Hydrolytic enzymes production by Aspergillus section Nigri in presence of butylated hydroxyanisole and propyl paraben on peanut meal extract agar / Producción de enzimas hidrolíticas por Aspergillus sección Nigri en presencia de hidroxianisol butilado y propilparabeno en medio de cultivo de agar con extracto de cacahuete

Background. In the last years, food grade antioxidants are used safely as an alternative to traditional fungicides to control fungal growth in several food and agricultural products. Aims. In this work, the effect of butylated hydroxyanisole (BHA) and propyl paraben (PP) on two hydrolytic enzyme activity (β-d-glucosidase and α-d-galactosidase) by Aspergillus section Nigri species under different water activity conditions (aW; 0.98, 0.95 and 0.93) and incubation time intervals (24, 48, 72 and 96 h) was evaluated on peanut-based medium. Methods. The activity of two glycosidases, β-d-glucosidase and α-d-galactosidase, was assayed using as substrates 4-nitrophenyl-β-d-glucopyranosido and 4-nitrophenyl-α-d-galactopyranosido, respectively. The enzyme activity was determined by the increase in optical density at 405 nm caused by the liberation of p-nitrophenol by enzymatic hydrolysis of the substrate. Enzyme activity was expressed as micromoles of p-nitrophenol released per minute. Results. The major inhibition in β-d-glucosidase activity of A. carbonarius and A. niger was found with 20 mmol l−1 of BHA or PP at 0.98 and 0.95 aW, respectively, whereas for α-d-galactosidase activity a significant decrease in enzyme activity with respect to control was observed in A. carbonarius among 5 to 20 mmol l−1 of BHA or PP in all conditions assayed. Regarding A. niger, the highest percentages of enzyme inhibition activity were found with 20 mmol l−1 of BHA or PP at 0.95 aW and 96 h. Conclusions. The results of this work provide information about the capacity of BHA and PP to inhibit in vitro conditions two of the most important hydrolytic enzymes produced by A. carbonarius and A. niger species (AU)

Antecedentes. En los últimos años, para controlar el crecimiento fúngico, en lugar de los fungicidas tradicionales, tanto en la industria alimentaria como en los productos agrícolas se utilizan antioxidantes como aditivos alimentarios bien tolerados y sin riesgos de efectos adversos. Objetivos. En el presente estudio, en un medio de cultivo con cacahuete, se examinó el efecto de hidroxianisol butilado (BHA) y propilparabeno (PP) sobre la actividad de 2 enzimas hidrolíticas (β-d-glucosidasa y α-d-galactosidasa) producidas por especies de Aspergillus sección Nigri, en función de diferentes valores de actividad de agua del sustrato (aW; 0,98, 0,95 y 0,93) y tiempos de incubación (24, 48, 72 y 96 h). Métodos. La actividad de las 2 glucosidasas (β-d-glucosidasa y α-d-galactosidasa) se evaluó usando como sustrato 4-nitrofenil-β-d-glucopiranósido y 4-nitrofenil-α-d-galactopiranósido, respectivamente. La actividad enzimática se determinó mediante el aumento de la densidad óptica a 405 nm provocado por la liberación de p-nitrofenol, resultado de la hidrólisis enzimática del sustrato. La actividad enzimática se expresó como micromoles de p-nitrofenol liberado por minuto. Resultados. La mayor inhibición en la actividad de β-d-glucosidasa de Aspergillus carbonarius y Aspergillus niger se observó con 20 mmol l−1 de BHA o PP a 0,98 y 0,95 aW, respectivamente. Comparado con el control, en A. carbonarius se detectó una disminución significativa de la actividad de α-d-galactosidasa con 5-20 mmol l−1 de BHA o PP en todas las condiciones examinadas. Con respecto a A. niger, los porcentajes mas elevados de inhibición enzimática se observaron con 20 mmol l−1 de BHA o PP a 0,95 aW y un tiempo de incubación de 96 h. Conclusiones. Los resultados del presente estudio proporcionan información sobre la capacidad de BHA y PP para inhibir dos de las enzimas más importantes producidas por las especies A. carbonarius y A. niger (AU)

Factors affecting distribution and abundance of Aspergillus section Nigri in vineyard soils from grapevine growing regions of Argentina.

BACKGROUND: Aspergillus species belonging to section Nigri are the main fungi responsible for ochratoxin (OTA) contamination in grapes and wine. These species live as saprophytes in the superficial layer of the vineyard soil. We evaluated the biodiversity of potentially ochratoxigenic strains of Aspergillus section Nigri isolated from vineyard soils from different grapevine growing regions of Argentina. The isolates were characterized by classical and molecular methods. A multiple correspondence analysis was performed to identify the overall correlation of the Aspergillus group distribution with environmental conditions, geographical characteristics and vineyard practices. RESULTS: Aspergillus niger aggregate was the prevalent group (71%) and A. carbonarius made up only 2%. Species discrimination by species-specific primers showed that in A. niger aggregate 89% were A. tubingensis; 97% of the uniseriate were A. japonicus/A. aculeatus. Isolates belonging to these groups were unable to produce OTA. Our results clearly demonstrate a strong association between presence of A. carbonarius, high average temperatures and drip irrigation. Precipitation levels appear as a secondary factor, and altitude, vineyard age, predominant species, grape variety or total fungal count showed no association with A. carbonarius. CONCLUSION: We demonstrated a low prevalence of ochratoxigenic species in vineyard soil from the grape-growing regions of Argentina.

Hydrolytic enzymes production by Aspergillus section Nigri in presence of butylated hydroxyanisole and propyl paraben on peanut meal extract agar.

BACKGROUND: In the last years, food grade antioxidants are used safely as an alternative to traditional fungicides to control fungal growth in several food and agricultural products. AIMS: In this work, the effect of butylated hydroxyanisole (BHA) and propyl paraben (PP) on two hydrolytic enzyme activity (ß-d-glucosidase and α-d-galactosidase) by Aspergillus section Nigri species under different water activity conditions (aW; 0.98, 0.95 and 0.93) and incubation time intervals (24, 48, 72 and 96h) was evaluated on peanut-based medium. METHODS: The activity of two glycosidases, ß-d-glucosidase and α-d-galactosidase, was assayed using as substrates 4-nitrophenyl-ß-d-glucopyranosido and 4-nitrophenyl-α-d-galactopyranosido, respectively. The enzyme activity was determined by the increase in optical density at 405nm caused by the liberation of p-nitrophenol by enzymatic hydrolysis of the substrate. Enzyme activity was expressed as micromoles of p-nitrophenol released per minute. RESULTS: The major inhibition in ß-d-glucosidase activity of A. carbonarius and A. niger was found with 20mmoll(-1) of BHA or PP at 0.98 and 0.95 aW, respectively, whereas for α-d-galactosidase activity a significant decrease in enzyme activity with respect to control was observed in A. carbonarius among 5 to 20mmoll(-1) of BHA or PP in all conditions assayed. Regarding A. niger, the highest percentages of enzyme inhibition activity were found with 20mmoll(-1) of BHA or PP at 0.95 aW and 96h. CONCLUSIONS: The results of this work provide information about the capacity of BHA and PP to inhibit in vitro conditions two of the most important hydrolytic enzymes produced by A. carbonarius and A. niger species.