Additive-Assisted Consolidated Bioprocessing of Untreated Desert Willow (Salix psammophila) for Bioethanol Production by a Thermophilic Co-Culture

Consolidated bioprocessing (CBP) using Acetivibrio thermocellus offers a promising route for the direct conversion of recalcitrant lignocellulose into ethanol. In this study, a synergistic co-culture system comprising A. thermocellus C1 and Thermoanaerobacterium thermosaccharolyticum DSM571 was established for the bioconversion of untreated Salix psammophila, a woody biomass native to the desert regions of Inner Mongolia. To enhance fermentation performance, exogenous additives—including Fe3O4 nanoparticles, biochar, and CaCO3—were introduced in combination with process parameter optimization. These additives significantly stimulated microbial ethanol synthesis. Under optimized co-culture conditions, the system demonstrated exceptional cell-wall deconstruction capability, achieving a cellulose degradation rate of 75.04% and a hemicellulose degradation rate of 65.30%. Bioethanol was produced at a yield of 28.95% of the theoretical maximum. These results confirm that simultaneous co-inoculation allows both strains to establish a balanced cooperative interaction from the onset of fermentation, effectively facilitating synergistic sugar utilization and metabolic carbon flux. This high efficiency in raw biomass deconstruction provides a solid laboratory-scale proof-of-concept, highlighting the strong potential of this direct CBP strategy for converting raw desert biomass into high-value bio-based chemicals and fuels.