Assas

Journalof Applied Phycology 6: 13-20, 1994. 1994 KluwerAcademic Publishers. Printed in Belgium.

13

Halotolerance studies on Chlamydomonas reinhardtii:

glycerol excretion by free andimmobilized cells
R. Le6n & F. Galvdn
Departamentode Bioquimica Vegetal y Biologla Molecular, Facultadde Qutmica, Apartado553, Universidadde Sevilla, 41080-Sevilla, Spain (FAX 95-4626853)
Received 13 May1993; revised 4 October 1993; accepted 5 October 1993

Key words: Alginate, Chlamydomonas, glycerol, halotolerance, immobilization

Abstract The freshwater green alga Chlamydomonas reinhardtiicantolerate a maximum saline concentration of 200 mM NaCI. In response to this osmotic shock, the cells accumulated during the first 24 h 15% of the total glycerol synthesized as osmoregulatorymetabolite, to provide the corresponding osmotic balance. After this period all glycerol synthesized was excreted to the medium, 4 g L - 1 at 120 h in optimal conditions, before cell degradation occurred. Thisexcretion was about 2-fold higher in Ca-alginate entrapped cells in the presence of 250 mM NaCi. It was concluded that immobilized cells may be of biotechnological interest for continuous glycerolphotoproduction in air-lift bioreactors. Introduction Glycerol is mainly produced by chemical synthesis from the petrochemical industry or as by-product from the soap industry. However, limitations ofpetrol reserves and replacement of soaps by detergents make a biological process for glycerol production avery attractive possibility (Chen & Chi, 1981). Much work has been carried out on the productionof glycerol from different kinds of microorganisms, but green algae have the added advantage of only requiring cheap inorganic sources and light. Dunaliella is a marine microalga well-known for itspotential to produce glycerol, but until now all the proposed processes for industrial glycerol production have assumed that there is no leakage of the polyol by this microorganism (Borowitzka &...