Influence of Light and Water Activity on Growth and Mycotoxin Formation of Selected Isolates of Aspergillus flavus and Aspergillus parasiticus (original) (raw)
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Toxins
Aspergillus flavus is the most important mycotoxin-producing fungus involved in the global episodes of aflatoxin B1 contamination of crops at both the pre-harvest and post-harvest stages. However, in order to effectively control aflatoxin contamination in crops using antiaflatoxigenic and/or antifungal compounds, some of which are photosensitive, a proper understanding of the photo-sensitive physiology of potential experimental strains need to be documented. The purpose of the study is therefore to evaluate the effect of visible (VIS) light illumination on growth and conidiation, aflatoxin production ability and modulation of A. flavus oxidative status during in vitro experiment. Aflatoxigenic A. flavus strain was inoculated in aflatoxin-inducing YES media and incubated under three different VIS illumination regimes during a 168 h growth period at 29 °C. VIS illumination reduced A. flavus mycelia biomass yield, both during growth on plates and in liquid media, promoted conidiation a...
2010
An experiment with a full factorial design was used to study the effects of and interactions among temperature, water activity (a w ), incubation period, and substrate on coproduction of aflatoxins (AF) and cyclopiazonic acid (CPA) by an isolate of Aspergillus flavus. Analysis of variance showed that there was a complex interaction among all of these factors and that this influenced the relative concentrations of the mycotoxins produced. The optimum temperatures for the production of AF and CPA were 30؇C and 25؇C, respectively. Both mycotoxins were maximally produced (0.306 to 0.330 g of AF ⅐ ml of medium ؊1 , 4.040 to 6.256 g of CPA ⅐ ml of medium ؊1 ) at an a w of 0.996 and after 15 days of incubation. No AF were produced in either yeast extract agar or Czapek yeast autolysate agar medium at an a w of 0.90 at 20 or 37؇C after 15 days (minimum conditions), while 0.077 to 0.439 g of CPA ⅐ ml of medium ؊1 was produced under the same conditions. Yeast extract agar favored maximum AF production, and Czapek yeast autolysate agar favored maximum CPA production.
1997
An experiment with a full factorial design was used to study the effects of and interactions among temperature, water activity (a w ), incubation period, and substrate on coproduction of aflatoxins (AF) and cyclopiazonic acid (CPA) by an isolate of Aspergillus flavus. Analysis of variance showed that there was a complex interaction among all of these factors and that this influenced the relative concentrations of the mycotoxins produced. The optimum temperatures for the production of AF and CPA were 30؇C and 25؇C, respectively. Both mycotoxins were maximally produced (0.306 to 0.330 g of AF ⅐ ml of medium ؊1 , 4.040 to 6.256 g of CPA ⅐ ml of medium ؊1 ) at an a w of 0.996 and after 15 days of incubation. No AF were produced in either yeast extract agar or Czapek yeast autolysate agar medium at an a w of 0.90 at 20 or 37؇C after 15 days (minimum conditions), while 0.077 to 0.439 g of CPA ⅐ ml of medium ؊1 was produced under the same conditions. Yeast extract agar favored maximum AF production, and Czapek yeast autolysate agar favored maximum CPA production.
