18 research outputs found
Enzymes involved in vinyl acetate decomposition by Pseudomonas fluorescens PCM 2123 strain
Esterases are widely used in food processing industry, but there is little information concerning enzymes involved in decompositions of esters contributing to pollution of environment. Vinyl acetate (an ester of vinyl alcohol and acetic acid) is a representative of volatile organic compounds (VOCs) in decomposition, of which hydrolyses and oxidoreductases are mainly involved. Their activities under periodically changing conditions of environment are essential for the removal of dangerous VOCs. Esterase and alcohol/aldehyde dehydrogenase activities were determined in crude cell extract from Pseudomonas fluorescens PMC 2123 after vinyl acetate induction. All examined enzymes exhibit their highest activity at 30–35 °C and pH 7.0–7.5. Esterase preferably hydrolyzed ester bonds with short fatty chains without plain differences for C2 or C4. Comparison of Km values for alcohol and aldehyde dehydrogenases for acetaldehyde suggested that this metabolite was preferentially oxidized than reduced. Activity of alcohol dehydrogenase reducing acetaldehyde to ethanol suggested that one mechanism of defense against the elevated concentration of toxic acetaldehyde could be its temporary reduction to ethanol. Esterase activity was inhibited by phenylmethanesulfonyl fluoride, while β-mercaptoethanol, dithiothreitol, and ethylenediaminetetraacetic acid had no inhibitor effect. From among metal ions, only Mg2+ and Fe2+ stimulated the cleavage of ester bond
Kinetics of styrene biodegradation by Pseudomonas sp. E-93486
The research into kinetics of styrene biodegradation
by bacterial strain Pseudomonas sp. E-93486 coming
from VTT Culture Collection (Finland) was presented in
this work. Microbial growth tests in the presence of styrene
as the sole carbon and energy source were performed both
in batch and continuous cultures. Batch experiments were
conducted for initial concentration of styrene in the liquid
phase changed in the range of 5–90 gm−3. The Haldane
model was found to be the best to fit the kinetic data, and
the estimated constants of the equation were: μm=
0.1188 h−1, KS=5.984 mg l−1, and Ki=156.6 mg l−1. The
yield coefficient mean value Yapp
xs for the batch culture was
0.72 gdry cells weight(gsubstrate)−1. The experiments conducted
in a chemostat at various dilution rates (D=0.035–0.1 h−1)
made it possible to determine the value of the coefficient
for maintenance metabolism md=0.0165 h−1 and the
maximum yield coefficient value YM
xs
¼ 0:913. Chemostatexperiments confirmed the high value of yield coefficient Yapp
xs
observed in the batch culture. The conducted experiments
showed high activity of the examined strain in the styrene
biodegradation process and a relatively low sensitivity to
inhibition of its growth at higher concentrations of styrene in
the solution. Such exceptional features of Pseudomonas sp.
E-93486 make this bacterial strain the perfect candidate for
technical applications
Kinetics of vinyl acetate biodegradation by Pseudomonas fluorescens PCM 2123
The microbial degradation of vinyl acetate (VA) by Pseudomonas fluorescens PCM 2123 strain was
studied in both batch and continuous modes. The purpose of the experiments was to determine the kinetic model
of the cell growth and biodegradation rate of vinyl acetate (VA), which was the sole carbon and energy source for
tested microorganisms. The experiments, carried out in a batch reactor for several initial concentrations of growth
substrate in the liquid phase ranging from 18.6 to 373 gsubstrate·m–3 (gs·m–3) made it possible to choose the kinetic
model and to estimate its constants. The Haldane inhibitory model with the values of constants: μm = 0.1202 h–1,
KS = 17.195 gs·m–3, Ki = 166.88 gs·m–3 predicted the experimental data with the best accuracy. To set the
parameters of maintenance metabolism it was necessary to carry out a series of continuous cultures at different
dilution rates (0.05 to 0.072 h–1) and concentrations of VA in the liquid supplied to the chemostat ranging from
30.9 to 123.6 gs·m–3. The obtained data-base enabled to determine the coefficient for maintenance metabolism
(me = 0.0251 gsubstrate·gcell dry weight
–1·h–1 (gs·gcdw
–1·h–1)) as well as the maximal and observed values of yield
coefficients, Yxs
M = 0.463 gcdw·gs
–1 and (Yxs)obs = 0.411 gcdw·gs
–1, respectively. The developed kinetics was verified
by comparison of the computed and obtained in batch experiments profiles of changes in biomass and growth
substrate concentrations
A comparative study of biodegradation of vinyl acetate by environmental strains
