嗜酸氧化亚铁硫杆菌生长动力学方程的应用

基于Monod模型推导出了A．f的生长动力学方程模型,采用Gauss-Newton算法确定了在不同初始条件下细菌生长的动力学参数,即最大比生长速率‰、Monod常数K及R0。通过在不同初始条件下细菌生长特性的研究,得到了相应初始生长条件下以限制性底物亚铁离子浓度为表征的生长动力学方程,理论上揭示了动力学参数变化对细菌生长的影响规律,其中生长动力学方程的数值模拟与实验数据相吻合。     

初始底物浓度对序批式培养光合细菌产氢动力学影响

实验研究了初始底物浓度对序批式培养光合细菌生长、降解及产氢过程的影响,根据最大比生长速率实验数据拟合得到其关于初始底物浓度影响的关联式,并在建立的修正Monod模型基础上建立了光合细菌比生长速率、基质比消耗速率和比产氢速率关于底物初始浓度影响的数学模型,模型预测值与实验结果在光合细菌生长期和稳定期内得到较好吻合,反映了光合细菌生长、降解和产氢过程中受底物初始浓度限制性和抑制性影响的基本规律。分析发现光合细菌生长、降解基质和产氢过程中最适底物浓度为50 mmol/L,初始底物浓度低于或高于该浓度时,光合细菌生长、降解及产氢过程都受到限制性或抑制性影响,且抑制性影响较限制性影响效果更明显;底物比消耗速率受初始底物浓度影响较小。     

L-异亮氨酸产生菌XQ-4在连续培养中的动力学特性

以黄色短杆菌（Brevibacterium flavum)ATCC14067诱变选育获得的L-异亮氨酸高产菌XQ－4（AHV^rSuc^gSG^rEth^rα-AB^rIleHx^r）在连续培养中进行动力学特性研究,以葡萄糖为限制性底物时,XQ－4菌株的生长符合Monod方程,其最大比生长速率μmax=0.265h^-1,饱和常数Ka=0.789g/L.XQ-4菌株L-异亮氨酸发酵时菌体最大实际转化率Yx=0.499g/g,产物最大实际转化率Yp=0.379g/g。     

甲醇产纤维素菌株的静态发酵动力学研究

目的:为实现甲醇资源化产细菌纤维素发酵过程的优化,研究纤维素生产菌株一木醋杆菌(Gluconacetobacter χγlinus)的静态发酵动力学特性.方法:将木醋杆菌接入甲醇浓度分别为2.7%和4.5%的培养基中驯化,根据Logistic方程和LuedekingPiret方程,研究周期为13d的静态发酵动力学过程.结果:确定静态发酵过程的菌体生长、细菌纤维素合成、底物消耗的动力学参数,得到动力学方程,拟合试验值与模型值,得到甲醇模拟废水培养基平均拟合误差为16%,略高于基础培养基的14%.结论:利用甲醇产纤维索的模型方程可预测菌浓、产物浓度及底物消耗规律,实现静态发酵过程的优化.     

氧化亚铁硫杆菌氧化亚硫酸盐的动力学研究

实验用Ms培养基,利用去除铁离子的氧化亚铁硫杆菌(Thiobacillus ferrooxidans)进行了细菌亚硫酸盐的生长代谢研究。实验结果表明氧化亚铁硫杆菌对亚硫酸根具有一定的氧化能力。用Origin 7.0对实验数据进行拟合处理,表明了氧化亚铁硫杆菌催化氧化亚硫酸盐的动力学方程符合Hill方程。氧化亚铁硫杆菌催化氧化亚硫酸盐是一个底物抑制的细胞反应,其KS值随pH值和底物浓度的改变而变化。pH值对反应有很大的影响,pH值越接近中性KS就越小,反应速率就越大。     

螺旋藻连续培养与动力学模型

在内循环气升式光生物反应器中 ,研究了钝顶螺旋藻 (SpirulinaplatensisGeitler)细胞的连续生长及其对碳源底物的利用特性。结果表明 :随着稀释率的增大 ,反应器中碳源浓度和细胞浓度分别呈上升和下降趋势 ,它们之间的关系可用Monod类型的方程很好地加以关联。细胞产率和碳消耗速率与稀释率的关系存在峰值现象 :在本实验条件下 ,最大细胞产率为 0 .36 2g/(L·d) ,最大碳消耗速率为 0 .177g/(L·d) ,此时稀释率为 0 .45 /d ,细胞浓度为OD560 =1.2 82 ,细胞对碳的得率系数为 2 .0 5 0g/g。所提出的连续培养动力学模型与实验数据拟合较好     

