| Corns and oil crops such as wheat, rice, barley, potato, sesame oil cake, etc. are useful sources of protein and energy for livestock. They are commonly used in animal feed and human food. One of the measurements of their nutritional worth is the content of phosphorus. In fact, phytate is a main storage form of phosphorus in legumes, cereal grains and oilseeds, which is not readily utilized by monogastrics and considered to be an anti-nutrition factor by many nutritionists. Phytates are regarded as decreasing feed qualities because they bind proteins and minerals to reduce the absorption of many nutrition factors so much that the nutritive value of the feed and food are lowed much in the end. Phytase (EC 3.1.3.8) is a phosphomonoesterase capable of hydrolysing phytic acid to inorganic orthophophate (Pi) and a series of lower esters of myo-inositol, thereby, releasing free myo-inositol. Supplementation of phytase to the feedstuff could reduce Pi release and have a dual benefit of increasing both the bioavailability of the phytin phosphorus and nutritional of feedstuff. Its weakness is present on it raises the costs of the feed when raising the nutritive value of it.Saccharomyces cerevisiae is one of the microorganisms generally regarded as safe (GRAS) and used among animal feed and human food as it not only provides rich fungal proteins, but also contains much nutritional ingredients such as sugars and some accessory enzymes. It is meaningful to reconstruct the bread yeast strains with high protein by gene engineering method to meet the requirements of being feed additives.In this study, the phyA gene encoding phytase (PHYA), which was cloned by PCR from Asperilliusg niger, was ligated into the multi-copy integration vector pYMIKP which contains an rDNA fragment as homologous recombination loci. The recombinant plasmid was named pYMIKP-phyA. The recombinant plasmid was transformed into the industrial strain of S. cerevisiae YW-006 by transformation... |
PDF Full Text Request