Four Gram-negative strains, E3_2001, EC1_2004, EC3_3502 and EC2_3502, previously isolated from soil samples, were subjected to comparative studies in order to select the best vinyl acetate degrader for waste gas treatment. Comparison of biochemical and physiological tests as well as the results of fatty acids analyses were comparable with the results of 16S rRNA gene sequence analyses. The isolated strains were identified as Pseudomonas putida EC3_2001, Pseudomonas putida EC1_2004, Achromobacter xylosoxidans EC3_3502 and Agrobacterium sp. EC2_3502 strains. Two additional strains, Pseudomonas fluorescens PCM 2123 and Stenotrophomonas malthophilia KB2, were used as controls. All described strains were able to use vinyl acetate as the only source of carbon and energy under aerobic as well as oxygen deficiency conditions. Esterase, alcohol dehydrogenase and aldehyde dehydrogenase were involved in vinyl acetate decomposition under aerobic conditions. Shorter degradation times of vinyl acetate were associated with accumulation of acetic acid, acetaldehyde and ethanol as intermediates in the culture fluids of EC3_2001 and KB2 strains. Complete aerobic degradation of vinyl acetate combined with a low increase in biomass was observed for EC3_2001 and EC1_2004 strains. In conclusion, P. putida EC1_2004 is proposed as the best vinyl acetate degrader for future waste gas treatment in trickle-bed bioreactors
Zróżnicowanie mieszanych populacji mikroorganizmów po skriningu w obecności wybranych lotnych związków organicznych
Biological methods of productive gases treatment from Volatile Organic Compounds are based on the
catalytic activities of degradative enzymes from environmental microorganisms. That is why screening for
microorganisms able to degrade xenobiotics is performed. In order to isolate microorganisms able do degrade
selected VOCs (vinyl acetate and styrene), soil sampling was performed in the area of Synthos S.A. in Oswiecim
(Poland) (formerly Chemical Company “Dwory” S.A.) in August 2006. Two independent localizations were
chosen for the collection of samples, and they were the outlet of gases arising during polymerisation of polyvinyl
acetate and polystyrene. Different selection media were applied. They consisted of mineral salts solution, buffer
components, and selective factor. As the selective factor increasing concentrations (50÷4000 mg/dm3) of vinyl
acetate or constant concentration of styrene (100 mg/dm3) were applied. There was no increase of styrene
concentration due to the significant drop in the amount of mixed population of microorganisms after application of
that selective factor. Isolation, determination of microorganisms’ amount on the grounds of colony morphology
and results of the Gram staining of cells, were carried out after introduction of vinyl acetate in the concentrations
of 1500, 2000, 2500, 3000 and 3500 mg/dm3, and at the end of 6 weeks adaptation to styrene. Presence of selected
VOCs caused significant changes in the amount and composition of mixed population of microorganisms. Both,
vinyl acetate and styrene, resulted in the decrease of the initial number of populations. The ratio of Gram-negative
to Gram-positive cells was changing in the presence of selected VOCs. In the beginning Gram-negative bacteria
predominated. Increasing concentrations of vinyl acetate brought about gradual decrease in the number of Grampositive
bacteria, and finally after application of 3000 mg/dm3 of vinyl acetate mixed populations consisted of only
Gram-negative bacteria. Different chemical structure of styrene probably caused almost complete decay of Gramnegative
bacteria in the presence of that selective factor. Differences in the structure of the bacterial cell envelopes
are most likely the reason of increased survivability of Gram-positive bacteria, mainly filiform cells of
Actinomycetes
Modelling of the process of air purification from volatile organic compounds; the one-substrate models
Badano efektywność procesu oczyszczania powietrza z octanu winylu, prowadzonego w systemie ciągłej pracy przez około 115 dni w pilotowej instalacji bioreaktora strużkowego (TBB). Bazę danych eksperymentalnych, otrzymanych dla szerokiego zakresu zmian parametrów procesowych, wykorzystano do weryfikacji dwóch jedno-substratowych modeli procesu. Oba proponowane modele aproksymowały dane eksperymentalne z zadowalającą dokładnością.The effectiveness of the air bio-purification process from vinyl acetate carried out in a pilot-scale trickle-bed bioreactor (TBB) was investigated in a continuous system for about 115 days. The experimental database, obtained for a wide range of changes in process parameters, was exploited to validate the two one-substrate models. Both proposed models approximated experimental data with a satisfactory accuracy