For the first time, scientists at The Novo Nordisk Foundation Center for Biosustainability (DTU Biosustain) have examined the contaminant population in sugarcane bioethanol production at a strain-level resolution. This groundbreaking research, published in Nature Communications, demonstrates the direct impact of strain dynamics on process performance, highlighting the need for advanced microbial control methods to improve industrial efficiency.
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Enhanced Process Yield and Environmental Benefits
Bioethanol, a key renewable energy source, is produced through the fermentation of sugars by the yeast Saccharomyces cerevisiae. The presence of contaminant bacteria in the raw material can greatly reduce fermentation efficiency. Previous methods of characterizing these contaminant microbes have failed to fully account for their diversity and impact.
Our research provides a comprehensive analysis of microbial populations across all stages of the industrial bioethanol process in two major Brazilian biorefineries. By using a combination of shotgun metagenomics and cultivation-based methods, we identified ecological factors that influence community dynamics and bioconversion efficiency. The study demonstrates that specific bacterial strains, influenced by temperature, can either hinder or enhance ethanol yield. This improvement could only be achieved with the advanced techniques we utilized.
Felipe Lino, Postdoc, The Novo Nordisk Foundation Center for Biosustainability
When taking into account Brazil alone, the findings could lead to a reduction in CO2 emissions by about 2 million tons annually and an increase in process yield of more than 5 %, translating into an additional $1.6 billion in revenue.
Strain-Level Resolution: Uncovering Hidden Bacterial Dynamics
The researchers found that the interaction between different species significantly influences ethanol yield. Specifically, when Lactobacillus amylovorus is present in higher concentrations, the yields are noticeably improved.
We have mapped the microbial populations at strain-level resolution to uncover the true impact of non-yeast microbes on fermentation performance. We identified specific strains of the L. fermentum species causing the most damage to the process, while other strains are neutral and should even be kept as a buffer against harmful ones. Increased temperatures were linked to the growth of specific L. fermentum strains that negatively affect yeast viability and fermentation efficiency. This underscores the importance of adopting higher resolution methods in the future to monitor microbial communities.
Morten Sommer, Professor, The Novo Nordisk Foundation Center for Biosustainability
Paving the Way for Novel Microbial and Process Control Solutions
The findings of this research may contribute to the creation of innovative microbial and process control strategies that can manage unwanted microorganisms and yield notable enhancements in bioethanol production efficiency. This could lead to more affordable biofuels, higher productivity, and a significant drop in CO2 emissions, assisting in the global effort to cut greenhouse gas emissions.
Implications Beyond Bioethanol Production
The study's findings are especially important for businesses involved in industrial biotechnology and biofuels, as well as for research teams working on bioinformatics tools for strain-level microbiome analysis.
This study’s unique gene catalog and functional analyses provide important tools for finding novel enzymes and metabolic features for resilient industrial strains. These findings may also be used in other metagenomics research on soil and crop-related microbiomes, as well as the dynamics of the gut microbiome.
Journal Reference:
Panagiotou, G., et al. (2024) Strain dynamics of contaminating bacteria modulate the yield of ethanol biorefineries. Nature Communications. doi.org/10.1038/s41467-024-49683-2