Strain Improvement Of Rhizopus Oryzae For Fumaric Acid Production And Optimization Of Cultures Conditions

Fumaric acid occurs naturally in many plants and is named after Fumaria officinalis, and it is a promising candidate in the manufacture of polymer and a sizing resin in paper factory .A systematic investigation was carried out to improve the productivity of fumaric acid producing strain by UV irritation and bioprocess optimization. During the selection procedure, a simple way of screening for high-yield fumaric acid producing strain was developed and evaluated, in which, area ratio of area of colored ring to that of colony was designed as an indicator.Fermentation medium of the parent strain was simply optimized as follows: Glucose 85; KNO₃ 1.24; KH₂PO₄ 0.16; ZnSO₄·7H₂O 0.04; MgSO₄·7H₂O 0.25, and 10 ug/l biotin, 15 ml/1 methnol.When the cultures were grown in the optimized fermentation medium, the fumaric acid yield 28 g/l, 55.6% higher than the original fermentation medium.Strain improvement has been conventionally achieved through mutation and selection. A fumaric acid over-producing strain mutant, Rhizopus oryzae ZJU11, was isolated by mutagenizing the parent strain by UV mutagenesis. Starting with an optimized concentration of 85 g/1 glucose, the mutant Rhizopus oryzae ZJU11 produced 57.3 g/1 fumaric acid in shaking-flask fermentation and 41 g/l in 5-L fermentor, which were 105% and 57% higher than that of the parent strain produced respectively.The influences of nitrogen sources, carbon sources, concentration of CaCO₃ and its addition method CaCO₃ in culture medium on fumaric acid production by the mutant Rhizopus oryae ZJU11 were investigated. The final optimized fermentation medium, which was the same as the optimized fermentation medium for the parent strain. When the cultures were grown in the optimized fermentation medium, the fumaric acid yield and conversion ratio (fumaric acid produced / glucose consumed)with the mutant Rhizopusoryae ZJU11 were 57.3g/l and 0.675(g/g) respectively.At last, to systematically describe the effect of nystatin on mycelium growth and fumaric acid production, according to the experimental data and supposed model, equations of concentration of nystatin and concentrations ofbiomass and fumaric acid were obtained as follows:...