MECHANISMS OF INCREASED LINAMARIN DEGRADATION DURING SOLID-SUBSTRATE FERMENTATION OF CASSAVA

Several fungi and bacteria, isolated from Ugandan domestic fermented c assava, released HCN from linamarin in defined growth media. In 72 h, a Bacillus sp. decreased the linamarin to 1% of initial concentrations , Mucor racemosus to 7%, Rhizopus oryzae and R. stolonifer to 30%, but Neurospora sitophila and Geotrichum candidum hardly degraded the lina marin. Adding pectolytic and cellulolytic enzymes, but not linamarase, to root pieces under aseptic conditions, led to root softening and si gnificantly lower linamarin contents. Neurospora sitophila showed no l inamarase activity, in contrast to M. racemosus and Bacillus sp., both of which were less effective in root softening and decreasing the roo t linamarin content. The most important contribution of microorganisms to linamarin decrease in the solid-substrate fermentation of cassava is their cell-wall-degrading activity, which enhances the contact betw een endogenous linamarase and linamarin.