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 fun ction during aerobic biological wastewater treatment was investigated. Cont inuous cultures, fed a complex growth medium containing gelatin and alpha-l actose as the principal carbon and energy sources, supported mixed bacteria l consortia at temperatures ranging from 25-65 degrees C. These temperature - and substrate-acclimated organisms were then used as inocula for batch gr owth experiments in which the kinetics of microbial growth and substrate ut ilization, efficiency of substrate removal, and mechanism of substrate remo val were compared as functions of temperature. Bacterial community analysis by denaturing gradient gel electrophoresis (DGGE) revealed that distinct b acterial consortia were supported at each temperature. The efficiency of su bstrate 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 s pecific 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 portion s 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.