Effect of temperature and water activity on the production of fumonisins by Aspergillus niger and different Fusarium species.
BACKGROUND
Fumonisins are economically important mycotoxins which until recently were considered to originate from only a few Fusarium species. However recently a putative fumonisin gene cluster was discovered in two different Aspergillus niger strains followed by detection of an actual fumonisin B2 (FB2) production in four strains of this biotechnologically important workhorse.


RESULTS
In the present study, a screening of 5 A. niger strains and 25 assumed fumonisin producing Fusarium strains from 6 species, showed that all 5 A. niger strains produced FB2 and 23 of 25 Fusarium produced fumonisin B1 and other isoforms (fumonisin B2 and B3). Five A. niger and five Fusarium spp. were incubated at six different temperatures from 15-42 degrees C on Czapek Yeast Agar +5% salt or Potato Dextrose Agar. A. niger had the highest production of FB2 at 25-30 degrees C whereas Fusarium spp. had the maximal production of FB1 and FB2 at 20-25 degrees C. Addition of 2.5-5% NaCl, or 10-20% sucrose increased the FB2 production of A. niger, whereas addition of glycerol reduced FB2 production. All three water activity lowering solutes reduced the fumonisin production of the Fusarium species.


CONCLUSIONS
The present study shows that the regulation of fumonisin production is very different in A. niger and Fusarium, and that food and feeds preserved by addition of sugar or salts may be good substrates for fumonisin B2 production by A. niger.
Mogensen
Jesper M
JM
Center for Microbial Biotechnology, Department of Systems Biology, Technical University of Denmark, Søltofts Plads 221, DK-2800 Kgs, Lyngby, Denmark. jemo@bio.dtu.dk
Nielsen
Kristian F
KF
Samson
Robert A
RA
Frisvad
Jens C
JC
Thrane
Ulf
U
D001234:Aspergillus niger / Q000254:growth & development* / Q000378:metabolism; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D037341:Fumonisins / Q000378:metabolism*; D005670:Fusarium / Q000254:growth & development* / Q000378:metabolism; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013696:Temperature; D014867:Water
D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D037341:Fumonisins; D014867:Water