International Journal of Food Microbiology, 2011
The aim of this study was to assess the impact of suboptimal environmental conditions on the intraspecific variability of A. carbonarius growth and OTA production using thirty isolates of A. carbonarius. Three a w /temperature conditions were tested, one optimal (0.98a w /25°C) and two suboptimal: 0.90a w /25°C and 0.98a w /37°C as suboptimal water activity and temperature, respectively, which might take place through over ripening and dehydration of grapes. For each condition, 12 Petri dishes were inoculated, and colony growth and OTA production were measured over time. ANOVA revealed significant differences among μ and λ within the 30 assayed isolates. Coefficients of variation (CV%) revealed a wider dispersion of growth rates at 0.90a w /25°C compared to 0.98a w /25°C, and a more than 4-fold higher CV at 0.98a w /37°C compared to 0.98a w /25°C. However, dispersion of lag phases was similar at 0.98a w /25°C and 0.90a w /25°C and wider at 0.98a w /37°C. There were significant differences (p b 0.05) among OTA levels (ng/mm 2 ) for the different conditions, values being lower under marginal conditions, and particularly at 0.98a w /37°C. Coefficients of variation (CV%) revealed a wider dispersion of OTA production at 0.90a w /25°C compared to 0.98a w /25°C, while CV at 0.98a w /37°C was similar to that at 0.98a w /25°C. In order to address the strain variability in growth initiation and prove the well-established notion of reducing OTA in foods by preventing fungal growth, a greater number of strains should be included when developing models for conditions that are suboptimal both for a w for OTA production and temperature levels for growth.
Revista Argentina de Microbiología, 2016
An experiment with a full factorial design was used to study the effects of and interactions among temperature, water activity (a w), incubation period, and substrate on coproduction of aflatoxins (AF) and cyclopiazonic acid (CPA) by an isolate of Aspergillus flavus. Analysis of variance showed that there was a complex interaction among all of these factors and that this influenced the relative concentrations of the mycotoxins produced. The optimum temperatures for the production of AF and CPA were 30؇C and 25؇C, respectively. Both mycotoxins were maximally produced (0.306 to 0.330 g of AF ⅐ ml of medium ؊1 , 4.040 to 6.256 g of CPA ⅐ ml of medium ؊1) at an a w of 0.996 and after 15 days of incubation. No AF were produced in either yeast extract agar or Czapek yeast autolysate agar medium at an a w of 0.90 at 20 or 37؇C after 15 days (minimum conditions), while 0.077 to 0.439 g of CPA ⅐ ml of medium ؊1 was produced under the same conditions. Yeast extract agar favored maximum AF production, and Czapek yeast autolysate agar favored maximum CPA production.
Exogenous factors affecting growth of Aspergillus species
Indian Journal of Animal Research
Aflatoxins are the most deleterious fungal metabolites in humans, animals and plants. Recently, more attention has been paid to the occurrence and growth of Aspergillus spp. In this study, the effects of pH, light, relative humidity (RH) and temperature on the growth of Aspergillus spp. were investigated using broth medium. Results revealed highest mean of dried mycelial weight (365.67mg) at pH 4.0. The highest spores per ml (8.243 × 107) at pH 5.0. Similarly, growth during darkness was higher on first day of incubation in A. candidus and A. niger, while A. flavus and A. fumigatus showed the highest growth under continuous light. Lower RH% (32.5%) favored only the growth of A. niger. However, the growth in other Aspergillus species was significantly increased by RH% (50.5%, 85.0% and 100%). At 40ºC, only A. fumigatus and A. flavus showed significant (P less than 0.05) growth. There were significant differences in all the treatments (P less than 0.05). This proposes that these intera...
Applied Engineering in Agriculture, 2020
HighlightsInfrared heating was used to deactivate Aspergillus flavus.Treating samples for 150 s at the 3.24 kW/m2 intensity resulted in complete deactivation of A. flavus.Adding a tempering step at 70°C for 4 h significantly increased deactivation of A. flavus.Corn treated at IR intensity =3.24 kW/m2 showed no potential for A. flavus regrowth or aflatoxin persistence.The study demonstrated a non-chemical approach to deactivate mycotoxigenic fungi on corn..The objectives of this study were to determine the suitable combinations of infrared (IR) heating duration and intensity, followed by tempering treatments to maximize the deactivation of aflatoxin-producing mold spores, specifically Aspergillus flavus (A. flavus). Corn samples at moisture content of 24% wet basis were inoculated with spore suspension of A. flavus and incubated to allow microbial attachment on the kernels. Corn samples were then heated using IR energy and then tempered for 4 h. Following the treatments, the samples ...
