DESC:[Field of the Invention]
[001] The field of the invention relates to sustainable dyeing solutions, specifically focusing on the production of concentrated pre-reduced natural indigo solutions using biochemical processes. This invention finds application in textile dyeing and related industries, offering a novel and environmentally friendly alternative to conventional indigo dyeing methods.
[Object of the Invention]
[002] Some of the objects of the present invention, which at least one embodiment herein satisfies, are as listed herein below.
[003] It is an object of the present invention to provide a sustainable and efficient solution for textile dyeing by introducing a novel method and system for producing concentrated pre-reduced natural indigo solutions through biochemical processes, thereby overcoming the limitations associated with traditional indigo dyeing methods.
[004] It is an object of the present invention to offer a concentrated pre-reduced natural indigo solution that can be easily produced without the need for hydrogenation or electrolysis, simplifying the production process and reducing production costs.
[005] It is an object of the present invention to promote environmental sustainability in the textile industry by minimizing the use of alkalis during dyeing, thus reducing the salt load and mitigating sludge formation in wastewater treatment plants associated with dyeing units.

[Background]
[006] Indigo, a natural dye derived from plants such as Indigofera tinctoria, possesses remarkable color properties but presents challenges in its application due to its water-insolubility. However, under alkaline conditions and using reducing agents, indigo undergoes a transformation into a water-miscible leuco compound. This chemical alteration renders indigo suitable for textile dyeing purposes.
[007] In its reduced state, indigo readily binds to textile materials, imparting a rich blue hue upon oxidation. This characteristic makes indigo highly desirable in the textile industry for its vibrant and enduring color.
[008] Presently, the production of concentrated pre-reduced liquid indigo predominantly relies on two methods: hydrogenation or electrolysis processes. While effective, these methods come with inherent drawbacks such as high production costs, environmental concerns, and complex manufacturing processes.
[009] In the hydrogenation process, indigo is mixed with hydrogen gas in the presence of a catalyst, typically palladium or platinum, under high pressure and temperature conditions. This chemical reaction converts the insoluble indigo into its water-soluble leuco form, which can then be concentrated to obtain a liquid solution. While effective, hydrogenation requires specialized equipment and precise control of reaction parameters, making it costly and energy-intensive.
[010] Alternatively, the electrolysis process involves passing an electric current through a solution containing indigo and a suitable electrolyte, such as sodium hydroxide. This electrical current induces chemical reactions that convert indigo into its reduced, water-soluble form. The resulting solution can be concentrated to obtain a liquid indigo dye. Electrolysis offers advantages such as relatively lower operating costs and scalability, but it still requires careful control of conditions and may generate undesirable by-products.
[011] Moreover, traditional dyeing processes involving indigo often require the use of alkalis, which not only complicates the dyeing process but also contributes to the salt load and sludge formation in wastewater treatment plants associated with dyeing units. This poses significant challenges in terms of environmental sustainability and regulatory compliance for textile manufacturers.
[012] Therefore, there exists a need for a more sustainable and environmentally friendly approach to the production and application of indigo dye in the textile industry. By addressing these challenges and leveraging advancements in biochemical processes, the present invention aims to revolutionize the production of concentrated pre-reduced natural indigo solutions, offering a cost-effective, eco-friendly, and efficient alternative to conventional methods.
[Summary]
[013] The present invention discloses a novel and sustainable solution for textile dyeing, specifically a Biochemically Pre-reduced Indigo Solution derived from the plant Indigofera tinctoria. Embodied within this invention is a concentrated liquid indigo solution containing 20% to 50% indigotin content, produced through a biochemical process employing microbial and enzymatic reactions.
[014] Traditional indigo dye production methods often involve hydrogenation or electrolysis processes, which can be costly, energy-intensive, and environmentally harmful. In contrast, the disclosed invention offers a greener and more efficient approach to indigo production. By harnessing the power of microbial and enzymatic reactions, indigo is pre-reduced to its water-soluble form without the need for hazardous chemicals or energy-intensive processes.
