Physiological and genetic differences amongst Rhodococcus species for using glycerol as a source for growth and triacylglycerol production

ALVAREZ HM; MONCALIAN G; HERRERO M

MICROBIOLOGY-UK

SOC GENERAL MICROBIOLOGY

Lugar: London; Año: 2016 vol. 162 p. 384 - 397

1350-0872

We analyzed the ability of five different rhodococcal species to grow and produce triacylglycerols (TAG) from glycerol, the main by-product of biodiesel production. R. fascians and R. erythropolis grew fast on glycerol, whereas R. opacus and R. jostii exhibited a prolonged lag phase of several days before growing. R. equi only exhibited poor growth on glycerol. R. erythropolis DSMZ 43060 and R. fascians F7 produced 3.9 to 4.3 (g/L) of cell biomass and 28.4 to 44.6 % (of CDW) of TAG after 6 days of incubation; whereas R. opacus PD630 and R. jostii RHA1 produced 2.5 to 3.8 (g/L) of cell biomass and 28.3 to 38.4% (of CDW) of TAG after 17 days of growth on glycerol. Genomic analyses revealed two different sets of genes for glycerol uptake and degradation (here named clusters 1 and 2) among rhodococci. Those species that possess cluster 1 (glpFK1D1) (R. fascians and R. erythropolis) exhibited fast grow and lipid accumulation, whereas those containing cluster 2 (glpK2D2) (R. opacus, R. jostii and R. equi) exhibited delayed grow and lipid accumulation during cultivation on glycerol. Three glycerol-negative strains were complemented for their ability to grow and produce TAG by heterologous expression of glpK2 from R. opacus PD630. In addition, we significantly reduced the extension of the lag phase and improved glycerol assimilation and oil production of R. opacus PD630 when expressing glpK1D1 from R. fascians. Results demonstrated that rhodococci are a flexible and amenable biological system for further biotechnological applications based on the reutilization of glycerol.