枯草芽孢杆菌E79分批发酵动力学

基于Logistic和Leudeking-Piret方程,根据分批发酵过程中菌体生长、产物积累、总糖消耗、还原糖消耗及反应体系pH值的变化规律构建枯草芽孢杆菌E79发酵过程中菌体细胞生长、产物合成及基质消耗的动力学模型,应用SPSS11.5软件对数据进行计算与分析,Oirgin 7.5软件经非线性拟合与优化,获得了最佳...     

Development of a mathematical model for Bacillus circulans growth and alkaline protease production kinetics

BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism‐related protease production (using logistic and Luedeking–Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 10³ U g^?1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L^?1). The developed model could be effectively utilised for designing, controlling and up‐scaling the protease production process in high‐density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry     

Statistical optimization of fermentation conditions for the improved production of poly-β-hydroxybutyrate from Bacillus subtilis

Poly-β-hydroxybutyrate (PHB) has been an effective biodegradable plastic obtained by microbial fermentation. Batch fermentation of Bacillus subtilis features an attractive system for the production of PHB. Identification of appropriate media components and cultivation conditions are extremely important for the optimal production of biomass and/or PHB production. Statistical media design was utilized for the optimization of different fermentation variables (glucose, peptone, sodium chloride, K₂HPO₄, KH₂PO₄, ammonium sulfate, ammonium chloride, sodium sulfate, temperature, inoculum size, and pH). The optimized media predicted the optimal dry cell weight of 7.54?g?L^?1 and PHB production of 77.2?mg?L^?1 at 1?g?L^?1 of peptone, 1.46?g?L^?1 sodium sulfate, and pH 6.8 in 24?h. Glucose utilization, batch growth, and PHB production kinetics of B. subtilis were determined experimentally. The effect of substrate inhibition on specific growth rate was also determined experimentally for B. subtilis. The values of kinetic and substrate inhibition parameters obtained from this study shall be utilized to develop a mathematical model for PHB production for further improving the production of PHB.     

Mathematical model for lactic acid production from lactose in batch culture: Model development and simulation

The models available to describe lactic acid production do not seem to fit the experimental data very well, especially at the end of batch cultures. From a careful analysis of batch data, an unstructured model of the process has been derived, in which the specific growth rate variations and lactic acid concentration with time have been described by complemented logistic functions. Also, an additional term has been introduced into the Luedeking–Piret expression, taking into account the reduction in rate of lactic acid production observed at very low growth rate.     

Batch kinetics and modelling of propionic acid fermentation

Batch propionic acid fermentation kinetics was studied using five different initial concentrations of lactose (i.e., 37 g/L, 45g/L, 50g/L, 57 g/L and 73 g/L) at constant temperature (30°C) and pH (6.5) under anaerobic conditions using Propionibacterium acidipropionici (ATCC 4875). When the initial substrate concentration was 37 g/L, 45 g/L, 50 g/L, 57 g/L and 73 g/L, then, correspondingly, 16 g/L, 19 g/L, 22.25 g/L, 25.3 g/L and 26.3 g/L of propionic acid was accumulated in the fermentation broth. Increasing the supply of lactose in the fermentation medium led to the accumulation of by products succinate, acetate and pyruvate. Maximum propionate yield (0.44 g/g) and comparatively lesser impurities (byproducts) were achieved with 57 g/L initial lactose concentration. The batch growth kinetics was eventually used to develop and test a mathematical model for propionic acid fermentation by P. acidipropionici at pH 6.5 and S_o = 57 g/L. Y_X/S^max was found to be the most sensitive parameter of the model. The same model also successfully simulated the batch kinetics observed at S_o = 37 g/L. However the model failed to simulate the fermentation kinetics observed at S_o = 73 g/L. The developed model can be used for process optimization studies.     

氨基甲酸乙酯水解酶在枯草芽孢杆菌中的表达及发酵优化

将来源于赖氨酸芽孢杆菌SC02的氨基甲酸乙酯水解酶(UH)基因在枯草芽孢杆菌Bacillus subtilis WB600中进行克隆和表达,在枯草芽孢杆菌中实现了UH活性表达,在摇瓶水平通过单因素考察和响应面分析实验对氨基甲酸乙酯水解酶发酵进行优化. 结表明,酶活最高可达到14.20 U/mL,产酶最佳培养基成分为：淀粉10 g/L、磷酸氢二钾9 g/L、麦芽浸膏25 g/L、硫酸镁1 g/L、胰蛋白胨55 g/L,最适发酵温度为37℃,最佳接种量4%. 在3 L发酵罐中采用最优发酵条件,酶活在16 h达到18.03 U/mL.     

Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

生物表面活性剂生产Bacillus subtilis-1101发酵过程优化

应用中心组合试验设计和响应面分析方法对影响枯草芽孢杆菌Bacillus subtilis-1101产生表面活性剂的发酵过程进行优化。结果表明,枯草芽孢杆菌Bacillus subtilis-1101产生表面活性剂的最佳发酵条件为发酵温度29.1℃,初始pH值为4.9,装液量为56mL。在此条件下进行实验,结果最大排油圈为7.08cm,与模型预测值接近。说明响应面分析方法是优化表面活性剂生产的有力工具。     

Analysis of the kinetics of growth and lactic acid production for Lactobacillus helveticus growing on supplemented whey permeate

Growth of Lactobacillus helveticus on supplemented whey permeate was divided into five phases: lag, exponential, deceleration, stationary and decline phases. Each phase was characterized by simple model kinetics. From this and by considering a partial association of lactic acid production with growth, with an additional term introduced to account for cessation of production when the carbon substrate became limiting, the lactic acid production was analytically deduced for each growth phase. For both growth and production data, on the whole culture, the calculated values were found to match experimental data. All the model parameters can be easily deduced from experimental data. The model allows therefore a fine analysis of growth and production kinetics. Copyright © 2005 Society of Chemical Industry     

