ORIGIN OF ENZYMES INVOLVED IN DETOXIFICATION AND ROOT SOFTENING DURING CASSAVA RETTING

The origin of root softening during cassava retting was investigated i n a natural retting and in a sterile fermentation. Softening only occu rred in the natural retting. Although high activities of endogenous pe ctin methyl esterase were found in cassava extracts from both fermenta tions, the depolymerizing enzymes polygalacturonase, active at low pH, and pedate lyase were only found in the non-sterile retting. No cellu lase or xylanase activity was observed. The role of pectinases in the softening of cassava roots was confirmed in vitro using commercial enz ymes. Root softening is therefore due to the combined action of endoge nous pectin methyl esterase and exogenous bacterial depolymerizing enz ymes. Detoxification occurred in both fermentations, confirming that t he linamarase responsible for the destruction of cassava cyanide glyco sides was mainly endogenous, even though microbial beta-glucosidases m ay help in the detoxication.