十三碳二元酸发酵过程菌体生长期动力学模型及其应用

介绍了由十三碳烷烃生产十三碳二元酸的发酵过程,对其中的菌体生长期的代谢过程进行了分析。提出了以CO₂释放率判断菌体生长状况的方法,据此可确定进入产酸期的最佳时间．建立了菌体生长期底物消耗及菌体生长的动力学模型,对模型参数进行了回归估值。并对菌体生长期进行了拟合。结果表明,模型的计算值和实测值吻合得较好,平均相对偏差为2．4％。利用所建模型对菌体生长期进行多种操作条件下的模拟计算,结果表明,提高蔗糖浓度及初始菌体浓度均能显著地提高菌体生长期结束时的菌体浓度。     

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。     

Kinetic Self-Cleavage Models for Permuted Variants of the Antigenomic HDV Ribozyme

The kinetic characteristics have been studied for noncircularly permuted variants of the human hepatitis delta virus antigenomic ribozyme to find out the cause of the two-phase kinetics of the self-cleavage reaction. Different ways of reaction initiation, suboptimal conditions, and jumpwise changes of reaction conditions have been used, and the temperature dependences have been studied. A correlation has been shown between the apparent kinetic constant of the first reaction phase and the portion of the ribozyme molecules that self-cleaved during the first phase. Partial restoration of the initial reaction characteristics has been shown by the reinitiation of reaction being stopped after completing the first phase. On the basis of all the data obtained, a scheme of the self-cleavage reaction has been proposed including: (i) activation of the ribozyme with energy of 40–50 kcal/mol and a characteristic time of several deciminutes under optimal reaction conditions; (ii) fast and reversible reaction of the phosphodiester bond cleavage; (iii) reaction leading to isomerization of the 3",5"-phosphodiester bond to the 2",5" bond in the self-cleavage site with a characteristic activation time of tens of minutes; and (iv) practically irreversible conformational change leading to fixation of the cleavage by immobilization of the 5"-terminal nucleotide of the product in the center of the formed structure and displacement of the 3"-terminal nucleotide to the periphery. The latter process has a characteristic time of tens of minutes and a low activation energy.     

Rapid Kinetic Analysis of Ethylene Growth Responses in Seedlings: New Insights into Ethylene Signal Transduction

Ethylene is a phytohormone that influences diverse processes in plants. Ethylene causes various changes in etiolated seedlings that differ between species and include reduced growth of shoots and roots, increased diameter of shoots, agravitropic growth, initiation of root hairs, and increased curvature of the apical hook. The inhibition of growth in etiolated seedlings has become widely used to screen for and identify mutants. This approach has led to an increased understanding of ethylene signaling. Most studies use end-point analysis after several days of exposure to assess the effects of ethylene. Recently, the use of time-lapse imaging has re-emerged as an experimental method to study the rapid kinetics of ethylene responses. This review outlines the historical use of ethylene growth kinetic studies and summarizes the recent use of this approach coupled with molecular biology to provide new insights into ethylene signaling.     

Evaluation of Various Unstructured Kinetic Models for the Production of Protease by Bacillus sphaericus MTTC511

Bacillus sphaericus MTCC511 was used for the production of protease in submerged batch fermentation. Maximum protease activity of 1010 U/L was obtained during a fermentation period of 24 h under optimized conditions of 30 °C in a medium with an initial pH of 7 and at a shaking rate of 120 rpm. The maximum biomass obtained in the batch fermentation was 2.55 g/L after 16 h. Various unstructured models were analyzed to simulate the experimental values of microbial growth, protease activity and substrate concentration. The unstructured models, i.e. the Monod model for microbial growth, the Monod incorporated Luedeking‐Piret model for the production of protease and the Monod‐incorporated modified Luedeking‐Piret model for the utilization of substrate were capable of predicting the fermentation profile with high coefficient of determination (R²) values of 0.9967, 0.9402 and 0.9729, respectively. The results indicated that the unstructured models were able to describe the fermentation kinetics more effectively.     

