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Biotin, also known as vitamin H, is the cofactor of various carboxylases, decarboxylases and transcarboxylases. Most living systems need biotin for normal growth, however, only some can synthesize it. Though biotin deficiency is not serious among human beings and animals, the circumstance may be critical upon genetic defect and nutritional imbalance. The production of biotin nowadays is still by the way of chemical synthesis and the cost is usually high. Therefore, I attempted to construct high biotin production strain of animal-feeding yeast by genetic engineering. In addition to produce high biotin yeast, other products such as health-food, cosmetic and even pharmaceutical grade biotin may be obtained. To construct the YIp plasmids (yeast integrative plasmid), the 5SrDNA, 18SrDNA, 26SrDNA and leu2d gene (selection marker) were assembled to facilitate selection of the plasmid and the integration of these YIp into yeast chromosome by homologous recombination for long-term and stable expression of foreign genes. The BIO2 gene (biotin synthase gene) and BIO4 gene (dethiobiotin synthetase gene) were cloned to the plasmids and integrated into yeast chromosome to test the feasibility of these constructs. Primary results indicated that the transformal yeast can grow in SD medium (without leucine) and express the BIO2 gene product properly. The production of biotin by the transformal yeast is much higher than that of the parent strains.
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