Elevated, non-proliferative temperatures change the profile of fermentation products in Corynebacterium glutamicum

Although temperature is a crucial factor affecting enzymatic activity on biochemical and biofuel production, the reaction temperature for the generation of these products is usually set at the optimal growth temperature of the host strain, even under non-proliferative conditions. Given that the production of fermentation products only requires a fraction of the cell's metabolic pathways, the optimal temperatures for microbial growth and the fermentative production of a target compound may be different. Here, we investigated the effect of temperature on lactic and succinic acids production, and related enzymatic activities, in wild-type and succinic acid-overproducing strains of Corynebacterium glutamicum. Interestingly, fermentative production of lactic acid increased with the temperature in wild-type: production was 69% higher at 42.5 °C, a temperature that exceeded the upper limit for growth, than that at the optimal growth temperature (30 °C). Conversely, succinic acid production was decreased by 13% under the same conditions in wild-type. The specific activity of phosphoenolpyruvate carboxylase decreased with the increase in temperature. In contrast, the other glycolytic and reductive TCA cycle enzymes demonstrated increased or constant activity as the temperature was increased. When using a succinic acid over-producing strain, succinic acid production was increased by 34% at 42.5 °C. Our findings demonstrate that the profile of fermentation products is dependent upon temperature, which could be caused by the modulation of enzymatic activities. Moreover, we report that elevated temperatures, exceeding the upper limit for cell growth, can be used to increase the production of target compounds in C. glutamicum. KEY POINTS: • Lactate productivity was increased by temperature elevation. • Succinate productivity was increased by temperature elevation when lactate pathway was deleted. • Specific activity of phosphoenolpyruvate carboxylase was decreased by temperature elevation.