Changes in activities of cell wall degrading enzymes during fermentation of cassava (<i>Manihot esculenta</i> Crantz) with <i>citrobacter freundii</i>

Abstract

Abstract The cell wall degrading enzymes polygalacturonase (EC 3.2.1.15),pectinase (EC 3.1.1.11), cellulose (EC 3.2.1.4) and xylanase (EC 3.2.1.8), as well as α‐amylase (EC 3.2.1.1) and phosphorylase (EC 2.4.1.1), were monitored during fermentation of cassava (Manihot esculenta Crantz) with Citrobacter freundii. All the enzymes were detected in cassava at the start. During fermentation, initial decreases in polygalacturonase, cellulase and xylanase were followed by increases which peaked as the tissue softened. There were significant (P&lt;0.05) increases in pectinase, xylanase, cellulase, polygalacturonase and phosphorylase in inoculated cassava and the fermentation medium relative to controls (uninoculated cassava and medium) during the softening period. The control cassava did not ferment, indicating that the textural changes in inoculated cassava were due to enzymes secreted by C freundii. Studies on the effect of enzyme inhibition on fermentation showed that the pectic enzymes and cellulase were of primary importance and that inhibition of α‐amylase and phosphorylase had no effect on the process.