Improvement of Bioconversion of Vitamin D₃ into Calcitriol by Actinomyces hyovaginalis through Protoplast Fusion and Enzyme Immobilization
Pages 32-40
Ahmad M. Abbas, Khaled M. Aboshanab, Walid F. Elkhatib, Mohammad M. Aboulwafa and Nadia A. Hassouna

DOI: https://doi.org/10.6000/1927-3037.2017.06.01.4

Published: 21 April 2017

Abstract: Protoplast fusion and enzyme immobilization techniques were applied to increase calcitriol production from vitamin D₃ using Actinomyces hyovaginalis, a local isolate recovered from Egyptian soil, that has a potential bioconversion activity of vitamin D₃ into calcitriol. A total of sixteen protoplast hybrids, formed between Actinomyces hyovaginalis isolate and two Bacillus species (B. thuringiensis and B. weihenstephanensis)were screened for vitamin D₃ bioconversion activity. Compared to wild type isolate, four hybrids (formed between Actinomyces hyovaginalis isolate and B. thuringiensis)were found to preserve the bioconversion activity; out of which, three hybrids coded V2B, V3B and V8A exhibited higher calcitriol production. The hybrids coded V2B and V8A produced, per 1 L culture medium, about 0.5 and 0.4 mg calcitriol corresponding to 350% and 280%, respectively, increase compared to the wild type isolate. Among different alginate concentrations applied, immobilization of cell lysate of Actinomyces hyovaginalis isolate using 2% alginate showed 140% increase in calcitriol production from vitamin D₃ compared to the free cell lysate. Activity of the immobilized form was preserved for five repetitive uses over a period of 15 days but with a 50% decline in production occurring at the fifth use.

Keywords: Bioconversion, protoplast fusion, immobilization, vitamin D₃, calcitriol, Actinomyces hyovaginalis.

Download