An Improved Genome-Scale Metabolic Model of C1 (AK888) and Its Application in Glycogen Overproduction.

Glycogen-enriched biomass of has increasingly gained attention as a source for bioethanol production. To study the metabolic capabilities of glycogen production in C1, a genome-scale metabolic model (GEM) could be a useful tool for predicting cellular behavior and suggesting strategies for glycogen overproduction. New experimentally validated GEM of C1 namely AK888, which has improved metabolic coverage and functionality was employed in this research. The AK888 is a fully functional compartmentalized GEM consisting of 888 genes, 1,096 reactions, and 994 metabolites. This model was demonstrated to reasonably predict growth and glycogen fluxes under different growth conditions. In addition, AK888 was further employed to predict the effect of deficiencies of NO₃, PO₄, or SO₄ on the growth and glycogen production in C1. The simulation results showed that these nutrient limitations led to a decrease in growth flux and an increase in glycogen flux. The experiment of C1 confirmed the enhancement of glycogen fluxes after the cells being transferred from normal Zarrouk's medium to either NO₃, PO₄, or SO₄-free Zarrouk's media. Therefore, AK888 could be served as a predictive model for glycogen overproduction and a valuable multidisciplinary tool for further studies of this important academic and industrial organism.