Enhanced Production of 1,3-Propanediol in Klebsiella pneumoniae Induced by Dielectric Barrier Discharge Plasma in Atmospheric Air

Most studies concerned with the interactions between plasma discharges and bacteria have mainly focused on the germicidal effects and inactivation mechanisms, with little attention given to the survivor bioeffects, such as changes in metabolism. This paper investigated the production of 1,3-propanediol (1,3-PD) from glycerol by Klebsiella pneumoniae after exposure to dielectric barrier discharge (DBD) plasma in air at atmospheric pressure. Increase in 1,3-PD production as determined from flask culture was dependent on treatment time, and the highest production was observed for cells that were treated with DBD plasma for 4 min. Changes in the specific activities of the three key enzymes (glycerol dehydrogenase, glycerol dehydratase, and oxidoreductase) involved in the conversion of glycerol to 1,3-PD were detected in the extracts of treated cells. Increase in 1,3-PD production correlated with an increase in the activity levels of all three enzymes. Batch-fermentation results showed that DBD plasma-treated cells had a 59% increase in both 1,3-PD production (23.8 g/L versus 15 g/L) and productivity (1.19 g/L middoth versus 0.75 g/L middoth) over untreated cells. DBD plasma, therefore, can alter the metabolic activities of K. pneumoniae, resulting in enhanced production of 1,3-PD.