Fig. 4

Batch fermentation and nitrate feeding fermentation of JHM805 strain in continuous stirred bioreactor. A Growth and D-LA production of JHM805 strain in a 5L bioreactor containing 3 L NMS medium, supplemented with 10 μg/mL kanamycin and 50 μM of IPTG. A gas mixture of 20% (v/v) of methane and 80% (v/v) of air was continuously supplied and the initial inoculation OD₆₀₀ was 0.1. Nitrate depletion coincides with the onset of D-LA production, indicating a shift in metabolic flux upon nitrogen limitation. B Growth of JHM805 in NMS media containing various concentrations of KNO₃ to evaluate the effect of nitrate availability. The initial inoculation OD₆₀₀ was 0.2 and error bars indicate the standard deviation of two independent experiments. C JHM805 fermentation in a 5-L bioreactor with modified NMS medium (6 × KNO₃) with 10 μg/mL kanamycin and 50 μM of IPTG. Nitrate was replenished before depletion to prevent nitrogen limitation and 20% (v/v) of methane and 80% (v/v) of air were continuously supplied and the initial inoculation OD₆₀₀ was 0.1. Cell growth, D-LA production, and nitrate consumption were monitored during the growth