Optimization Of Fermentation Conditions And Kinetics Models Of Fermentation For Cellulase Produced By Rhizopus Stolonifer

In terms of the cellulase enzyme production status, the production cost is too high and the enzyme deactivation easily, that is why the cellulase can not application widely. So we need to improve the yield of cellulase by strain selection to screening out the strains which can high-yielding of cellulases, then establishing the kinetic model of fermentation to optimize the fermentation process to achieve the purpose of reducing cost.In this experiment, the filter paper activity as index, through single factor experiment investigated the types of carbon and particle size, the type of nitrogen source, inorganic salts dosage, affect the fermentation temperature, shake flask fermentation liquid volume and the initial pH of the enzyme production. Application of uniform design method to optimize rice straw powder, urea, bean dregs, potassium dihydrogen phosphate, Tween 80which five factors in the fermentation medium proportions. Finally got the optimum fermentation conditions for cellulase production by Rhizopus stolonifer, rice straw10g/L, urea1.7g/L, dregs1.7g/L, potassium dihydrogen phosphate1.1g/L, Tween800.27mL/L, magnesium sulfate15g/L, Calcium chloride30g/L, The volume of liquid50mL/250mL, the initial fermentation pH6.5, at30℃,180rpm/min for4days, The results indicated that at84h the filter paper activity reached13.16IU/mL, more than149%before optimization, Cut in the activity under the same conditions the highest Endocellulases activity, Cellobiohydrolases activity and β-Glucosidases activity were45.81IU/mL,0.537IU/mL and12.45IU/mL.On the basis of the shaking flask fermentation, enlarge experiment was carried out.3L fermentation tank are installed in the liquid amount of2L, not investigated pH control, using ammonia and phosphoric acid to control fermentation pH5.0, the constant aeration during fermentation, the fermentation process by adjusting the amount of aeration to maintain a dissolved oxygen conditions for four fermentation of cellulase production by Rhizopus stolonifer. When the dissolved oxygen in the fermentation process control30-40%, fermentation pH control at5.0, got the maximum filter paper activity which was16.98IU/mL and compared with fermentation improved29.03%. Under the same conditions the maximum endocellulases activity value was41.33IU/mL and compared the fermentation dropped 10.78%, the maximum value of cellobiohydrolases activity was3.65IU/mL, compared with fermentation improved579.70%, P-glucosidases highest value was15.98IU/mL, compared with fermentation improved28.35%β-glucosidases activity in addition to advance24h, the maximum activity of other enzymes were ahead12h.Using the Logistic equation and Luedeking-Piret equation establishes dynamic models with the fermentation data by the3L fermenter. Kinetic models are as follows:Cell growth kinetics model:X=12.0792e0.3158t/(21.01+0.56e0.3158t), Filter paper activity dynamics model: P1=0.21168e0.3158t/(21.01+0.56e0.3158t)+0.855421n((21.01+0.56e0.3158t)/21.57), Microcrystalline cellulose synthesis kinetics model:P2=0.59548e0.3158t/(21.01+0.56e0.3158t)+2.109191n((21.01+0.56e0.3158t)/21.57) Endocellulase synthesis kinetics model:P3=0.36118e0.3158t/(21.01+0.56e0.3158t)+0,150061n((21.01+0.56e0.3158t)/21.57), β-glucosidase synthesis kinetics model:P4=0.78891n((21.01+0.56e0.3158t)/21.57)-0.5853e0.3158t/(21.01+0.56e0.3158t), Substrate consumption dynamics model:S=68.89-(26.0195e0.3158t)/(21.01+0.56e0.3158t)-0.562921n((21.06+0.56e0.3158t)/21.57), all of the R2by the models were0.9801,0.9947,0.9908,0.9761,0.9711and0.9954,so the models fitted well. At the same time through the model parameter that the synthesis of filter paper activity, endocellulase activity, exocellulase activity and P-glucosidase activity were partially coupled relationship with cell growths.