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Biological Agents
Published in Katarzyna Majchrzycka, Małgorzata Okrasa, Justyna Szulc, Respiratory Protection Against Hazardous Biological Agents, 2020
Under conditions of batch culture in a closed system, microorganisms grow until a complete depletion of nutrients or such accumulation of metabolic products that prevents their further growth. Microbial growth can be described graphically as a growth curve with a sigmoid shape, which shows the dependence of the number of cells (or biomass yield) over culture time. The course of the curve reflects the reactions of cells to the produced metabolites, and the interactions between the cells and the environment as individual phases of growth [Amézquita 2011]. A typical growth curve includes the following phases: lag phase (adaptive phase); acceleration phase (boost phase); exponential growth phase (logarithmic phase); slow growth phase, stationary phase, slow death phase and logarithmic death phase (Figure 2.10) [Libudzisz 2019; Vasanthakumari 2007].
Stoichiometry and the Kinetics of Cell Cultivation
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
The data of a cell culture process is typically presented as time profiles of the concentrations of cell biomass, nutrients, metabolites, and product. A typical cell growth curve can be divided into a number of growth stages: lag phase, exponential growth phase, stationary phase, and death (or the decline phase) (Figure 5.1). The exponential growth phase is characterized by an exponential increase in biomass, or a period of constant slope in biomass increase on a semi-logarithmic plot over time. For mammalian cells, the period of exponential cell expansion in a culture is often relatively short (typically no more than a 10-fold increase in cell concentration). In some cases, a period of stagnant cell concentration may precede the exponential phase, called a lag phase. A lag phase may be caused by using an inoculum from a culture that has already reached a stationary phase, or by using an inoculum grown previously in a vastly different medium. Initiating a culture with a suboptimal cell concentration may also cause poor initial growth. In general, anchorage-dependent cells should be inoculated at a minimum density of 104 cells/cm2 while also maintaining a cell concentration of 105 cells/mL. Cells grown in suspension are generally started at about 105 cells/mL, but are at a higher level for very small blood cells such as natural killer cells.
View-count based modeling for YouTube videos and weighted criteria–based ranking
Published in Mangey Ram, J. Paulo Davim, Advanced Mathematical Techniques in Engineering Sciences, 2018
N. Aggrawal, A. Arora, A. Anand, M.S. Irshad
Consider an example of exponential growth which is seen in view count. View count is increased by the viewers. One viewer influences the other viewer to watch the video by sharing it and by word-of-mouth. This influence takes time depending on each person. If 1000 viewers are placed in a large hall with an unlimited supply of people who have not watched that video (i.e., they can influence as many people as they wish), after an hour there will be the first round of influence (with each influencing one), resulting in 2000 viewers. In another hour, each of the 2000 viewers will influence double, resulting in 4000 viewers; after the third hour, there should be 8000 viewers in the hall; and so on. The important concept of exponential growth is that the population growth rate, the number of viewers increased after every hour, is accelerating; that is, it is increasing at a greater and greater rate. After 1 day and 24 of these cycles, the viewers would have increased from 1000 to more than 16 billion. When the population size, N, is plotted over time, a J-shaped growth curve is produced.
Identification, characterization and optimization of culture medium conditions for organic acid-producing lactic acid bacteria strains from Chinese fermented vegetables
Published in Preparative Biochemistry & Biotechnology, 2023
Charles Obinwanne Okoye, Lu Gao, Yanfang Wu, Xia Li, Yongli Wang, Jianxiong Jiang
The growth curve data is usually beneficial to defining the functional properties of bacteria, such as fermentation time, adequacy of the substrate, and metabolite production, and could be used to determine the optimal culture conditions for LAB species.[25,26] Fermented vegetables are a good source for the growth of LAB due to their broad diversity of nutrients that can maintain remarkable cell viability over time.[27–29] Although OD is challenging to relate to actual cell count, calibrating to an expected cell count (OD = 0.5) through serial dilutions has resulted in a highly accurate growth estimation.[30] The LAB strains were able to grow at lower pH until 24hr, which was similar to the study of Isas et al.,[31] which reported a similar growth trend of different LAB strains after 24 hr but at lower optical densities. On the contrary, Yang et al.[32] reported that the optimal pH for four LAB growth was pH 7.4 and 8.5, which could not grow at a low pH of 4.5. The lower pH of PC-C1 and YC1-1-4B in this study supports the speculation that specific LAB strains are required as starter cultures in industrial fermentation due to their extreme tolerance to acidic environments and remarkable growth ability. However, these results raised the need to focus on the early acidification process of these LAB species.
Sustainable approach for biodiesel production and wastewater treatment by cultivating Pleusrastrum insigne in wastewater
Published in International Journal of Phytoremediation, 2023
Michael Van Lal Chhandama, Kumudini Belur Satyan
Growth analysis (Figure 1) showed that P. insigne exhibited a full growth cycle (lag phase, exponential phase, and stationary phase) in samples 1, 2, 3, 6, and 7 similar to the control, where the exponential phase ends on the 14th day. But in samples 4, 5, 8, and 9, growth was observed only till the lag phase. The difference in the growth curve may be attributed to the number of nutrients, pH, and the presence of toxic compounds (Pittman et al. 2011; Jeong and Jang 2020). TN: TP ratio higher than 16:1 is optimal for microalgal cultivation whereas pH < 5 and pH higher than 8.0 is toxic (Azov and Shelef 1987; Monfet and Unc 2017). The samples where P. insigne exhibited a full growth cycle have TN:TP higher than 16:1. and a pH between 6.6 and 7.4. P. insigne cannot exhibit a full growth cycle in samples 8 (pH 3.0) and samples 4 (pH 9.0) and 5 (pH 9.8). Sample 9 has a neutral pH of 7.2 but cannot exhibit a full growth cycle as TN:TP is <16:1. Zhang et al. 2021 mentioned the need to supply additional nutrients in wastewater which did not meet the required nutritional value. Even with the supply of additional nutrients and trace elements cultivating microalgae in wastewater still cuts down the cost and the need for water resources. It is important to note that even if P. insigne cannot exhibit a full growth cycle in all the samples, the different parameters of the wastewater studied were significantly reduced in all the samples after it was treated with P. insigne.
Development of a carbon accumulation model for estimating the concentration of 14C in Japanese radish
Published in Journal of Nuclear Science and Technology, 2023
The data of measured growth curves are often limited in actual fields, and plant growth changes with environmental conditions. Therefore, the present model was modified from our previous model to describe temporal changes in ML(t) and MR(t) via environmental responses of photosynthesis and respiration in Japanese radish without using measured growth curves as input data. The model was modified by incorporating the following four parameters (Figure 1(b)): rate of photosynthesis per plant (P(t), mol C plant−1 s−1), allocation ratio of photosynthetically fixed carbon between the two compartments (α(t)), and temperature-dependent respiration rate coefficients in the leaf and root (kL(t) and kR(t), s−1, respectively). The parameter P(t) describes light and temperature dependence of the inflow rates of carbon into the leaf and root compartments and is calculated using Equations (1)–(7) described below. The value of α(t) is set to 1 at 4 DAS, i.e. the day of seedling emergence, and then decreases linearly to 0 until 76 DAS to express a shift in sink strength for carbon from the leaf to the root during growth [29,32]. Temperature dependence of respiration rate coefficients (kL(t) and kR(t)) is introduced in Equation (8) described below. Values of kL(t) and kR(t) at an air temperature of 23°C (i.e. kL and kR in Figure 1(a)) and the redistribution ratio (r) obtained in our previous study [15] have been used in our present model.