In vitro effect of phenolic antioxidants on germination, growth and aflatoxin B1 accumulation by peanut Aspergillus section Flavi. J Appl Microbiol

Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas Físico Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional 36, 5800 Córdoba, Argentina.
Journal of Applied Microbiology (Impact Factor: 2.48). 02/2005; 99(3):682-91. DOI: 10.1111/j.1365-2672.2005.02661.x
Source: PubMed


The effectiveness of the food-grade antioxidants butylated hydroxytoluene (BHT), trihydroxybutyrophenone (THB), propyl paraben (PP) and butylated hydroxyanisole (BHA) at 1, 10 and 20 mmol l(-1) concentrations on germination, growth, and aflatoxin B(1) (AFB(1)) production by Aspergillus section Flavi strains was determined.
Assays on the lag phase of germination, germination percentage, germ tube elongation rate, lag phase, growth rate and AFB(1) production by three strains of Aspergillus flavus and three of Aspergillus parasiticus were carried out in vitro on peanut extract meal agar conditioned at different water activities (a(w): 0.982, 0.971, 0.955, 0.937). The antioxidants PP and BHA efficiently inhibited the germination of the two species tested at the doses 10 and 20 mmol(-1). The antioxidants PP and BHA at 1 mmol l(-1) and THB at 20 mmol l(-1) reduced the germ tube elongation rate most effectively, regardless of a(w) levels. An increase in the lag time and a reduction in the growth rate of 100% of the strains was observed, this was due to the action of BHT at the doses 10 and 20 mmol(-1) at 0.982, 0.971 and 0.955 a(w), although these treatments stimulated the AFB(1) accumulation in most of the fungi tested. The more effective antioxidants were PP and BHA, which increased the lag phase, reduced the growth rate and AFB(1) production in all of the strains at the four a(w) assayed. At concentrations 10 and 20 mmol l(-1), these antioxidants totally inhibited fungal development.
The study shows that the antioxidants BHA and PP are effective fungal inhibitors to peanut Aspergillus section Flavi in wide range of water activity.
The results suggest that phenolic antioxidants, BHA and PP, can be effective fungitoxicants on aflatoxigenic strains in peanut at industrial level.

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Available from: Silvia Resnik, Oct 13, 2014
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    • "Thirty grams of ground peanut per liter was boiled for 45 min and the resultant mixture filtered through a double layer of muslin . The volume was made up to 1 L and agar‐agar at 2% (w/v) was added (Passone et al., 2005). The water activity (a W ) of the basic medium (0.99) was adjusted to 0.98, 0.95 and 0.93 with known amounts of glycerol (Dallyn and Fox, 1980). "
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    ABSTRACT: Essential oils (EOs) from boldo [Pëumus boldus Mol.], poleo [Lippia turbinata var. integrifolia (Griseb.)], clove [Syzygium aromaticum L.], anise [Pimpinella anisum] and thyme [Thymus vulgaris]) obtained by hydrodistillation were evaluated for their effectiveness against the growth of Aspergillus niger aggregate and A. carbonarius and accumulation of ochratoxin A (OTA). The evaluation was performed by compound dissolution at the doses of 0, 500, 1500 and 2500μL/L in peanut meal extract agar (PMEA) and exposure to volatiles of boldo, poleo (0, 1000, 2000 and 3000μL/L) and clove oils (0, 1000, 3000 and 5000μL/L), taking into account the levels of the water activity of the medium (a(W) 0.98, 0.95, 0.93). Statistical analyses on growth of Aspergillus strains indicated that the major effect was produced by oil concentrations followed by substrate a(W), and that reductions in antifungal efficiency of the oils tested were observed in vapor exposure assay. At all a(W) levels, complete fungal growth inhibition was achieved with boldo EO at doses of 1500 and 2000μL/L by contact and volatile assays, respectively. Contact exposure by poleo and clove EOs showed total fungal inhibition at the middle level tested of 1500μL/L, regardless of a(W), while their antifungal effects in headspace volatile assay were closely dependent on medium a(W). The fumigant activity of poleo (2000μL/L) and clove oils (3000μL/L) inhibited growth rate by 66.0% and 80.6% at a(W) 0.98 and 0.93, respectively. OTA accumulation was closely dependent on a(W) conditions. The antiochratoxigenic property of the volatile fractions of boldo, poleo and clove EOs (1000μL/L) was more significant at low a(W) levels, inhibition percentages were estimated at 14.7, 41.7 and 78.5% at a(W) 0.98, 0.95 and 0.93, respectively. Our results suggest that boldo, poleo and clove oils affect the OTA biosynthesis pathway of both Aspergillus species. This finding leaves open the possibility of their use by vapor exposure as effective non-toxic biopreservatives against OTA contamination in stored peanuts.
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    • "The basic medium used in this study was 3% peanut meal extract agar (PMEA), made by boiling 30 g of dried peanut meal in 1 l water for 60 min. The resulting mixture was filtering through a double layer of muslin, and 15 g l À1 agar was added (Passone et al., 2005). "
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    ABSTRACT: The antifungal potential of five plant-derived essential oils (EOs) (boldo [Pëumus boldus Mol.], poleo [Lippia turbinata var. integrifolia (Griseb.)], clove [Syzygium aromaticum L.], anise [Pimpinella anisum], and thyme [Thymus vulgaris]) was evaluated against aflatoxigenic Aspergillus strains on peanut-based medium conditioned at different water activity (aW) levels (0.98, 0.95, 0.93). Effects of EOs added to the peanut meal extract agar on the lag phase, growth rate, and aflatoxin B1 (AFB1) accumulation by Aspergillus flavus and A. parasiticus were evaluated. The five EOs analyzed have been shown to influence lag phase, growth rate, and AFB1 accumulation. Although the low dose (500 ppm) of boldo, poleo, and clove showed no significant effects on lag phase (range of increase = 0–75%) and growth rate (range of reduction = 0–65%), the application of high concentrations of these EOs (2500 μl l−1 for boldo and poleo and 1500 μl l−1 for clove) completely inhibited growth of Aspergillus species, regardless of aqueous medium availability. The anti-aflatoxigenic property of boldo and poleo EOs (500 μl l−1) was more marked with the medium aW reduction; inhibition percentages were estimated at 75, 83, and 100% at 0.98, 0.95, and 0.93 aW, respectively.These findings support the application of boldo, poleo, and clove EOs for surface treatment and leave open the possibility of using them as vapor exposure to prevent mold contamination in stored peanut.
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    • "Phenolic antioxidants also inhibit ochratoxin A production by Aspergillus spp. (Palumbo et al., 2007; Passone et al., 2005). Ascorbate enhances aflatoxin biosynthesis by Aspergillus parasiticus, yet caffeine, flavonoids, gallic acid and phenolics repress its biosynthesis (Holmes et al., 2008; Patel et al., 1990). "
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