Elucidation of the metabolic mechanism for malate production in Myceliophthora thermophila via 13C metabolic flux analysis

Abstract

Background Myceliophthora thermophila has been engineered to be an important cell factory for malic acid production, however detail information on how carbon fluxes are distributed in the high production strain is still not clear. 13C-MFA (13C metabolic flux analysis) can help to understand cellular metabolic mechanisms and identify important targets for deciphering the carbon flux distribution and improving product synthesis. Here, we used 13C-MFA to study metabolic flux distribution of high malate production strain of M. thermophile for the first time. Results Higher glucose uptake and carbon dioxide release rate, together with lower oxygen consumption rate and biomass yield was found in malate high production strain M. thermophila JG207 compared to the wild strain. Corresponding to the above phenotypes, it is found that in JG207 both pentose phosphate pathway flux and oxidative phosphorylation flux decreased, while TCA downstream flux increased. Higher PPP flux in WT strain accompanied with higher energy state, and corresponding high ATP concentration inhibited glucose-6-phosphate isomerase activity. Several intermediates of reduced TCA pathway in JG207 were accumulated due to high reduction power state, which benefits the conversion of oxalate to malate. The reduced flux of oxidative phosphorylation is shown to be able to cover extra supply of NADH for high malate production. Conclusions This work revealed the intracellular metabolic fluxes distribution for the high malic acid production strain M. thermophile JG207 for the first time. The flux distribution results showed that higher NADH supply was of high importance for higher accumulation of malic acids, this may be guidance for further improvement of the productivity.

Construction of an enzyme-constrained metabolic network model for Myceliophthora thermophila using machine learning-based kcat data

“…In experimental condition, growth rate of M. thermophila is 0.2573 h −1 with maximum glucose uptake rate of 3.0676 mmol/gDW/h when abundant oxygen and glucose are supplied [33]. The PhPP analysis of iYW1475 exhibited linear growth as a function of carbon source and oxygen uptake rates (Fig.…”

“…In detail, biomass components were adjusted based on experimental data (Additional file 1: Table S1). Precise corrections were applied to RNA, DNA, protein and amino acid content [33], according to measured data. Subsequently, the content of lipids and cell wall was adjusted according to literatures [34] and [30], respectively.…”

“…To enhance the alignment between model predictions and experimental data, additional fine-tuning of the original k cat values was necessary for the enzyme-constrained model. The iterative calibration for k cat was carried out utilizing two methods outlined in ECMpy [17]: the enzyme usage method and the 13 C flux consistency method, relying on measured 13 C flux data [33].…”

Construction of an enzyme-constrained metabolic network model for Myceliophthora thermophila using machine learning-based kcat data

“…In detail, biomass components were adjusted based on experimental data (Additional le 1: Table S1). Precise corrections were applied to RNA, DNA, protein and amino acid content [32], according to measured data. Subsequently, the content of lipids and cell wall was adjusted according to literatures [33] and [29], respectively.…”

“…To enhance the alignment between model predictions and experimental data, additional ne-tuning of the original k cat values was necessary for the enzyme-constrained model. The iterative calibration for k cat was carried out utilizing two methods outlined in ECMpy [17]: the enzyme usage method and the 13 C ux consistency method, relying on measured 13 C ux data [32].…”