Towards closed carbon loop fermentations: co-feeding of Yarrowia
lipolytica with glucose and formic acid
Abstract
A novel fermentation process was developed in which renewable
electricity is indirectly used as a fermentation substrate,
synergistically decreasing both the consumption of sugar as a first
generation carbon source and emission of the greenhouse gas CO2. To
achieve this, a glucose-based process is co-fed with formic acid, which
can be generated by capturing CO2 from fermentation offgas followed by
electrochemical reduction with renewable electricity. This ‘closed
carbon loop’ concept is demonstrated by a case study in which co-feeding
formic acid is shown to significantly increase the yield of biomass on
glucose of the industrially relevant yeast species Yarrowia lipolytica.
First, the optimal feed ratio of formic acid to glucose is established
using chemostat cultivations. Subsequently, guided by a dynamic
fermentation process model, a fed-batch protocol is developed and
demonstrated on laboratory scale. Finally, the developed fed-batch
process is proven to be scalable to pilot scale. An extension of this
proven concept to also recycle the O2 that is co-generated with the
formic acid to the fermentation process for intensification purposes,
and a potential further application of the concept to anaerobic
fermentations are discussed.