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1.
Candida shehatae ATCC 22984, a xylose-fermenting yeast, showed an ability to produce ethanol in both glucose and xylose medium. Maximum ethanol produced by the yeast was 48.8?g/L in xylose and 52.6?g/L in glucose medium with ethanol yields that varied between 0.3 and 0.4?g/g depended on initial sugar concentrations. Xylitol was a coproduct of ethanol production using xylose as substrate, and glycerol was detected in both glucose and xylose media. Kinetic model equations indicated that growth, substrate consumption, and product formation of C. shehatae were governed by substrate limitation and inhibition by ethanol. The model suggested that cell growth was totally inhibited at 40?g/L of ethanol and ethanol production capacity of the yeast was 52?g/L, which were in good agreement with experimental results. The developed model could be used to explain C. shehatae fermentation in glucose and xylose media from 20 to 170?g/L sugar concentrations. 相似文献
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Jyoti B.D. Suresh A.K. Venkatesh K.V. 《World journal of microbiology & biotechnology》2003,19(5):509-514
Lactobacillus rhamnosus is a heterolactic acid bacterium, which can be used to produce flavour compounds like diacetyl and acetoin. Various startegies have been applied to improve the growth rate and diacetyl yield. The use of multiple substrates affected growth as well as the yield of diacetyl. Growth on a medium containing glucose demonstrated a diauxic growth profile, with the second phase of growth being on the product, lactic acid. L. rhamnosus also grew on a medium containing citrate. Growth on medium containing glucose+citrate demonstrated simultaneous utilization of carbon sources. L. rhamnosus did not grow in a medium containing acetate and also did not co-metabolize it with glucose. Maximum specific growth rate (
max) was found to increase in the case of simultaneous utilization of glucose+citrate (0.38 h–1) as compared to glucose as the sole carbon source (0.28 h–1). The yields of diacetyl were also found to increase for glucose + pyruvate and glucose + citrate (0.10 and 0.05 g g–1 of glucose, respectively) as compared to glucose alone (0.01 g g–1 of glucose). The productivity of diacetyl on medium containing glucose and citrate was double that of a medium containing only citrate, although the yields were comparable. 相似文献
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固定化细胞的混合糖连续发酵动力学模型 总被引:3,自引:0,他引:3
利用固定化啤酒酵母和固定化毕赤酵母在两个串联的固定床内连续发酵由葡萄糖和木糖组成的混合糖制取酒精的过程,建立了连续发酵的非结构动力学模型。该模型以带抑制项的米氏动力学方程为酶动力学基础,考虑了抑制物抑制、底物抑制、轴向弥散及膜传质等因素。成功地引入了一个综合考虑颗粒相内外传质的总有效因子简化模型的计算,并取得了较为满意的仿真结果。 相似文献
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耐高温酵母乙醇间歇发酵动力学研究 总被引:2,自引:0,他引:2
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
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基于动力学模型的法夫酵母发酵生产虾青素的补料策略优化 总被引:2,自引:0,他引:2
对法夫酵母的不同补料发酵方式进行了研究.基于底物抑制模型,提出了一种优化的两阶段补料策略,用于法夫酵母产虾青素的高密度发酵.在发酵的延迟期和对数生长期早期,糖浓度控制在25 g/L左右,在此条件下,生物量可以达到最大,且时间缩短.在对数生长期后期及稳定期,糖浓度控制在5 g/L,虾青素的合成时间可以有效延长.与传统的补料方式相比,采用此补料策略取得了较好的发酵效果.发酵终点细胞干重达到23.8g/L,虾青素产量达到29.05 mg/L,分别比分批发酵提高了52.8%和109%. 相似文献
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研究了金龟子绿僵菌IMI330189的液体发酵动力学。利用Sigmoid函数构建了该菌株液体发酵过程中的菌体生长和底物消耗的动力学模型,并运用Origin7.5软件拟合求解出各模型参数。结果表明,模型能够较好地拟合绿僵菌IMI330189液体发酵过程,其比生长速率在发酵第22.8h达到最大值,为0.084h-1;总糖比消耗速率在第9.6h达到最大值,为0.246h-1;总氮比消耗速率在第10.3h达到最大值,为0.007h-1;菌体对总糖的得率系数在39.8h达到最高,为0.861g/g。模型拟合和实验数据具有良好的适应性,基本反映了绿僵菌IMI330189液体发酵过程的动力学特征,为其液体发酵工艺的优化和发展奠定了基础。 相似文献
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温度对谷胱甘肽分批发酵的影响及动力学模型 总被引:16,自引:2,他引:16
研究了24~32℃范围内产朊假丝酵母生产谷胱甘肽的分批发酵过程,发现较高温度对细胞生长有促进作用,而较低温度则更有利于谷胱甘肽产量的提高。应用改进的Logistic和LuedekingPiret方程分别对细胞生长动力学和谷胱甘肽合成动力学进行了模拟,得到不同温度下各种动力学参数。在此基础上,进一步研究了温度同细胞生长动力学参数之间的内在联系,得到谷胱甘肽分批发酵过程中细胞浓度的变化同温度以及底物浓度之间的一般关系式:dX-dt=[0.0224(T+1.7)]2X(1-X/Xmax)1+S{8.26×10.6×exp[-31477/R/(T+273)]}。验证实验结果表明,该模型具有很好的适用性。 相似文献