氮源NH4Cl浓度对粪产碱杆菌发酵生产热凝胶的影响

研究了利用粪产碱杆菌(Alcaligenes faecalis)发酵生产热凝胶的发酵条件,氮源是菌体生长的限制性底物,单纯地提高初始底物(氮源)浓度并不一定能促进细菌的生长和产物的合成.在分批发酵过程中,底物消耗导致培养环境pH的改变也是影响细菌进一步生长和产物合成的重要因素.通过增加培养基中初始氯化铵的浓度并同时控制发酵过程的pH条件,得到了较高的菌体浓度,热凝胶的合成水平也得到了显提高.当培养基中NH4Cl浓度提高到3.6g/L时,菌体浓度达到7.2g/L,热凝胶合成的产量可达30.5g/L,比原来NH4Cl浓度为1.1g/L时提高了51.7%.提高菌体浓度意味着需要提高溶氧水平来满足细菌的生长和代谢.初始氮源NH4Cl浓度的增加虽然能使菌体浓度得到提高,但发酵过程对溶氧的需求也相应增加,需要提高搅拌转速和通风以增加供氧水平.但高搅拌速率产生的高剪切力对热凝胶的凝胶性能将产生破坏作用,因此在发酵过程中需要综合考虑细菌培养密度对合成热凝胶产量和质量的影响.     

产酸丙酸杆菌生长特性及5L罐发酵动力学研究

论文在摇瓶水平对产酸丙酸杆菌基本生长特性（温度、pH、摇床转速、接种量、种龄等）、碳源、氮源利用情况、产物抑制及5 L罐发酵动力学进行了研究。结果表明,该菌在32℃,初始pH 6．5,摇床转速150 r/min,接种24 h的种子液,接种量为5％条件下,产酸丙酸杆菌生长及产酸水平达最高值;该菌可利用碳源十分广泛,但对氮源要求比较高,只可利用有机氮源;在不同初始葡萄糖浓度下,产酸丙酸杆菌生长及产酸水平差异不大,无明显底物抑制现象;在2g/L的初始丙酸盐浓度下,该菌生长受到明显抑制;在5L发酵罐中,初始葡萄糖浓度为58．8 g/L,发酵72 h,葡萄糖消耗完全,丙酸终浓度达22．4 g/L,丙酸得率和产率分别达0．381 g/g和0．295 g/（L·h）,丙酸占总酸比例达72．10％。     

耐高温酵母乙醇间歇发酵动力学研究

该研究采用耐高温型酵母,在不同葡萄糖浓度(5%~30%wt)下进行了乙醇间歇发酵的动力学研究,确定了适合该酵母的最佳底物浓度范围为16%~20%(wt)。同时选取合适的动力学模型,通过实验数据的非线性性拟合,得出了不同底物浓度下对应的动力学参数值,并分析了各动力学参数值随底物浓度增加而变化的趋势。结果显示,该酵母的最大比生长速率μmax随着葡萄糖浓度的增加而有所降低,且呈线性关系:μmax=0.3161-4.1820×104s(100g/L相似文献   

用遗传算法进行重组大肠杆菌发酵动力学的分析

重组大肠杆菌在诱导表达人表皮生长因子的过程促使细菌的生长受到抑制,一部分重组菌丧失了分裂能力,但仍保持着一定的代谢活力,分离成为存活但不能培养的细菌,根据大肠杆菌在表达外源蛋白过程中细胞生理状态的不同将细菌分为三类,提出一个描述诱导表达过程中重组大肠杆菌分离、生长的动力学模型．应用遗传算法对不同底物浓度的细胞生长、分离和产物合成的动力学参数进行了有效地估计,避免了传统算法可能陷于局部最优的问题,模型计算结果与实验结果吻合良好．分离模型在初始糖浓为5-20g/L的范围内可以较好地描述发酵过程中细胞生长、分离和目标产物表达的过程并具有一定的预测能力．     

Nonlinear estimation of Monod growth kinetic parameters from a single substrate depletion curve

