AFB1 Production Research Articles

In vitro impact on growth, fumonisins and aflatoxins production by Fusarium verticillioides and Aspergillus flavus using anti-fungal compounds and a biological control agent.

The temporal efficacy of three different chemical fungicides (Folicur®, Proline®, Sportak 45EW®) and a biocontrol bacterium (Serenade, B. subtilis ) in reducing growth and toxin production by isolates of F. verticillioides and A. flavus was studied in vitro under different water activity regimes (0.99, 0.98 and 0.95). All the fungicides significantly inhibited mycelial growth compared with the control; the most effective treatment, both against F. verticillioides and A. flavus , was Sportak 45EW® (approx. 99%). The inhibitory effect of all fungicides generally improved with increasing concentration. Serenade always decreased fungal growth, with optimal results at concentrations of 104 and 106 (70‒75% reduction). All the fungicide treatments resulted in a significant reduction in both FB1+FB2 and AFB1 production when compared to the control, at the end of the incubation period and with the 2 concentrations used (approx. 99%). A threshold concentration inoculum of at least 104 CFUs of B. subtilis per g was required to achieve a significant control of mycotoxin production. Sportak 45EW® and Serenade gave the best control of mycotoxin production with a reduction of 95% compared to the controls. Use of Serenade in the field should include due consideration to its sensitivity to low water activities, when compared to the target pathogens.

Effect of acid lactic bacteria isolated from faeces of healthy dogs on growth parameters and aflatoxin B1 production by Aspergillus species in vitro

The aim of the present study was to evaluate the inhibitory effect of Enterococcus faecium and Lactococcus lactis subsp. lactis isolated from faeces of healthy dogs on (i) lag phase, (ii) growth rate, and (iii) aflatoxin B1 production by Aspergillus section Flavi on in vitro assays. Thirteen lactic acid bacteria (LAB) isolates were used as antagonist microorganisms. Antagonistic activity was assayed against four potentially aflatoxigenic Aspergillus section Flavi isolates: A. flavus (AF210 and AF281), A. parasiticus (AP245) and A. parasiticus (NRRL 2999). In general, the longest lag phases of Aspergillus isolates were obtained with E. faecium GJ40. Respecting the growth rate, no significant reduction was found in this parameter in the interaction assays with A. flavus and antagonist isolates respecting the control. While in A. parasiticus a significant reduction in growth rate was only observed in the interaction among reference strain and E. faecium MF5 isolate (p < 0.05). In general, AFB1 production was reduced by most of the LAB isolates assayed, except for E. faecium GJ18, GJ20, MF3 and MF4. This study provides the first data about the antiaflatoxigenic activity of autochthonous LAB isolated from dog faeces.

Taxol as chemical detoxificant of aflatoxin produced by aspergillus flavus isolated from sunflower seed

Aflatoxins are the potent toxic, mutagenic, heterogenic and carcinogenic metabolites produced by species of A. flavus and A. parasiticus. In the present study, an attempt has been made to prevent aflatoxin production using an anticancerous drug taxol. Taxol (Paclitaxel) is a well known drug for its anticancerous property mainly to treat breast and ovarian cancers. It was obtained from Taxus brevifolia and it was also obtained from the endophytic fungi present in Taxus brefivolia [1]. Therefore, this drug is specifically selected to screen its activity on the control of A. flavus and AFB1 production at various concentrations. Among the 6 concentrations used, 3 μg of taxol was found to be suitable to control the growth and AFB1 production. The content of AFB1 found at this concentration was 6 ppm by TLC and 6.3 ppm by HPTLC. The complete elimination of AFB1 might require higher concentrations of taxol.

Effect of Soybean Volatile Compounds on Aspergillus flavus Growth and Aflatoxin Production

Soybean homogenates produced volatile compounds upon exposure to lipase. These induced volatiles were identified by SPME. Seventeen volatile compounds identified by SPME were chosen for determination of their ability to inhibit Aspergillus flavus growth and aflatoxin B(1) (AFB1) production in a solid media assay. These volatiles included aldehydes, alcohols, ketones, and furans. Of the tested compounds, the aldehydes showed the greatest inhibition of fungal growth and AFB1 production. These compounds inhibited up to 100% of the observed growth and AFB1 production as compared to the controls. The greatest activity by the aldehydes to disrupt growth was ranked as follows: 2,4 hexadienal > benzaldehyde > 2-octenal > (E)-2-heptenal > octanal > (E)-2-hexenal > nonanal > hexanal. The greatest activity by the aldehydes to reduce AFB1 was ranked as follows: (E)-2-hexenal > 2,4 hexadienal > (E)-2-heptenal > hexanal > nonanal. (E)-2-hexenal and (E)-2-heptenal were tested further in an A. flavus-inoculated corn kernel assay. Both compounds prevented colonization by A. flavus and eliminated AFB1 production when exposed to compound volumes < 10 muL as also shown in the solid media assay. The results suggest that soybeans react to lipase by production of potent antifungal volatiles.

A novel combination of the essential oils of Cinnamomum camphora and Alpinia galanga in checking aflatoxin B1 production by a toxigenic strain of Aspergillus flavus

The growth of a toxigenic strain (Saktiman 3Nst) of Aspergillus flavus decreased progressively with increasing concentration of essential oils from leaves of Cinnamomum camphora and rhizome of Alpinia galanga incorporated into SMKY liquid medium. The oils significantly arrested aflatoxin B1 elaboration by A. flavus. The oil of C. camphora completely checked aflatoxin B1 elaboration at 750 ppm (mg/L) while that of A. galanga showed complete inhibition at 500 ppm only. The oil combination of C. camphora and A. galanga showed more efficacy than the individual oils showing complete inhibition of AFB1 production even at 250 ppm.

