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The present study evaluated the effects of dietary microbial phytase on the growth and gut health of hybrid tilapia (Oreochromis niloticus ♀×Oreochromis aureus ♂), focusing on the effect on intestinal histology, adhesive microbiota and expression of immune-related cytokine genes. Tilapia were fed either control diet or diet supplemented with microbial phytase (1000 U/kg). Each diet was randomly assigned to four groups of fish reared in cages (3×3×2 m). After 12 weeks of feeding, weight gain and feed conversion ratio of tilapia were not significantly improved by dietary microbial phytase supplementation. However, significantly higher level of P content in the scales, tighter and more regular intestinal mucosa folds were observed in the microbial phytase group and the microvilli density was significantly increased. The adhesive gut bacterial communities were strikingly altered by microbial phytase supplementation (0·41

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Phytase 50104 enzyme (also known as VR003) can be added to swine and poultry diets to catalyze the hydrolysis of phosphate from phytic acid, thereby increasing phosphorus bioavailability in these animals. This enzyme was produced from a Pseudomonas fluorescens (P. fluorescens) production strain and was tested in acute, subchronic and genotoxicity studies. Dosages of the test article preparation ranged from 5000µg/plate for in vitro toxicity studies to 2000mg/kg/day for in vivo toxicity studies. The highest oral dose tested in vivo (NOAEL of 2000mg/kg/day) resulted in a safety margin of 5870 based on TOS and a conservative estimate of total poultry consumption at the highest inclusion rate. There was no toxicity reported for any of these studies or in the following additional safety studies: eye irritation, dermal irritation, and delayed hypersensitivity studies. A review of the public literature indicated that P. fluorescens fulfilled the recognized safety criteria pertinent to microbial production strains used in the manufacture of food/feed enzyme preparations. The results of the toxicity studies presented herein attest to the safety of phytase 50104 enzyme for its intended use.

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BACKGROUND: Although fungal phytase is frequently used as an additive to animal feed few investigations of its allergenic property have been conducted. METHODS: Fifty-three subjects occupationally exposed to powdered phytase from Aspergillus niger were studied. Exposure data and symptoms were registered by the company physician. RESULTS: Thirty-eight subjects complained of work-related respiratory symptoms and 14 of them showed phytase-specific IgE antibodies; only one asymptomatic subject revealed such antibodies. IgE antibodies were significantly more frequently found in the high-exposure group (technical centre) when compared with the low-exposure group (laboratories, experimental animal husbandry). Phytase-specific IgG antibodies were present in 19 symptomatic (50%) and five (33%) asymptomatic subjects. CONCLUSIONS: Our results demonstrate that powdered fungal phytase is a highly sensitizing substance whose inhalation exposure should be avoided. Hypersensitivity symptoms could be prevented by means of extensive hygienic measures and ongoing medical surveillance.

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OBJECTIVES: Occupational asthma is the principal cause of respiratory disease in the workplace. The enzymes phytase and beta-glucanase are used in the agricultural industry to optimise the nutritional value of animal feeds. A relation between these enzymes and occupational asthma in a 43 year old man was suspected. METHODS: Inhalation challenge tests were performed with the enzymes phytase, beta-glucanase, and amylase. Skin prick tests were performed with the enzymes diluted to a concentration of 1 mg/ml and 5 mg/ml. Specific IgE to phytase and beta-glucanase were measured with a radioallergosorbent test. RESULTS: Baseline spirometry values were normal. A histamine challenge test showed bronchial hyperreactivity. Exposure to phytase and beta-glucanase led to significant reductions in forced vital capacity and forced expired volume in 1 second. No significant differences were noted after exposure to amylase. Skin tests showed a positive reaction to beta-glucanase (5 mm) at a concentration of 1 mg/ml and positive reactions to beta-glucanase (7 mm) and phytase (5 mm) at a concentration of 5 mg/ml. Similarly specific IgE was present against both phytase and beta-glucanase, at 2.5% and 9.3% binding respectively (2% binding is considered positive). CONCLUSIONS: This is the first description of occupational asthma due to the enzymes phytase and beta-glucanase. Their addition to the ever increasing list of substances associated with occupational asthma will have notable implications for those exposed to these enzymes.

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