Monod growth kinetic parameters were estimated by fitting sigmoidal substrate depletion data to the integrated Monod equation, using nonlinear least-squares analysis. When the initial substrate concentration was in the mixed-order region, nonlinear estimation of simulated data sets containing known measurement errors provided accurate estimates of the mu max, Ks, and Y values used to create these data. Nonlinear regression analysis of sigmoidal substrate depletion data was also evaluated for H2-limited batch growth of Desulfovibrio sp. strain G11. The integrated Monod equation can be more convenient for the estimation of growth kinetic parameters, particularly for gaseous substrates, but it must be recognized that the estimates of mu max, Ks, and Y obtained may be influenced by the growth rate history of the inoculum.     

Nonlinear estimation of Monod growth kinetic parameters from a single substrate depletion curve.

Monod growth kinetic parameters were estimated by fitting sigmoidal substrate depletion data to the integrated Monod equation, using nonlinear least-squares analysis. When the initial substrate concentration was in the mixed-order region, nonlinear estimation of simulated data sets containing known measurement errors provided accurate estimates of the mu max, Ks, and Y values used to create these data. Nonlinear regression analysis of sigmoidal substrate depletion data was also evaluated for H2-limited batch growth of Desulfovibrio sp. strain G11. The integrated Monod equation can be more convenient for the estimation of growth kinetic parameters, particularly for gaseous substrates, but it must be recognized that the estimates of mu max, Ks, and Y obtained may be influenced by the growth rate history of the inoculum.     

Re-interpretation of the logistic equation for batch microbial growth in relation to Monod kinetics

Aims:  To determine the underlying substrate utilization mechanism in the logistic equation for batch microbial growth by revealing the relationship between the logistic and Monod kinetics. Also, to determine the logistic rate constant in terms of Monod kinetic constants.
Methods and Results:  The logistic equation used to describe batch microbial growth was related to the Monod kinetics and found to be first-order in terms of the substrate and biomass concentrations. The logistic equation constant was also related to the Monod kinetic constants. Similarly, the substrate utilization kinetic equations were derived by using the logistic growth equation and related to the Monod kinetics.
Conclusion:  It is revaled that the logistic growth equation is a special form of the Monod growth kinetics when substrate limitation is first-order with respect to the substrate concentration. The logistic rate constant ( k ) is directly proportional to the maximum specific growth rate constant ( μ _m) and initial substrate concentration ( S ₀) and also inversely related to the saturation constant ( K _s).
Significance and Impact of the Study:  The semi-empirical logistic equation can be used instead of Monod kinetics at low substrate concentrations to describe batch microbial growth using the relationship between the logistic rate constant and the Monod kinetic constants.     

The removal of nitrogen and organics in vertical flow wetland reactors: predictive models

Three kinetic models, for predicting the removal of nitrogen and organics in vertical flow wetlands, have been developed and evaluated. These models were established by combining first-order, Monod and multiple Monod kinetics with continuous stirred-tank reactor (CSTR) flow pattern. Critical evaluations of these models using three statistical parameters, coefficient of determination, relative root mean square error and model efficiency, indicated that when the Monod/multiple Monod kinetics was combined with CSTR flow pattern it allowed close match between theoretical prediction and experiment data of nitrogen and organics removal. The kinetic coefficients (derived from Monod/multiple Monod kinetics) was found to increase with pollutant loading, indicating that the coefficients may vary based on different factors, such as influent pollutant concentration, hydraulic loading, and water depth. Overall, this study demonstrated the validity of combining Monod and multiple Monod kinetics with CSTR flow pattern for the modelling and design of vertical flow wetland systems.     

Practical identifiability of growth and substrate consumption models

The estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss-Newton-type method. The four models considered are Monod, Contois, linear specific growth rate, and an enzyme kinetic model. The initial values of the differential equations are included in the parameter vector which will be estimated. The efficiency of the method and the confidence limits of the parameters were studied using simulated measurement noise. The experimental results describe Trichoderma viride growing on glucose as the main carbon source.     

