With the rapid advancement of industrialization, the global over-reliance on non-renewable fossil fuels has accelerated their depletion and triggered severe environmental crises, such as escalating greenhouse gas emissions, air pollution, and ecosystem degradation. Consequently, the exploration and development of sustainable biomass resources have become a critical strategic focus to address long-standing challenges in energy security and environmental sustainability. Lignocellulose, as one of the most abundant renewable biomass resources on Earth with an estimated annual yield of approximately 1.7 trillion tons, holds immense potential for producing biofuels and high-value biochemicals. However, only about 3% of this vast resource is currently utilized in the circular bioeconomy.

Lignocellulose is composed of cellulose, hemicellulose, and lignin. This intricate composition severely hinders the efficiency of lignocellulose biotransformation, posing significant obstacles to large-scale industrial application. To tackle this issue, effective pretreatment techniques are essential, including: physical methods that reduce cellulose crystallinity and increase specific surface area; chemical methods that break chemical bonds in the lignin matrix; and biological methods that utilize microbial activity to mildly and sustainably disrupt the structure. Additionally, suitable microbial hosts play a pivotal role in facilitating degradation by secreting hydrolytic enzymes.

Furthermore, selecting appropriate conversion processes is crucial for optimizing target product synthesis. These processes include Separate Hydrolysis and Fermentation (SHF), which allows each step to operate under optimal conditions but increases equipment costs and processing time. Simultaneous Saccharification and Fermentation (SSF) alleviates enzyme inhibition by promptly consuming hydrolyzed sugars but suffers from temperature mismatches between thermophilic enzyme activity and mesophilic microbial fermentation. Consolidated Bioprocessing (CBP) integrates enzyme production, hydrolysis, and fermentation in a single reactor, eliminating the need for exogenous enzymes and significantly reducing production complexity and cost. Among these approaches, microbial co-culture systems established via CBP are regarded as a particularly promising strategy: they enable metabolic division of labor (e.g., one strain degrades lignocellulose to release fermentable sugars, while another converts these sugars into target products), thereby reducing the metabolic burden on individual strains and enhancing overall efficiency.

Additionally, integrating co-culture systems with synthetic biology (e.g., engineering strains to enhance tolerance to low pH or toxic byproducts) and metabolic engineering (e.g., redirecting carbon flux to boost product yields via gene knockout/overexpression) offers valuable theoretical guidance for constructing efficient, stable lignocellulose biotransformation systems. The integration of this technology is expected to overcome current bottlenecks—such as low degradation rates, strain incompatibility, and high production costs—and pave the way for the large-scale, sustainable utilization of lignocellulose toward a green, circular bioeconomy.