鲜切生菜中沙门氏菌二级生长预测模型的建立

以鲜切生菜为研究对象,比较了修正的Gompertz、Gompertz、Logistic和MMF 4种一级模型对不同温度下鲜切生菜中沙门氏菌生长曲线的拟合情况,发现在36℃、20℃和10℃时,修正的Gompertz模型均为最佳的拟合模型,4℃时沙门氏菌生长受到抑制,对失活/存活曲线进行"镜像化"处理后发现拟合程度相对较低,相关系数为0.962 7,故未用于二级模型中;采用其他温度下的修正的Gompertz模型中的最大比生长速率作为二级模型的响应值,建立平方根二级模型;准确因子和偏差因子对二级模型的准确性验证结果表明,两者均接近1.0,说明所建立的二级模型用于预测鲜切生菜中沙门氏菌生长情况。本研究为鲜切生菜的微生物安全控制提供科学依据。     

Growth characteristics of Tyzzer''s organism in cultured mouse hepatocytes

The growth characteristics of Tyzzer's organisms in cultured mouse hepatocytes were examined by direct bacterial counting and plaque assay. The viability of propagated bacteria and time required for the maximum titers depended on incubation time and inoculum dose, respectively. Both infectious titers and bacterial counts at optimum harvests were much higher than those obtained from infected mouse livers. Immunofluorescence revealed, after a lag phase of about 2 h, a linear multiplication during a 6 h period.     

Revision of the genus Clathrina (Porifera, Calcarea)

The genus Clathrina has one of the most difficult systematic arrangements in the Porifera, Class Calcarea. Few morphological characters can be used to describe its species, and the systematics and the geographical distribution of its species have changed several times, according to the point of view of the systematists. 'Lumpers' consider that clathrinas are morphologically plastic, while 'splitters' believe that even slight morphological differences should be considered sufficient to distinguish between species. The morphology of several specimens/species of Clathrina , including the type species, when possible, was studied and used to produce the first revision of this genus. Using results obtained from previous morphological and molecular studies, the morphological characters were chosen and analysed in all studied specimens. In total, 43 species were found, nine of which are new to science. These results agree with the viewpoint that morphological characters such as type and distribution of spicules, size of actines, spines, anastomosis of the cormus, organization of the osculum and presence of granules in cells, are useful when establishing the taxonomy of the genus.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 1−62.     

十三碳二元酸发酵过程产酸期拟均相动力学模型及其应用

分析了十三碳二元酸发酵过程中产酸期的代谢特点,对产酸期四相体系发酵动力学进行了研究。提出了菌体生长、产物形成及底物消耗的动力学模型,对模型参数进行了回归估值,并对产酸期进行了拟合,结果表明,模型的计算值和实测值较为吻合,平均相对偏差为3．6％。利用所建模型对产酸期进行了多种操作条件下的模拟计算,结果表明,提高进入产酸期的菌体浓度、缩短菌体生长期时间及降低发酵液中产物浓度具有提高产物形成速率的有效途径。     

生长模型的误差函数及其数学特征

生长曲线是估计动物年龄的重要方法之一,在野生动物生态学中,动物的体重往往被用作估计动物年龄的主要指标。然而,在动物体重测定过程中经常会出现一些偏差。例如,动物的日常活动（ 进食、饮水、排泄等）通常会引起动物体重的变化,这样在不同时间测定动物的体重就会产生偏差;此外,在测定动物体重的过程中,我们往往称量到一定的精确度。这些偏差将直接导致对动物年龄的估计误差。本文分析了4种常见生长模型（Logistic、Gompertz、Bertalanffy、Richards)的误差函数的数学特征。结果表明,由动物日常活动导致的年龄估计误差在动物的幼龄阶段为量小,而由称量精确度导致的年龄估算误差在生长曲线的拐点处为最小。     

高静水压对小球藻的生理生化效应

对小球藻(Chlorella Vulgaris)进行高静水压处理,分别通过80MPa,300MPa静水压处理,观察高静水压处理时小球藻生理生化效应。实验结果表明,300MPa压力处理1h能够导致小球藻的大量死亡,少量存活的藻细胞经过5d的“停滞期”后开始正常生长。80MPa的压力下处理2h、6h、12h后小球藻的初期的生长速度明显加快,而到生长末期小球藻生长开始趋于平缓。小球藻干质量为12h实验组最大,而单位蛋白含量随着干质量的增加而下降,几种抗氧化酶活性为6h实验组具有最大活性。经过300MPa压力预处理1h后的小球藻再在80MPa压力下进行处理,发现小球藻干质量为2h再处理实验组最大,蛋白含量为6h再处理实验组最高,抗氧化酶的活性随着压力处理时间的增加而下降。     

A Mathematical Model for the Effect of Water Pollutants on the Growth Pattern of Pollen

The heavy metals as water pollutants had some adverse effects on the growth pattern of pollen grains of the aquatic macrophytes viz. Ottelia, Vallisneria, Hyderilla and Eichhornia. The germination of pollen grains were inversely proportional and the abnormality of pollen tube and the flowering time were directly proportional to the concentration of the heavy metal. In this paper we have presented a mathematical model that is the germinability and the abnormality changes with the log-value of concentration in a straight line fashion. Also the flowering time changes with treatment time in an exponential pattern.     

