Monitoring the Effects of Sodium Lactate Amendment for Enhancing Bioremediation of TCE.

Overview

• Location with TCE contamination.

• A baseline sampling event was done to characterize the microbial community prior to the injection of sodium lactate.

• Sodium lactate was added as a substrate for fermentation to "push" conditions to be more anaerobic.

• Samples were taken 6 months after the addition of sodium lactate to characterize the changes in the microbial comunity.

Question

What was the effect within the microbial community when sodium lactate is added as a substrate?
 
Analyses Requested:
           
            PLFA

Results:

• PLFA analysis showed that biomass content increased approximately 1 order of magnitude in locations receiving lactate, and remained static in MW-11, which did not receive lactate.

• PLFA profiles showed that both areas which received sodium lacate had a marked increase in the proportion of Firmicutes, which include Clostridia-like fermenting bacteria. This suggests that the lactate provided easily used substrate for fermentation, resulting in shift in the community towards a more anaerobic population in which fermenting bacteria were dominant members of the community.

• The microbial community in MW-11, which did not receive lactate, remained primarily composed of Gram negative Proteobacteria, suggesting more aerobic conditions at this location.

• Metabolic status ratios indicated that at all sampling locatins, the Gram negative population was growing at a slower rate at 6 months as copared to the baseline event.  This suggests that at MW-11, substrate may be a limiting factor since overall biomass also did not increase. At locations MW-2 and MW-3, where biomass increased, the slower growth rate of the Gram negative population may be due to utilization of resources by Firmicutes.

Answer:

Results from the PLFA analysis showed that the sodium lactate amendments stimulated both overall biomass and a shift in the microbial community towards a more anaerobic population with comparativley high proportions of Firmicutes.