Fatty acid methyl ester production from industrial waste by Rhodococcus erythropolis IGTS8 and Rhodococcus gordoniae R3

Experiments were performed to test the ability of R. erythropolis IGTS8 and R. gordoniae R3 to accumulate non-polar lipids from industrial waste (molasses and glycerol) to yield fatty acid methyl esters (FAMEs). The bacterium strain IGTS8 grew well in glycerol and yielded 0.11 g/l per day of FAMEs, while the strain R3 used only molasses as a carbon source and yielded 0.03 g/l per day of FAMEs. Fatty acids produced by both strains had 10-22 carbon atoms. Most were C16 fatty acids that are suitable for biodiesel production. Most fatty acids produced are saturated fatty acids with even-numbered carbons, while R. gordoniae R3 grown in molasses produced unsaturated-fatty acids as the major fatty acids. Fatty acids containing two or more double bonds were barely observed. Nitrogenous compounds in molasses had an effect on R. gordoniae R3 growth, yield of FAMEs, and composition of fatty acid produced. In the case of R. erythropolis IGTS8, only the growth of bacteria was noticeably affected. The effect of incubation time on the type of fatty acid was also noted in molasses grown cells. Glycerol and molasses were selected for the large-scale cultivation of R. erythropolis IGTS8 and R. gordoniae R3, respectively, in a 2-l continuously stirred tank bioreactor. The lipid contents produced by R. erythropolis IGTS8 grown in glycerol were increased, whereas the lipid contents produced by R. gordoniae R3 grown in molasses was found to decrease with increasing feeding time. In conclusion, the large-scale experiments gave higher lipid productivity than those performed in the laboratory scale, with the FAMEs productivity of 40 and 0.27 g/l per day for R. erythropolis IGTS8 and R. gordoniae R3, respectively.