Abstract A study of the kinetics of the anaerobic digestion process of wastewater derived from the production of protein isolates from extracted sunflower flour was carried out in a laboratory-scale fluidised bed reactor with saponite as support for the mediating bacteria at mesophilic temperature (35°C). The reactor operated satisfactorily between hydraulic retention times (HRT) of 1.1 to 20.0 days, removing between 98.3 and 80.0% of the initial chemical oxygen demand (COD). Macroenergetic parameters, calculated using Guiot's kinetic model, gave a yield coefficient for the biomass ( Y) of 0.075 g VSS/g COD and a specific rate of substrate uptake for cell maintenance ( m) of 0.021 g COD/g VSS day. The experimental results also showed the rate of substrate uptake, R s (g COD/g VSS day) correlated with the concentration of biodegradable substrate, S (g COD/l), through an equation of the Michaelis-Menten type. This proposed model predicted the behaviour of the reactor very accurately showing deviations lower than 10% between the experimental and theoretical values of substrate uptake rates.