Breeding Of Strain By Co60-γ-rays Mutation For Producing Citric Acid Using Wheat Starch As Raw Material

A. Niger Co827 is a stably producing strain, which has fixed citric acid production,transformation ratio,fermentation cycle. But at present looked from the production cost , the citric acid ferments the raw material price high causes production cost of citric acid to be high and strain of Co827 is suits to the mold mushroom spawn which raw material and so on powder ,maize meal ferments but does not suit the pure starch fermentation.This article mainly product the strain using the Co⁶⁰–γto the citric acid, the goal is in uses as produces the raw material take the wheat starch in the foundation, after removes nutrition source which must add, increase inorganic nitrogen source and inorganic salt ingredient simultaneously to embarks the fungus in this culture medium foundation to carry on the mold mushroom spawn obtains the strain of high production acid .[1] In this carried on the optimization take the wheat starch as in the raw material foundation to the existing production mold mushroom spawn production formula , including to carbon, nitrogen source, the inorganic salt density determination, had determined embarks culture medium formula which the fungus needs.[2] The effects of the different mutagens (the ultraviolet raw, the radial of Co⁶⁰ -γ, particleα)on the citric acid producing strain A. niger were studied. It was demonstrated that the effect of the radial of Co⁶⁰ -γwas more efficient.[3] A high citric acid producing strain was obtained by a series of screenings. After having optimized the culture media (carbon source, nitrogen source, mineral salts, etc.). The optical medium was obtained. And has carried on the heredity stability test to the strain, proved its heredity performances is stable. It has determined the citric acid strain growth and the fermentation curve on the rocker.[4] By comparing the specialties of the original strain and the high citric acid producing strain in the genetic stability, in the different original densities of sugar in 5 m³ fermentation tank , it was concluded that the strain COFCO～518 was more suitable to the original density of sugar than the original strain. The photo of two mold mushroom spawn's shapes carried on in the experiment produces has certain instruction significance.