For future iGEM teams: Think Big, Start Small, and keep moving forward with creativity and persistence.
Throughout our project, our vision has always been to go beyond conventional solutions and explore innovative ways to address global challenges. Lignocellulosic biomass, though abundant and renewable, remains underutilized due to its structural complexity and resistance to biodegradation. Inspired by one of the most efficient natural systems—the rumen of ruminants—we sought to replicate and extend its power in a synthetic context.
By designing and applying rumen biomimetic microbiota, we demonstrated that corn straw, a common agricultural waste, can be efficiently degraded and converted into volatile fatty acids (VFAs), which serve as valuable bio-based resources. We applied the approach of biomimicry and innovation beyond biomimicry. We first started small and simple experiment and primarily achieved a biomimetic approach, in which rumen biomimetic microbiota efficiently hydrolyzed and acidified corn straw. Subsequently we further advanced the process by transforming the traditional batch fermentation mode into a semi-continuous fermentation system, thereby improving the stability and efficiency of VFA production.Our system not only mimics natural microbial communities but also advances them through semi-continuous fermentation, enabling higher stability and productivity across varying substrate loads.
For future iGEM teams, our work illustrates the importance of bridging inspiration from nature with engineered improvements. From bioenergy to waste valorization, and from microbial community engineering to reactor design, the possibilities are vast. By following similar paths—starting with nature’s wisdom and moving toward synthetic advancement—future teams can contribute to addressing some of the world’s most pressing environmental and resource challenges.
First Construction and Validation of a Semi-Continuous Rumen Bioreactor This study not only conducted traditional batch fermentation experiments but also designed and operated a long-term (180 days) semi-continuous reactor, successfully achieving stable VFA production under high substrate loads (up to 8.0% w/v), breaking through the low-load limitations (typically ≤2.5%) of previous studies.
Systematic Investigation of Substrate Load Effects on Microbial Community and Function
By gradually increasing the corn straw load (2.5% → 5.0% → 8.0%), the study revealed the dynamic effects of load changes on bacterial diversity, core genera, CAZyme expression, and metabolic pathways, providing a theoretical basis for high-load fermentation.
Multi-Omics Integration Reveals Mechanistic Depth
By combining metagenomics, 16S/ITS amplicon sequencing, co-occurrence network analysis, CAZyme annotation, and KEGG metabolic pathway analysis, the study systematically revealed the response mechanisms of the rumen microbial community structure, functional genes, and enzyme systems during substrate degradation and VFA synthesis.
Focus on Fungal Community and Bacterial-Fungal Interactions
Compared to previous studies focusing mostly on bacteria, this paper systematically analyzed the role of the fungal community (e.g., Piromyces, Neocallimastix) in corn straw degradation for the first time and constructed fungal co-occurrence networks, revealing their synergistic and competitive relationships within the rumen ecosystem.
Identified pH and VFA Accumulation as Key Factors Affecting Microbial Community Structure
Through CCA and correlation heatmap analyses, it was confirmed that low pH and VFA accumulation are the main causes of the restructuring of bacterial and fungal communities and the decrease in CAZyme expression, providing key targets for regulating the fermentation process.
Revealed the Adaptive Response of Core Functional Genera under High Load At the 8% load, the relative abundance of core genera such as Prevotella, Saccharofermentans, and Ruminococcus increased significantly, while some low-abundance genera (e.g., Pyramidobacter, Acetobacter) also became key drivers, indicating functional redundancy and niche compensation mechanisms within the microbial community.
Proposed "Timely VFA Separation" Mimicking Ruminant Absorption Strategy Based on the physiological mechanism of VFA absorption by rumen epithelial cells in ruminants, the study proposed introducing membrane separation technology in future research to alleviate acid inhibition and improve degradation efficiency, showing clear potential for engineering application.
Provides a Technical Prototype for High-Load Continuous Fermentation of Biomass Waste
This study demonstrates that rumen microbiota can achieve efficient and stable VFA production in a semi-continuous system, providing experimental basis and operational parameters for industrial scaling.
Promotes the Application of Rumen Microorganisms from "Natural System" to "Artificial System"
By simulating the rumen environment in vitro, it not only deepens the understanding of the ecological functions of rumen microorganisms but also lays a theoretical foundation for their engineering applications in areas like biorefining and waste resource recovery.
The core innovation of this research lies in successfully transforming the rumen – nature's most efficient lignocellulose degradation system – into a controllable, scalable artificial fermentation system. It is not merely an imitation of natural mechanisms but involves parsing its internal logic through systems biology approaches and subsequently optimizing and enhancing its functions. This research paradigm:
Embodies the scientific philosophy of "Learning from Nature, Excelling in Engineering".
Provides a microbe-driven solution for global biomass energy and carbon neutrality technology pathways.
Initiates a new chapter for the application of "Microbial Ecological Engineering" in waste resource recovery.
This paper demonstrates significant innovation in experimental design, mechanistic elucidation, system integration, and application orientation. It not only advances fundamental research on rumen microorganisms in biomass conversion but also provides scientific basis and technical pathways for efficient, continuous industrial-level VFA production, holding important academic value and broad application prospects.
Integrated Human Practices Summary
The project aims to convert lignocellulosic biomass into high-value volatile fatty acids (VFAs) using a rumen-inspired microbial system. To ensure the work is practical, safe, and socially relevant, the team integrated human practices through public engagement and expert consultation.
Based on Public Engagement, we find that limited awareness of VFAs, but strong recognition of the urgency of agricultural waste utilization (88% agreed it’s urgent). We need more science communication to help the public understand these cutting-edge technologies, and to strengthen confidence in our ability to tackle environmental challenges effectively. Frome Expert Engagement, we can see that different stakeholders prioritize safety and economic feasibility differently, and our design need iteratively balance scientific rigor, cost-effectiveness, and practical usability through modular units, pilot-scale validation, and a biosafety certification framework.