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Bioproduction of [14C]ochratoxin A in submerged culture
Abstract:
A number of Aspergillus and Penicillium species were tested for production of ochratoxin A (OA) in several media. After 8 days of static incubations of submerged cultures at 28 degrees C, toxin yields of 25 and 30 micrograms/ml were obtained with Aspergillus alliaceus NRRL 4181 in Ferreirás and 2% yeast extract-4% sucrose media, respectively. However, the largest production observed in the preliminary screening was 54 micrograms/ml; this highest level was produced by A. sulphureus NRRL 4077 in a modified Czapek solution. The medium contained the basal salts and sucrose of Czapek plus urea (3%) and corn steep liquor (0.5% solids). A time study of toxin production demonstrated maximum yield of 350 micrograms/ml by the A. sulphureus isolate in the modified Czapek medium after 11 days of static incubation at 28 degrees C. The optimal production conditions were employed in additional tests designed to measure the efficiency of 14C incorporation from sodium [1-14C]-acetate into OA. Samples (20 microCi) of sodium acetate were added to separate culture flasks at 24-h intervals during the initial 9 days of the fermentation. Addition of [14C]acetate on day 4 of incubation provided the maximum yield of labeled OA. The highest specific activity of labeled toxin obtained was 0.07 microCi/mg of OA and the maximum incorporation rate of labeled acetate was 5.3%.
Insights
Aspergillus sulphureus NRRL 4077 produced the highest levels of ochratoxin A (OA), reaching 350 µg/ml in a modified Czapek medium. Optimal conditions were identified for OA production and [14C]-acetate incorporation.
Area of Science:
- Mycology
- Food Science
- Toxicology
Background:
- Ochratoxin A (OA) is a mycotoxin produced by several Aspergillus and Penicillium species.
- Understanding optimal production conditions is crucial for controlling OA contamination in food and feed.
Purpose of the Study:
- To screen Aspergillus and Penicillium species for ochratoxin A (OA) production.
- To determine optimal culture media and conditions for maximizing OA yield.
- To investigate the efficiency of [14C]-acetate incorporation into OA.
Main Methods:
- Screening of fungal isolates for OA production in various media.
- Optimization of culture conditions including medium composition, incubation time, and temperature.
- Radiolabeling studies using sodium [1-14C]-acetate to assess precursor incorporation.
Main Results:
- Aspergillus sulphureus NRRL 4077 demonstrated the highest OA yield (350 µg/ml) in a modified Czapek medium after 11 days at 28°C.
- Optimal [14C]-acetate incorporation occurred when added on day 4 of incubation.
- Maximum specific activity of labeled OA was 0.07 µCi/mg, with a 5.3% incorporation rate.
Conclusions:
- A modified Czapek medium with urea and corn steep liquor is highly effective for OA production by A. sulphureus.
- The timing of precursor addition significantly impacts labeled OA yield and specific activity.
- These findings provide valuable insights for mycotoxin research and control strategies.