Impact of gas–liquid mass transfer on organic acids production by Corynebacterium glutamicum in unbaffled shake flasks

• C. glutamicum can exhibit both oxidative and fermentative metabolisms.
• Experimental determination of kLa in glass shake flask with optical sensors.
• kLa influences on C. glutamicum physiological response was established.
• Growth or organic acids production is targeted through optimal kLa ranges.

Corynebacterium glutamicum is widely used for industrial production of amino acids. Recently, its ability to produce organic acids in oxygen-deprived or anaerobic conditions has also been demonstrated. In this study, the effects of oxygenation on C. glutamicum growth and organic acids production were investigated through cultures in shake flask at different kLa conditions of 0.6, 3, 11, 19, 33, 36, 48, 77, 120 and 164 h−1. These values were experimentally determined in unbaffled glass shake flasks patched with oxygen probe by using the PreSens system. The results showed that increasing kLa values systematically increased growth performance. Our study also showed kLa ranges where C. glutamicum growth was altered while organic acids production was improved. In fact, the different experiments showed that (i) kLa between 10 and 19 h−1 resulted in optimal succinic acid production (63 mM), (ii) kLa values between 19 and 33 h−1 favored high acetic acid concentrations (135 mM) and (iii) kLa values higher than 164 h−1 led to biomass accumulation.