High-Titer Glutamic Acid Production from Lignocellulose Using an Engineered Corynebacterium glutamicum with Simultaneous Co-utilization of Xylose and Glucose

Abstract

Xylose utilization by Corynebacterium glutamicum is an essential but unresolved issue in glutamic acid production from lignocellulose biomass. Coexistence of xylose with inhibitors requires a selective removal of inhibitors while the xylose is still well retained in the pretreated lignocellulose feedstock. Not only is xylose assimilation in C. glutamicum at low efficiency, but also there are unique challenges, which eliminate the generation of glutamic acid from xylose when lignocellulose is used. There include excessive biotin content in lignocellulose blocking intracellular secretion of glutamic acid, complicated organic acid generation pathways decreasing the glutamic acid conversion yield from xylose, and transmembrane resistance of xylose limiting the xylose utilization efficiency. Here, we applied a unique biodetoxification on pretreated wheat straw solids, which resulted in a complete removal of inhibitors and a high conservation of xylose sugar. The major focus of the study is a stepwise metabolic engineering of C. glutamicum to trigger high-titer glutamate production by coordinated assimilation of xylose and glucose from a typical lignocellulosic sugar. First, the secretion channel protein MscCG was modified to initiate glutamic acid secretion in biotin-rich environments from almost zero glutamic acid accumulation. Next, the byproduct generation pathways of lactate, acetate, and succinate were knocked out or attenuated to redirect carbon flux to glutamic acid accumulation. Further overexpression of the pentose transporter gene araE increased the xylose utilization rate and glutamic acid production. The finally obtained C. glutamicum GJ04 produced 39.8 g/L of glutamate from 60.3 g/L of glucose and 38.8 g/L of xylose in synthetic medium and produced 61.7 g/L of glutamate from 116.1 g/L of glucose and 39.6 g/L of xylose using wheat straw feedstock. This is the first example of the practical utilization of lignocellulose-derived xylose and glucose for cellulosic glutamic acid production.

Self-generated peroxyacetic acid in phosphoric acid plus hydrogen peroxide pretreatment mediated lignocellulose deconstruction and delignification

“…Then H 2 O 2 in PHP solvent system reacted with acetic acid in acidic environment to form peroxyacetic acid, which initiated the selective lignin oxidation and degradation. Peroxyacetic acid then oxidized xylose and lignin to produce more acetic acid [ 48 ], which consequently boosted the peroxyacetic acid formation and biomass deconstruction. Due to the continuous production of peroxyacetic acid, the cyclic synergistic effect of PHP pretreatment was continuously increasing.…”

Coculture of Gluconobacter oxydans and Escherichia coli for 3,4-Dihydroxybutyric Acid Production from Xylose

“…Successive metabolic engineering related to the glyoxylate shunt was performed with the use of glucose as the sole feedstock − Via a nonphosphorylative xylose metabolic pathway in E. coli , , 3,4-DHBA at a concentration of 1.27 g/L was produced from 20 g/L xylose in 51 h …”

Utilization of a Wheat Sidestream for 5-Aminovalerate Production in Corynebacterium glutamicum

“…In recent years, the model organism C. glutamicum was extensively engineered to broaden its substrate spectrum according to the flexible feedstock concept ( Wendisch et al, 2016 ). Thereby, access to the lignocellulosic pentoses arabinose ( Kawaguchi et al, 2008 ; Schneider et al, 2011 ; Meiswinkel et al, 2013 ) and xylose ( Kawaguchi et al, 2006 ; Jin et al, 2020 ) for growth and production of amino acids was enabled. Recently, it could also be demonstrated that production of sarcosine from the pentose xylose was more efficient than that from glucose ( Mindt et al, 2019b ).…”