High-cell-density cultivation of the lipid accumulating yeast Cryptococcus curvatus using glycerol as a carbon source
Cryptococcus curvatus is a yeast with industrial potential because it can grow and accumulate lipid on a very broad range of substrates. In this study we describe growth and lipid accumulation on glycerol in a fed-batch fermentation mode. We performed a fermentation consisting of two phases. The first phase is the biomass production phase in which there is no nutrient limitation except for very short periods of glycerol exhaustion. The substrate feed was controlled by the dissolved oxygen tension. In the second phase nitrogen limitation was introduced, which causes lipid accumulation. This way very high cell densities of 118 g/l in a 50-h fermentation could be reached. With a lipid production rate of 0.59 g lipid l-1h-1, a cellular lipid content of 25% was obtained. The growth and lipid accumulation phase are characterized by different cellular fatty acid compositions. In the growth phase, a relatively high amount of C18:2 (linoleic acid) is present, which is a major component of membrane lipids. C18:0 (stearic acid) and C18:1 (oleic acid) are major constituents of the accumulated triglycerides and therefore the relative amount of C18:2 decreases during the lipid accumulation phase.
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