Experimental aflatoxin production in Manchego-type cheese

Manchego-type cheese, a typical Spanish cheese, was inoculated in various ways with an aflatoxigenic organism, Aspergillus parasiticus NRRL 2999, to study the production of aflatoxin. When the original milk was contaminated with a spore suspension, aflatoxin was not detected in paraffin-covered cheeses although it was present in the top layer of non-paraffin-covered cheeses after ripening at 15 degrees C for 60 d. When the cheese surface was inoculated, no aflatoxins were detected in paraffin-covered cheeses after ripening for 60 d although they were found when the cheeses were ripened for 30 d. In non-paraffin-covered cheeses aflatoxins were detected only in the top layer and in the second 10 mm layer when cheeses were incubated after the normal ripening at 28 degrees C for 30 d. When the centre of the cheese was inoculated, no aflatoxins were detected although Aspergillus grew slightly along the inoculation area. When cheese portions were inoculated, fungal growth was evident after incubation at 28 degrees and 15 degrees C for 6 d but there was no growth at 10 degrees C after 50 d. At 28 degrees C aflatoxins were detected at a concentration of 132 micrograms/g after 13 d, the highest level obtained. In cheese paste at 28 degrees and 15 degrees C, growth was intense, but the level of aflatoxins detected was lower than in cheese portions. At 10 degrees C the growth was heavy, but aflatoxins were not detected.     

Role of lipoperoxidation in aflatoxin production

Summary Lipoperoxidation appears to play a role in inducing aflatoxin biosynthesis. In vitro, synthetic lipoperoxides greatly stimulate aflatoxin production when added to cultures of toxigenic strains of Aspergillus parasiticus or A. flavus. In vivo, the amount of toxin formed in sunflower seeds of different ages inoculated with A. parasiticus is directly related to the peroxide number of their oil content: the higher the peroxide number, the higher the aflatoxin production. In cultures of A. parasiticus carbon tetrachloride (CCl₄) greatly stimulates aflatoxin biosynthesis. This effect might be due to the peroxidation of lipids of the endoplasmic reticulum of Aspergillus by the highly reactive CCl _. ³ radicals formed by interaction with the NADPH-cytochrome P-450 system.     

Cardoon-based rennets for cheese production

Applied Microbiology and Biotechnology - The use of crude aqueous extracts of Cynara cardunculus flowers as coagulants in the production of high-quality sheep and goat cheeses—as are the...     

Inhibition of aflatoxin production by selected insecticides

The insecticide naled completed inhibition production of aflatoxins B1, B2, G1, and G2 by and growth of Aspergillus parasiticus at a 100-ppm (100 microgram/ml) concentration. The insecticides dichlorvos, Landrin, pyrethrum, Sevin, malathion, and Diazinon significantly (P = 0.05) inhibited production of aflatoxins at a 100-ppm concentration. However, at a concentration of 10 ppm, significant inhibition in production of aflatoxins was found only with naled, dichlorvos, Sevin, Landrin, and pyrethrum. Dichlorvos, Landrin, Sevin, and naled inhibited growth of A. parasiticus by 28.9 , 18.9, 15.7, and 100%, respectively, at 100 ppm. Stimulation of growth was observed when diazinon was added to cultures. Aflatoxin B1 was most resistant to inhibition by insecticides, followed by G1, G2, and B2, respectively.     

The production of aflatoxin M on various substrates

Summary The ability of 44 strains ofA. flavus and 6 strains ofA. parasiticus to produce aflatoxin M on various substrates was examined. It was found that these strains produced aflatoxin M only with larger quantities of aflatoxin B. The presence of several other minor metabolites in culture extracts is described. The highest yield of aflatoxin M was produced by a strain ofA. flavus grown on maize meal.     

Inhibition of aflatoxin production by selected insecticides.

The insecticide naled completed inhibition production of aflatoxins B1, B2, G1, and G2 by and growth of Aspergillus parasiticus at a 100-ppm (100 microgram/ml) concentration. The insecticides dichlorvos, Landrin, pyrethrum, Sevin, malathion, and Diazinon significantly (P = 0.05) inhibited production of aflatoxins at a 100-ppm concentration. However, at a concentration of 10 ppm, significant inhibition in production of aflatoxins was found only with naled, dichlorvos, Sevin, Landrin, and pyrethrum. Dichlorvos, Landrin, Sevin, and naled inhibited growth of A. parasiticus by 28.9 , 18.9, 15.7, and 100%, respectively, at 100 ppm. Stimulation of growth was observed when diazinon was added to cultures. Aflatoxin B1 was most resistant to inhibition by insecticides, followed by G1, G2, and B2, respectively.     

Effect of initial pH on aflatoxin production.

The effect of initial pH on aflatoxin production by Aspergillus parasiticus NRRL 2999 was examined in a semisynthetic medium. Maximal growth, aflatoxin production, and aflatoxin production per unit of growth occurred at initial pH levels of 5.0, 6.0, and 7.0 respectively. Initial pH levels less than pH 6.0 favored production of the B toxins, whereas levels greater than pH 6.0 favored production of the G toxins.     

