The indiscriminate released of heavy metals and xenobiotics into soils and aquatic bodies
severely alter soil organisms and the ecosystem. The isolation of xenobiotics degrading
microorganisms is cost-effective and naturally pleasant approach. Lately, the toxicological effect
of molybdenum to the spermatogenesis of several organisms has been record. This present study
is aimed at the isolation and characterization of a bacterium capable of converting molybdenum
to the colloidal molybdenum blue. Bacteria characterization was performed in a microplate
format using resting cells. Thus, the reduction process can be employed as a device for
molybdenum bioremediation. The results of the study revealed an optimum reduction at pH
between 6.0 and 6.3 and temperatures of between 25 and 40 oC. Similarly, it was also observed
that a phosphate concentration not greater than 5.0 mM and a sodium molybdate concentration
at 20 mM was required for reduction. Glucose was observed as the best carbon source to support
reduction. Following the scanning of molybdenum blue, it revealed an absorption spectrum
indicating the characteristics of molybdenum blue as a reduced phosphomolybdate. Molybdenum
reduction is inhibited by heavy metals like silver, lead, arsenic and mercury. Furthermore, the
ability of the bacterium (Pseudomonas sp. strain Dr.Y Kertih) to utilize several organic
xenobiotics such as phenol, acrylamide, nicotinamide, acetamide, iodoacetamide, propionamide,
acetamide, sodium dodecyl sulfate (SDS) and diesel as electron donor sources for aiding
reduction or as carbon sources for growth was also examined. Finding showed that none was
capable of aiding molybdenum reduction, however the bacterium was capable of growing on both
diesel and phenol as carbon sources. GC analysis was used to confirmed diesel degradation.
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).
Heavy metals pollution has become a great threat to the world. Since instrumental methods are
expensive and need skilled technician, a simple and fast method is needed to determine the
presence of heavy metals in the environment. In this work, a preliminary study was carried out
on the applicability of various local plants as a source of protease for the future development of
the inhibitive enzyme assay for heavy-metals. The crude proteases preparation was assayed using
casein as a substrate in conjunction with the Coomassie dye-binding assay. The crude protease
from the kesinai plant was found to be the most potent plant protease. The crude enzyme
exhibited broad temperature and pH ranges for activity and will be developed in the future as a
potential inhibitive assay for heavy metals.
Biosurfactants are surface active compounds and amphiphatic in nature which consist of
hydrophilic head and hydrophobic tail accumulating at the interphase of two immiscible liquid
with different polarity. A study was conducted to investigate the effectiveness of sunflower oil in
the production of rhamnolipids (RLs) by locally isolated Pseudomonas aeruginosa in shake flask
fermentation. In this process, four different fermentation treatments were done for seven days at
30°C and 180 rpm. Sampling was carried out in time intervals of 24 h followed by monitoring of
cell growth and biosurfactants production. Colorimetric Orcinol analysis was used for
determination of RLs concentrations (g/L). The RLs were studied for emulsification activity
using emulsification index (E24%) methods. In addition, oil displacement activity and thermal
stability were also studied (4-120°C). All treatments allow the growth of P. aeruginosa and the
utilization of sunflower oil as carbon source and glucose as growth initiator were observed to be
the best strategy for maximum RLs production. The maximum RLs production was achieved
after 120 h with 3.18 g/L of RLs. Diesel shows the highest emulsification activity among the
substrate tested ranging from 55.56% - 60.00%. The oil displacement activity was corresponding
to RLs concentration with stability up to 120°C (for 60 min). Therefore, from this research a
good potential of RLs that may provide good application for industry were produced.
Acetylcholinesterase (AChE) is usually used as an inhibitive assay for insecticides. A lesser
known property of AChE is its inhibition by heavy metals. In this work we evaluate an AChE
from brains of striped snakehead (Channa striatus) wastes from aquaculture industry as an
inhibitive assay for heavy metals. We discovered that the AChE was inhibited almost completely
by Hg2+, Ag2+ and Cu2+ during an initial screening. When tested at various concentrations, the
heavy metals exhibited exponential decay type inhibition curves. The calculated IC50 for the
heavy metals Hg2+, Ag2+, Pb2+, Cu2+ and Cr6+ were 0.08432, 0.1008, 0.1255, 0.0871, and 0.1771,
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.
