FAME and bio-oil properties and carbon yield coefficients of Chlorella sorokiniana cultivated heterotrophically with industrial effluents

Abstract

The fatty acid (FA) distribution of bi-oil derived from Chlorella sorokiniana and FAME basic properties were examined. C. sorokiniana was cultivated heterotrophically in two very different growth media: a) glycerol and inorganic salts (GLIN) and b) glycerol and anaerobic digestate (GLAD), as well as in two different modes: a) semi-batch (GLIN) and b) batch (GLAD). The cultivation took place in 42 L bioreactors and from the biomass collected the bio-oil was extracted, converted to the corresponding fatty acid methyl esters (FAME) and subsequently their distribution was determined in a gas chromatograph. The protein and lipid content were also determined and were used for the estimation of the carbon yield coefficients, which are equal to 0.13 and 0.25 for the GLIN and GLAD treatments respectively. The fatty acid distribution covered chain lengths from C10 to C26. The great proportion of the FA were of medium chain FA C16–C18 constituting about 85% and 53% of the total fatty acids of the GLIN and GLAD treatments respectively. Also, the distribution of saturated, monounsaturated and polyunsaturated FA differed. The basic properties of the biodiesel such as the density, the kinematic viscosity, the acid value, the cetane number, the iodine value and the heating value are within acceptable ranges and differences in the properties of the two treatments are due to differences in FA distribution.