Abstract
Several models are available to determine the effect of temperature on the growth rate of microorganisms on substrates. An example is Arrhenius model, which is very popular because it has few parameters. For the first time, a discontinuous chevron-like graph of apparent activation energy based on the Arrhenius plot on the growth of 2-chloro-4-nitrophenol by Cupriavidus sp. is reported. The plot of ln mm against 1/T shows a discontinuous chevron-like graph for the entire investigated temperature range with an inflection at 27.75°C. This indicates that the existence of 2 activation energies for growth on 2-chloro-4-nitrophenol ranges from 20 to 40°C. Furthermore, a regression analysis from 20–25°C and 30–40°C results in activation energies of 88.71 kJmol-1 and 75.16kJ mol-1, respectively. This is probably the first time a Chevron-like graph was observed for the Arrhenius plot on the effect of temperature on the growth rate of 2-chloro-4-nitrophenol.
Highlights
Even at low doses, the toxicity of phenols and phenolic compounds is well known and their existence as toxins in the atmosphere is progressively recorded (Christen et al, 2012; Luo et al, 2012; Zulkharnain et al, 2013; Affandi et al, 2014; Bay et al, 2014; Ghazali& Johari, 2015)
A Chevron-like graph was obtained when plotting ln m against 1/T showing a discontinuous part for the whole temperature range studied (Fig. 1)
Increasing the temperature reduces the energy needed. This is probably the reason for the lower activation energies observed in the degradation of polychlorinated biphenyl (PCB) by the thermophilic Bacillus sp
Summary
The toxicity of phenols and phenolic compounds is well known and their existence as toxins in the atmosphere is progressively recorded (Christen et al, 2012; Luo et al, 2012; Zulkharnain et al, 2013; Affandi et al, 2014; Bay et al, 2014; Ghazali& Johari, 2015). There are some physicochemical methods for the removal of these toxins, these include biodegradation, which is still being studied to date as an environmentally friendly process (Saravanan et al, 2008; Hasan & Jabeen, 2015). & Jain, 2011; Pandey et al, 2011) This isomer has caused significant degradation to agricultural soils and water supplies due to its solubility and high mobility, which results in the extreme negative health effects on humans and animals. The removal of 2chloro-4-nitrophenol from the environment has recently aroused wide biodegradation concern, which had been presented as a potential environmentally friendly method as several degrading bacterium have been isolated (Ghosh et al, 2010; Arora & Jain, 2011; Pandey et al, 2011). It is used to quantify the apparent activation energy or H*, for growth or degradation on substrates
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