HYDROLYSIS OF ALPHA(1-4) GLUCAN BONDS IN ACTIVATED-SLUDGE MIXED BACTERIAL COMMUNITIES

Hydrolytic processes acting on macromolecular carbohydrates in municipal wastewater treatment involve a number of extracellular enzymes. An assay was developed for determination of the hydrolysis rate of alpha(1-4) glucan bonds in activated sludge, using p-nitrophenyl alpha-D-glucopyranoside (PNPG) as model substrate. Batch experiments using activated sludge from a full-scale system demonstrated that: (1) changing oxygen tension and/or alternate electron acceptors influenced the hydrolysis rate significantly; (2) the hydrolysis rate was depressed in the presence of high concentrations of soluble substrate (glucose > 1000 mg L-1); (3) the enzymes are associated with the solid phase, and no enzymatic activity was observed in the bulk solution; (4) the specific hydrolysis rate in samples drawn from an aerated batch of activated sludge over a period of four days exhibited an exponential decrease with time - the rate of decrease paralleled the rate of decrease in oxygen utilization rate measured in the batch system.