INFLUENCE OF NITROGEN AND IRON LIMITATIONS ON LIPID PRODUCTION BY CRYPTOCOCCUS-CURVATUS GROWN IN BATCH AND FED-BATCH CULTURE

Cryptococcus curvatus, an oleaginous yeast, was grown under iron (Fe) and nitrogen (N)-limited conditions to produce lipid with a high stear ic acid (C18:0) content in batch and fed-batch culture. In batch cultu re, lack of ferrous ions had no evident effect on growth, lipid produc tion or lipid composition. The highest steal ic acid content in the to tal lipid was 14% in N-limited medium in batch culture. The combined e ffect of Fe and N-limitation in fed-batch culture was to increase the stearic acid content to 19% of the total lipids and the consumed carbo n to nitrogen (C:N) ratio to 20 g/g. The highest biomass concentration achieved was 70 g/litre and 53% (w/w) lipid accumulated when grown fo r about 172 h in fed-batch culture. A C:N ratio between 20 and 50 was optimal for intracellular lipid accumulation and re ratio > 50 g/g bec ame crucial for both growth and lipid production in fed-batch culture. The maximal C: N ratio achieved at the end of the culture was 75 g/g. Lipid yield from glucose (g lipid) g glucose) was 0.14 and the fatty acids of lipids obtained were mainly oleic (C18:1), palmitic (C16:0) a nd stearic (C18:0).