The aim of this study is to develop bioplastic film from a combination of two biopolymers of same
source, namely banana peel and corn starch. Five banana peel films (BP film) were prepared with
different concentrations of corn starch (1% up to 5%) as co-biopolymer and film without corn
starch acted as a control. The films were carried out with several durability tests and
characterization analyses. Based on the results obtained, the BP film with 4% corn starch gave the
highest tensile strength 34.72 N/m2 compared to other samples. The water absorption test showed
that BP films with 3% corn starch were resistant to water uptake by absorbing water up to 60.65%.
In terms of characterization, spectra of Fourier Transform Infrared Spectroscopy (FTIR) obtained
for BP control film and BP film with 4% corn starch were comparable with most of the peaks were
present. The thermal analysis by differential screening calorimetric (DSC) detected the melting
temperature for both BP control film and BP film with 4% corn respectively at Tonset of 54.41°C
and 67.83°C. Overall, combination of starches from two different sources can be used as an
alternative in producing bioplastics.
Bacterial based remediation of environmental toxicants is a promising innovative technology
for molybdenum pollution. To date, the enzyme responsible for molybdate reduction to Moblue
from bacteria show that the Michaelis-Menten constants varies by one order of magnitude.
It is important that the constants from newer enzyme sources be characterized so that a
comparison can be made. The aim of this study is to characterize kinetically the enzyme from a
previously isolated Mo-reducing bacterium; Bacillus pumilus strain Lbna. The maximum
activity of this enzyme occurred at pH 5.5 and in between 25 and 35 oC. The Km and Vmax of
NADH were 6.646 mM and 0.057 unit/mg enzyme, while the Km and Vmax of LPPM were 3.399
mM and 0.106 unit/mg enzyme. The results showed that the enzyme activity for Bacillus
pumilus strain Lbna were inhibited by all heavy metals used. Zinc, copper, silver, chromium,
cadmium and mercury all caused more than 50% inhibition to the Mo-reducing enzyme activity
with copper being the most potent with an almost complete inhibition of enzyme activity
observed.
The issue of heavy metal contamination and toxic xenobiotics has become a rapid global
concern. This has ensured that the bioremediation of these toxicants, which are being carried out
using novel microbes. A bacterium with the ability to reduce molybdenum has been isolated
from contaminated soils and identified as Serratia marcescens strain DR.Y10. The bacterium
reduced molybdenum (sodium molybdate) to molybdenum blue (Mo-blue) optimally at pHs of
between 6.0 and 6.5 and temperatures between 30°C and 37°C. Glucose was the best electron
donor for supporting molybdate reduction followed by sucrose, adonitol, mannose, maltose,
mannitol glycerol, salicin, myo-inositol, sorbitol and trehalose in descending order. Other
requirements include a phosphate concentration of 5 mM and a molybdate concentration of
between 10 and 30 mM. The absorption spectrum of the Mo-blue produced was similar to the
previously isolated Mo-reducing bacterium and closely resembles a reduced phosphomolybdate.
Molybdenum reduction was inhibited by Hg (ii), Ag (i), Cu (ii), and Cr (vi) at 78.9, 69.2, 59.5
and 40.1%, respectively. We also screen for the ability of the bacterium to use various organic
xenobiotics such as phenol, acrylamide, nicotinamide, acetamide, iodoacetamide, propionamide,
acetamide, sodium dodecyl sulfate (SDS) and diesel as electron donor sources for aiding
reduction. The bacterium was also able to grow using amides such as acrylamide, propionamide
and acetamide without molybdenum reduction. The unique ability of the bacterium to detoxify
many toxicants is much in demand, making this bacterium a vital means of bioremediation.
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.
Acrylamide is a synthetic monomer that has been classified as toxic and carcinogenic apart
from its diverse application in the industry. Its application is in the formation of
polyacrylamide. Polyacrylamide usage is diverse and is found as herbicide formulation, as soil
treatment agent and in water treatment plants. Deaths and sickness due to the accidental
exposure to acrylamide have been reported while chronic toxicity is also a source of the
problem. This review highlighted the toxic effect of acrylamide to various organisms like
human, animal and plant. This review also discusses on the potential use of biological
technologies to remediate acrylamide pollution in the environment and the degradation
pathways these microorganisms utilize to assimilate acrylamide as a nitrogen, carbon or both as
carbon and nitrogen sources.
Petroleum hydrocarbons remain as the major contaminants that could be found across the world.
Remediation approach through the utilisation of microbes as the bioremediation means widely
recognised due to their outstanding values. As a result, scientific reports on the isolation and
identification of new hydrocarbon-degrading strains were on the rise. Colourimetric-based assays
are one of the fastest methods to identify the capability of hydrocarbon-degrading strains in both
qualitative and quantitative assessment. In this study, the hydrocarbon-degrading potential of
nine bacterial isolates was observed via 2,6-dichlorophenolindophenol (DCPIP) test. Two potent
diesel-utilising isolates show a distinctive tendency to utilise aromatic (ADL15) and aliphatic
(ADL36) hydrocarbons. Both isolates prove to be a good candidate for bioremediation of wide
range of petroleum hydrocarbon components.
