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Archives of Industrial Biotechnology | Volume 2
May 14-15, 2018 | Montreal, Canada
World Yeast Congress
C
hlorophenols (CPs) and cresols are used as a precursor
in the production of higher chlorophenols and dyestuffs,
and as a preservative. The taste and odour thresholds
levels of CPs in water are 0.1µg/L and 10µg/L, respectively.
Contamination levels of CPs in ground water are located
in the range 0.15-100mg/L. The EU has set maximum
concentration limits for pesticides and their degradation
products of 0.1μg/L and 0.5μg/L, respectively. People
working in industries which produce textiles, leather
products, domestic preservatives, and petrochemicals are
most heavily exposed to CPs. The International Agency for
Research on Cancers categorised CPs as potential human
carcinogens. Also CPs are very hazardous to the environment
and animals. Existing multistep water purification processes
for CPs such as hydrogenation, ion exchange, liquid-liquid
extraction, adsorption by activated carbon, forward and
inverse osmosis, electrolysis, sonochemistry, UV irradiation,
and chemical oxidation are not always cost effective and can
cause the formation of more toxic or mutagenic derivatives.
Bioremediation of CP derivatives applying microorganisms
results in 60 to 100% decontamination efficiency and the
process ismoreenvironmentally friendly compared toexisting
physicochemical methods. Microorganisms immobilised
onto a substrate show many advantages over free bacteria
systems, such as higher biomass density, higher metabolic
activity, and resistance to toxic chemicals. They also enable
continuous operation, avoiding the requirement for biomass-
liquid separation.
Pseudomonas sp., Rhodococcus sp.,
Acinetobacter sp. and Bacillus sp. illustrated
a high capacity
to degrade phenol derivatives and other nondegradable
organic compounds. The work is devoted to the development
of a bioremediation system for phenol derivatives based on
macroporous materials, which can be used efficiently for
wastewater treatment. Conditions for the preparation of
the macroporous material from specific bacterial strains
(
Pseudomonas mendocina
and
Rhodococcus koreensis,
Acinetobacter sp and Arthrobacter chlorophenolicus) were
optimised. The concentration of bacterial cells was kept
constant; the difference was only the type and concentration
of crosslinking agents used e.g. glutaraldehyde, or novel
polymers (0.5 to 1.7 wt/v %). SEM image analysis of the
material indicated a monolithic macroporous structure;
4-chlorophenol (4CP), 2-chlorophenol (2CP), m-cresol and
phenol were chosen as a model system to estimate the
enzymatic activity of the cryogel. The viability of the cross-
linked bacteria was checked using Live/Dead assay and
Laser Scanning Confocal Microscopy and colorimetric assay
MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide), which revealed the presence of viable bacteria
with the novel cross-linkers, whereas the control material
cross-linked with glutaraldehyde, contained mostly dead
cells. Degradation rates of the CPs, phenol and m-cresol
are compared with free bacteria. Elasticity modulus of
macroporous materials was evaluated using Texture analyser.
Efficiency of free bacteria suspension and macroporous
material based on bacteria was tested on degradation of
phenol derivatives. Monitoring the turbidity of the solution
at 600nm were concluded that most of free bacteria died
within 6-12h due to high toxicity of 4CP and 2CP, however
commercial strains were resistant to p- and m-cresols and
were therefore exploited without additional adaptation. CP
resistant strains were grown in minimal salt media (MSM)
withintwoweeks.The3-D-bioreactorsbasedonthesebacteria
and free bacterial suspension (
Pseudomonas mendocina,
Rhodococcus koreensi
, Acinetobacter sp. and Arthrobacter
chlorophenolicus A6) were used for 4CP, 2CP and m-cresol
degradation in batch mode at an initial concentration of 50
mg/L in MSM at 30oC. The concentrations of the phenol
derivatives were estimated using spectrophotometric
assay using aminoantipyrine and K3[Fe(CN)6] at alkaline
Macroporous materials for biodegradation of phenol derivatives
Dmitriy Berillo
1
, Andrew Cundy
2
, Jonathan L Caplin
1
and
Irina Savina
1
1
University of Brighton, United Kingdom
2
University of Southampton, United Kingdom