Vinasse is a solid waste left-over of raw materials like sorghum and wheat after they undergo steaming, fermentation, and distillation in the brewing process. It is a major by-product of the liquor industry, characterized by high output, high moisture content, corrosive acidity, and a tendency to decay. Improper handling of vinasse can lead to severe ecological pollution.
In China, where the Baijiu liquor industry is well-developed, the total output of Baijiu vinasse remains high, with a production and discharge of approximately 20–30 million tons per year. However, to date, most enterprises in the country still struggle to manage and utilize Baijiu vinasse appropriately. Due to various constraints in transportation, treatment, and storage, it is highly prone to causing serious environmental pollution and significant resource waste. Therefore, the need to reduce, detoxify, and recycle vinasse is urgent[1].
| Treatment & Utilization Pathway | Method Principle | Main Advantages | Main Disadvantages & Challenges |
|---|---|---|---|
| 1. Chemical Degradation | |||
| ▪ Acid Hydrolysis | Uses strong acids to hydrolyze cellulose and hemicellulose into reducing sugars. | High saccharification efficiency, provides feedstock for fermentation. | Equipment corrosion, generates large amounts of acidic wastewater, high cost. |
| ▪ Alkaline Treatment | Uses alkaline agents to disrupt the lignin structure and improve polysaccharide extraction. | Effectively breaks down the lignin barrier. | Causes sugar degradation, produces hard-to-treat waste liquid, risk of environmental pollution. |
| ▪ Oxidation Method | Uses oxidizing agents to degrade organic matter. | Relatively mild reaction conditions. | Oxidizing agents are costly, may produce toxic intermediates. |
| ▪ Solvent Extraction | Uses organic solvents to extract functional compounds (e.g., polyphenols). | Good selectivity for target components. | High energy consumption for solvent recovery, fire and explosion hazards, high operational cost. |
| 2. Low-Cost Animal Feed | Direct use or simple drying/fermentation for use as animal feed. | Direct, low-cost resource utilization of waste. | 1. Nutritional Limitations: High fiber and
lignin reduce digestibility in monogastric animals. 2. Safety & Storage Risks: Risk of mycotoxin contamination; high moisture content leads to rapid spoilage. |
| 3. Composting | Controlled microbial conversion of organic matter into stable humus under aerobic conditions. | Produces organic fertilizer, enabling nutrient recycling. | 1. Process Challenges: Low C/N ratio and
high acidity hinder fermentation; requires careful supplementation and
aeration. 2. Quality & Pollution: Variable composition leads to uneven fertilizer quality; incomplete lignin degradation produces phytotoxic phenols; ammonia volatilization causes nitrogen loss and odors. |
| 4. Thermochemical Conversion | Converts material via high-temperature chemical reactions. | ||
| ▪ Combustion/Incineration | Direct burning for heat or power generation. | Recovers energy. | High nitrogen content leads to significant NOx emissions during combustion, causing severe air pollution; high energy consumption. |
| ▪ Pyrolysis | Heats material in the absence of oxygen to produce biochar, bio-oil, etc. | Products (especially biochar) have high value for environmental applications (soil amendment, wastewater treatment). | Requires precise process control and significant equipment investment; products like bio-oil may need further refinement. |
| 5. Anaerobic Digestion | Microbial degradation under anaerobic conditions to produce biogas (primarily methane). | Generates renewable energy (biogas), stabilizes waste. | 1. Efficiency Bottleneck: Lignocellulosic
structure limits hydrolysis rate, reducing biogas yield. 2. Operational Challenges: Process instability (e.g., acidification) and management of the digestate residue. |
| 6. Material Extraction | Extracts bioactive compounds (e.g., proteins, polyphenols) from vinasse via physical or chemical methods. | Produces high-value products, enhancing economic return. | 1. Technical Bottleneck: Complex structure
limits extraction efficiency. 2. Economic & Environmental Cost: Solvent-based methods pose environmental risks; physical methods like ultrafiltration are energy-intensive. |
Summary
As shown in the table, each traditional treatment method for vinasse has its own trade-offs in efficiency, economics, environmental compatibility, and product value. Single-method approaches often struggle to overcome all limitations. In light of these challenges, there is an urgent need to develop new treatment methods that are efficient, environmentally friendly, and cost-effective.
Despite possessing properties that can easily cause environmental pollution, vinasse is not without potential for utilization. It is rich in organic matter and can be utilized for energy production through the application of physical, chemical, and bioconversion technologies[2]. Particularly, compared to traditional chemical products derived from non-renewable resources like petroleum and coal, chemical products produced from renewable resources such as vinasse have garnered widespread attention due to their environmentally friendly characteristics[1].
Among all the components of vinasse, cellulose and lignin are considered the most challenging carbon sources to utilize. Furthermore, the presence of lignin impedes the degradation of cellulose[3]. Given the substantial proportion of cellulose and lignin in vinasse, the resulting loss and waste of resources due to ineffective utilization is truly regrettable. However, with advances in synthetic biology and the maturation of fermentation technologies, it may be possible today to resolve this long-standing issue.
Guided by the principles of the Sustainable Development Goals (SDGs) and underpinned by responsibly executed human practice initiatives, our project, Ducon—A Dual-microbe System for Vinasse Recycling Through Conversion to Succinate—presents an innova tive, integrated solution. At its core, the project features a genetically engineered dual-microbe system meticulously designed to degrade lignin and cellulose present in vinasse, transforming these waste materials into succinate, a high-value chemical product.
