Safety assessment of phytase transgenic maize 11TPY001 by 90-day feeding study in rats.

11TPY001 is a transgenic maize that expresses the Aspergillus niger phyA2 gene which could significantly improve phosphorus bioavailability in monogastric animals. The present study was conducted to investigate the potential health effects of phytase transgenic maize 11TPY001 through a 90-day subchronic rodent feeding study. Maize grains from 11TPY001 or its parental counterpart maize OSL963 were incorporated into rodent diets at 12.5%, 25% and 50% concentrations by mass and administered to Sprague-Dawley rats (n = 10/sex/group) for 90 days. An additional control group of rats (n = 10/sex/group) were fed with common maize Zhengdan958 diets at 50% by mass. All formulated diets were nutritionally balanced. Body weights, food intake, hematology, serum chemistry, absolute and relative organ weights were measured, and gross as well as microscopic pathology were examined. Compared with rats fed OSL963 maize and the common maize diet groups, no adverse diet-related differences were observed in rats fed 11TPY001 maize diets with respect to clinical signs of toxicity, body weight/gain, food consumption/efficiency, hematology, clinical chemistry, organ weights, and gross and microscopic pathology. Under the conditions of this study, the results indicated that 11TPY001 did not cause any treatment related adverse effects in rats compared with its non-transgenic parental maize OSL963.

Toxicological studies on a novel phytase expressed from synthetic genes in Aspergillus oryzae.

Phytases are widely used as feed additives for monogastric animals, which cannot easily utilise the phosphorus bound in phytate (myo-inositol hexakisphosphate). The current study presents a safety evaluation of a 6-phytase produced by an Aspergillus oryzae strain expressing two synthetic genes, both mimicking a phytase gene from a Citrobacter braakii strain. Oral administration of the phytase preparation to rats at a dose level of 0.86 g total organic solids/kg body weight/day for 13 weeks did not cause any adverse effect. The phytase preparation did not exhibit irritative potential when applied locally to the eyes of rabbits or when applied to the skin using the in vitro three-dimensional epidermis model of adult human-derived epidermal keratinocytes. Furthermore, the phytase preparation was found not to represent mutagenic or clastogenic potential in the bacterial reverse mutation assay and in the in vitro micronucleus assays. Based on the toxicological data, the large safety factors calculated under common recommended dose assumptions for broiler chickens and weaned piglets, and the fact that Aspergillus oryzae is considered a safe strain lineage, it is concluded that there are no reasons for safety concerns when using this phytase as a feed additive.

Hypersensitivity pneumonitis caused by occupational exposure to phytase.

A 43-yr-old male presented with a 6-month history of episodes of coughing, shortness of breath and fever. He suffered from dyspnoea on minor exertion. The patient worked in a cattle feed factory and noticed that he had more complaints after his working hours. His symptoms could be ascribed to hypersensitivity pneumonitis due to contact with phytase, an enzyme added to cattle feed to strengthen bone and diminish phosphorus excretion. The diagnosis was supported by bibasal lung crackles on physical examination, restrictive ventilatory defect (with decreased diffusion capacity for carbon monoxide), typical radiographical findings, lymphocytosis in bronchoalveolar lavage fluid and a positive exposure test performed at the workplace. Blood examination showed high immunoglobulin G levels to phytase. After treatment and cessation of phytase contact the patient became symptom free and lung function normalised. Phytase should be considered as a cause of occupational hypersensitivity pneumonitis in the animal feed industry.

[Occupational allergies to phytase]. / Berufliche Allergien gegen Phytasen1.

Phytases are phosphatases that can break down the undigestible phytic acid (phytate). They are frequently used as an animal feed supplement - often in poultry and swine - to enhance the nutritive value of plant material by liberation of inorganic phosphate from phytate. Exposure to enzyme dusts has long been known to cause occupational allergies. The present paper reviews the results of the evaluation of literature data concerning occupational airway sensitization due to phytases. Cases of specific airway sensitization caused by phytases could be shown clearly by the presented studies. As symptoms, results of skin prick tests, detection of specific IgE-antibodies and results of specific challenge tests are consistent, an immunologic mechanism can be assumed.

Safety evaluation of a phytase, expressed in Schizosaccharomyces pombe, intended for use in animal feed.

BD006 phytase is the product of the Escherichia coli B app A gene expressed in Schizosaccharomyces pombe strain ASP595-1. This enzyme preparation is intended for use in animal feed applications where it improves the bioavailability of phosphate for monogastric animals. BD006 phytase was tested as an unrefined (DV006U) and a refined (DV006R) preparation for its effects on genotoxicity and in acute, inhalation and subchronic toxicity studies. Dosages ranged from 5000 microg/plate for in vitro toxicity studies to a high of 2000X for oral in vivo toxicity studies. The highest oral dose tested (2000X) is 2000 times the highest expected consumption of product by poultry or swine (X=50 units of phytase per kg bwt/day). There was no genotoxicity or any in vivo toxicity reported which could be directly related to systemic effects of the product. Other additional safety studies conducted were devoid of any relevant toxicity. The historic safety profile of the production organism S. pombe, and the results of the toxicity studies presented herein, attest to the safety of BD006 phytase for use in animal feed applications.