PHYSIOLOGICAL AND BIOCHEMICAL STUDIES ON THE LONGEVITY OF ASPERGILLUS ORYZAE CONIDIA STORED UNDER VARIOUS ENVIRONMENTAL CONDITIONS

Abstract

Fresh and dry conidia of Aspergillus oryzae were examined for their longevity under various storage conditions by testing germination rate at intervals over a year.
Powdery conidia were stable for years when they were kept dry at 4°. Conidia stored in moist air (more than 70% relative humidity) survived for a few months, while those stored in moist nitrogen gas for less than a week. Washed conidia stored in water by shaking survived a little longer than powdery conidia stored in moist air.
Characteristic difference between the storage of conidia in water and in moist air was that in the former case, but not in the latter, an acceleration of germination was observed at the initial phase of storage. The acceleration seemed to be caused by the fact that germination reaction proceeds partially even in water as demonstrated by ¹⁴CO₂-incorporation into biopolymers.
Deterioration of conidia appeared to be partially dependent on the consumption of mannitol, an intracellular storage substance. Modes of deterioration processes under different storage conditions were discussed based on the observations on respiratory and biosynthetic activities of conidia.