[015] The present invention describes a novel method for producing concentrated pre-reduced natural indigo solutions using biochemical processes. The process begins with soaking Indigo (Indigofera tinctoria) leaves in water within horizontal fermentation tanks for a period of time. After fermentation, the extract is transferred to a settling tank to allow the sedimentation of natural indigo. Alkaliphilic bacteria are then inoculated to initiate the primary reduction process, followed by the introduction of eco-friendly chemicals for stabilization. Subsequently, sugar and yeast suspension are added for secondary reduction. The solution is then transferred to vertical tanks containing a buffer solution to maintain pH. This innovative method offers a sustainable and environmentally friendly alternative to conventional indigo dyeing methods, providing a stable and concentrated indigo solution for use in textile dyeing and related industries. The patent application acknowledges that variations in compositions, process steps, and operating conditions are possible, allowing for flexibility and adaptation to specific applications.

[Detailed Description]
[016] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit, and scope of the present disclosure as defined by the appended claims.
[017] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[018] The word “exemplary” and/or “demonstrative” is used herein to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as “exemplary” and/or “demonstrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art. Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising” as an open transition word without precluding any additional or other elements.
[019] Reference throughout this specification to “one embodiment” or “an embodiment” or “an instance” or “one instance” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[020] The invention presented herein addresses a significant need in the field of sustainable dyeing solutions by introducing a method for producing concentrated pre-reduced natural indigo solutions using biochemical processes. Indigo, derived from the Indigofera tinctoria plant, has long been utilized as a dye in textile industries worldwide. However, traditional methods of indigo extraction and dye preparation often involve harsh chemicals and energy-intensive processes, resulting in adverse environmental impacts.
[021] In response to these challenges, the invention focuses on harnessing the power of biochemical processes to create a sustainable and environmentally friendly alternative. By leveraging natural fermentation, bacterial reduction, and eco-friendly chemical stabilized the bacterial pathway for efficient extraction and concentrate indigo, the method offers a pathway to efficiently extract and concentrate indigo in its soluble form, known as leuco-indigo. This concentrated indigo solution provides a viable substitute for conventional indigo dyeing methods, offering improved stability, reduced environmental footprint, and enhanced dyeing performance.
[022] The invention's versatility allows for customization and adaptation to various industrial applications, including textile dyeing, where demand for eco-friendly and sustainable dyeing solutions continues to rise. Moreover, the invention's acknowledgment of potential variations in compositions, process steps, and operating conditions ensures its applicability across diverse settings and industries.
[023] Fig. 1 illustrates an embodiment of the novel method. The process begins at step 102.
[024] Step 102: Soaking of Indigo Leaves
[025] The process begins with the selection and preparation of Indigo (Indigofera tinctoria) leaves. Freshly harvested leaves are chosen for soaking, ensuring they are free from any contaminants such as dirt or debris to maintain the purity of the final indigo solution. For instance, a batch of 50 kg of fresh indigo leaves is collected and thoroughly rinsed to remove any surface impurities.
[026] Next, the cleaned indigo leaves are placed in horizontal fermentation tanks. These tanks are typically constructed from non-reactive materials like stainless steel or high-density polyethylene to prevent any unwanted chemical reactions during the process. For example, the 50 kg of rinsed indigo leaves are evenly distributed in a 1000-liter stainless steel horizontal fermentation tank.
[027] Water is then added to the tank, fully submerging the leaves. The leaf to water ratio is critical and typically ranges from 1:10 to 1:15 (water by volume) to facilitate optimal fermentation. For instance, 500 liters of water are added to the tank containing 50 kg of indigo leaves, maintaining a 1:10 leaf to water ratio.
[028] The indigo leaves are allowed to soak in the water for a period sufficient to initiate fermentation, generally around 8-12 hours. During this time, natural enzymes in the leaves start breaking down the plant material, releasing indican, the precursor to indigo dye. For example, the tank with indigo leaves and water is left undisturbed for 12 hours in a controlled environment with an ambient temperature of 25-30°C to promote optimal fermentation.
[029] Throughout the soaking period, the mixture is monitored for temperature, pH, and the presence of any undesirable odors that may indicate contamination. Adjustments, such as regulating the temperature or adding more water, may be made to maintain optimal conditions. For instance, during the 12-hour fermentation, periodic checks are conducted to ensure the temperature remains within the desired range. If the temperature drops below 25°C, warm water can be added to maintain consistency.