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The quality of silicon wafers used as substrates for microelectronic devices is measured in terms of the type, size and density of defects formed during crystal growth process. The native point defects such as vacancies and self-interstitials diffuse, react and aggregate to form intrinsic defects in the silicon wafers. We investigated the point defect behaviour using the kinetic lattice Monte Carlo (KLMC) model. The KLMC method has been applied extensively in various forms to the study of microdefects in silicon wafers. The purpose of this paper is to demonstrate the phenomena of void defect formation. The size and density of void defects are usually affected by system temperature, vacancy–vacancy reaction and vacancy–impurity reaction. In this paper, we study the temperature effect and the vacancy concentration effect. The simulation results with various temperatures are well matched with our experimental data, and the relationship between temperature and vacancy density describes well the phenomena of void defect formation. This is the first time such KLMC simulation results have been reported. 相似文献
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地衣芽孢杆菌产生碱性蛋白酶的动力学研究 总被引:17,自引:0,他引:17
应用自动控制发酵设备,首先进行分批发酵试验摸索了地衣芽孢杆菌2709生长与代谢的基本规律。然后采用补料分批发酵方法限制生长基质浓度,测定了一系列(SI,μI)、(μj,qpj)数据,获得KS、μmax、α、β等参数的值,并且推导出了细胞生长与产物合成的动力学公式,从而证明了用Monod方程描述地衣芽孢杆菌2709生长速率与基质浓度关系的合理性和合成碱性蛋白酶的发酵属于生长部分关联型。 相似文献
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Jurascík M Guimarães P Klein J Domingues L Teixeira J Markos J 《Biotechnology and bioengineering》2006,94(6):1147-1154
This work presents a multi-route, non-structural kinetic model for interpretation of ethanol fermentation of lactose using a recombinant flocculent Saccharomyces cerevisiae strain expressing both the LAC4 (coding for beta-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces lactis. In this model, the values of different metabolic pathways are calculated applying a modified Monod equation rate in which the growth rate is proportional to the concentration of a key enzyme controlling the single metabolic pathway. In this study, three main metabolic routes for S. cerevisiae are considered: oxidation of lactose, reduction of lactose (producing ethanol), and oxidation of ethanol. The main bioprocess variables determined experimentally were lactose, ethanol, biomass, and dissolved oxygen concentrations. Parameters of the proposed kinetic model were established by fitting the experimental data obtained in a small lab-scale fermentor with the initial lactose concentrations ranging from 5 g/dm3 to 50 g/dm3. A very good agreement between experimental data and simulated profiles of the main variables (lactose, ethanol, biomass, and dissolved oxygen concentrations) was achieved. 相似文献
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通过三联30L全自动发酵罐对虾青素产生菌法夫酵母的分批发酵动力学进行了研究,结果表明,法夫酵母的生长与限制性基质葡萄糖浓度之间符合Logistic方程,建立了细胞生长、产物合成和基质消耗随时间变化的数学模型。应用MATLAB软件对发酵动力学模型进行最优参数估计和非线性拟和,获得最大比生长速率(umax)和产物得率(Yp/x)分别为0.1829/h、0.1524g/g,虾青素分批发酵中细胞生长与产物合成属于偶联型,模型模拟计算结果和实验值能较好地吻合,动力学研究结果表明该模型能较好地反映细胞的生长、底物消耗和产物合成过程机制。 相似文献
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Furfural is an important inhibitor of yeast metabolism in lignocellulose-derived substrates. The effect of furfural on the physiology of Saccharomyces cerevisiae CBS 8066 was investigated using anaerobic continuous cultivations. Experiments were performed with furfural in the feed medium (up to 8.3 g/L) using three different dilution rates (0.095, 0.190, and 0.315 h(-1)). The measured concentration of furfural was low (< 0.1 g/L) at all steady states obtained. However, it was not possible to achieve a steady state at a specific conversion rate of furfural, q(f), higher than approximately 0.15 g/g.h. An increased furfural concentration in the feed caused a decrease in the steady-state glycerol yield. This agreed well with the decreased need for glycerol production as a way to regenerate NAD+, i.e., to function as a redox sink because furfural was reduced to furfuryl alcohol. Transient experiments were also performed by pulse addition of furfural directly into the fermentor. In contrast to the situation at steady-state conditions, both glycerol and furfuryl alcohol yields increased after pulse addition of furfural to the culture. Furthermore, the maximum specific conversion rate of furfural (0.6 g/g.h) in dynamic experiments was significantly higher than what was attainable in the chemostat experiments. The dynamic furfural conversion could be described by the use of a simple Michaelis-Menten-type kinetic model. Also furfural conversion under steady-state conditions could be explained by a Michaelis-Menten-type kinetic model, but with a higher affinity and a lower maximum conversion rate. This indicated the presence of an additional component with a higher affinity, but lower maximum capacity, either in the transport system or in the conversion system of furfural. 相似文献