The combined effect of water activity (a~), pH, storage temperature, headspace oxygen and carbon dioxide concentration on the growth of, and aflatoxin production by, Aspergillus flavus on synthethic media were examined using a multifactorial experimental design termed Response Surface Methodology. Regression analysis of the data indicated that aw, pH, storage temperature and initial concentration of headspace oxygen in the gas mix were all highly significant factors (p<O.01) in controlling the growth of A. flavus on synthetic media. Mold growth was either completely inhibited or was visible after 1-2 days. Growth was more extensive in plates stored at higher storage temperatures (25--35°C) and packaged with 10-20% 02 (54 48 % C02). Growth of A. fiavus was inhibited in certain treatment combinations stored at 25°C and completely inhibited in all plates stored at 15-20°C irrespective of the gas atmosphere. A curvilinear relationship was found between mold colony diameter (mm) and aflatoxin production. Aflatoxin production was maximum at a colony diameter of 7 mm and then decreased with increasing colony diameter. However, in all cases where growth occurred, the level of aflatoxin was less than the current regulatory standard of 20 ng g-1. This study has shown that A. flavus can grow in a C02 enriched atmosphere if headspace oxygen is present. It also emphasizes the combined effect of several 'barriers' to either completely inhibit mold growth or to reduce aflatoxin in MAP products containing various levels of headspace oxygen to safe and acceptable levels (<20 ng g-~), particularly at temperature abuse storage conditions.
Food Additives and Contaminants, 1991
Water activity (a w) and temperature are two pivotal environmental factors affecting Aspergillus flavus growth and aflatoxin production. Here, we found that AFB 1 production on polished rice can occur over a wider range of temperature × a w levels than that on paddies. For fungal growth on polished rice, the optimum conditions were a w 0.92-0.96 and 28-37°C. The maximum amounts of AFB 1 on polished rice was observed at 33°C and a w 0.96. Compared to 33°C, all tested genes of A. flavus on polished rice were significantly up-regulated at 25°C under a w 0.96. The late structural genes of pathway were significantly down-regulated at 37°C under a w 0.96, although aflR and aflS and most of early structural genes were up-regulated. Compared to a w 0.96, most of pathway genes were significantly down-regulated at a w 0.90 and 0.99 under 33°C, although two regulatory genes were upregulated at a w 0.90. water activity (a w), pH, light and nature of substrate (Schmidt-Heydt,
Food Microbiology, 1993
The combined effect of water activity (a~), pH, storage temperature, headspace oxygen and carbon dioxide concentration on the growth of, and aflatoxin production by, Aspergillus flavus on synthethic media were examined using a multifactorial experimental design termed Response Surface Methodology. Regression analysis of the data indicated that aw, pH, storage temperature and initial concentration of headspace oxygen in the gas mix were all highly significant factors (p<O.01) in controlling the growth of A. flavus on synthetic media. Mold growth was either completely inhibited or was visible after 1-2 days. Growth was more extensive in plates stored at higher storage temperatures (25--35°C) and packaged with 10-20% 02 (54 48 % C02). Growth of A. fiavus was inhibited in certain treatment combinations stored at 25°C and completely inhibited in all plates stored at 15-20°C irrespective of the gas atmosphere. A curvilinear relationship was found between mold colony diameter (mm) and aflatoxin production. Aflatoxin production was maximum at a colony diameter of 7 mm and then decreased with increasing colony diameter. However, in all cases where growth occurred, the level of aflatoxin was less than the current regulatory standard of 20 ng g-1. This study has shown that A. flavus can grow in a C02 enriched atmosphere if headspace oxygen is present. It also emphasizes the combined effect of several 'barriers' to either completely inhibit mold growth or to reduce aflatoxin in MAP products containing various levels of headspace oxygen to safe and acceptable levels (<20 ng g-~), particularly at temperature abuse storage conditions.