Driving Sustainable Energy Solutions
Energy is the fundamental basis and driving force of human societal development, intrinsically linked to national economy, public welfare, and national security. Energy security, a global and strategic imperative for economic and social progress, is paramount for national prosperity, improved living standards, and enduring social stability.
For nearly two centuries, from the 19th to the 20th, fossil fuels such as coal, oil, and natural gas served as crucial material foundations for human survival and development, underpinning the progress of civilization and socio-economic growth. Yet, the non-renewable nature and immense consumption of these resources are inevitably leading to their gradual depletion.
Bioenergy presents distinct and irreplaceable advantages over other renewable energy sources, particularly in enhancing energy and resource supply, improving ecological environments, and supporting carbon neutrality objectives. Synthetic biology research offers substantial application value and immense potential in bioenergy R&D. Its principles are already widely applied in areas like biomass feedstock production and conversion, as well as the design and construction of biocatalysts and cell factories, thereby playing a pivotal role in resolving critical bioenergy development challenges.
Key Applications in Bioenergy Development:
1. Optimized Raw Material Supply
Photosynthetic organisms, including plants and algae, capture carbon dioxide through photosynthesis to generate biomass. This biomass is then transformed into fermentable sugar feedstocks via biological or chemical catalysis, which are subsequently converted into biofuel products by microbial cell factories. Additionally, certain microorganisms naturally exist that can directly utilize one-carbon (C1) compounds (such as carbon dioxide, carbon monoxide, and methanol) to produce bioenergy products (Jiang et al., 2021).
Through synthetic biology, engineering these energy-producing organisms can dramatically improve conversion efficiencies across all stages: from carbon dioxide to biomass, from biomass to sugars, and from sugars to final bioenergy products.
2. Enhanced Raw Material-to-Product Conversion
Yeast can synthesize ethanol from diverse sugar feedstocks. Saccharomyces cerevisiae (brewer's yeast) has emerged as a vital ethanol cell factory, owing to its Generally Recognized As Safe (GRAS) status, well-characterized genetic background, established genetic manipulation techniques, and commendable tolerance to environmental stresses (Favaro et al., 2019). Nevertheless, S. cerevisiae cannot directly metabolize starch, necessitating a two-step saccharification-then-fermentation process for ethanol production. When lignocellulose serves as a feedstock, S. cerevisiae is limited to utilizing only glucose from the hydrolysate, leaving xylose unutilized. Moreover, industrial fermentation subjects S. cerevisiae to multiple environmental stressors, such as high temperatures, elevated osmotic pressure, and high ethanol concentrations.
By leveraging synthetic biology approaches, coupled with functional genomics research, we can optimize the capabilities of S. cerevisiae cell factories. This enables enhanced synthesis efficiency of target metabolites, expanded metabolic capacities, and ensures robust cellular performance even under the demanding conditions of industrial production.
3. Efficient C1 Resource Utilization
One-carbon (C1) compounds, including carbon dioxide, carbon monoxide, and methanol, represent ideal feedstocks for the biomanufacturing industry. They have attracted considerable attention due to their abundant availability, ease of preparation, and cost-effectiveness. The progress in synthetic biology has significantly accelerated the development of microbial cell factories capable of utilizing these C1 compounds.
Syngas, a mixed gas primarily composed of carbon monoxide, carbon dioxide, and hydrogen, is a particularly versatile C1 source. Its origins are diverse, ranging from the incomplete combustion of fossil fuels and the gasification of plant biomass or municipal waste to industrial processes like steel production. Clostridia that utilize syngas (also known as acetogens or gas-fermenting clostridia) constitute a crucial group within acetogenic bacteria. Strains such as Clostridium ljungdahlii and Clostridium autoethanogenum are among the most extensively researched in syngas fermentation. While acetate and ethanol are the main fermentation products for most gas-fermenting clostridia, some strains can also synthesize high-value compounds like lactate, butanol, and 2,3-butanediol under C1 gas-enriched growth conditions, showcasing excellent industrial application potential.