Abstract: A biomass processing system is disclosed whereby a counter flow path is provided for recovering yielded product from at least two fermentation stages. In certain configurations, the counter flow path is associated with respective extraction stages that correspond to each respective fermentation stages. To enhance product recovery, certain configurations also disclose mechanical grinding of biomass between fermentation stage to enhance a surface area for further subsequent processing of the biomass. To yet further enhance the system, certain configurations discloses a cell recovery sub-system that agitates processed biomass to separate cells from undigested residues. The recovered cells may be recycled to fermentation stages in the system.