Redox governed electro-fermentation improves lipid production by the oleaginous yeast Rhodosporidium toruloides

Electro-fermentation (EF) is a promising technique to increase the performance of bioprocesses. Here, the effect of EF on the lipid production by the yeast Rhodosporidium toruloides is studied. First, an in silico analysis was performed to unveil possible lipid yield increase and metabolic shifts by EF. Subsequently, cathodic EF (CEF) and anodic EF (AEF) were experimentally tested at different pO₂ levels. CEF enabled artificial lowering of the extracellular redox potential to less than -200 mV even under strictly aerobic conditions. CEF and AEF both positively affected lipid yield and productivity. Additional CEF cultivations with the redox mediator Neutral Red yielded an immense increase in the ratio of saturated fatty acids (from 37% to 50%). Overall, this work demonstrates that EF offers broad potential to improve microbial lipid production. In this context, the use of redox mediators might be of special future interest for the production of cocoa-butter equivalents.