Profile of hydrolases and biogas production during two-stage mesophilic anaerobic digestion of solid potato waste

Two two-stage systems, one consisting of a solid-bed reactor for hydrolysis/acidification connected to an upflow anaerobic sludge blanket methanogenic reactor, and the other consisting of a solid-bed reactor connected to a methanogenic reactor packed with wheat straw biofilm carriers, were investigated with regard to hydrolytic enzymes and methane production during mesophilic anaerobic digestion of solid potato waste. Some of the enzymes used by microorganisms to degrade the potato were found to be amylase, carboxymethyl cellulase, filter paper cellulase, xylanase, pectinase and protease. Both free and cell-bound enzyme activities were measured. The activity of the free enzyme was higher than that of the cell-bound for all the enzymes. The amylase activity was highest, followed by carboxymethyl cellulase and filter paper cellulase, while the other hydrolytic enzymes had low activities. The methane yield (0.39 m3/kg VSadded) and the cumulative methane production was the same in both systems. The system with packed straw bed degraded the organic matter faster than the system with the UASB methanogenic reactor.