Phenol Biodegradation Using a Repeated Batch Culture of

ABSTRACT. As in many other microorganisms, the growth rate of C. tropicalis is affected by phenol. Be-sides, when the yeast is aerobically cultivated in a medium containing phenol, using a bubble column, the yeast cell flotation phenomenon occurs, which makes the continuous operation of this type of reactor diffi-cult. Therefore, a system of phenol degradation, which recycles the biomass separated by flotation, was devised in this work. In order to reduce the substrate toxicity observed at high phenol concentrations, the bubble column used in the biodegradation studies was fed in a semibatch mode. So, a semicontinuous sys-tem was implemented to treat effluents with relatively high concentrations (> 9,000 ppm) of phenol, by replacing periodically about 22 % of the bioreactor operational volume. The phenol removal efficiencies obtained with this system were higher than 98.7%. Key words: Candida tropicalis, phenol biodegradation, bubble column, froth flotation. RESUMEN Como en muchos otros microorganismos, la velocidad de crecimiento de C. tropicalis es afec-tada por fenol. Además, cuando la levadura se cultiva aeróbicamente en una columna de burbujeo, en un medio que contiene fenol, ocurre el fenómeno de flotación celular, lo que dificulta la operación continua de este tipo de reactor. Por consiguiente, en este trabajo se propone un sistema de degradación de fenol en el cual se recicla la masa celular separada por flotación. Además, con la finalidad de reducir la toxicidad de