Thomas, B.T. and Ogunkanmi, L.A. 2014. Influence of Water Activity and Temperature on the Growth and Accumulation of Ochratoxin A Produced by Aspergillus carbonarius Isolated from Garri. International journal of Microbiological Research. 5 (3):152-159
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Date
2014-05
Authors
Thomas, B.T.
Ogunkanmi, L.A.
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Publisher
IDOSI publications
Abstract
This study determined the influence of water activity, temperature and their interactions on
growth, asexual sporulation and ochratoxin A accumulation in
Aspergillus carbonarius using standard microbiological techniques. Results obtained shows that at 35°C, OTA was more produced than at other
temperatures while both sporulation and mycelial growth were more enhanced at 25°C. A water activity of 0.99
produced the greatest interactions for all except for asexual sporulation that was best at 0.96a . No growth was
w
seen at water activity range of 0.90 to 0.94 for plates incubated at 40°C. The peak time for ochratoxin A was at
56 day with rapid production within the first 28days while the rate of production between 28 and 56 days
th
th
were relatively slower. When the two factors ( water activity and temperature) were treated as combined
variables for regression analysis, it was disclosed that both have a statistical significant relationship
with ochratoxin A production and their regression equation were given as Y = 31.029 -29.14a -0.052t,
1w
Y = -16.881+ 12.12a -0.073t and Y = -17.217 +22.02aw-0.082t for concentration of OTA in spores, biomass
2
w3
and medium respectively. Regression determinant confirmed that both water activity and temperature
accounted for 60%, 52.6% and 42.6% of the total ochratoxin A content present respectively. This observation
was also ascertained by the distribution of the bell shaped regression standardized residual histogram
around zero. In conclusion, the results of this study reject the null hypothesis which states that the ability to
complete wild type asexual sporulation could be a prerequisite for toxin biosynthesis. Rather, such attribute
could be linked to certain extrinsic factors that includes temperature and water potential.
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Keywords
Water Activity, Temperature, OTA, Garri
Citation
Influence of Water Activity and Temperature on the Growth and Accumulation of Ochratoxin A Produced by Aspergillus carbonarius Isolated from Garri.