Under oxygen deprivation, C. glutamicum cell growth is arrested, but the cells retain the capability to produce organic acids, such as L-lactate, succinate and acetate, from glucose in mineral salts medium. In our laboratory, the ability to produce organic acids has been improved by metabolism engineering more, and we perform to produce organic acids with mixed sugar derived from lignocellulosic biomass.

Lactic acid

Lactic acid and its derivative sodium lactate are widely used in food, cosmetic, pharmaceutical industries. Increased environmental awareness has brought lactic acid into focus as a building block of the biodegradable plastic, polylactic acid (PLA). PLA is polymerized from optically pure lactic acid and has good processability, stiffness, and clarity. Stereocomplexed polylactic acid, a mixture of the same amount of poly-L-lactic acid and poly-D-lactic acid, is an improvement on PLA that has properties comparable to those of petroleum-based polymers. Although the microbial production of L-lactic acid is well advanced because of the chemical's current demand as a food additive, there are relatively few studies on D-lactic acid production. In our laboratory, the construction of a high D-lactic acid producing strain and producing D-lactate from mixed sugar derived from corn stover was succeeded.

Succinic acid

Succinic acid may be of interest as a key building block for deriving various commodity chemicals including 1,4-butanediol, adipic acid and tetrahydrofuran as well as biodegradable polymers such as polybutylene succinate and polybutylene succinate adipate. It is currently primarily produced from fossil fuels by a chemical synthetic process, which comes at a high environmental cost, particularly in the form of higher CO₂ emission. As environmental awareness increases, biological processes for succinic acid production may become both more economical and acceptable.