The growth of microorganism on substrates, whether toxic or not usually exhibits sigmoidal
pattern. This sigmoidal growth pattern can be modelled using primary models such as Logistic,
modified Gompertz, Richards, Schnute, Baranyi-Roberts, Von Bertalanffy, Buchanan threephase
and Huang. Previously, the modified Gompertz model was chosen to model the growth of
Burkholderia sp. strain Neni-11 on acrylamide, which shows a sigmoidal curve. The modified
Gompertz model relies on the ordinary least squares method, which in turn relies heavily on
several important assumptions, which include that the data does not show autocorrelation. In this
work we perform statistical diagnosis test to test for the presence of autocorrelation using the
Durbin-Watson test and found that the model was adequate and robust as no autocorrelation of
the data was found.
Most often than not, microorganism’s growth curve is sigmoidal in characteristics.
The modified Gompertz model via nonlinear regression using the least square method
is one of the most popular methods to describe the growth curve. One of the
assumptions of a good model is that the variance of the data must be homogenous
(homoscedasticity). In this work, two statistical diagnostics; the Bartlett and the
Levene’s tests was performed to a modified Gompertz model utilized to model the
growth of the bacterium Burkholderia sp. strain Neni-11 on acrylamide in order to
satisfy the requirement above and found that data conformed to the requirement
indicating the modified Gompertz model is a robust model for modelling the bacterial
growth process.
Environmental pollution is one of the major concerns in the 21st century; where billions of tonnes
of harmful chemicals are produced by industries such as petroleum, paints, food, rubber, and
plastic. Phenol and its derivatives infiltrate the ecosystems and have become one of the top major
pollutants worldwide. This review covers the major aspects of immobilization of phenoldegrading
bacteria as a method to improve phenol bioremediation. The use of various forms of
immobilization matrices is discussed along with the advantages and disadvantages of each of the
immobilization matrices especially when environmental usage is warranted. To be used as a
bioremediation tool, the immobilized system must not only be effective, but the matrices must be
non-toxic, non-polluting and if possible non-biodegradable. The mechanical, biological and
chemical stability of the system is paramount for long-term activity as well as price is an
important factor when the very large scale is a concern. The system must also be able to tolerate
high concentration of other toxicants especially heavy metals that form as co-contaminants, and
most immobilized systems are geared towards this last aspect as immobilization provides
protection from other contaminants.
Commercialisation of glyphosate [N-(phosphonomethyl)glycine] in the early 1970s has left a big leap in the agriculture sector. This is due to its effectiveness in controlling a wide range of weeds. Glyphosate translocates well in plants. In addition, with added surfactant in its formulae, it can also be used in wet conditions. Its ability to kill weeds by targeting the 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) makes no competing herbicide analogs in its class. Considering its cost effectiveness, only small amount is needed to cover a large sector in agricultural land. The most important aspect in the success of glyphosate is the introduction of transgenic, glyphosate-resistant crops in 1996. However, glyphosate is not an environmental friendly herbicide. This systematic herbicide has raised environmental concern due to its excessive use in agriculture. Studies have shown traces of glyphosate found in drinking water. Meanwhile, it's rapid binding on soil particles possesses adverse effect to soil organisms. Glyphosate degradation in soil usually carried out by microbial activity. Microbes’ capable utilising glyphosate mainly as phosphate source. However, the activity of C-P lyase in breaking down glyphosate have not clearly understood. This review presents a collective summary on the understanding on how glyphosate works and its environmental fate.
Isolate JR1 was isolated from the polluted textile industry activities site in the Juru Penang area.
This bacterium was characterized as a gram-positive Bacillus bacterium and also gave a
positive biochemical test for catalase test and oxidase test. The isolate JR1 gave a maximum
decolourization of Amaranth dye under static conditions with the rate of decolorization of
98.82%. Seven variables which are pH, temperature (°C), ammonium acetate (g/L), glucose
(g/L), sodium chloride (g/L), yeast (g/L) and dye concentration (ppm) was run by using
Plackett-Burman design for the effective parameter of the decolourization of Amaranth. From
the seven variables, three effective variables which were ammonium acetate, glucose, and dye
concentration were further optimized by using a central composite design. The optimum value
of ammonium acetate concentration at 0.74 g/L, glucose concentration at 3.0 g/L and a dye
concentration at 58.1 ppm gave the highest percentage of decolourization. Thus, this isolate
could provide an alternate solution in removing toxic dyes from environments.