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.
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.
The presence of both heavy metals and organic xenobiotic pollutants in a contaminated site
justifies the application of either a multitude of microbial degraders or microorganisms having
the capacity to detoxify a number of pollutants at the same time. Molybdenum is an essential
heavy metal that is toxic to ruminants at a high level. Ruminants such as cow and goats
experience severe hypocuprosis leading to scouring and death at a concentration as low as
several parts per million. In this study, a molybdenum-reducing bacterium with amide-degrading
capacity has been isolated from contaminated soils. The bacterium, using glucose as the best
electron donor reduces molybdenum in the form of sodium molybdate to molybdenum blue. The
maximal pH reduction occurs between 6.0 and 6.3, and the bacterium showed an excellent
reduction in temperatures between 25 and 40 oC. The reduction was maximal at molybdate
concentrations of between 15 and 25 mM. Molybdenum reduction incidentally was inhibited by
several toxic heavy metals. Other carbon sources including toxic xenobiotics such as amides
were screened for their ability to support molybdate reduction. Of all the amides, only
acrylamide can support molybdenum reduction. The other amides; such as acetamide and
propionamide can support growth. Analysis using phylogenetic analysis resulted in a tentative
identification of the bacterium as Pseudomonas sp. strain 135. This bacterium is essential in
remediating sites contaminated with molybdenum, especially in agricultural soil co-contaminated
with acrylamide, a known soil stabilizer.
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.
Contamination of organic xenobiotic pollutants and heavy metals in a contaminated site allows
the use of multiple bacterial degraders or bacteria with the ability to detoxify numerous toxicants
at the same time. A previously isolated SDS- degrading bacterium, Acinetobacter baumannii
strain Serdang 1 was shown to reduce molybdenum to molybdenum-blue. The bacterium works
optimally at pH 6.5, the temperature range between 25 and 34°C with glucose serves as the best
electron donor for molybdate reduction. This bacterium required additional concentration of
phosphate at 5.0 mM and molybdate between 15 and 25 mM. The absorption spectrum of the
molybdenum blue obtained is similar to the molybdenum blue from other earlier reported
molybdate reducing bacteria, as it resembles a reduced phosphomolybdate closely. Ag(i), As(v),
Pb(ii) and Cu(ii) inhibited molybdenum reduction by 57.3, 36.8, 27.7 and 10.9%, respectively, at
1 p.p.m. Acrylamide was efficiently shown to support molybdenum reduction at a lower
efficiency than glucose. Phenol, acrylamide and propionamide could support the growth of this
bacterium independently of molybdenum reduction. This bacterium capability to detoxify several
toxicants is an important tool for bioremediation in the tropical region.
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.
In this work, a temporal monitoring work for heavy metals from an effluent discharge point in
the Juru Industrial Estate was carried out using the protease extracted from garlic (Allium
sativum) as the principal bioassay system. casein-Coomassie-dye binding assay method has
utilized this purpose. The periodic sampling results for one day of a location in the Juru
Industrial Estate showed temporal variation of copper concentration coinciding with garlic
protease inhibition with the highest concentrations of copper occurring between 12.00 and 16.00
hours of between 3 and 3.5 mg/L copper. The crude proteases extracted from Allium sativum
successfully detect temporal variation of copper form this location. In conclusion, this assay
method has the potential to be a rapid, sensitive, and economic inhibitive assay for the largescale
biomonitoring works for the heavy metal copper from this area.
Molybdenum is an emerging pollutant. Bioremediation of this heavy metal is possible by the
mediation of Mo-reducing bacteria. These bacteria contain the Mo-reducing enzymes that can
conver toxic soluble molybdenum into molybdenum blue; a less soluble and less toxic form of the
metal. To date only the enzyme has been purified from only one bacterium. The aim of this study is
to purify the Mo-reducing enzyme from a previously isolated Mo-reducing bacterium Bacillus
pumilus strain Lbna using ammonium sulphate fractionation followed by ion exchange and then
gel filtration. Two clear bands were obtained after the gel filtration step with molecular weights
of 70 and 100 kDa. This indicates that further additional purification methods need to be used
to get a purified fraction. Hence, additional steps of chromatography such as hydroxyapatite or
chromatofocusing techniques can be applied in the future.