Inhibitory activity of compounds isolated from Polymnia sonchifolia on aflatoxin production by Aspergillus flavus

Polymnia sonchifolia, commonly known as ;yacon;, was originally cultivated at Andes moutains in South America. Recently, the specie attracted worldwide attention because of its wide range of uses, for example in the control of diabetes melitus, besides the antifungal and pesticidal compounds were found in the leaves. This study describes the identification of two flavonoids: 3', 5, 7 trihydroxy-3, 4'-dimethoxyflavone (compound 1) and 3', 4', 5- trihydroxy-7-methoxy flavanone (compound 2) and two sesquiterpenes lactones: enhydrin (compound 3) and a mixture of enhydrin and uvedalin (compound 4) isolated from Polymnia sonchifolia leaves and their effects on the aflatoxin production by Aspergillus flavus. The identification of the compounds were achieved by 1H and 13C NMR. All compounds were tested in different concentration, to evaluate the growth of Aspergillus flavus culture and the production of aflatoxin. The compound 1, at the concentration 15 mg/mL, inhibited 25% of the aflatoxin B1 production (p<0.01). The compound 4 inhibited 34% and 76% of the fungal growth and AFB1 production respectively. These results show that Polymnia sonchifolia can be used for the development of agents to control aflatoxin B1 production by Aspergillus flavus.

The effect ofLactobacillusandBifidobacteriumstrains on the growth and AFB1production ofAspergillus flavus

The effect of three individual strains of Lactobacillus (L. acidophilus NCC 12, L. acidophilus NCC 36, L. acidophilus NCC 68)and two Bifidobacterium strains (B. bifidum Bb13, B. bifidum NCC 381) on the growth and AFB1 production of Aspergillus flavus NRRL 2999 was determined. The commercial MRS broth and skim milk medium were used to determine the effect of tested bacteria on the growth and AFB1 production of A. flavus NRRL 2999. The bacteria were not effective in preventing the growth of A. flavus NRRL 2999 both in MRS broth and skim milk. However, higher levels of AFB1 were obtained in the presence of individual strains of Lactobacillus and Bifidobacterium. The greatest difference was observed in the AFB1 production of A. flavus NRRL 2999 in skim milk medium compared with MRS broth.

Pesticide Use and Mycotoxin Production in Fusarium and Aspergillus Phytopathogens

The major mycotoxigenic species of Fusarium and Aspergillus phytopathogens have been identified in this review. Since fungicides are widely used to control crop diseases caused by these fungi, it is pertinent to assess efficacy with respect to mycotoxin production. In both laboratory studies with pure cultures of phytopathogens and field trials with crop plants, the overall evidence concerning the effectiveness of fungicides is contradictory and in certain cases somewhat unexpected. In particular, at sub-lethal doses of a number of fungicides including carbendazim, tridemorph, difenoconazole and tebuconazole with triadimenol, mycotoxin production from Fusarium phytopathogens may increase. Furthermore, the efficacy of propiconazole and thiabendazole in the control of deoxynivalenol production from F. graminearum is not consistent. Evidence has been presented to suggest, for the first time, that fungicide-resistance in F. culmorum may be accompanied by a more persistent pattern of mycotoxin production. The limited evidence on the effects of fungicides on mycotoxin production in Aspergillus species is also conflicting. Under laboratory conditions, miconazole and fenpropimorph have been shown to increase aflatoxin production from A. parasiticus. Moreover, fenpropimorph increased production of the more toxic aflatoxin B1. Since fungal infection of plant products is often preceded by insect damage, there is interest in the effectiveness of insecticides to reduce infestation, infection and mycotoxin contamination. Additionally, insecticides may be effective in their own right, causing a direct effect on mycotoxin synthesis. The bulk of the evidence relates to effects on aflatoxin (AF) components B1, B2, G1 and G2. Under laboratory conditions, AFB1 production was most resistant to inhibition by insecticides, followed by AFG1, AFG2 and AFB2. This pattern of inhibition was particularly consistent for the organophosphorus insecticides. In one field study, Bux and carbaryl were considerably more effective than naled in reducing AFB1 contamination of maize kernels. It is concluded that if pesticide control is to be more effective in the future, additional criteria may be required in developing evaluation protocols for candidate compounds. In particular, the issue of fungicide-resistance in relation to mycotoxin production needs to be addressed in a concerted programme of research. Additionally, the potential of breeding and selecting cultivars resistant to disease caused by toxigenic fungi needs to be exploited in a parallel search for an environmentally acceptable solution to the question of mycotoxin contamination of plant products.

Conversion of a new metabolite to aflatoxin B2 by Aspergillus parasiticus.

A new metabolite which could be converted to aflatoxin (AF) B2 was detected during cofermentation analysis of two nonaflatoxigenic strains (SRRC 2043 and SRRC 163) of Aspergillus parasiticus. SRRC 2043, which accumulates the xanthone O-methylsterigmatocystin (OMST), a late precursor in the AFB1 pathway, was observed to accumulate another chemically related compound (HOMST; molecular weight, 356); SRRC 163 is blocked early in the pathway and accumulates averantin. During cofermentation of the two strains, levels of OMST and HOMST were observed to be greatly reduced in the culture, with simultaneous production of AFB1, AFB2, and AFG1. Intact cells of SRRC 163 were able to convert pure OMST or its precursor, sterigmatocystin, to AFB1 and AFG1 without AFB2 accumulation; the same cells converted isolated HOMST to AFB2 with no AFB1 or AFG1 production. The results indicate that AFB2 is produced from a separate branch in the AF biosynthetic pathway than are AFB1 and AFG1; AFB2 arises from HOMST, and AFB1 and AFG1 arise from sterigmatocystin and OMST.