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在1.5L搅拌式发酵罐中,使用葡萄糖质量浓度分别为120、200、280g/L的培养基进行酿酒酵母Saccharomyces cerevisiae连续发酵生成酒精的动力学研究。研究发现,当培养基中葡萄糖浓度为200和280g/L时,发酵液中残糖浓度、酒精浓度以及菌体生物量从小幅度波动的准稳态发展到大幅度波动的振荡状态。提出了伴有周期性振荡现象准稳态过程的概念,并针对该过程,建立了兼有底物和产物抑制的酵母细胞生长和产物酒精生成动力学模型。 相似文献
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Modeling of Xanthophyllomyces dendrorhous growth on glucose and overflow metabolism in batch and fed-batch cultures for astaxanthin production 总被引:1,自引:0,他引:1
An astaxanthin-producing yeast Xanthophyllomyces dendrorhous ENM5 was cultivated in a liquid medium containing 50 g/L glucose as the major carbon source in stirred fermentors (1.5-L working volume) in fully aerobic conditions. Ethanol was produced during the exponential growth phase as a result of overflow metabolism or fermentative catabolism of glucose by yeast cells. After accumulating to a peak of 3.5 g/L, the ethanol was consumed by yeast cells as a carbon source when glucose in the culture was nearly exhausted. High initial glucose concentrations and ethanol accumulation in the culture had inhibitory effects on cell growth. Astaxanthin production was partially associated with cell growth. Based on these culture characteristics, we constructed a modified Monod kinetic model incorporating substrate (glucose) and product (ethanol) inhibition to describe the relationship of cell growth rate with glucose and ethanol concentrations. This kinetic model, coupled with the Luedeking-Piret equation for the astaxanthin production, gave satisfactory prediction of the biomass production, glucose consumption, ethanol formation and consumption, and astaxanthin production in batch cultures over 25-75 g/L glucose concentration ranges. The model was also applied to fed-batch cultures to predict the optimum feeding scheme (feeding glucose and corn steep liquor) for astaxanthin production, leading to a high volumetric yield (28.6 mg/L) and a high productivity (5.36 mg/L/day). 相似文献
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Disaccharides were microbaially transformed to their corresponding 3-keto-derivatives by resting cells of Agrobacterium tumefaciens NCPPB 396. The kinetics and yield of this highly specific oxidation depend on several factors. The oxygen concentration especially has a major influence on the production of 3-keto-derivatives and was investigated kinetically with respect to low stationary oxygen concentrations in solution. Experiments showed unconventional results that conflicted with normal Michaelis-Menten kinetics. A kinetic model was developed and the kinetic constants were calculated. The model and experimental data for sucrose, maltose, iso-maltulose (palatinose), and leucrose are in good agreement with each other. Initial reaction rates with different sugars using constant oxygen concentrations resulted in a Michaelis-Mentent type function. The complete kinetics, including the effect of disaccharide and oxygen concentrations, are presented. (c) 1995 John Wiley & Sons, Inc. 相似文献
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Eun Yeol Lee 《Biotechnology and Bioprocess Engineering》2002,7(2):117-120
The effect of cell density on cell growth was investigated in a suspension batch culture of hybridoma cells. The specific
growth rate was found to increase with increasing initial cell density and then to decrease with further increases in initial
cell density. In order to quantitatively describe the dependence of specific growth rate on cell density, a kinetic model
is proposed, which satisfactorily represents the experimental data. 相似文献
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生物量、葡萄糖浓度和乙醇浓度是乙醇发酵过程的重要参数,传统的方法通常对发酵液取样作离线测量,不仅需要采用多种仪器进行测试分析,而且耗时耗力,成为实时过程调控和优化的障碍。文中针对这些重要过程参数提出了一个基于近红外光谱技术的原位实时检测方法。通过采用浸入式近红外光谱仪对发酵溶液进行原位测量,基于多输出最小二乘支持向量机回归(MLS-SVR)方法建立了利用近红外光谱同时分析葡萄糖浓度、生物量和乙醇浓度的多输出预测模型。实验结果表明,该方法能实时准确地检测乙醇发酵过程中的葡萄糖浓度、生物量和乙醇浓度,而且相对于现有的偏最小二乘法(PLS)分别对各组分建模和预测,能明显提高测量准确性和可靠性。 相似文献