High-cell-density batch fermentation of Rhodococcus opacus PD630 using a high glucose concentration for triacylglycerol production

Biodiesel, monoalkyl esters of long-chain fatty acids with short-chain alcohols derived from triacylglyc- erols (TAGs), can be produced from renewable biomass sources. Recently, there has been interest in producing microbial oils from oleaginous microorganisms. Rhodococcus opacus PD630 is known to accu- mulate large amounts of TAGs. Following on these earlier works we demonstrate that R. opacus PD630 has the uncommon capacity to grow in defined media supplemented with glucose at a concentration of 300 gl −1 during batch-culture fermentations. We found that we could significantly increase concentra- tions of both glucose and (NH4)2SO4 in the production medium resulting in a dramatic increase in fatty acid production when pH was controlled. We describe the experimental design protocol used to achieve the culture conditions necessary to obtain both high-cell-density and TAG accumulation; specifically, we describe the importance of the C/N ratio of the medium composition. Our bioprocess results demonstrate that R. opacus PD630 grown in batch-culture with an optimal production medium containing 240 g l −1