Synergistic co-utilization of biomass-derived sugars enhances aromatic amino acid production by engineered Escherichia coli

Authors: LIU, ARREN - Arizona State University; MACHAS, MICHAEL - Arizona State University; MHATRE, APURY - Arizona State University; HAJINAJAF, NIMA - Arizona State University; SARNAIK, ADITYA - Arizona State University; Nichols, Nancy; Frazer, Sarah; WANG, XUAN - Arizona State University; VARMAN, ARUL - Arizona State University; NIELSEN, DAVID - Arizona State University

Submitted to: Biotechnology and Bioengineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2023
Publication Date: 11/5/2023
Citation: Liu, A., Machas, M., Mhatre, A., Hajinajaf, N., Sarnaik, A., Nichols, N.N., Frazer, S.E., Wang, X., Varman, A.M., Nielsen, D.R. 2023. Synergistic co-utilization of biomass-derived sugars enhances aromatic amino acid production by engineered Escherichia coli. Biotechnology and Bioengineering. https://doi.org/10.1002/bit.28585.
DOI: https://doi.org/10.1002/bit.28585

Interpretive Summary: A significant challenge in biomanufacturing continues to be efficient utilization of mixed sugars. This collaboration between ARS and academic scientists focused on co-utilizing two important sugars, glucose and xylose, for production of phenylalanine, an essential amino acid that also has applications in the personal care industry. Aromatic biochemicals in general are appealing bioproduction targets due to their potential to replace many conventional, bulk petrochemicals. This study identified a metabolic bottleneck for phenylalanine production using E. coli and developed a strategy to circumvent the bottleneck that resulted in a three-fold increase in production of phenylalanine from pure sugar mixtures and a 1.9-fold increase when authentic biomass sugars were used. These results will be of interest to scientists interested in metabolic engineering and to the biomass conversion and green chemical industries.

Technical Abstract: Efficiently co-utilizing mixed sugar feedstocks in biomanufacturing is a challenge, driving ongoing efforts to engineer microbes for improved glucose-xylose mixture conversion. This study focuses on enhancing phenylalanine production by engineering E. coli to efficiently co-utilize glucose and xylose. Flux balance analysis identified E4P flux as a bottleneck for phenylalanine production, which can be alleviated by increasing the ratio of xylose flux-to-glucose flux. Introducing a mutant copy of the xylose-specific activator into phenylalanine-overproducing E. coli NST74 relieved carbon catabolite repression and enabled efficient glucose-xylose co-utilization. Carbon contribution analysis through 13C-fingerprinting showed a higher preference for xylose in the engineered strain (NST74X), suggesting superior catabolism of xylose than that of glucose. NST74X achieved 1.76 g/L phenylalanine, a 3-fold increase over NST74, from model-sugar mixtures. When using biomass-derived sugars, NST74X produced 1.2 g/L L-phenylalanine, representing a 1.9-fold increase over NST74. Notably, the xylR* mutation increased the maximum rate of xylose consumption by 4-fold without significantly impeding the maximum rate of total sugar consumption (0.87 vs. 0.70 g/L-h). This study presents a novel strategy for enhancing phenylalanine production through the co-utilization of glucose and xylose in aerobic E. coli cultures, highlighting the synergistic benefits of substrate mixtures over single substrates when targeting specific products.