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Penicillium roqueforti s.l. : growth and roquefortine C production in silages

Eva Wambacq (UGent)
(2017)
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Abstract
On Belgian farms, visible fungal growth is regularly encountered in ensiled feed commodities. The toxigenic fungal species Penicillium roqueforti sensu strictu (s.s.) and P. paneum, designated together as P. roqueforti sensu lato (s.l.) in this dissertation, are the most frequently isolated fungi in silages. Since the inhalation of fungal spores as well as the consumption of mycotoxin contaminated feed comprise serious health risks, it is of the outmost importance to prevent fungal contamination of silages. In this dissertation, general preventory measures are described. The final goal of this PhD research was to contribute to the prevention of specifically P. roqueforti s.l. development in silage. To achieve this goal, multiple in vitro lab experiments and in vivo trials with microsilos have been conducted, evaluating the effect of several abiotic and biotic factors on P. roqueforti s.l. growth and mycotoxin production. Roquefortine C, a mycotoxin that can be produced by both P. roqueforti s.s. and P. paneum, is considered to be an indicator of mycotoxin production by P. roqueforti s.l. in silages. Therefore, this particular mycotoxin has been determined to evaluate mycotoxin production. During the ensiling process, lactic acid bacteria convert sugars to mainly lactic acid, but also some acetic acid, methanol, ethanol, etc. These compounds can be used by P. roqueforti s.l. as a carbon source. Lactic acid as sole carbon source was not very conducive for fungal growth, while acetic acid (inhibiting aerobic deterioration and subsequent fungal development in silages) as sole carbon source facilitated good fungal growth. This illustrates that P. roqueforti s.l. is very well adapted to its silage-habitat, rendering prevention difficult. The bacterium Bacillus velezensis displayed antagonistic properties towards P. roqueforti s.l. in an in vitro experiment: both culture supernatant as cell suspension reduced spore germination and spore survival and inhibited fungal growth, without triggering an increased roquefortine C production. These observations seemed promising towards the capability of B. velezensis to prevent P. roqueforti s.l. development in silages, but the applied cell suspension could not live up to the great expectations regarding antagonism in an in vivo microsilo trial. Future research is required to investigate the potential of B. velezensis as a silage additive to counter P. roqueforti s.l. in silage. Oxygen appears to play a crucial role in the development of P. roqueforti s.l.: in anaerobic conditions, no fungal growth can occur. An in vivo microsilo trial with artificially infected whole-crop maize (@ 1500 conidia per gram fresh matter) desiled after 50, 100 or 150 days demonstrated that at desiling after 50 days some P. roqueforti s.l. propagules (66 per gram verse stof) had survived, while after an ensiled period of 100 days no active P. roqueforti s.l. propagules were detected. This experiment emphasizes the importance of a sufficiently long ensiled period, during which the integrity of the silo coverage needs to be maintained. In order to prevent the development of P. roqueforti s.l. in silages, the strict application of good agricultural practices regarding ensiling and desiling, limiting air ingress into silages, is the key factor to success.
Keywords
silage, mycotoxins, Penicillium, roquefortine C

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Citation

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Chicago
Wambacq, Eva. 2017. “Penicillium Roqueforti S.l. : Growth and Roquefortine C Production in Silages”. Ghent, Belgium: Ghent University. Faculty of Bioscience Engineering.
APA
Wambacq, E. (2017). Penicillium roqueforti s.l. : growth and roquefortine C production in silages. Ghent University. Faculty of Bioscience Engineering, Ghent, Belgium.
Vancouver
1.
Wambacq E. Penicillium roqueforti s.l. : growth and roquefortine C production in silages. [Ghent, Belgium]: Ghent University. Faculty of Bioscience Engineering; 2017.
MLA
Wambacq, Eva. “Penicillium Roqueforti S.l. : Growth and Roquefortine C Production in Silages.” 2017 : n. pag. Print.
@phdthesis{8536374,
  abstract     = {On Belgian farms, visible fungal growth is regularly encountered in ensiled feed commodities. The toxigenic fungal species Penicillium roqueforti sensu strictu (s.s.) and P. paneum, designated together as P. roqueforti sensu lato (s.l.) in this dissertation, are the most frequently isolated fungi in silages. Since the inhalation of fungal spores as well as the consumption of mycotoxin contaminated feed comprise serious health risks, it is of the outmost importance to prevent fungal contamination of silages. In this dissertation, general preventory measures are described. The final goal of this PhD research was to contribute to the prevention of specifically P. roqueforti s.l. development in silage. To achieve this goal, multiple in vitro lab experiments and in vivo trials with microsilos have been conducted, evaluating the effect of several abiotic and biotic factors on P. roqueforti s.l. growth and mycotoxin production. Roquefortine C, a mycotoxin that can be produced by both P. roqueforti s.s. and P. paneum, is considered to be an indicator of mycotoxin production by P. roqueforti s.l. in silages. Therefore, this particular mycotoxin has been determined to evaluate mycotoxin production.
During the ensiling process, lactic acid bacteria convert sugars to mainly lactic acid, but also some acetic acid, methanol, ethanol, etc. These compounds can be used by P. roqueforti s.l. as a carbon source. Lactic acid as sole carbon source was not very conducive for fungal growth, while acetic acid (inhibiting aerobic deterioration and subsequent fungal development in silages) as sole carbon source facilitated good fungal growth. This illustrates that P. roqueforti s.l. is very well adapted to its silage-habitat, rendering prevention difficult.
The bacterium Bacillus velezensis displayed antagonistic properties towards P. roqueforti s.l. in an in vitro experiment: both culture supernatant as cell suspension reduced spore germination and spore survival and inhibited fungal growth, without triggering an increased roquefortine C production. These observations seemed promising towards the capability of B. velezensis to prevent P. roqueforti s.l. development in silages, but the applied cell suspension could not live up to the great expectations regarding antagonism in an in vivo microsilo trial. Future research is required to investigate the potential of B. velezensis as a silage additive to counter P. roqueforti s.l. in silage.
Oxygen appears to play a crucial role in the development of P. roqueforti s.l.: in anaerobic conditions, no fungal growth can occur. An in vivo microsilo trial with artificially infected whole-crop maize (@ 1500 conidia per gram fresh matter) desiled after 50, 100 or 150 days demonstrated that at desiling after 50 days some P. roqueforti s.l. propagules (66 per gram verse stof) had survived, while after an ensiled period of 100 days no active P. roqueforti s.l. propagules were detected. This experiment emphasizes the importance of a sufficiently long ensiled period, during which the integrity of the silo coverage needs to be maintained. In order to prevent the development of P. roqueforti s.l. in silages, the strict application of good agricultural practices regarding ensiling and desiling, limiting air ingress into silages, is the key factor to success.},
  author       = {Wambacq, Eva},
  isbn         = {9789463570466},
  keyword      = {silage,mycotoxins,Penicillium,roquefortine C},
  language     = {eng},
  pages        = {IX, 262},
  publisher    = {Ghent University. Faculty of Bioscience Engineering},
  school       = {Ghent University},
  title        = {Penicillium roqueforti s.l. : growth and roquefortine C production in silages},
  year         = {2017},
}