Heterotrophic growth and lipid production of Chlorella protothecoides on glycerol.

During the production of biodiesel, a significant amount of glycerol is generated which currently has little commercial value. A study on the growth and lipid production of Chlorella protothecoides using glycerol as the carbon source was performed to demonstrate the utility of recycling crude glycerol created during biodiesel production. Glycerol was examined as both the sole carbon source and in combination with glucose. Algae cultures grown on only glycerol in shake flasks showed a specific growth rate and final lipid yield of 0.1/h and 0.31 g lipid/g substrate, respectively. The values were similar to those observed on pure glucose, 0.096/h and 0.24 g lipid/g substrate. When the media contained a mixture of glycerol and glucose, simultaneous uptake of the two substrates was observed. Due to the difference in rates of lipid storage, lipid production was 0.077 g lipid/(l h) during growth on glycerol, while growth on glucose had a productivity of 0.096 g lipid/(l h). During growth on the 9:1 mixture of both glucose and glycerol, lipid productivity was 0.098 g lipid/(l h). In order to simulate the use of waste glycerol from biodiesel production the experiments were repeated and similar growth rates, yields, and lipid productivities were achieved. Therefore, we have demonstrated the promise for simultaneous high growth rates and lipid yields of C. protothecoides heterotrophically grown on mixtures of glycerol.