It was shown that waste fiber sludge is a suitable raw material for production of bacterial cellulose andenzymes through sequential fermentation. The concept studied offers efficient utilization of the various components infiber sludge hydrolysates and affords a possibility to combine production of two high value-added products usingresidual streams from pulp mills and biorefineries. Cellulase produced in this manner could tentatively be used tohydrolyze fresh fiber sludge to obtain medium suitable for production of BC in the same biorefinery.