Kinetic study of the conversion of different substrates to lactic acid using Lactobacillus bulgaricus

Lactic acid fermentation includes several reactions in association with the microorganism growth. A kinetic study was performed of the conversion of multiple substrates to lactic acid using Lactobacillus bulgaricus. Batch experiments were performed to study the effect of different substrates (lactose, glucose, and galactose) on the overall bioreaction rate. During the first hours of fermentation, glucose and galactose accumulated in the medium and the rate of hydrolysis of lactose to glucose and galactose was faster than the convesion of these substrates. Once the microorganism built the necessary enzymes for the substrate conversion to lactic acid, the conversion rate was higher for glucose than for galactose. The inoculum preparation was performed in such a way that healthy young cells were obtained. By using this inoculum, shorter fermentation times with very little lag phase were observed. The consumption patterns of the different substrates converted to lactic acid were studied to determine which substrate controls the overall reaction for lactic acid production. A mathematical model (unstructured Monod type) was developed to describe microorganism growth and lactic acid production. A good fit with a simple equation was obtained. It was found experimentally that the approximate ratio of cell to substrate was 1 to 10, the growth yield coefficient (Y(XS)) was 0.10 g cell/g substrate, the product yield (Y(PS)) was 0.90 g lactic acid/g substrate, and the alpha parameter in the Luedeking-Piret equation was 9. The Monod kinetic parameters were obtained. The saturation constant (K(S)) was 3.36 g/L, and the specific growth rate (microm ) was 1.14 l/h.     

Analytical solution for a hybrid Logistic-Monod cell growth model in batch and continuous stirred tank reactor culture

Monod and Logistic growth models have been widely used as basic equations to describe cell growth in bioprocess engineering. In the case of the Monod equation, the specific growth rate is governed by a limiting nutrient, with the mathematical form similar to the Michaelis–Menten equation. In the case of the Logistic equation, the specific growth rate is determined by the carrying capacity of the system, which could be growth-inhibiting factors (i.e., toxic chemical accumulation) other than the nutrient level. Both equations have been found valuable to guide us build unstructured kinetic models to analyze the fermentation process and understand cell physiology. In this work, we present a hybrid Logistic-Monod growth model, which accounts for multiple growth-dependent factors including both the limiting nutrient and the carrying capacity of the system. Coupled with substrate consumption and yield coefficient, we present the analytical solutions for this hybrid Logistic-Monod model in both batch and continuous stirred tank reactor (CSTR) culture. Under high biomass yield (Y_x/s) conditions, the analytical solution for this hybrid model is approaching to the Logistic equation; under low biomass yield condition, the analytical solution for this hybrid model converges to the Monod equation. This hybrid Logistic-Monod equation represents the cell growth transition from substrate-limiting condition to growth-inhibiting condition, which could be adopted to accurately describe the multi-phases of cell growth and may facilitate kinetic model construction, bioprocess optimization, and scale-up in industrial biotechnology.     

Kinetics of microbial growth on pentachlorophenol

Batch and fed-batch experiments were conducted to examine the kinetics of pentachlorophenol utilization by an enrichment culture of pentachlorophenol-degrading bacteria. The Haldane modification of the Monod equation was found to describe the relationship between the specific growth rate and substrate concentration. Analysis of the kinetic parameters indicated that the maximum specific growth rate and yield coefficients are low, with values of 0.074 h-1 and 0.136 g/g, respectively. The Monod constant (Ks) was estimated to be 60 micrograms/liter, indicating a high affinity of the microorganisms for the substrate. However, high concentrations (KI = 1,375 micrograms/liter) were shown to be inhibitory for metabolism and growth. These kinetic parameters can be used to define the optimal conditions for the removal of pentachlorophenol in biological treatment systems.     

Kinetics of microbial growth on pentachlorophenol.

Batch and fed-batch experiments were conducted to examine the kinetics of pentachlorophenol utilization by an enrichment culture of pentachlorophenol-degrading bacteria. The Haldane modification of the Monod equation was found to describe the relationship between the specific growth rate and substrate concentration. Analysis of the kinetic parameters indicated that the maximum specific growth rate and yield coefficients are low, with values of 0.074 h-1 and 0.136 g/g, respectively. The Monod constant (Ks) was estimated to be 60 micrograms/liter, indicating a high affinity of the microorganisms for the substrate. However, high concentrations (KI = 1,375 micrograms/liter) were shown to be inhibitory for metabolism and growth. These kinetic parameters can be used to define the optimal conditions for the removal of pentachlorophenol in biological treatment systems.