Background: L-ornithine (L-Orn), is an intermediate metabolite in the urea cycle that plays a significant role in humans. L-Orn can be obtained from the catalysis of L-arginine (L-Arg) by arginase. The Pichia pastoris expression system offers the possibility of generating a large amount of recombinant protein. The immobilized enzyme technology can overcome the difficulties in recovery, recycling and long-term stability that result from the use of free enzyme. Methods: The recombinant human arginase I (ARG I) was obtained using an optimized method with the Pichia pastoris GS115 as the host strain. Chitosan paticles were cross-linked with glutaraldehyde and rinsed exhaustively. Then the expressed ARG I was immobilized on the crosslinked chitosan particles, and the enzymatic properties of both the free and immobilized enzymes were evaluated. At last, the immobilized ARG I was employed to catalyze L-Arg to L-Orn. Results: The results indicated that these two states both exhibited optimal activity under the same condition of pH10 at 40 °C. However, the immobilized ARG I exhibited the remarkable thermal and long-term stability as well as broad adaptability to pH, suggesting its potential for wide application in future industry. After a careful analysis of its catalytic conditions, immobilized ARG I was employed to catalyze the conversion of L-Arg to L-Orn under optimal condition of 1 % glutaraldehyde, 1 mM Mn 2+, 40 °C, pH10 and an L-arginine (L-Arg) concentration of 200 g/L, achieving a highly converted content of 149.g/L L-Orn. Conclusions: In this work, ARG I was abundantly expressed, and an efficient, facile and repeatable method was developed to synthesize high-quality L-Orn. This method not only solved the problem of obtaining a large amount of arginase, but also provided a promising alternative for the future industrial production of L-Orn.
CITATION STYLE
Zhang, X., Liu, J., Yu, X., Wang, F., Yi, L., Li, Z., … Ma, L. (2015). High-level expression of human arginase I in Pichia pastoris and its immobilization on chitosan to produce L-ornithine. BMC Biotechnology, 15(1). https://doi.org/10.1186/s12896-015-0184-2
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