Abstract
Phytases are widely utilized in feed industry to increase the utilization of phosphorus, minerals, and amino acids for improvement of animal and human nutrition. At present, all known β-propeller phytases (BPP) have been generated from bacteria, particularly Bacillus. In this work we report for the first time a new fungal-derived BPP phytase. We identified a phytase highly differentially expressed only in the parasitic stage of a nematophagous fungus, Arhtrobotrys oliogospora, during the development of the 3D traps. We found that this phytase was homologous to the known bacterial BPP phytase, thus we referred the new phytase to Aophytase. The heterologous expression of codon-optimized Aophytase gene in Pichia pastoris was successfully investigated to yield recombinant Aophytase (r-Aophytase) with high specific enzyme activity of 74.71 U/mg, much higher than those of recombinant BPP phytases derived bacteria. The kinetic parameters of the r-Aophytase, the optimum pH and temperature, as well as the effects of surfactant, EDTA and different ions on its enzyme activity were further investigated. The potential utilization of r-Aophytase in feed processing was finally explored. We found that the optimal pH value was about 7.5, and the optimal temperature was 50 °C.; r-Aophytase significantly increased the release of inorganic phosphorus from soybean meal, and improved the release of soluble minerals from the durum wheat flour and finger millet flour. The findings indicate its potential utilization in the feed processing to ameliorate nutritional value of cereals and animal feed in the future.
Highlights
Phytases are widely used in feed industry to increase the utilization of phosphorus, minerals, and other nutrients such as protein, starch and fat [1,2,3]
We found that this phytase was found to be homologous to the known bacterial BPP phytase, we referred the new phytase to Aophytase
We found that the fungal-derived Aophytase had a high specific enzyme activity and effectively improved the release of inorganic phosphorus and soluble minerals from different feedstuffs, suggesting its potential uses in feed processing in the future
Summary
Phytases are widely used in feed industry to increase the utilization of phosphorus, minerals, and other nutrients such as protein, starch and fat [1,2,3]. The diversity and abundance of phytases in nature were widely reported [4]. Plants, including rice, wheat, corn, soybeans and other plant seeds, are traditionally important sources for phytase production [5]. Microbes, such as bacteria, yeast, and filamentous fungi are major sources for the discovery and production of novel phytases. Owing to the excellent physical and chemical properties of known fungal phytases, filamentous fungi, especially Aspergillus spp., are promising source of the development of novel commercial phytases [6].
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