[030] Step 104: Transfer to Settling Tank
[031] Following the fermentation period, the extract of Indigo (Indigofera tinctoria) leaves is transferred to a settling tank. This step is essential for separating the solid leaf material from the liquid extract.
[032] To begin, the contents of the horizontal fermentation tanks, which include the soaked indigo leaves and the fermenting liquid, are carefully transferred to the settling tank. This transfer is typically done using pumps designed to handle slurry-like mixtures to ensure that both liquid and solid components are efficiently moved. For example, a peristaltic pump might be used to gently transfer the mixture from the fermentation tank to the settling tank without causing excessive agitation.
[033] During the settling process, the mixture is monitored to ensure proper separation. Clear layers of sediment and supernatant liquid should form, with the natural indigo settling at the bottom. Depending on the quantity and concentration of the indigo leaves, the settling time can vary. For example, a batch containing 50 kg of indigo leaves may require 6 to 8 hours for complete sedimentation.
[034] Once sedimentation is complete, the clear supernatant liquid can be decanted or siphoned off, leaving the concentrated indigo sediment in slurry form at the bottom of the tank. For example, the supernatant liquid might be carefully siphoned off using a flexible hose, ensuring that the indigo sediment remains undisturbed. This concentrated indigo sediment is then ready for further processing in subsequent steps of the method.
[035] This step is critical for isolating the natural indigo particles from the fermentation mixture, ensuring that a high-quality, concentrated indigo solution is obtained for use in the subsequent reduction and stabilization processes.
[036] Step 106: Primary Reduction
[037] After the indigo particles have settled, the next step involves initiating the primary reduction process by adding alkaliphilic bacteria to the settled extract. This step is converts the insoluble indigo pigment into a soluble form, known as leuco-indigo with low redox potential.
[038] To begin, the concentrated indigo sediment obtained from the settling tank is transferred to a new container or kept in the same tank if it has the appropriate stirring mechanism. The selection of alkaliphilic bacteria is critical as these bacteria thrive in alkaline conditions and facilitate the reduction of indigo. Common species used for this purpose include Bacillus subtilis or Bacillus alcalophilus, known for their ability to perform biological reduction in high pH environments.
[039] For example, a batch of alkaliphilic bacteria culture can be prepared by growing Bacillus subtilis in a nutrient-rich medium at an optimal temperature of 30-37°C for 24-48 hours. Once the bacterial culture is ready, it is added to the settled indigo extract. Typically, the bacterial culture is added at a concentration of about 1-5% by volume of the indigo extract to ensure effective reduction.
[040] The bacteria are introduced to the indigo extract with slow stirring to distribute the bacteria evenly throughout the mixture. Slow stirring is essential to maintain a homogeneous mixture and to prevent the indigo particles from settling again. For instance, a mechanical stirrer set at a low speed of around 50-100 RPM can be used to gently mix the bacteria with the indigo extract.
[041] During the primary reduction process, the bacteria metabolize the indigo pigment under alkaline conditions, converting it to leuco-indigo, which is soluble in water. The process typically takes around 24-48 hours, depending on the concentration of indigo and the activity of the bacteria. The mixture is kept at a controlled temperature and pH to ensure optimal bacterial activity. For example, maintaining the temperature at 30°C and the pH between 9 and 11 creates an ideal environment for Bacillus subtilis to perform the reduction.
[042] Monitoring the progress of the reduction is essential. Indicators such as a change in color from blue to yellow-green suggest successful reduction. Additionally, chemical tests can be performed to measure the concentration of leuco-indigo in the solution. For example, a sample of the mixture can be periodically tested using spectrophotometry to determine the presence and concentration of leuco-indigo.
[043] Once the primary reduction is complete, the mixture contains soluble leuco-indigo, ready for further stabilization and use in dyeing processes. This step ensures that the indigo is converted into a form that can be easily applied to textiles, providing a sustainable and environmentally friendly dyeing solution.
