Transgenic microalgae expressing <Emphasis Type="Italic">Escherichia coli</Emphasis> AppA phytase as feed additive to reduce phytate excretion in the manure of young broiler chicks |
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Authors: | So-Mi Yoon So Young Kim Kun Feng Li Byung Hak Yoon Senyon Choe Mario Meng-Chiang Kuo |
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Institution: | (1) Protein Engineering Laboratory, Joint Center for Biosciences at LCDI, Gachon University of Medicine and Science, 7-45 Songdo-dong, Yeonsu-ku, Incheon, 406–840, South Korea;(2) Structural Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd, La Jolla, CA 92037, USA; |
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Abstract: | Microbial phytases are widely used as feed additive to increase phytate phosphorus utilization and to reduce fecal phytates
and inorganic phosphate (iP) outputs. To facilitate the process of application, we engineered an Escherichia coli appA phytase gene into the chloroplast genome of the model microalga, Chlamydomonas reinhardtii, and isolated homoplasmic plastid transformants. The catalytic activity of the recombinant E. coli AppA can be directly detected in the whole-cell lysate, termed Chlasate, prepared by freeze-drying the transgenic cell paste
with liquid nitrogen. The E. coli AppA in the Chlasate has a pH and temperature optima of 4.5 and 60°C, respectively, which are similar to those described
in the literature. The phytase-expressed Chlasate contains 10 phytase units per gram dry matter at pH 4.5 and 37°C. Using
this transgenic Chlasate at 500 U/kg of diet for young broiler chicks, the fecal phytate excretion was reduced, and the iP
was increased by 43% and 41%, respectively, as compared to those of the chicks fed with only the basal diet. The effectiveness
of the Chlasate to break down the dietary phytates is compatible with the commercial Natuphos fungal phytase. Our data provide
the first evidence of functional expression of microbial phytase in microalgae and demonstrate the proof of concept of using
transgenic microalgae as a food additive to deliver dietary enzymes with no need of protein purification. |
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