Microbial mineralization of diisopropanolamine

Diisopropanolamine (DIPA) is a "sweetening agent" used to remove hydrogen s ulfide from sour natural gas, and it is a contaminant at some sour gas trea tment facilities in western Canada. To investigate the biodegradation of th is alkanolamine, C-14-DIPA was used in anaerobic and aerobic mineralization studies. Between 3 and 78% of the radioactivity from this compound was rel eased as (CO2)-C-14 in sediment-enrichment cultures incubated under nitrate -reducing conditions. Similarly, 12-78% of the label was converted to (CO2) -C-14 in sediment-enrichment cultures incubated under Mn(IV)-reducing condi tions. These activities were observed at 8 degrees C, a typical groundwater temperature in western Canada, and at 28 degrees C. In contrast, DIPA-degr ading activity was difficult to sustain under Fe(III)-reducing conditions, and <25% of the radioactive label from C-14-DIPA was liberated as (CO2)-C-1 4. TWO mixed cultures and two isolates (both irregular, non-sporeforming, G ram-positive rods) were used to assess aerobic mineralization of C-14-DIPA. The aerobic mixed cultures released 73 and 79% of the radioactive label as (CO2)-C-14, whereas the pure cultures liberated only 39 and 47% as (CO2)-C -14. Between one-third and one-half of the nitrogen from DIPA was found as ammonium-N in aerobic batch cultures. These results clearly demonstrate tha t DIPA is mineralized under a variety of incubation conditions.