Secondary growth is a common post-harvest
problem when pre-infected crops are attacked by filamentous
fungi during storage or processing. Several antifungal
approaches are thus pursued based on chemical, physical,
or bio-control treatments; however, many of these methods
are inefficient, affect product quality, or cause severe side
effects on the environment. A protein that can potentially
overcome these limitations is the antifungal protein AFP, an
abundantly secreted peptide of the filamentous fungus
Aspergillus giganteus. This protein specifically and at low
concentrations disturbs the integrity of fungal cell walls and
plasma membranes but does not interfere with the viability
of other pro- and eukaryotic systems. We thus studied in
this work the applicability of AFP to efficiently prevent
secondary growth of filamentous fungi on food stuff and
chose, as a case study, the malting process where naturally
infested raw barley is often to be used as starting material.
Malting was performed under lab scale conditions as well
as in a pilot plant, and AFP was applied at different steps
during the process. AFP appeared to be very efficient
against the main fungal contaminants, mainly belonging to
the genus Fusarium. Fungal growth was completely
blocked after the addition of AFP, a result that was not
observed for traditional disinfectants such as ozone,
hydrogen peroxide, and chlorine dioxide. We furthermore
detected reduced levels of the mycotoxin deoxynivalenol
after AFP treatment, further supporting the fungicidal
activity of the protein. As AFP treatments did not
compromise any properties and qualities of the final
products malt and wort, we consider the protein as an
excellent biological alternative to combat secondary growth
of filamentous fungi on food stuff. |
