BIOTECHNOLOGY OF ALGAL BIOMASS PRODUCTION - A REVIEW OF SYSTEMS FOR OUTDOOR MASS-CULTURE

Microalgae are very efficient solar energy converters and they can pro duce a great variety of metabolites. Man has always tried to take adva ntage of these properties through algal mass culture. Despite the fact that many applications for microalgae have been described in the lite rature, these microorganisms are still of minor economic importance. I ndustrial reactors for algal culture are at present, all designed as o pen race-ways (shallow open ponds where culture is circulated by a pad dle-wheel). Technical and biological limitations of these open systems have given rise to the development of enclosed photoreactors (made of transparent tubes, sleeves or containers and where light source may b e natural or artificial). The present review surveys advances in these two technologies for cultivation of microalgae. Starting from publish ed results, the advantages and disadvantages of open systems and close d photobioreactors are discussed. A few open systems are presented for which particularly reliable results are available. Emphasis is then p ut on closed systems, which have been considered as capital intensive and are justified only when a fine chemical is to be produced.