Corynebacterium glutamicum is an important organism for industrial biotechnology; particularly, in amino acid production (e.g. L-lysine). Production scales often reach reactor working volumes of several hundred cubic meters, which triggers inhomogeneous distribution of substrates and dissolved gasses due to increasing mixing times. Individual cells which follow the flow profile through the reactor are experiencing oscillating microenvironments. Oscillations can have an influence on the process performance, which is a subject of scale-down experiments. In this work, L-lysine-producing C. glutamicum DM1933 was assessed for its robustness against continuous dissolved oxygen and substrate supply oscillation in two-compartment scale-down bioreactors. Aerobic, substrate-limited stirred tank and non-aerated, substrate-excess plug flow compartments were applied for oscillation. Inhomogeneity of substrate and oxygen supply was observed to cause rapid side product turnover, redistribution of oxygen uptake from oxygen limited into fully aerobic zones, and intermediate medium acidification. However, process inhomogeneity did not impair productivity or growth at plug flow residence times of several minutes. In a focused analysis of proteome, metabolome, transcriptome, and other physiological parameters, no changes were identified in response to process inhomogeneity. In conclusion, fed-batch processes with C. glutamicum DM1933 possess remarkable robustness against oxygen and substrate supply oscillation, which is a unique property in the field of published scale-down studies. Microbial physiology of C. glutamicum appears to be ideally adapted to both homogeneous and inhomogeneous conditions. This ensures exceptional suitability for cultivation at increased mixing times, which is suggested to constitute an important basis for the long-lasting success in large scale bioprocess application.

Corynebacterium glutamicum, a model organism in microbial biotechnology, is known to metabolize glucose under oxygendeprived conditions to L-lactate, succinate, and acetate without significant growth. This property is exploited for efficient production of lactate and succinate. Our detailed analysis revealed that marginal growth takes place under anaerobic conditions with glucose, fructose, sucrose, or ribose as a carbon and energy source but not with gluconate, pyruvate, lactate, propionate, or acetate. Supplementation of glucose minimal medium with tryptone strongly enhanced growth up to a final optical density at 600 nm (OD 600 ) of 12, whereas tryptone alone did not allow growth. Amino acids with a high ATP demand for biosynthesis and amino acids of the glutamate family were particularly important for growth stimulation, indicating ATP limitation and a restricted carbon flux into the oxidative tricarboxylic acid cycle toward 2-oxoglutarate. Anaerobic cultivation in a bioreactor with constant nitrogen flushing disclosed that CO 2 is required to achieve maximal growth and that the pH tolerance is reduced compared to that under aerobic conditions, reflecting a decreased capability for pH homeostasis. Continued growth under anaerobic conditions indicated the absence of an oxygen-requiring reaction that is essential for biomass formation. The results provide an improved understanding of the physiology of C. glutamicum under anaerobic conditions. C orynebacterium glutamicum is a Gram-positive soil bacterium belonging to the order Corynebacteriales within the Actinobacteria (1, 2). It is used for the industrial production of the bulk products L-glutamate and L-lysine (3.0 and 2.2 million tons per year, respectively) (3) and of several other amino acids with a lower market volume. C. glutamicum has become a model organism in microbial biotechnology, and it was shown that a variety of other products besides amino acids can be efficiently synthesized with strains of this species, such as organic acids, diamines, or biofuels (4-7). Therefore, C. glutamicum has become a platform organism for white biotechnology (8-11).C. glutamicum is nowadays described as a facultative anaerobic organism, based on studies showing that the type strain ATCC 13032 as well as strain R can grow under anoxic conditions when nitrate is present as terminal electron acceptor (12, 13). Negligible growth was observed in the absence of nitrate. Nitrate is reduced by the membrane-bound nitrate reductase NarGHIJ to nitrite, which accumulates in the medium under strictly anoxic conditions, as C. glutamicum does not possess a nitrite reductase (14). Due to the toxicity of nitrite (15), anaerobic growth of C. glutamicum by nitrate respiration in axenic culture is poor (12, 13). Nitrate is also reduced to nitrite under oxygen-limited conditions, but in this case nitrite can be partially metabolized again (16).Under oxygen-limited conditions in the absence of nitrate, C. glutamicum was found to convert glucose to lactate, succinate, and acetate, which ar...

Corynebacterium glutamicum is the major host for the industrial production of amino acids and has become one of the best studied model organisms in microbial biotechnology. Rational strain construction has led to an improvement of producer strains and to a variety of novel producer strains with a broad substrate and product spectrum. A key factor for the success of these approaches is detailed knowledge of transcriptional regulation in C. glutamicum. Here, we present a large compendium of 927 manually curated microarray-based transcriptional profiles for wild-type and engineered strains detecting genome-wide expression changes of the 3,047 annotated genes in response to various environmental conditions or in response to genetic modifications. The replicates within the 927 experiments were combined to 304 microarray sets ordered into six categories that were used for differential gene expression analysis. Hierarchical clustering confirmed that no outliers were present in the sets. The compendium provides a valuable resource for future fundamental and applied research with C. glutamicum and contributes to a systemic understanding of this microbial cell factory. Measurement(s) Gene Expression Analysis Technology Type(s) Two Color Microarray Factor Type(s) WT condition A vs. WT condition B • Plasmid-based gene overexpression in parental strain vs. parental strain with empty vector control • Deletion mutant vs. parental strain Sample Characteristic - Organism Corynebacterium glutamicum Sample Characteristic - Environment laboratory environment Sample Characteristic - Location Germany

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