[044] Step 108: Stabilization
[045] Following the primary reduction process, where alkaliphilic bacteria convert the indigo pigment into soluble leuco-indigo, the next crucial step is to stabilize the reduced indigo solution. This stabilization is achieved by introducing eco-friendly chemicals, which help maintain the reduced state of indigo and prevent it from reverting back to its insoluble form.
[046] After the primary reduction has been allowed to proceed for approximately 24 hours, the mixture containing leuco-indigo is ready for stabilization. At this point, eco-friendly stabilizing agents are added to the solution. These chemicals are selected based on their ability to maintain the reduced state without introducing harmful byproducts into the environment.
[047] Sorbic acid is a natural preservative is used as a stabilizer. A calculated amount of sorbic acid, typically around 0.5-0.1% by weight of the indigo extract, is slowly added to the solution while stirring gently to ensure even distribution. Sorbic acid does not kill yeast cells but instead inhibits the yeast cell from being able to multiply, grow and begin a new fermentation..
[048] Another natural stabilizer is Potassium sorbate . It also does not kill yeast cells but instead inhibits the yeast cell from being able to multiply, grow and begin a new fermentation. It is often added in a concentration of about 0.5-1% by weight of the indigo extract. The Potassium sorbate acts as a stabilizing agent, further ensuring that the leuco-indigo remains in its reduced, soluble form.
[049] Throughout the stabilization process, it is essential to maintain the pH and temperature within optimal ranges to ensure the effectiveness of the stabilizing agents. For instance, the pH should be kept between 9 and 11, and the temperature should remain around 25-30°C. Continuous monitoring and adjustments may be necessary to maintain these conditions.
[050] The successful stabilization of the reduced indigo solution is indicated by the sustained yellow-green color and the absence of blue indigo particles precipitating out of the solution. This stabilized leuco-indigo can now be stored or used directly in dyeing processes, offering an environmentally friendly alternative to conventional indigo dyeing methods.
[051] By using eco-friendly chemicals for stabilization, this step ensures that the reduced indigo solution remains in a usable form for extended periods, thereby enhancing the overall efficiency and sustainability of the dyeing process.
[052] Step 110: Secondary Reduction
[053] Following the primary reduction process and stabilization, the next crucial step is the secondary reduction, which further enhances the reduction of indigo to its soluble form, leuco-indigo. This step involves the addition of sugar and yeast to the solution, which act as reducing agents to facilitate the conversion of any remaining indigo to leuco-indigo.
[054] After the primary reduction and stabilization steps have been completed, the reduced indigo solution is allowed to rest for approximately 12 hours to ensure stabilization and proper distribution of the stabilizing agents. Once this period has elapsed, the solution is ready for secondary reduction.
[055] To initiate the secondary reduction, a mixture of sugar and yeast is added to the solution. The sugar acts as a food source for the yeast, while the yeast serves as a catalyst for the reduction reaction. Common sugars used include sucrose, glucose, or molasses, while yeast strains such as Saccharomyces cerevisiae are typically employed due to their well-known ability to ferment sugars.
[056] For example, a solution containing 50 grams of glucose or sucrose per liter of indigo solution can be prepared. Additionally, a small amount of yeast, typically around 1-2 grams per liter of solution, is added to the sugar solution and allowed to dissolve. Once dissolved, the sugar-yeast mixture is added to the reduced indigo solution with gentle stirring to ensure thorough mixing.
[057] The addition of sugar and yeast initiates a fermentation process in the solution, where yeast enzymes break down the sugar molecules into alcohol and carbon dioxide. During this process, the yeast also reduces any remaining indigo molecules to leuco-indigo, further enhancing the concentration of soluble indigo dye in the solution.
[058] Throughout the secondary reduction process, it is essential to maintain suitable environmental conditions to promote yeast activity. This includes maintaining a warm temperature, typically around 25-30°C, and providing adequate aeration to ensure oxygen availability for yeast metabolism. Continuous monitoring of temperature and pH levels is necessary to optimize yeast activity and ensure effective reduction.
[059] Successful secondary reduction is indicated by the continued yellow-green color of the solution and the absence of blue indigo particles. Additionally, chemical tests can be performed to confirm the presence and concentration of leuco-indigo in the solution.