Use of Growth Indices in Markov Chain Models for Crop Yield Forecasting

An improved Markov chain model has been developed for forecasting of sugarcane yields in which growth indices of biometrical characters based on data from two stages simultaneously have been utilised. Comparisons were also made with the models in use viz. the regression model and the first order Markov chain model.     

S形增长模型之比较、组合预测及应用

对５种Ｓ形增长模型进行比较,以组合模型的误差平方和最小为目标建立组合预测模型,并以实例说明其应用。     

应加强对单细胞生物分批培养生长曲线中减速期的认识和教学

根据单细胞生物分批培养过程中比生长速率(μ)的变化,其生长曲线分为延滞期、加速期、对数期、减速期、稳定期和衰亡期6个时期.与其他生长时期相比,在减速期生物的生长、基质的利用、产物的合成和基因表达谱等方面有显著的不同,并对发酵生产有着重要作用.然而,长期以来,对减速期的认识和教学相当薄弱,亟需加强对减速期的认识和教学.     

Morphological quantification of filamentous fungal development using membrane immobilization and automatic image analysis

Mycelial morphology is a critically important process property in industrial fermentations of filamentous micro-organisms, as particular phenotypes are associated with maximum productivity. However, the accurate quantification of complex morphologies still represents a significant challenge in elucidating this relationship. A system has been developed for high-resolution characterisation of filamentous fungal growth on a solid substrate, using membrane immobilization and fully-automatic plug-ins developed for the public domain, Java-based, image-processing software, ImageJ. The system has been used to quantify the microscopic development of Aspergillus oryzae on malt agar, by measuring spore projected area and circularity, the total length of a hyphal element, the number of tips per element, and the hyphal growth unit. Two different stages of growth are described, from the swelling of a population of conidiospores up to fully developed, branched hyphae 24 h after inoculation. Spore swelling expressed as an increase in mean equivalent spore diameter was found to be approximately linear with time. Widespread germination of spores was observed by 8 h after inoculation. From approximately 12 h, the number of tips was found to increase exponentially. The specific growth rate of a population of hyphae was calculated as approximately 0.24–0.27 h⁻¹. A wide variation in growth kinetics was found within the population. The robustness of the image-analysis system was verified by testing the effect of small variations in the input data.     

Growth of the Thermophilic Bacterium Geobacillus uralicus as a Function of Temperature and pH: An SCM-Based Kinetic Analysis

The synthetic chemostat model (SCM), originally developed to describe nonstationary growth under widely varying concentrations of the limiting substrate, was modified to account for the effects of nontrophic factors such as temperature and pH. The bacterium Geobacillus uralicus, isolated from an ultradeep well (4680 m), was grown at temperatures ranging from 40 to 75°C and at pH varying from 5 to 9. The biomass kinetics was reasonably well described by the SCM, including the phase of growth deceleration observed in the first hours after a change in the cultivation temperature. At an early stage of batch growth in a neutral or alkalescent medium, bacterial cells showed reversible attachment to the glass surface of the fermentation vessel. The temperature dependence of the maximum specific growth rate (_m) was fitted using the equation _m = Aexp(T)/{1 + expB[1 – C/(T + 273)]}, where A, , B, and C are constants. The maximum specific growth rate of 2.7 h^–1 (generation time, 15.4 min) was attained on a complex nutrient medium (peptone and yeast extract) at 66.5°C and pH 7.5. On a synthetic mineral medium with glucose, the specific growth rate declined to 1.2 h^–1, and the optimal temperature for growth decreased to 62.3°C.     

Heteroscedastic Nonlinear Regression Models with Random Effects and Their Application to Enzyme Kinetic Data

We present a new modification of nonlinear regression models for repeated measures data with heteroscedastic error structures by combining the transform-both-sides and weighting model from Caroll and Ruppert (1988) with the nonlinear random effects model from Lindstrom and Bates (1990). The proposed parameter estimators are a combination of pseudo maximum likelihood estimators for the transform-both-sides and weighting model and maximum likelihood (ML) or restricted maximum likelihood (REML) estimators for linear mixed effects models. The new method is investigated by analyzing simulated enzyme kinetic data published by Jones (1993).