Raw glycerol, produced in significant quantities during several industrial processes, could be further considered as a potential substrate for microbial conversions. In the present report, modelling approaches are used in order to quantify the kinetic behavior of microorganisms capable of producing growth-and non growth-associated metabolites when cultivated on raw glycerol. Citric acid production by Yarrowia lipolytica strain ACA-DC 50109 was successfully simulated by Monod-, Verhlust-and Williams-type models, while the optimized parameter values were found to be similar to those experimentally measured. It has been demonstrated that the production of citric acid from raw glycerol, in terms of specific production rate and conversion yield, was similar or even better as compared with that obtained during cultivation of yeasts or molds on various conventional (eg sugar-based) media. The production of 1,3-propanediol by Clostridium butyricum strain F2b from raw glycerol was successfully simulated by a Contois-type model. It was found that the maximum theoretical 1,3-propanediol productivity was comparable with the highest one achieved during growth of various bacterial strains on pure glycerol in batch and continuous cultures. Raw glycerol could be used as an alternative substrate for citric acid and 1,3-propanediol production, and possibly for other microbial products. (C) 2003 Society of Chemical Industry.