核黄素基因工程菌的构建及其发酵的初步研究

构建整合型核黄素质粒pRB63,该质粒含有解调的B.subtilis核黄素操纵子,将其转化入B.subtilisRH13并在染色体上进行适当的扩增后得到RH13::[pRB63]n系列工程菌,其核黄素合成能力随着pRB63扩增程度的增加而增强,最终达到RH13的6～7倍.随后以RH13::[pRB63]n系列工程菌和B.subtilis YB1为亲株进行原生质体融合,筛得重组菌B.subtilis RH33.该菌在含10%葡萄糖或蔗糖的分批发酵中培养64h可产核黄素量4.2 g·L-1.采用以葡萄糖为碳源的流加发酵工艺,24 h可积累核黄素7～8 g·L-1,48 h达11～12 g·L-1,核黄素对葡萄糖的得率为0.056 g·g-1.     

Metabolic engineering of Bacillus subtilis for high-titer production of menaquinone-7

Menaquinone-7 (MK-7) is a member of vitamin K₂ used for prevention from osteoporosis and cardiovascular calcification. This study constructed Bacillus subtilis strains for high-titer production of MK-7 through metabolic engineering approaches. In B. subtilis, MK-7 biosynthesis was categorized into five modules: glycerol dissociation pathway, shikimate pathway, pyrimidine metabolic pathway, methylerythritol phosphate pathway, and MK-7 pathway. Overexpression of GlpK and GlpD (glycerol dissociation pathway) led to a ~10% increase in the MK-7 titer. Deletion of the genes mgsA and araM increased the MK-7 production by 15%. Furthermore, overexpression of AroG^D146N (shikimate pathway), PyrG^E156K (pyrimidine metabolic pathway), HepS (methylerythritol phosphate pathway), and VHb could also increase the MK-7 titer. Finally, we obtained a recombinant strain BSMK_11 with simultaneous overexpressing the genes glpK, glpD, aroG ^fbr, pyrG ^fbr, hepS, vgb, and knockouting the genes mgsA and araM, and the MK-7 titer reached 281.4 ± 5.0 mg/L (i.e., 12.0 mg/g DCW) in a 5 L fermenter.     

苏云金芽孢杆菌固态发酵条件的优化

利用农产品下脚料作培养基,对菌株Bt HD-1的固态发酵工艺条件进行了优化,确定其发酵的最优条件为:初始含水量60%,pH值7.5～8.0,种子液接种量15%,种龄7 h,固态发酵时间42 h.测定表明最佳发酵条件下产品的毒力效价可稳定在18000 IU·mg-1,超过了国内文献报道的最高发酵水平,同时发酵时间缩短了8 h.     

醋糟酶解液的制备及其发酵生产枯草芽孢杆菌TS-02

采用水热处理技术对醋糟进行预处理,优化了醋糟的纤维素酶酶解条件,制得葡萄糖浓度27.00 g/L的醋糟酶解液. 以醋糟酶解液为基础培养基替代培养基中的葡萄糖,发酵生产枯草芽孢杆菌TS-02活菌制剂. 结果表明,在醋糟酶解液培养基中摇瓶发酵44 h时活菌数活菌数最高达4.64×1010个/mL, 7 L发酵罐中发酵周期为22 h,活菌数达6.16×1010个/mL,芽孢率达80%以上.     

Mathematical model for growth process of a recombinant yeast having saccharification and fermentation activities

A mathematical model for direct alcohol fermentation from starch was proposed using an amylase‐producing recombinant yeast, Saccharomyces cerevisiae SR93. This model consisted of the reaction rate equations for glucoamylase synthesis in the recombinant yeast, starch degradation by a glucoamylase, cell growth, production of glucose, and production of ethanol. The rate of glucoamylase synthesis was expressed on the basis of the diauxic growth model that represents catabolite repression and enzyme induction. The rate of starch degradation was expressed on the basis of the enzymatic hydrolysis model representing the change of structure resulting from starch degradation. The calculated values were in satisfactory agreement with the experimental data in a batch culture of direct alcohol fermentation from starch using S cerevisiae SR93. Furthermore, the calculated values obtained by changing only one parameter concerning the synthesis rate of glucoamylase were in satisfactory agreement with the experimental data using another recombinant yeast, S cerevisiae SR96. Copyright © 2003 Society of Chemical Industry     

Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP). RESULTS: Batch cultivations carried out at different initial levels of glucose (G₀) in the presence of 10 g L^?1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G₀≤10 g L^?1 (B_max = 104–110 mg L^?1). The recombinant strain exhibited slightly lower levels of biosurfactants (B_max = 90–104 mg L^?1) but only at higher glucose concentrations (G₀ ≥ 20 g L^?1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase. CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry     

辅酶Q10的发酵动力学

在5 L发酵罐实验数据基础上,应用Logistic方程基于Agrobacterium tumefaciensATCC4452(根癌农杆菌)菌种的生长、辅酶Q10的产量、底物的消耗、生物量的形成和维持创建动力学模型。应用MATLAB 7.0软件经非线性拟合和优化,获得了最佳的模型参数值,确定了菌体最大比生长速率为0.105 h-1和较大的生物量对辅酶Q10的得率系数YP/X=2.445 5,拟合模型R2均大于0.996,结果显示模型与实验数据能较好地吻合,确定了细菌合成辅酶Q10分批发酵过程的动力学特征。