Inactivation Mechanism of Aspergillus flavus Conidia by High Hydrostatic Pressure

This study investigated the inactivation mechanism of Aspergillus flavus conidia by high hydrostatic pressure (HHP). Activity counts, scanning electron microscopic (SEM) analysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to study the effects of the HHP treatment on the morphology and protein composition of A. flavus spores. The results showed that that a 3-min-lasting 600 MPa treatment could completely abolish 107 colony-forming units/mL of live fungi. Furthermore, we also observed that lower spore viability corresponded to a higher Propidium Iodide absorption rate. The SEM images revealed that HHP disrupted the spore morphology and resulted in pore formation that led to the release of intracellular molecules, such as nucleic acids and proteins. The nucleic acid and protein concentration in the spore suspension increased in parallel with the increasing treatment pressure. The SDS-PAGE analysis showed that there were differences in the protein bands between the HHP-treated and untreated A. flavus spores, as the HHP treatment caused partial protein degradation and extracellular release. Therefore, the results of this study proved that high pressure could induce a morphological disruption in the internal and external cellular structures and degrade intracellular and extracellular proteins leading to an inactive state in A. flavus.