Magnetic Immobilization as a Tool for Efficient Recycling of Biocatalysts in Solid-Rich Medium During Consolidated Bioprocessing of Sugarcane Bagasse

Consolidated Bioprocessing (CBP) is a promising technology that integrates enzyme production, biomass hydrolysis, and sugars fermentation. However, CBP is underexplored from a process engineering point of view. Considering that cell recycling can increase process economic viability and that the selection of a bioreactor is a key factor to ensure process effectiveness, this study demonstrates the feasibility of recycling cells during sugarcane bagasse CBP by using magnetic immobilized enzyme producer yeast and a low shear stress vortex flow bioreactor. In the first step, Ca-alginate immobilized strains achieved good productivities (0.48 g/L/h) and 5.7 g/L of ethanol in only 12 h, but cell recovery was hindered by residual solids. To overcome this limitation, magnetic particles were incorporated into the spheres, allowing for rapid post-fermentation, maintaining ethanol production and productivity (6.1 g/L and 0.51 g/L/h). Three repeated batches were successful performed (producing an average of 5.5 g/L of ethanol, 0.46 g/L/h) with complete cell recovery from the remaining solid after biomass hydrolysis, maintaining high cell viability and bead integrity, highlighting the robustness of the immobilization strategy and the suitability of the bioreactor for the process. The successful cell recovery accomplished overcomes a fundamental limitation of bioprocesses carried out in the presence of solids. This strategy represents an important step for biorefineries development, with potential applicability to other bioprocesses using solid substrates.