BIOTECHNOLOGY TECHNIQUES VoErrme IO No.5 (May 1996) p.329-334 Received as revised I I th March. OPTIMIZATION OF LIGHT AND TEMPERATURE FOR GROWING CHLURELLA SP. USING RESPONSE SURFACE METHODOLOGY. J.L. Garcia Sanchez”, J.A. Sanchez Perez, F. Garcia Camacho, J.M. Fernandez Sevilla and E. Molina Grima. Departamento de Ingenieria Quimica Facultad de Ciencias Experimentales, Universidad de Almeria, E-04071 ALMERk4, (SPAIN). Fax: 34-50-215070. E-mail: jlgarcia@ualm.es Summary. The simultaneous effect of temperature and photon flux density on microalga Chlorella sp. growth was analysed by response surface methodology of two consecutive full factorial designs. Maximum specific growth rate was 0.128 he’ at 35°C and 2400 ymol photon me2se1. A photoinhibition effect was observed at high photon flux densities with temperatures far below the optimum. Temperature was the main factor affecting specific growth rate. INTRODUCTION. Microalgal mass culture is needed for the development of aquaculture technology (Glaude and Maxey, 1994). a4ttainable outdoor cultures are preferred especially when a resistant strain is available. Thus, the ChZorelIa sp. strain used in this work is advantageous since, as it naturally becomes the dominating species under a wide range of conditions in outdoor culturing, it is isolated in non-axenic conditions (Bengoa- Ruigomez et al., 1995; unpublished). The successful use of a microalga requires the optimization of its growing conditions, namely temperature and light intensity. Interaction between these two variables in outdoor cultures determines the biochemical profile of biomass and growth state (Goldman and Mann, 1980; Richmond, 1990). Likewise, when dealing with optimization of the specific growth rate, regardless of the culture system, both these factors must be considered first In this paper, we present a rapid method for studying the influence of temperature and photon flux density leading to an optimum policy for these factors in this microalga. 329