Characteristics of cured and wild strains of Enterobacter cloacae IIT-BT 08 for the improvement of biohydrogen production

Enterobacter cloacae IIT-BT 08 was found to harbor multiple endogenous plasmids. The plasmids were successfully cured by the combined action of SDS and mitomycin C. The cured strain exhibited an altered pattern of antibiotic and metal resistance. The effect of plasmid curing on biohydrogen production was determined. LP model showed that hydrogen was a growth associated product for both the wild type and the cured strain. However, modified Gompertz equation showed that the productivity of the cured strain was comparable to the wild type. Further, comparative kinetic parameter analysis showed that the maximum specific growth rate (μmax) and saturation constant (Ks) were 1.26 and 2.2 times higher respectively, for the cured strain as compared to the wild type. Similarly, maintenance coefficient (m) was determined to be function of fermentation time and was lower for the cured strain. This was related to the decrease in plasmid load in the cured strain.