Denitrification activity of isolate CD I-III in nitrate broth medium with carbon source variation and identification using VITEK-2

Denitrification is a reducing process of nitrate into nitrogen gases. Bacteria are able to do this process in high nitrate and low oxygen concentration. Fresh sediment from Cideng River, Jakarta, was incubated in Nitrate Broth medium then spread on Potato Dextrose Agar. Nine isolates was grown separately and inoculated in Oxidative/Fermentative medium to determine the denitrification ability. One isolate, named Isolate CD I-III, showed a positive result of denitrification activity. This isolate was inoculated in a Nitrate Broth medium with carbon source variations for 19 days to optimize its denitrification process. Parameters measured for indicating the denitrification activity were nitrate concentrations by the Spectrophotometric method and the bacterial viability by the total plate count method. This isolate was also identified by using the VITEK-2. The result revealed that glucose and glycerol as carbon source variations gave a significant difference (α = 0,05) in nitrate concentrations, whilst there was no difference in bacterial viability. The isolate CD I-III was identified by the VITEK-2 as Escherichia hermannii with 97% probability.