Role of water mobility on mold spore germination

A sugar transport defected strain of Aspergillus nidulans (biA-1 sorA-2) wa s tested for spore germination in nutrient media containing various water a ctivity (a(w)) values and varying amounts of non-nutritive, nontoxic carboh ydrates (L-sorbose and cellulose). Freeze-dried media [containing the same nutrient level but different in sorbose/cellulose (s:c) ratio] were adjuste d to 0.75-0.97a(w) at 25 degrees C before inoculation. Minimum a(w) for ger mination varied with s:c ratio. Because both sorbose and cellulose were not metabolizable and unable to be transported into the cells, the results ref lected the molecular mobility of water. H-2 NMR T-2 relaxation time correla ted well with spore germination time, and it distiguished the difference be tween water sorbed to cellulose and water in a solution associated with dis solved sorbose. On the other hand, mold germination time correlated poorly with a(w). It was highly dependent on the s:c ratio. Water mobility was fou nd to correlate better with biological activity than a, because it differen tiated the availability between water in dissolved sorbose and adsorbed wat er in cellulose.