NOVELTY - Continuously hydrolyzing cellulosic biomass comprises: (P) providing at least one reactor, which can be operated at steady state; (A) adding a predetermined amount of cellulosic biomass to the reactor, where the cellulosic biomass has a solid content of at least 10%; (A') adding a predetermined amount of enzymes to the reactor; and (E) performing at least a partial enzymatic hydrolysis of the cellulosic biomass in the reactor.    USE - The processes are useful for continuously hydrolyzing cellulosic biomass; and for producing monosaccharides, sugar based chemicals, biofuels or materials together with sulfonated lignin from lignocellulosic biomass (all claimed).    ADVANTAGE - The invention provides improved hydrolysis for overall biomass conversion for cellulose, i.e. the process of converting cellulosic biomass into useful chemicals or commodities, for example biofuels.    DETAILED DESCRIPTION - Continuously hydrolyzing cellulosic biomass comprises: (P) providing at least one reactor, which can be operated at steady state; (A) adding a predetermined amount of cellulosic biomass to the reactor, where the cellulosic biomass has a solid content of at least 10%; (A') adding a predetermined amount of enzymes to the reactor; and (E) performing at least a partial enzymatic hydrolysis of the cellulosic biomass in the reactor, where a steady state is achieved in the process, in which cellulosic biomass is continually added to the reactor, while at least partially hydrolyzed cellulosic biomass is continually removed from the reactor, where the at least partially hydrolyzed cellulosic biomass that is continually removed has a viscosity, as measured in a Physica MCR 101 rheometer in a cup with a stirrer (FL 100/6W), of not more than 25 Pa-second. An INDEPENDENT CLAIM is a process for producing monosaccharides, sugar based chemicals, biofuels or materials together with sulfonated lignin from lignocellulosic biomass comprising at least the following steps: (i) pretreatment of a lignocellulosic biomass, preferably in a sulfite cooking step; (ii) separation of the pretreated lignocellulosic biomass from step (i) into: (a) a liquid spent sulfite liquor phase, preferably comprising 50% or more of the lignin of the lignocellulosic biomass in the form of sulfonated lignin, and into: (b) a pulp, preferably comprising 70% or more of the cellulose of the lignocellulosic biomass; (iii) hydrolysis of the pulp (b) from step (ii) into a sugar chemistry platform comprising monosaccharides; where the hydrolysis step is the process above; (iv) optionally further processing of the monosaccharides from step (iii) resulting in useful chemicals, biofuels and/or proteins; and (v) direct conversion or further processing of the sulfonated lignin of the liquid phase (a) from step (ii) into useful chemicals, biofuels and/or materials.