Carbon addition reduced lag time for 2,4,6-trichlorophenol degradation

The effect of grass root exudates and glucose on the lag time associated with 2,4,6-trichlorophenol (TCP) degradation by an unacclimated microbial inoculant and an acclimated microbial inoculant was investigated. The experimental medium was a nutrient solution containing TCP spiked with radiolabeled TCP and amended with either glucose or root exudates collected from fescue grass. Treatments containing TCP as the sole organic carbon source served as biotic controls. The acclimated microbial inoculant was not provided with TCP for 4 weeks prior to the experiment. The presence of an alternate organic carbon source reduced lag time for both the acclimated microbial inoculant and the unacclimated microbial inoculant. For the latter, three ratios of alternate organic carbon content to inoculant biomass were tested. The lag time for acclimation depended on this ratio. A lag time in excess of 11 days was observed for the biotic controls. The shortest lag time with the addition of an alternate organic carbon source was between 2 and 4 days for glucose and between 5 and 9 days for root exudates. It is proposed that the presence of a readily available, alternate organic carbon source affected lag time through promotion of microbial population growth and provision of a preferred source of carbon and energy.