[060] Once the secondary reduction is complete, the solution contains a highly concentrated and stable form of soluble leuco-indigo, ready for use in dyeing processes. By employing sugar and yeast as reducing agents, this step enhances the efficiency and sustainability of the indigo dyeing process, providing an eco-friendly alternative to conventional methods.
[061] Step 112: pH Maintenance
[062] After the secondary reduction process, the indigo solution is transferred to vertical tanks where pH level maintenance ensures the stability and effectiveness of the dyeing solution. This step involves the addition of a buffer solution to the tanks, which helps maintain the pH balance of the indigo solution within the desired range.
[063] To begin, the reduced indigo solution is carefully transferred from its current vessel to vertical tanks designed for dye solution storage. These tanks are typically made of materials resistant to chemical reactions, such as polyethylene or stainless steel, to prevent contamination of the dye solution.
[064] Once the solution is transferred to the vertical tanks, a buffer solution is added to maintain the pH balance. A buffer solution consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) and is capable of resisting changes in pH when small amounts of acid or base are added. Common buffer systems used for maintaining the pH of indigo solutions include citric acid/sodium citrate or acetic acid/sodium acetate.
[065] For example, a citric acid/sodium citrate buffer solution can be prepared by dissolving a known quantity of citric acid and sodium citrate in water to achieve the desired pH. The buffer solution is then added to the vertical tanks containing the reduced indigo solution. The concentration of the buffer solution and the volume added depend on the initial pH of the indigo solution and the desired pH range for dyeing.
[066] Maintaining the pH of the indigo solution within the optimal range, typically between 10 to 12, is crucial for several reasons. Firstly, the reduction of indigo to its soluble form (leuco-indigo) is pH-dependent, with higher pH values favoring the reduction process. Additionally, maintaining a stable pH ensures consistent dyeing results and prevents the precipitation of indigo particles, which can cause uneven dyeing or clogging of dyeing equipment.
[067] Continuous monitoring of the pH level in the vertical tanks is necessary to ensure that the buffer solution is effectively maintaining pH stability. pH meters or indicator papers can be used for accurate pH measurements, with adjustments made as needed by adding more buffer solution or adjusting the concentration of the buffer components.
[068] By maintaining the pH balance of the indigo solution within the optimal range, this step ensures the stability and effectiveness of the dyeing solution, leading to consistent and high-quality dyeing results.
[069] Maintaining a stable pH in the vertical tanks is essential to ensure the long-term stability and usability of the indigo solution. Fluctuations in pH can lead to changes in the chemical properties of the dye solution, affecting its dyeing performance and consistency.
[070] Continuous monitoring of the pH levels in the vertical tanks is necessary to ensure that the buffer solution effectively maintains pH stability. pH meters or indicator papers can be used for accurate pH measurements, with adjustments made as needed by adding more buffer solution or adjusting the concentration of buffer components.
[071] By transferring the indigo solution to vertical tanks with a buffer solution for consistent pH maintenance, this step ensures the stability and usability of the dye solution for extended periods, providing a reliable resource for dyeing processes in textile and related industries.
[072] Step 114: Final Transfer
[073] In the final stage of the process, the pre-reduced indigo solution, after undergoing the necessary reduction and pH maintenance, is transferred to vertical tanks for storage and further use. This step involves transferring the solution to vertical tanks containing a buffer solution to ensure consistent pH maintenance, thereby preserving the stability of the indigo dye solution.
[074] To begin, the reduced indigo solution, which has been appropriately stabilized and pH-adjusted in previous steps, is carefully transferred from its current vessel to vertical storage tanks. These tanks are specifically designed for the storage of dye solutions and are constructed from materials that are resistant to chemical reactions, such as polyethylene or stainless steel.
[075] Once transferred to the vertical tanks, a buffer solution is added to maintain consistent pH levels within the indigo solution. The buffer solution helps prevent fluctuations in pH that could adversely affect the stability and effectiveness of the dye solution during storage.
[076] In some embodiments, Quality control measures may be implemented throughout the production process to ensure the purity, consistency, and efficacy of the concentrated indigo solution. Analytical techniques such as spectroscopy, chromatography, and colorimetry may be utilized for testing and assessment purposes to verify product quality and suitability for textile dyeing applications.
