Effects of elevated temperature on bacterial community structure and function in bioreactors treating a synthetic wastewater

The impact of elevated temperature on bacterial community structure and function during aerobic biological wastewater treatment was investigated. Continuous cultures, fed a complex growth medium containing gelatin and alpha-lactose as the principal carbon and energy sources, supported mixed bacterial consortia at temperatures ranging from 25-65 degrees C. These temperature- and substrate-acclimated organisms were then used as inocula for batch growth experiments in which the kinetics of microbial growth and substrate utilization, efficiency of substrate removal, and mechanism of substrate removal were compared as functions of temperature. Bacterial community analysis by denaturing gradient gel electrophoresis (DGGE) revealed that distinct bacterial consortia were supported at each temperature. The efficiency of substrate removal declined at elevated temperatures. Maximum specific growth rates and the growth yield increased with temperature from 25-45 degrees C, but then decreased with further elevations in temperature. Thus, maximum specific substrate utilization rates did not vary significantly over the 40 degrees C temperature range (0.64 +/- 0.04 mg COD mg(-1) dry cell mass h(-1)). A comparison of the degradation of the protein and carbohydrate portions of the feed medium revealed a lag in alpha-lactose uptake at 55 degrees C, whereas both components were utilized simultaneously at 25 degrees C.