Aspergillus growth and aflatoxin production on black pepper

Black peppercorns supported the growth of Aspergillus parasiticus (flavus) NRRL 3145. Incubation at 28 C and RH of 85% for 30 days resulted in profuse conidial production on the reticulate ridges of the peppercorns. An SEM study of these ridges showed that they were cortical eruptions, and the particulate matter present favored mycelial establishment. Hyphal anastamoses were commonly observed. Following this incubation the inoculated peppercorns were stored in the dark at room temperature and ambient humidity for 15 days. Aflatoxin was detected on a minicolumn. Aflatoxin B₁ was produced at levels of 60 g/kg with traces of aflatoxins B ₂, G₁ and G₂. Quantitative estimation was based on a visual comparison with standards by thin-layer chromatography.     

Effect of temperature on aflatoxin production in Mucuna pruriens seeds

This paper describes the effect of temperature on the level of aflatoxin production in Mucuna pruriens seeds. The highest level of aflatoxin B1 (1.75 micrograms/g) was detected in the samples incubated at 25 degrees C for three weeks. At 20, 30, and 35 degrees C, aflatoxin levels were 0.30 to 0.56, 0.37 to 1.20, and 0.26 to 0.65 micrograms/g, respectively. The lowest concentration of aflatoxin B1 (0.10 to 0.29 microgram/g) was produced at 15 degrees C.     

Influence of inoculum size on aflatoxin production in home-made yoghurt

In previous works we have studied the influence of different factors on the aflatoxin production in yoghurt. In the present paper we complete our investigations with the study of the influence of the inoculum size. The inoculum sizes used by us were from 4 × 10¹ to 4 × 10⁶. As can be expected, the fungal growth, expressed as dry mycelium weight, was lower in 4 × 10¹ and higher in 4 × 10⁶. The amount of aflatoxin in the mycelium was stable, or increased slightly with the inoculum size. In the substrate, the amount of aflatoxin was stable with little fluctuations, with a higher level of toxin in 4 × 10³ and lower one in 4 × 10⁶. We detected a higher aflatoxin level in the mycelium than in the substrate.     

Improved methodology for detecting aflatoxin production quantitatively in natural media

This report describes a simple, rapid, and quantitative method for screening the aflatoxin production by moulds of theAspergillus flavus group, using a natural media (moist wheat or rice), and a single chloroform extraction for aflatoxins. The aflatoxins were detected and quantified by thin layer chromatography. The methodology proposed was useful in detecting aflatoxin production on the 3rd day of incubation in more than 85 % of the strains studied (both culture collection strains and field isolates).     

Examination of fungal growth and aflatoxin production on marihuana

Under favorable growth conditions,Aspergillus flavus andA. parasiticus produced aflatoxins on marihuana. Cultures ofA. flavus ATCC 15548 produced both aflat oxin B₁(AFB₁) and G₁(AFG₁). The production of AFG₁ was substantially greater than that of AFB₁. Cultures ofA. flavus NRRL 3251 andA. parasiticus NRRL 2999 produced only AFB₁. All natural flora cultures tested negative for aflatoxins. NoAspergilli sporulations were observed in these cultures. In the cultures inoculated with known toxigenic fungi, the highest mean level for total aflatoxins was 8.7 g/g of medium. Marihuana appears not to yield large quantities of these mycotoxins but sufficient levels are present to be a potential health hazard for both the user and the forensic analyst who is in daily contact with such plant material. Careful processing, storage, and sanitation procedures should be maintained with marihuana. If these conditions are disregarded due to the illicit status of marihuana, the potential for mycotoxin contamination must be considered.     

Effect of fatty acids on aflatoxin production byAspergillus parasiticus

The effect of saturated and unsaturated fatty acids on aflatoxin production was studied in a synthetic medium. The aflatoxin production decreased (10-75%) in the presence of lauric acid and palmitic acid but the addition of behenic and sebacic acid stimulated aflatoxin production by 125-541%. Linolenic and linoleic acids effected aflatoxin production and mycelium growth. An 34-fold increase in aflatoxin production was observed with 50 mM linoleic acid. An inverse relationship was observed between aflatoxin production and mycelium mass, irrespective of the nature of the fatty acid.     

N-carboxymethylchitosan inhibition of aflatoxin production: Role of zinc

Aqueous Solutions of N-carboxymethylchitosan (NCMC) suppressed both growth and aflatoxin production byAspergillus flavus andA. parasiticus in submerged culture (Adye and Mateles A&M). Test media were amended with various concentrations of zinc (15, 30, 45, 60 uM), and NCMC solution (0.62 uM). After 8 days incubation NCMC-treated cultures showed marked reduction of aflatoxin production and fungal growth. Enhanced levels of zinc did not overcome the NCMC-mediated inhibition of fungal growth or aflatoxin production.     

Inhibition of aflatoxin production by trifluoperazine in Aspergillus parasiticus NRRL 2999

Trifluoperazine, an anti-calmodulin agent, inhibited aflatoxin production by Aspergillus parasiticus NRRL 2999, without affecting the growth significantly. Culturing the organism for 3 days in the presence of 0.14mm trifluoperazine resulted in a generalized decrease in the production of all aflatoxins; the production of aflatoxin B1, a potent hepatocarcinogen, was inhibited to 88% under such conditions. Culturing 7-day-old preformed cultures in the presence of higher concentrations of trifluoperazine (>1mm) completely abolished production of all aflatoxins including AFB1. The inhibitory influence of trifluoperazine on aflatoxin production was accompanied by calmodulin-dependent phosphorylation of an 85kDa cytoplasmic calmodulin-binding protein. While the functions of calmodulin in mediating primary events of germination, growth and differentiation in fungi have earlier been reported, the present results indicate a possible role for calmodulin in the production of fungal toxins.