension of Bacillus subtilis inoculum (… Dilute with an equal volume of sterile water and spray onto the surface of wet fertilizer granules under the same conditions.

[0066] S6. Post-processing: Same as in Example 1, dry at 35°C to obtain finished fertilizer E.

[0067] Comparative Example 3

[0068] This comparative example is intended to illustrate the synergistic effect of a specific combination of mineral conditioners in this invention, wherein calcined oyster shell powder is omitted.

[0069] S1 to S3: Same as in Example 1, prepare activated chitin material.

[0070] S4. Material Mixing: Only attapulgite clay is used; calcined oyster shell powder is omitted. The ratio is: 25 kg activated chitin material, 15 kg humic acid, 30 kg attapulgite clay, and 30 kg nitrogen, phosphorus, and potassium basic fertilizer.

[0071] S5 to S6: Granulation, microbial loading, and post-treatment are the same as in Example 1, to obtain finished fertilizer F.

[0072] Application effect experiment

[0073] To verify the overall effectiveness of the product of this invention, a pot experiment was conducted at a facility vegetable base in Shandong Province. The test crop was cucumber. Seven treatments were set up: T1 (application of conventional compound fertilizer with equal nutrients), T2 (application of Product A from Example 1), T3 (application of Product B from Example 2), T4 (application of Product C from Example 3), T5 (application of Product D from Comparative Example 1), T6 (application of Product E from Comparative Example 2), and T7 (application of Product F from Comparative Example 3). All fertilization treatments ensured equal input of nitrogen, phosphorus, and potassium nutrients. Each treatment was replicated five times. After one season of cultivation, relevant indicators were measured and are shown in Tables 1 and 2 below.

[0074] Table 1. Effects of different treatments on soil physicochemical properties and microbial activity

[0075]

[0076] Note: Microbial survival rate is the percentage of viable bacteria count measured after the finished fertilizer has been sealed and stored at room temperature for 30 days, relative to the initial viable bacteria count.

[0077] Table 2. Effects of different treatments on cucumber growth and yield

[0078]

[0079] Results analysis:

[0080] 1. As shown in Table 1, the embodiments of the present invention (T2-T4) are all superior to conventional fertilizers (T1) in terms of adjusting soil pH, increasing organic matter, reducing effective cadmium content, and improving soil microbial activity. Among them, embodiment 1 (T2) shows the most outstanding effect.

[0081] 2. Although Comparative Example 1 (T5, traditional strong alkali method) has a certain improvement effect, it is not as good as the embodiments of the present invention in terms of pH adjustment range, heavy metal passivation and activation of microbial activity.

[0082] 3. The soil improvement indicators of Comparative Example 2 (T6, without specific protectant) were similar to those of the Example, but the survival rate of microorganisms in its fertilizer granules was only 45%, lower than the approximately 90% of the Example. This resulted in it being inferior to the Example in both increasing soil microbial biomass carbon and final crop yield.

[0083] 4. The soil pH improvement effect of Comparative Example 3 (T7, lacking calcined oyster shell powder) was weaker than that of the Example, and the fruit yield and quality were also lower.

[0084] 5. The yield and quality data in Table 2 show that the embodiments of the present invention optimize the crop root growth environment and nutrient absorption efficiency by adjusting soil pH, increasing organic matter content, and enhancing soil microbial activity, ultimately achieving an improvement in crop yield and quality.

[0085] The above experimental results demonstrate that the preparation method defined in the claims of this invention is an organic whole. Each step and its parameters work synergistically to contribute to the soil conditioning effect and agronomic benefits of the final product, and its effect is superior to the prior art or the scheme lacking certain technical features represented by the comparative examples.

[0086] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a soil conditioning compound fertilizer based on chitin waste, characterized in that, Includes the following steps: S1. Chitin powder preparation: Shrimp or crab shells are washed, dried and then crushed to obtain chitin powder with a particle size of 60-100 mesh. S2. Preparation of activation solution: Lactic acid or malic acid as the first component, glycerol as the second component, and a third component consisting of choline chloride and urea are mixed in a mass ratio of (3-5):(2-4):2 and stirred at 60-80℃ and 200-500 rpm for 30-60 minutes to form a homogeneous chitin activation solution; the mass ratio of choline chloride to urea in the third component is 1:

1. S3. Activation reaction: The chitin powder obtained in step S1 and the chitin activation solution obtained in step S2 are mixed at a mass ratio of 1:3-1:

5. The mixture is reacted at 70-85℃, normal pressure and 100-300rpm for 2-4 hours. After the reaction, the solid and liquid are separated by centrifugation or filtration. The solid is then washed and dried to obtain the activated chitin material. S4. Material mixing: By weight percentage, 15%-30% of the activated chitin material, 10%-20% of humic acid, 10%-25% of mineral conditioner and 35%-55% of nitrogen, phosphorus and potassium basic fertilizer are mixed evenly to obtain a mixture. S5. Granulation and Microbial Loading: The mixture obtained in step S4 is granulated to obtain fertilizer granules; a functional microbial agent suspension and a protective agent solution are mixed at a volume ratio of 1:1 and sprayed onto the surface of the fertilizer granules; the functional microbial agent is selected from Bacillus subtilis, Bacillus amyloliquefaciens, or other beneficial agricultural Bacillus species, and its suspension viable cell concentration is [missing information]. The protective agent solution is an aqueous solution containing 2% trehalose and 5% bentonite by mass. S6. Post-processing: The fertilizer granules processed in step S5 are dried at a temperature not exceeding 40°C until the moisture content is ≤5%, and then sieved to obtain the soil conditioning compound fertilizer.

2. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S4, the mineral conditioning agent includes attapulgite and calcined oyster shell powder, which is obtained by grinding oyster shells after calcining them at 800-900℃ for 2-3 hours.

3. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S5, the granulation is completed using a disc granulator, and a 5% polyvinyl alcohol solution is sprayed as a binder during the granulation process.

4. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S5, the spraying is performed using a pressure spraying device with a spraying pressure of 0.1-0.3 MPa.

5. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S3, the stirring speed is 100-300 rpm, and the stirring duration is the same as the reaction time.

6. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S3, the drying conditions are to dry to constant weight at 50-70°C.

7. The method for preparing a soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S1, the drying process involves drying at 70-90°C to a constant weight.

8. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S6, the particle size of the finished fertilizer after screening is 2-4 mm.

9. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S4, the weight ratio of attapulgite clay to calcined oyster shell powder is 1.5:

1.

10. The method for preparing the soil conditioning compound fertilizer based on chitin waste according to claim 1, characterized in that, In step S5, the composite bacterial agent suspension is prepared by mixing Bacillus subtilis suspension and Bacillus spp. gelatinosa suspension at a 1:1 volume ratio, and the total viable bacteria concentration after mixing is [missing information]. .

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