Optimization of lipid production in the oleaginous bacterium Rhodococcus erythropolis growing on glycerol as the sole carbon source

Abstract

The growth of an oleaginous bacteria strain Rhodococcus erythropolis on glycerol was studied. Lipid accumulation was influenced by the glycerol concentration, nitrogen source, nitrogen concentration, pH medium, incubation time and aeration rate. Under the best optimized flask culture medium; 30 g/L glycerol plus 0.75 g/L urea, incubation temperature at 30°C, agitation rate of 150 rpm and 96 h of cultivation time, 3.93 g/L of dry biomass, 1.84 g/L cellular lipid accumulation and 45.8% accumulated lipid of total dry biomass were produced. The scaling up of R. erythropolis in bioreactors yielded the biomass and lipid content of 11.74 g/L and 14.1% of total dry biomass, respectively. The lipid composition of oleaginous microorganisms contained a high proportion of C16 and C18 fatty acids. The extracted lipids were mainly 16.48% C14:1, 16.69% C16:1, 20.16% C16:0, 18.90% C18:1. R. erythropolis could be directed to using raw glycerol obtained from biodiesel by-product as substrate, in order to accumulate lipids for biodiesel production.

Key words: Rhodococcus eryhropolis, glycerol, lipid accumulation, biodiesel, fatty acid composition.