The biological preparation of aflatoxins was accomplished by
culturing the mold Aspergillus flavus on various media. Aflatoxin
was isolated by chloroform extraction of the culture, and purified
by column fractionation and crystallization. Rice, wheat, soya bean,
peanut and YES media were found to give high yields of aflatoxin. It
was also found that A. flavus could grow and produce toxin on fresh
tomatoes and grapes.
The pure aflatoxins B₁ and G₁ were treated separately with
standardized NaOH and NH₄OH solutions. Changes in solvent system,
exposure time and alkali concentration were found to affect the stability
of aflatoxin. Solutions of aflatoxins B₁ and G₁ in ethanol and
methanol were quite unstable when treated with strong base even
after a short exposure period. The aflatoxins were quite stable, however,
if treated in a chloroform solution at a lower base concentration.
Several crude chloroform extracts containing aflatoxins were
prepared from various culture media with different mold strains.
These extracts were then shaken gently with an equal volume of
0.25 N NaOH solution for several seconds. This treatment produced
final chloroform extracts which were lower in pigments, total
solids, and lower R [subscript f]-value compounds than similar extracts which
received no base treatment. The decolorizing ability of the alkali
treatment was demonstrated by comparison of the ultraviolet absorption
spectra of the treated samples and control samples. This base
treatment shortened the preparation time and increased the yield
of aflatoxins from crude chloroform extracts.
Photodegradation of aflatoxins B₁ and G₁ was observed in both
ethanol and chloroform solutions. After an induction period, the
aflatoxin was degraded to low R [subscript f]-value compounds, which were then
converted to non-fluorescent products. Aflatoxin G₁ was found to be
more stable than aflatoxin B₁ to light exposure. Base treatment as
described above was found suitable for purifying aflatoxin which contained
photodegraded contaminants. / Graduation date: 1967
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26795 |
| Date | 12 May 1967 |
| Creators | Chen, Tsun-Chieh |
| Contributors | Sinnhuber, Russell O. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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