Overproduction of L‐tryptophan via simultaneous feed of glucose and anthranilic acid from recombinant Escherichia coli W3110: Kinetic modeling and process scale‐up

Abstract

L-tryptophan is an essential amino acid widely used in food and pharmaceutical industries. However, its production via Escherichia coli fermentation suffers severely from both low glucose conversion efficiency and acetic acid inhibition, and to date effective process control methods have rarely been explored to facilitate its industrial scale production. To resolve these challenges, in the current research an engineered strain of E. coli was used to overproduce L-tryptophan. To achieve this, a novel dynamic control strategy which incorporates an optimized anthranilic acid feeding into a dissolved oxygen-stat (DO-stat) glucose feeding framework was proposed for the first time. Three original contributions were observed. Firstly, compared to previous DO control methods, the current strategy was able to inhibit completely the production of acetic acid, and its glucose to L-tryptophan yield reached 0.211 g/g, 62.3% higher than the previously reported. Secondly, a rigorous kinetic model was constructed to simulate the underlying biochemical process and identify the effect of anthranilic acid on both glucose conversion and L-tryptophan synthesis. Finally, a thorough investigation was conducted to testify the capability of both the kinetic model and the novel control strategy for process scale-up. It was found that the model possesses great predictive power, and the presented strategy achieved the highest glucose to L-tryptophan yield (0.224 g/g) ever reported in large scale processes, which approaches the theoretical maximum yield of 0.227 g/g. This research, therefore, paves the way to significantly enhance the profitability of the investigated bioprocess.

Application of fermentation process control to increase l‐tryptophan production in Escherichia coli

“…The transcriptional levels of genes required for gluconeogenesis ( pck A, pps A) and the PP pathway ( pgdh D1, ybh E, and ara D) increased with higher DO level . Furthermore, the higher transcriptional levels of pps A and tkt A increased the supply of PEP and E4P, and higher transcriptional levels of genes ( aro G, aro K, and trp EDBA) increased biosynthesis l ‐tryptophan . At high DO levels, the high transcriptional rates of genes required for gluconeogenesis increased the conversion of pyruvate to glucose and reduced the concentrations of pyruvate and acetate, leading to increased conversion efficiency of glucose …”

“…Due to its commercial importance, there is increasing interest in improving the production of l ‐tryptophan . l ‐tryptophan produced by direct fermentation can be increased by genetic modification of strains and optimization of culture parameters . In our previous study, a recombinant strain of Escherichia coli D mtr / pta ‐Y was constructed from E. coli TRTH0709/pMEL03 by deletion of pta ‐ mtr and overexpression of ydd G to produce a high level of l ‐tryptophan .…”

Hybrid physics‐based and data‐driven modeling for bioprocess online simulation and optimization

“…With the rapid development of digital computing technologies, industrially focused mathematical modeling tools have been extensively applied to chemical engineering systems for process simulation, optimization, control, and design (Marchetti, François, Faulwasser, & Bonvin, ; Voll & Marquardt, ; Zhang, del Rio‐Chanona, & Shah, ). Strong global demand for innovative biotechnologies to sustainably produce energy, food, pharmaceuticals, and platform chemicals (Harun et al, ; Jeandet, Vasserot, Chastang, & Courot, ; Jing et al, ) has opened up great opportunities for computer‐aided technologies in various bio‐production industries, for example, fermentation and photo‐production (Jing et al, ; Wagner, Lee‐Lane, Monaghan, Sharifzadeh, & Hellgardt, ). As most bioprocesses rely on microorganisms to synthesize the desired products, the simulation of the complex microbial activities has become a critical task, requiring the use of state‐of‐the‐art process systems engineering tools for bioprocess optimization and scale‐up.…”

Comparison of physics‐based and data‐driven modelling techniques for dynamic optimisation of fed‐batch bioprocesses

“…Microbe‐based biosynthetic systems are a central feature of most industrial bioprocesses. For instance, bacteria and yeasts have been utilised extensively to yield a large variety of commercial products ranging from fuels and platform chemicals to pharmaceuticals (Bankar, Dhumal, Bhotmange, Bhagwat, & Singhal, ; Jing et al, ). Recently, attention has increasingly shifted towards microalgae and cyanobacteria to produce renewable biofuels and sustainable high‐value products (Harun et al, ; Zhang & Vassiliadis, ).…”