Influence of nitrogen and iron limitations on lipid production by Cryptococcus curvatus grown in batch and fed-batch culture

Abstract

Cryptococcus curvatus, an oleaginous yeast, was grown under iron (Fe) and nitrogen (N)-limited conditions to produce lipid with a high stearic acid (C18:0) content in batch and fed-batch culture. In batch culture, lack of ferrous ions had no evident effect on growth, lipid production or lipid composition. The highest stearic acid content in the total lipid was 14% in N-limited medium in batch culture. The combined effect 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 carbon 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 for about 172 h in fed-batch culture. A C:N ratio between 20 and 50 was optimal for intracellular lipid accumulation and a ratio > 50 g/g became 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) and stearic (C18:0).