[077] Once quality control standards are met, the concentrated pre-reduced indigo solution is packaged into suitable containers for storage and transportation. Unlike traditional indigo solutions, which often require nitrogen atmospheric conditions for storage to prevent oxidation, embodiments of the biochemically derived solution may be stored under normal atmospheric conditions without compromising stability or efficacy.
[078] The processes and compositions described herein are provided for illustrative purposes only and are not intended to be limiting. It is understood that variations in compositions, process steps, and operating conditions may be made by those skilled in the art without departing from the scope or spirit of the invention. The embodiments disclosed herein are exemplary and should not be construed as exhaustive or exclusive. Other compositions, process parameters, and variations thereof may be utilized to achieve similar or equivalent results.
[Advantages]
[079] Advantages of the present invention include but are not limited to:
[080] The invention offers a cost-effective alternative to traditional indigo dyeing methods by eliminating the need for expensive hydrogenation or electrolysis processes.
[081] By utilizing biochemical processes to produce concentrated pre-reduced natural indigo solutions, the invention reduces the reliance on toxic chemicals and minimizes environmental pollution associated with conventional dyeing methods.
[082] The use of plant-derived indigo and biochemically-driven reduction processes promotes sustainability in textile dyeing, aligning with global efforts towards eco-friendly manufacturing practices.
[083] The concentrated nature of the indigo solution allows for easier handling, storage, and transportation, streamlining industrial processes and improving overall efficiency in textile dyeing operations.
[084] By eliminating the need for alkalis during dyeing, the invention minimizes the salt load and reduces sludge formation in wastewater treatment plants, contributing to cleaner waterways and ecosystems.
[085] The concentrated pre-reduced natural indigo solution simplifies the dyeing process by eliminating the requirement for additional reducing agents, alkalis, or complex dyeing procedures, thereby enhancing operational convenience and reducing labor costs.
[086] The invention's compatibility with various textile materials and dyeing techniques makes it suitable for a wide range of applications, offering flexibility and versatility to textile manufacturers and designers.
,CLAIMS:We claim:
1. A method for producing concentrated pre-reduced natural indigo solution, comprising:
soaking Indigofera tinctoria leaves in water within horizontal fermentation tanks for a period of about 10-14 hours;
transferring the fermented extract of Indigofera tinctoria leaves to a settling tank to sediment natural indigo;
adding alkaliphilic bacteria to the settled extract with slow stirring to initiate primary reduction;
introducing eco-friendly chemicals after 20-28 hours to stabilize the reduction process;
adding sugar and yeast after 8 hours to the solution to facilitate secondary reduction;
transferring the solution to vertical tanks containing a buffer solution to maintain pH balance.
2. The method of claim 1, wherein the alkaliphilic bacteria are selected from the group consisting of Bacillus subtilis.
3. The method of claim 1, wherein the eco-friendly chemicals used for stabilization are selected from the group consisting of phosphate buffer.
4. The method of claim 1, wherein the buffer solution used to maintain pH in the vertical tanks comprises phosphate buffer.
5. A system for producing concentrated pre-reduced natural indigo solutions, comprising:
horizontal fermentation tanks for soaking Indigofera tinctoria leaves in water;
a settling tank for sedimentation of natural indigo from the fermented extract;
a mixing mechanism for adding alkaliphilic bacteria to the settled extract with slow stirring;
a means for introducing eco-friendly chemicals to stabilize the reduction process after 24 hours;
a mechanism for adding sugar and yeast to the solution after 12 hours to facilitate secondary reduction;
vertical tanks containing a buffer solution to maintain pH balance.
6. The system of claim 5, wherein the horizontal fermentation tanks are configured to soak the Indigofera tinctoria leaves for a period of 10-12 hours.
7. The system of claim 5, wherein the vertical tanks are configured to maintain the pH balance of the solution using a buffer solution comprising phosphate buffer.
8. A concentrated pre-reduced natural indigo solution produced by the method of claim 1.
9. The concentrated pre-reduced natural indigo solution of claim 8, wherein the solution exhibits improved stability and reduced environmental impact compared to conventional indigo dyeing methods.