Study On Fermentation L-(+)-lactic Acid From Cornstarch By Rhizopus Oryzae 3.242

Lactic acid is an important organic acid with extensive use. Lactic acid, lactate and their derivants are used in many fields such as food industry, medicine production, food industry, environmental protection and chemical industry. Poly(L-lactic acid), an biodegradable plastic without toxicity, can be thoroughly decomposed into carbon dioxide and water by organism. So poly(L-lactic acid) slakes'white pollution'caused by PVC, PP plastic and has a great meaning to settle white pollution problem.The optimum culture and production condition of lactic acid batch fermentation for Rhizopus oryzae by cornstarch is studied in this paper. Several fermentation optimum conditions including carbon source concentration, nitrogen source and its concentration, phosphate, temperature and pH are determined in the experiment. Meanwhile, effects of rotation speed and aeration quantitative to fermentation are also studied. The optimum seed culture (g·L^-1) is: Glucose 50.0, (NH4)2SO₄ 2.0, KH2PO4 0.30, ZnSO₄ 0.50,MgSO₄ 0.50. And the optimum culture condition is: 34℃, 70ml in 500ml flask for 30 hours with CaCO₃ 10.0 g·L^-1. The optimum fermentation condition is: Carbon source concentration 108.0 g·L^-1, (NH4)2SO₄ 5g·L^-1, KH2PO4 0.30g·L^-1, ZnCl2 0.60g·L^-1, MgCl2 0.30g·L^-1. And the optimum fermentation temperature and inoculum concentration are 34℃and 12% separately. The pH of zymotic fluid is confined with the range of 5.5 to 6.0. Finally the obtained agitation rate and aeration rate are190r·min^-1 and 3vvm separately.Dynamics equation of fermentation is significant to optimize the conditions of production and study the reaction mechanics of biochemistry. A mathematical model of L-lactic acid fermentation is established in this thesis. The dynamics equation of Rhizopus orazae cell growth is obtained from the classical Logistic model. Meanwhile, the dynamics equations of Lactic acid produce and of glucose consumption are established from Luedeking-Piret equation and mass conservation with Logistic model separately.These three equations can accurately forecast the mycelium growth , Lactic acid produce of the zymotic fluid and glucose consumption, which can guide the optimization of fermentation.