Study On Degradation Of Straw From Fermentation Broth Of Aspergillus Oryzae CGMCC5992

The cellulose is the main component of the strain to produce bio-fuel.However,the lignin encased outer of cellulose and the small specific surface area are the cause of difficult use straw.The present dissert further optimized the medium components and culture condition that Aspergillus oryzae CGMCC5992 synthesized lignin peroxidase（LiP）,studied the kinetics degradation reaction lignin of corn straw（CS）by combination the A.oryzae broth as crude enzyme solution and H2O2 as oxidant and saccharification reaction pretreated CS,analyzed the effect of various reaction conditions on the kinetic’s parameters and disclosed the mechanism of degradation.The following main conclusions were obtained:（1）The optimum medium to produce LiP by the mono-factor-at-a-time design was constituted of（g/L）: 30 CS,2.5 maltose,2.5 glycerol,1.5 yeast extract,45（NH4）2SO₄,0.6MgSO₄,0.4 FeSO₄,0.4 CuSO₄,1.0 MnSO₄,0.1 VB₁₂,5.5 Glycine.The optimum culture condition included: temperature 35 ℃,the rotate speed 146 r/min,the loading medium 111 mL in 250 mL flask,the inoculated volume 12%.Under the optimum condition,the maximum LiP activity was 2267 U/L.（2）The guaiacol producing velocity was used as an index,effect of pretreated temperature,the reaction temperature and pH,the enzyme volume and H2O2 concentration and volume on the parameters including the apparent Michaelis constant（K_m）’ and the apparent maximum reaction velocity(μ_max)’ were studied.The optimum conditions to obtain the maximum(μ_max)’ and small the（K_m）’ included pretreatment temperature of 120 o C,pretreatment time of 5 min,reaction temperature of 30 ℃,enzyme amount of 3.75 U/100 mL,50 mM sodium lactate-hydrochloric acid buffer of pH 1.5,H2O2 concentration of 20 mM and H2O2 amount of 1 mL,respectively.（3）The yield of total reducing sugar(Y_trs)used as an index,we demonstrated the saccharification kinetics of pretreated CS by combination A.oryzae broth and H2O2.The Impeded Michaelis modelcould be applied in fitting all experimental data.The model gave the initial activity and accessibility of enzyme on the substrate(K_obs,0)and the gradual loss ofenzyme activity（Ki）.The maximum Y_trs（55.56%）was obtained under the following conditions: pH of 4.7,temperature of 48.6 ℃,cellulase concentration of 1.5% and water-to-material ratio of 12.4:1.Y_trs was significantly positively correlated with K_obs,0and negatively correlated with Ki.