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Lactic acid and its ramification are widely applyed in many domains,such as food, medicine, agriculture, commodities, environmental protection, chemical industry. Especially in recent years, use lactic acid producing biodegradable plastic polymer, green packaging materials and agricultural film to solve the growing shortage of resources and environmental pollution problems,demonstrating its broad application prospects.In this paper, Lactobacillus rhamnosus CICC6003 was treated with ultraviolet radiation,after the mutation,a mutated strain was selected with high glucose, high acid and succinic acid flat plate,the production of lactic acid reached 84.6 g/L, increased 25.9% than the original strain, and have good stability.Determined by single factor experiments for the best potato saccharification liquid carbon source, yeast extract as the most suitable nitrogen source, study the composition of potato saccharification liquid medium, yeast extract, diammonium citrate, sodium acetate, K2HPO4, Mg2+, Mn2+, Fe2+ eight factors on lactic acid yield. Using Plackett-Burman experimental design study of 8 factors in the medium fractions, the liquid of potato saccharification, yeast extract and manganese sulfate selected three significant factors, choose these three factors as the main subjects for further optimization work. Steepest ascent experiment factors determined the center of response surface experimental,the liquid of potato saccharification 100 g/L,yeast extract 14 g/L,manganese sulfate 0.015 g/L.Useing Minitab15 create and regression the equations, the liquid of potato saccharification 110.7 g/L,yeast extract 14.98 g/L,manganese sulfate 0.016 g/L, the maximum lactic acid yield was 94.09 g/L.To verify the optimal experimental conditions, an average of three experiments 93.2 g/L, and the error value was 0.9% between the predicted. Compared with the former, lactic acid production increased 11.2%, L-lactic acid purity was 94.8%. Single factor experiments to determine the best conditions,seed age 16h, inoculum 8%, volume 100mL, temperature 37℃, CaCO3 added before fermentation.The process of simultaneous saccharification and fermentation were optimized. Research shows that first liquefaction of starch and take the simultaneous saccharification and fermentation was the best way.single factor experiments confirmed the optimum starch concentration 300 g/L, glucoamylase dosage 250u/g starch, fermentation temperature 37℃, fermentation time 72h. By Plackett-Burman screening experiment starch concentration, glucoamylase, and fermentation temperature had significant effects,these three factors as the main research object for further optimization. Steepest ascent experiment factors determined the center of response surface experimental,starch concentration 260 g/L, glucoamylase dosage 260 U/g starch, fermentation temperature 38℃. Experiments carried out using central composite response surface experiment, Useing Minitab15 create and regression the equations,starch concentration 271.89 g/L, glucoamylase dosage 265.09 U/g starch, fermentation temperature 39.05℃, the maximum lactic acid production reached 196.99 g/L. In the verification experiments under optimal conditions, an average of three experiments 193.6 g/L, error value was 1.7%, compared with before optimization, the production of lactic acid increased 13.9%, L-lactic acid purity was 95.2%.This paper also studied the altering temperature strategy in simultaneous saccharification and fermentation, the best conditions was after fermentation began 8h warming up temperature to 42℃, maintain 2h and then t dropped to 37℃, the production of lactic acid increased 3.5% and 1.6% with constant temperature fermentation on37℃and 39℃
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