We take great pride in naming our dual-chassis system “DuCon.” This name pays homage to Dukang, the legendary originator of Chinese brewing who first taught humanity to transform grains into wine. Millennia later, facing the challenge of brewing byproducts—vinasse—we are determined to complete this historical resonance with the power of synthetic biology: If Dukang transformed grains into wine, then our “DuCon” system transforms the “remains” of wine into new value.
Rigorously validated through wet-lab experiments and robustly supported by dry-lab modeling, Ducon stands as a testament to scientific precision and feasibility. This pioneering project not only holds immense potential for collaboration with industries related to Baijiu (Chinese liquor) production but also paves the way for generating profits through succinate production. By doing so, it actively embodies and promotes responsible consumerism, contributing positively to both our planet and society.
| Core Dimension | Traditional Methods | DuCon | Core Advantage |
|---|---|---|---|
| Technical Concept | Waste Treatment | Bio-Manufacturing | Transforms waste into treasure, shifting from “treatment” to “creation” |
| Process Conditions | Harsh, High Energy Consumption | Mild, Low Energy Consumption | Green and eco-friendly, fundamentally reducing energy use and risks |
| Resource Utilization | Incomplete, Leaves Residue | Full-component, Efficient Conversion | Maximizes resource use, overcoming the challenge of lignin utilization |
| Final Output | Low-value Products (e.g., feed, fertilizer) | High-value Chemical (Succinate) | Economically efficient, significantly higher output value with strong drivers |
| Process & Environment | Multi-step, Polluting | Integrated, Clean | Streamlined and simple, short process with no secondary pollution |
Our DuCon system presents a groundbreaking advancement in vinasse recycling by operating under mild, pollution-free conditions, which fundamentally eliminates the risk of secondary environmental contamination. It embodies the principle of sustainable development by efficiently converting the recalcitrant lignocellulosic components of vinasse into a single, high-value product—succinate. This innovative approach not only maximizes resource utilization but also creates a compelling economic driver, seamlessly merging ecological responsibility with superior economic returns through high-value valorization.
In order to degrade inferior carbon sources in vinasse, we edited the genome of Trichoderma reesei by introducing the laccase gene of the white rot fungus into it, so that it could secrete laccase and cut lignin into short arenes (at the same time, the cellulase secreted by Trichoderma reesei could degrade cellulose, another common carbon source present in vinnase). Afterwards, another substrate organism, Pseudomonas putida, is introduced to absorb the short arenes and channel them into its own TCA pathway. Finally, we modified Pseudomonas putida’s TCA pathway to specifically enrich succinate, then introduced a succinate efflux channel to secrete it for further application.
To ensure the system’s feasibility and efficiency, we established a comprehensive dry lab framework that seamlessly connects computational models with hardware design and software tools. Our multi-scale mathematical modeling—including ODE kinetics, Flux Balance Analysis (FBA), and dual-species dynamics—guided the genetic and process design, predicting an ideal succinate yield and identifying key bottlenecks. These models directly informed the design of a full industrial-scale processing line, demonstrating the practical viability of converting 500 kg of vinasse into 34.3 kg of succinate in 10-12 days. Furthermore, to optimize gene expression in our chassis organisms, we developed a web-based UTR optimization platform, providing a high-throughput tool for screening high-efficiency genetic parts. This integrated approach provides a robust, data-driven foundation for scaling our dual-microbe system from concept to industrial application.
Due to time and other constraints, we may not be able to achieve a more comprehensive design and analysis of our DuCon system. However, we hope to make further efforts in the following aspects to make this project more complete:
Our dual-microbe system can not only be applied to vinasse but also to all kinds of agricultural wastes where lignin and cellulose serve as the primary hard-to-degrade carbon sources. Examples include agricultural residues like straw (corn, wheat, and rice straw), nutshells; by-products of food processing such as peanut meal/rapeseed meal (the residues after oil extraction), soybean dregs; as well as forestry wastes, etc. Our project can address common technical challenges, transform waste into valuable resources, achieve high-value utilization, and enhance economic benefits.
Succinate is a common raw material for chemical synthesis and also represents our high-value-added final product. The chemical synthesis of succinate relies on fossil fuels, which, although fast and cost-effective, results in significant environmental pollution and is unsustainable. In contrast, the biosynthesis of succinate through the bacterial tricarboxylic acid cycle pathway is more environmentally friendly and sustainable. Meanwhile, succinate serves as a raw material for synthesizing biodegradable plastics (PBS) with superior performance. Although PBS currently holds a relatively small market share due to its higher cost, its degradation rate, strength, and other properties are excellent. We believe that with bio-based succinate and PBS, we are moving towards a more sustainable future.
We have completed preliminary design of our industrial line. To further improve its practicability, more detailed instrument and pipeline arrangement should be designed and more experiments on a larger scale should be conducted. What’s more, more elements including labor, gas use and post-treatment should be considered for cost accounting.
In summary, our Ducon project presents a groundbreaking and sustainable resolution to the pressing challenge of vinasse pollution. By deploying a meticulously engineered dual-microbe system, we efficiently convert the recalcitrant lignin and cellulose in vinasse into high-value succinate under mild, pollution-free conditions. This innovative approach, rigorously validated through integrated wet-lab and dry-lab frameworks, successfully transforms a severe environmental liability into a valuable resource. Ducon thus establishes a new paradigm for waste valorization, seamlessly uniting ecological responsibility with compelling economic returns and offering a viable, closed-loop solution for the sustainable future of the liquor industry.