Sporidesmin A is the most important mycotoxin produced by the fungus Pithomyces chartarum that grows on pasture litter during late summer and autumn. This fungi produces several variants of sporidesmin (from A to J), with sporidesmin A accounting for 80-90% of congeners. Sporidesmins affect the hepatobiliary system of ruminants and lead to the retention of phytoporphyrin which, reacting with light in peripheral tissues, causes the photosensitivity reaction known as "facial eczema". The disease produces losses in animal production and serious animal welfare problems in farmed ruminants in New Zealand and in warm temperate regions of the world. Zinc in several forms and with high dose rates is used as a control measure for facial eczema, but it poses safety issues. Other additives for sporidesmins control in feeds have not been evaluated. The use of adsorbing agents to reduce the exposure to mycotoxins by decreasing their bioavailability is a valuable strategy to cope with mycotoxins. To this scope, this study examines the ability of a clay based agent in sequestering sporidesmins from liquid mediums at physiological pH values (2.5-6.5). The adsorption behaviour of the clay for sporidesmins was studied by equilibrium isotherms as a function of pH, clay dosage, initial toxin concentration, equilibrium time, and temperature. Physico-chemical, kinetic and thermodynamic parameters related to the adsorption process were calculated, including the adsorbent dosage to achieve a 50 (C50) and 100% (C100) of toxin adsorption, the maximum adsorption capacity (Bmax) and the affinity (KL), the rate constants, and the ?G°, ?H°, ?S° parameters. The results showed that the clay exhibited high affinity for sporidesmins at ruminal pH (6.5), while its adsorption capacity slightly decreased with increasing pH from 2.5 to 6.5. In particular, the values of C50 and C100, expressed as mg of clay/µg of sporidesmin A, were 10 and 64 mg/µg at pH 2.5 and 14 and 51 mg/µg at pH 6.5. Bmax values (ng of sporidesmin A adsorbed/mg of clay) calculated at pH 2.5 and 6.5, were 54 and 26 ng/mg, respectively. KL values (L/mg of sporidesmin A) were 16 and 7*102 L/mg at pH 2.5 and 6.5. Kinetic studies suggested that sporidesmin A was adsorbed in less than 60 min following the pseudo second order model. Considering that ruminants are susceptible to sporidesmin A contaminated feed on a µg/kg basis, the results of this study suggest that the clay is promising for use as an effective adsorbent for sporidesmin decontamination.
FIRST IN VITRO EVIDENCES OF SPORIDESMINS ADSORPTION BY A CLAY BASED MATERIAL
Vito D'Ascanio;Donato Greco;Mariagrazia Abbasciano;Giuseppina Avantaggiato
2022
Abstract
Sporidesmin A is the most important mycotoxin produced by the fungus Pithomyces chartarum that grows on pasture litter during late summer and autumn. This fungi produces several variants of sporidesmin (from A to J), with sporidesmin A accounting for 80-90% of congeners. Sporidesmins affect the hepatobiliary system of ruminants and lead to the retention of phytoporphyrin which, reacting with light in peripheral tissues, causes the photosensitivity reaction known as "facial eczema". The disease produces losses in animal production and serious animal welfare problems in farmed ruminants in New Zealand and in warm temperate regions of the world. Zinc in several forms and with high dose rates is used as a control measure for facial eczema, but it poses safety issues. Other additives for sporidesmins control in feeds have not been evaluated. The use of adsorbing agents to reduce the exposure to mycotoxins by decreasing their bioavailability is a valuable strategy to cope with mycotoxins. To this scope, this study examines the ability of a clay based agent in sequestering sporidesmins from liquid mediums at physiological pH values (2.5-6.5). The adsorption behaviour of the clay for sporidesmins was studied by equilibrium isotherms as a function of pH, clay dosage, initial toxin concentration, equilibrium time, and temperature. Physico-chemical, kinetic and thermodynamic parameters related to the adsorption process were calculated, including the adsorbent dosage to achieve a 50 (C50) and 100% (C100) of toxin adsorption, the maximum adsorption capacity (Bmax) and the affinity (KL), the rate constants, and the ?G°, ?H°, ?S° parameters. The results showed that the clay exhibited high affinity for sporidesmins at ruminal pH (6.5), while its adsorption capacity slightly decreased with increasing pH from 2.5 to 6.5. In particular, the values of C50 and C100, expressed as mg of clay/µg of sporidesmin A, were 10 and 64 mg/µg at pH 2.5 and 14 and 51 mg/µg at pH 6.5. Bmax values (ng of sporidesmin A adsorbed/mg of clay) calculated at pH 2.5 and 6.5, were 54 and 26 ng/mg, respectively. KL values (L/mg of sporidesmin A) were 16 and 7*102 L/mg at pH 2.5 and 6.5. Kinetic studies suggested that sporidesmin A was adsorbed in less than 60 min following the pseudo second order model. Considering that ruminants are susceptible to sporidesmin A contaminated feed on a µg/kg basis, the results of this study suggest that the clay is promising for use as an effective adsorbent for sporidesmin decontamination.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
