RESUMEN: Con el fin de aprovechar el subproducto de la fabricacion de queso blanco, se evaluo el suero de leche como sustrato para la produccion de acido citrico utilizando Aspergillus niger NRRL 2270. Para este sustrato se comparo la hidrolisis acida y enzimatica de la lactosa con el fin de proporcionar al microorganismo una fuente de carbono mas asimilable. En el suero entero (SE) y desproteinizado e hidrolizado (SDH), se estudio el efecto del pH y la adicion de nitrogeno, ademas en el suero hidrolizado (SH) la complementacion con sacarosa; posteriormente se estudio la adicion de nitrogeno y fosforo en el SE y SDH; se determino la produccion de acido citrico al agregar magnesio, carboximetil celulosa (CMC), gelatina y metanol al SE. El proceso fermentativo se realizo en cultivo sumergido discontinuo agitado y a las mejores condiciones nutricionales se hizo un seguimiento de las variables del proceso en el tiempo. PALABRAS CLAVE: Acido citrico, Suero de leche, Aspergillus niger , Hidrolisis, Carboximetil celulosa, Gelatina, Metanol. ABSTRACS: In order to take advantage of byproduct of white cheese production, the whey was evaluated as a substrate for the production of citric acid utilizing Aspergillus niger NRRL 2270. For this substrate the acid and enzymatic hydrolysis of the lactose are compared in order to provide the microorganism with an easily assimilated source of carbon. In the entire whey (EW) and unprotein hydrolyzed whey (UHW) was studied the effect of the pH, and the addition of nitrogen and phosphorus; besides, in the hydrolyzed whey (HW) the complementation with sucrose afterwards it was studied the addition of nitrogen and phosphorus in the (EW) and (UHW) the production of citric acid was evaluated by adding magnesium, carboxymethyl cellulose (CMC), gelatin and methanol to the whey. The fermentation process was carried out in a submerged, agitated batch cultivation. After determining the better nutritional conditions a were monitoring in the time of the process. KEY WORDS: Citric acid, Whey, Aspergillus niger , Hydrolysis, Carboxymethylcellulose, Gelatin, Methanol.