Biology subjects

Thusoo, E.

Publications and source records attributed to Thusoo, E..

3 recordsLinked to original sources

bioRxiv2026

Engineered Pseudomonas putida reconfigures metabolic fluxes to support energy demands during muconate bioproduction from lignin-related aromatics

Muconic acid is a versatile platform chemical that can be biologically produced from lignocellulosic substrates, including from lignin-related aromatic compounds. Pseudomonas putida has been previously engineered to convert lignin-related aromatic compounds to muconate at quantitative molar yields. This high atom efficiency requires a supplemental carbon and energy source to support bacterial growth, and central carbon metabolic efficiency and its interaction with aromatic catabolism are underexplored. Here, we applied proteomics, metabolomics, and 13C-fluxomics to quantitatively compare central carbon and energy metabolism in wild-type P. putida KT2440 and a muconate-producing strain, P. putida CJ781. During cultivation on glucose and 4-hydroxybenzoate, CJ781 showed increased glucose uptake, reconfigured central fluxes, and increased extracellular leakage of aliphatic acids relative to wild type. These altered fluxes supported a 3-fold higher ATP pool, in excess of demand. Pyruvate and acetate secretion in CJ781 was mitigated by debottlenecking TCA-cycle entry via citrate synthase overexpression. Furthermore, tuned expression of the catechol dioxygenase and protocatechuate decarboxylase enabled the production of 36.3 g L-1 muconate at 1.1 g L-1 h-1. Overall, this work reveals how P. putida redirects carbon and energy fluxes to support aromatic bioconversion for improved bioproduction from renewable feedstocks.

synthetic biology↗

bioRxiv2025

Metabolic imbalance limits fermentation in microbes engineered for high-titer ethanol production

Microbial strains engineered for high-titer ethanol production achieve lower maximum titers compared to native producers such as Zymomonas mobilis. A central unresolved question is why fermentation ceases before substrate has been exhausted by these strains. Here, we integrate metabolite profiling with thermodynamic analysis to examine this phenomenon in engineered strains of Escherichia coli and Thermoanaerobacterium saccharolyticum and compare them to Z. mobilis, a native ethanol producer. In the engineered strains, fermentation cessation coincided with marked pyruvate accumulation, due to a lack of ability to convert pyruvate to ethanol. This resulted in a local thermodynamic equilibrium at the pyruvate kinase reaction, as determined by Max-Min Driving Force (MDF) analysis. Relaxing constraints on pyruvate and related metabolites restored positive MDF values, implicating thermodynamic limitations as the underlying constraint. By contrast, Z. mobilis maintained a positive thermodynamic driving force throughout fermentation, suggesting that product titer is limited by a different mechanism in this organism. These findings establish a systems-level framework linking metabolite concentrations to pathway thermodynamics and highlight opportunities for improving microbial performance in ethanol and other bioproduction contexts.

systems biology↗

bioRxiv2025

Thermodynamics shape the in vivo enzyme burden of glycolytic pathways

Thermodynamically constrained reactions and pathways are hypothesized to impose greater protein demands on cells, requiring higher enzyme amounts to sustain a given flux compared to those with stronger thermodynamics. To test this, we quantified the absolute concentrations of glycolytic enzymes in three bacterial species --Zymomonas mobilis, Escherichia coli, and Clostridium thermocellum-- which employ distinct glycolytic pathways with varying thermodynamic driving forces. By integrating enzyme concentration data with corresponding in vivo metabolic fluxes and{Delta} G measurements, we found that the highly favorable Entner-Doudoroff (ED) pathway in Z. mobilis requires only one-fourth the amount of enzymatic protein to sustain the same flux as the thermodynamically constrained pyrophosphate-dependent glycolytic pathway in C. thermocellum, with the Embden-Meyerhof-Parnas (EMP) pathway in E. coli exhibiting intermediate thermodynamic favorability and enzyme demand. Across all three pathways, early reactions with stronger thermodynamic driving forces generally required lower enzyme investment than later, less favorable steps. Additionally, reflecting differences in glycolytic strategies, the highly reversible ethanol fermentation pathway in C. thermocellum requires 10-fold more protein to maintain the same flux as the irreversible, forward-driven ethanol fermentation pathway in Z. mobilis. Thus, thermodynamic driving forces constitute a major in vivo determinant of the enzyme burden in metabolic pathways.

systems biology↗