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Microbial Growth and Its Control
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
Bacterial growth refers to an increase in bacterial cell number and it normally happens by binary fission. During active bacterial growth, the size of the microbial population is continuously doubling. One cell divides to form two, each of these cells divides so that four cells form, and so forth in a geometric progression. The time required to achieve a doubling of the population size, known as the generation time or doubling time, is the unit of measure of the microbial growth rate. When a bacteria is inoculated into a new culture medium, it exhibits a characteristic pattern or change in cell numbers. This pattern is a growth curve. The normal growth curve of bacteria has four phases, the lag phase. the log phase or exponential growth phase, the stationary phase, and the death or logarithmic decline phase.
Biological Applications
Published in Yong Yang, Young I. Cho, Alexander Fridman, Plasma Discharge in Liquid, 2017
Yong Yang, Young I. Cho, Alexander Fridman
The bacteria selected for the biological validation test was a nonpathogenic (i.e., noninfectious) strain of E. coli, which was considered the most reliable measure of public risks in drinking water since its presence was an indicator of fecal pollution and the possible presence of enteric pathogens. Bacterial growth and measurement techniques included the production of agar plates, incubating and growing bacteria, and performing bacterial colony counts on the plates. This method of counting bacteria colonies is a widely accepted practice in biology, called the heterotrophic plate counting method. The complete procedure for the growth and utilization of E. coli used in the present study can be found elsewhere (Madigan and Martinko, 2006). The results of the biological validation tests are given in Figures 5.2 and 5.3 for two different initial conditions. When the initial cell count was relatively low (i.e., 106 CFU/mL), the spark discharge could produce a total six-log reduction at an energy cost of 80 J/L per log. When the initial cell count was high (i.e., 108 CFU/mL), the spark discharge produced a four-log reduction at 800 J/L.
Technical Advancement for Retention of Probiotic Count During Spray-Drying Process
Published in M. Selvamuthukumaran, Handbook on Spray Drying Applications for Food Industries, 2019
Bacterial growth is classified as four phases; that of lag phase, exponential phase, stationary phase, and decline (death) phase. Among these phases, the stationary phase is the most important physiological stage for bacteria since many cells improve different responses due to depletion of nutrients and the formation of toxic metabolites. It was reported that, when the glucose starvation occurred in bacterial cells in the stationary phase, that could improve the resistance to many stresses such as osmotic and heat stress (van de Guchte et al., 2002). Therefore, these improved responses may enhance stress tolerance during the drying process (Morgan et al., 2006; Saarela et al., 2004).
Bioethanol production from sugarcane molasses with supplemented nutrients by industrial yeast
Published in Biofuels, 2023
Hasan Shahriar Raby, Md Anowar Saadat, Ahmed Nazmus Sakib, Fatema Moni Chowdhury, Abu Yousuf
Maintaining the appropriate pH level is essential for bacterial growth, with the ideal pH range for optimal growth typically being between 5 and 5.5 [44]. The contamination of CFU in different pH and supplements were investigated in this experiment. Research has shown that when yeast cells are cultured without supplements, an increase in pH (i.e. a more alkaline environment) is correlated with higher contamination levels. But the scenario was quite different in the presence of the supplement. It showed the minimum contamination level with pH 7 (Figure 4). The investigation was carried out four times to ensure the effect of supplementation on contamination level. The results indicated the presence of foreign bacteria in non-supplemented conditions. At pH 5.5 & 6, there were no foreign bacteria available in both non-supplemented or supplemented cultures. Contamination was found at pH 6.5 for the non-supplemented culture, although there was no contamination at this pH in supplemented culture. At elevated pH levels, the non-supplemented culture showed contamination with 4 CFU, while the initially supplemented culture had only 1 CFU contaminated. In contrast, no contamination was observed in the culture that was doubly supplemented, even when the pH was at 7.
A simple AI-enabled method for quantifying bacterial adhesion on dental materials
Published in Biomaterial Investigations in Dentistry, 2022
Hao Ding, Yunzhen Yang, Xin Li, Gary Shun-Pan Cheung, Jukka Pekka Matinlinna, Michael Burrow, James Kit-Hon Tsoi
Research on bacterial growth has been studied for decades. Conceptually, this is a simple process because most bacterial growth follows binary fission. Typically, bacterial growth on material in vitro follow a growth curve that includes four phases: (1) the (initial) lag phase: bacteria is maturing and metabolically active before the start of exponential growth; (2) the exponential (or log) phase: bacteria is growing at a constant rate; (3) the stationary phase: the growth rate of the bacteria is equal to the death rate due to limited nutrients; (4) and the death phase: a decrease in live bacteria due to lack of nutrients [6]. However, unlike controlled laboratory conditions, intraoral conditions such as environment, nutrients, temperature, and moisture levels are dynamic and diversified. Thus, the bacterial growth phases may coexist and overlap within the same biofilm. As such, the bacterial or biofilm growth and activity may be described more realistically as adhesion, growth, maturation and dispersion. This superimposition of phases makes it challenging when investigating the behavior of bacterial growth on materials surfaces. In fact, studying initial bacterial adhesion on the tooth or dental material surfaces [7–9] is of vital importance, because this can better understand the various types of bacterial adherence on different surfaces for anti-bacterial strategies of dental materials. Thus, the mechanisms of bacteria-material interaction and how bacteria react on different surfaces can be explored.
Bio-oil production from oleaginous microorganisms using hydrothermal liquefaction: A biorefinery approach
Published in Critical Reviews in Environmental Science and Technology, 2022
Tanushree Paul, Arindam Sinharoy, Divya Baskaran, Kannan Pakshirajan, G. Pugazhenthi, Piet N. L. Lens
Some of the bacteria, particularly those belonging to the Actinomycetes group such as Mycobacterium nocardia and Streptomyces sp., are capable of accumulating a high lipid content by utilizing simple carbon sources (Shruthi et al., 2014). Bacterial growth depends on macro and micro nutrients provided in the growth medium. Many species belonging to Rhodococcus such as Rhodococcus ruber, Rhodococcus erythropolis, Rhodococcus opacus and Rhodococcus fascians have been studied for biosynthesis of triacylglycerides (TAGs) and their application in energy production (Cortes & de Carvalho, 2015). The capability of these bacteria to grow on complex waste substrates such as wastewater from different industries is commercially attractive (Paul et al., 2019). Hence, this class of bacteria is often reported in the literature as a feedstock for the biodiesel industry. Microbial oils differ in composition and properties depending on the organism and substrate used (Albuquerque et al., 2011). In order to improve the lipid production, different strategies such as media optimization, genetic strain improvement, metabolic engineering and improvement in cultivation techniques can be followed. For example, Zhang et al. (2012) reported a more than 80% increase in fatty acid esters produced by E. coli by a change in cultivation method and optimization of the growth medium.