TY - JOUR
T1 - The preservative propionic acid differentially affects survival of conidia and germ tubes of feed spoilage fungi
AU - Dijksterhuis, Jan
AU - Meijer, Martin
AU - van Doorn, Tineke
AU - Houbraken, Jos
AU - Bruinenberg, Paul
N1 - Copyright © 2019. Published by Elsevier B.V.
PY - 2019/10/2
Y1 - 2019/10/2
N2 - Propionic acid is widely used as a preservative in (poultry) feed. In this study we have isolated and identified fungal strains from nine samples poultry feed originating from different countries. The majority of the strains were Aspergilli with a eurotium-morph, such as Aspergillus proliferans and A. chevalieri. These and three other species were selected and tested for their sensitivity towards the feed preservative propionic acid, among them Penicillium lanosocoeruleum. The determined MIC values of 6.1-31 mM of these poultry feed specific fungi were well in the range as described in literature. Propionic acid (at 31 mM) damages conidia (spores) in a species dependent fashion after a 24-hour-treatment. The majority of the conidia (over 70%) of P. lanosocoeruleum germinated within 60 h on agar medium, while 50 and 80% of the A. chevalieri and A. proliferans conidia did not, respectively. Dependent on the species, cell damage was visible after incubation with propionic acid. Germ tubes of P. lanosocoeruleum in a biofilm showed extensive (85%) cell death after a 30 min treatment with propionic acid and slightly lower sensitivity was observed with A. proliferans (62% cell death). Microscopic analysis of these fungal biofilms revealed extensive damage to the cell membrane and showed distorted intracellular structures. Fluorescent life-dead staining of the germ tubes showed a clear dose response of propionic acid indicating a fungicidal effect on these growing cells. These results show that conidia can be inactivated by propionic acid, but that germ tubes show a much higher sensitivity. These observations shed new light on the mode of action of this important preservative to prevent fungal contamination of feed.
AB - Propionic acid is widely used as a preservative in (poultry) feed. In this study we have isolated and identified fungal strains from nine samples poultry feed originating from different countries. The majority of the strains were Aspergilli with a eurotium-morph, such as Aspergillus proliferans and A. chevalieri. These and three other species were selected and tested for their sensitivity towards the feed preservative propionic acid, among them Penicillium lanosocoeruleum. The determined MIC values of 6.1-31 mM of these poultry feed specific fungi were well in the range as described in literature. Propionic acid (at 31 mM) damages conidia (spores) in a species dependent fashion after a 24-hour-treatment. The majority of the conidia (over 70%) of P. lanosocoeruleum germinated within 60 h on agar medium, while 50 and 80% of the A. chevalieri and A. proliferans conidia did not, respectively. Dependent on the species, cell damage was visible after incubation with propionic acid. Germ tubes of P. lanosocoeruleum in a biofilm showed extensive (85%) cell death after a 30 min treatment with propionic acid and slightly lower sensitivity was observed with A. proliferans (62% cell death). Microscopic analysis of these fungal biofilms revealed extensive damage to the cell membrane and showed distorted intracellular structures. Fluorescent life-dead staining of the germ tubes showed a clear dose response of propionic acid indicating a fungicidal effect on these growing cells. These results show that conidia can be inactivated by propionic acid, but that germ tubes show a much higher sensitivity. These observations shed new light on the mode of action of this important preservative to prevent fungal contamination of feed.
KW - Animal Feed/microbiology
KW - Animals
KW - Aspergillus/classification
KW - Biofilms/drug effects
KW - Culture Media/pharmacology
KW - Eurotium
KW - Food Microbiology/methods
KW - Fungicides, Industrial/pharmacology
KW - Microbial Sensitivity Tests
KW - Penicillium/classification
KW - Poultry
KW - Propionates/pharmacology
KW - Spores, Fungal/drug effects
U2 - 10.1016/j.ijfoodmicro.2019.108258
DO - 10.1016/j.ijfoodmicro.2019.108258
M3 - Article
C2 - 31362161
SN - 0168-1605
VL - 306
SP - 108258
JO - International Journal of Food Microbiology
JF - International Journal of Food Microbiology
ER -