The Q10 value is tied to an increase in the surrounding temperature with an increase in 10 ◦C,
and usually resulted in a doubling of the reaction rate. When this happens, the Q10 value for the
reaction is 2. This value holds true to numerous biological reactions. To date, the Q10 value for
the biodegradation of phenol is almost not reported. The Q10 values can be determined from the
Arrhenius plots. In this study, the growth rate or biodegradation rates in logarithmic value for
the bacterium Pseudomonas sp. AQ5-04 was plotted against 1000/temperature (Kelvin) and the
slope of the Arrhenius curve is the value of the Ea, which was utilized to obtain the Q10. The
value obtained in this work was 1.834, which is slightly lower than the normal range of between
2 and 3 for the biodegradation rates of hydrocarbon in general and shows that this bacterium is a
very efficient phenol-degrading bacterium.
Pollution in the environment is deteriorating the ecology due to human activities in a large array
of industrial and agricultural sectors. Bioassay of polluted waters using bioluminescent bacterium
has been touted as one of the most economical, rapid and sensitive tests. The growth of the
bacterium on seawater medium exhibited a typical sigmoidal profile. To extract important growth
parameters useful for further modelling exercise, various primary growth models were utilized in
this study such as Modified Logistic, modified Gompertz, modified Richards, modified Schnute,
Baranyi-Roberts, von Bertalanffy, Huang and the Buchanan three-phase model. The best
performance was Huang model with the lowest value for RMSE, AICc and the highest value for
adjusted R2. The AF and BF values were also excellent for the model with their values were the
closest to 1.0. The Huang parameters, which include A or Y0 (bacterial growth lower asymptote),
μm (maximum specific bacterial growth rate), l (lag time) and Ymax (bacterial growth upper
asymptote) were 7.866 (95% confidence interval of 7.850 to 7.883), 0.329 (95% confidence
interval of 0.299 to 0.359), 1.543 (95% confidence interval of 1.303 to 1.784) and 8.511 (95%
confidence interval of 0.299 to 0.359).
2,4-dinitrophenol (2,4-DNP) is utilized in the production of wood preservatives, dyes, and also
as a pesticide. Human acute (short-term) exposure to 2,4-DNP in humans by means of oral
exposure are nausea or vomiting, sweating, headaches, dizziness, and weight reduction. Thus, the
removal of this compound is highly sought. A 2,4-DNP-degrading bacterium (isolate 1) was
isolated from a sample soil from Terengganu. This bacterium (isolate 1) was characterized as a
rod Gram positive, non-sporulated, and non-motile bacterium. The bacterium is oxidase negative
and had catalase positive activity and was able to grow aerobically on 2,4-dinitrophenol as the
sole carbon source. This bacterium showed maximal growth on 2,4-DNP at the temperature
optimum of 30 oC, pH 5.0 and was tolerant to 2,4-DNP concentration of up to 0.5 mM (0.092
g/L). This bacterium prefers to use urea as the nitrogen source in addition to yeast extract for
mineral source and vitamin precursors.
Investigation on in vivo effects of copper (Cu) on the ultrastructure of P. javanicus liver was
carried out using transmission electron microscopy (TEM). The addition of sublethal
concentration of 5 mg/L of Cu caused abnormalities on the bile canaliculi (BC) including
dilation and elongation compared to control and at lower concentrations of copper with a normal
round shape form. Findings from this study support an alternative histological assessment of the
effects of Cu concentration on P. javanicus liver.
Acetylcholinesterase (AChE) is usually used as an inhibitive assay for insecticides. A lesserknown
property of AChE is its inhibition by heavy metals. In this work, we evaluate an AChE
from brains of Clarias batrachus (catfish) exposed to wastes from aquaculture industry as an
inhibitive assay for heavy metals. We discovered that the AChE was inhibited completely by
Hg2+, Ag2+, Pb2+, Cu2+, Cd2+, Cr6+ and Zn2+ during initial screening. When tested at various
concentrations, the heavy metals exhibited exponential decay type inhibition curves. The
calculated IC50 (mg/L) for the heavy metals Ag2+, Cu2+, Hg2+, Cr6+ and Cd2+ were 0.088, 0.078,
0.071, 0.87 and 0.913, respectively. The IC50 for these heavy metals are comparable, and some
are lower than the IC50 values from the cholinesterases from previously studied fish. The assay
can be carried out in less than 30 minutes at ambient temperature.