2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
of sampling. After 19 days of incubation, the degradation of
initial middle (34.34) and high (83.15) MTBE concentration
stopped, while the degradation of lowest MTBE concentration
(10.85) continued after incubation period (Table I).
Table I
The decreasing of MTBE concentration (ppm) caused by fungal
strain Paecilomyces variotii isolate 129b
MTBE [ppm] 5th day 12 th day 15 th day 19 th day
10.85 6.6 6.08 2.45 1.55
34.34 33.5 23.34 19.19 20.2
83.15 74.3 46.92 38.25 40.7
Moreover, even different pattern of degradation the fungal
strain of Paecilomyces variotii, isolate 129b, decreased
MTBE concentration in all treatments used (Table II). The
highest degradation rate (2.23 ppm per day) was in the treatment
with the highest concentration used, (from 83.15 to
40.70). In the middle treatment, the degradation rate decreased
to 0.744 ppm per day and in lowest concentration the
degradation rate further decrees to 0.490 ppm per day. However,
the total MTBE degraded by fungi is to be in highest
concentration used (42.7 ppm for 19 days). From the Table III
it can be seen that there is no substantial change in the fungus
yields (mg/ml) compared treatments and control.
Table II
The MTBE degradation rate [%] caused by fungal strain
Paecilomyces variotii isolate 129b
MTBE 5th day 12 th day 15 th day 19 th day
[ppm] [%] [%] [%] [%]
10.85 39.2 44.0 77.4 85.7
34.34 2.4 32.0 44.1 41.2
83.15 10.6 43.6 54.0 51.1
The highest yield of Paecilomyces variotii mycelia was
noticed at lowest initial MTBE concentration. The addition of
MTBE slightly affects mycelia yield and is similar to control.
The results of mycelia yield is in correlation with degradation
results, because the highest mycelia yield is noticed in variant
with lowest concentration used, but even that the difference
among treatments are not statistically significant.
Table III
Paecilomyces variotii mycelia biomass after 19 days of
MTBE treatments
MTBE initial
concentration
repeats [mg ml –1 ]
[ppm] I II III
average
[mg ml –1 ]
10.85 0.010 0.026 0.037 0.024
34.34 0.019 0.022 0.012 0.018
83.15 0.018 0.025 0.014 0.019
control 0.013 0.022 0.016 0.017
s407
The results of experiments showed that the fungal strain
Paecilomyces variotii isolate 129b, is capable of MTBE utilization
as sole source of carbon and energy to support growth.
The highest MTBE degradation rate was at the lowest initial
MTBE concentration. The addition of MTBE had a negative
effect on degradation rate but total MTBE degraded was
higher.
Discussion
Fungi are highly successful in survival because of their
great physiological versatility. Their ability to produce extracellular
enzymes is of great survival value. Fungi are involved
in the biodegradation processes of undesirable materials
(waste, pesticides, detergents, oil spills etc.) into harmless
products 19 . The utilization of filamentous fungi for bioremediation
processes has been limited compared with bacteria.
Because of enzyme production in different environmental
conditions, the fungi perform the degradation of broad
spectrum of pollutants 20 . One of enzyme that is responsible
for MTBE degradation is alcohol dehydrogenase 14 , who affects
the TBF formation during the MTBE oxidation. Because
of its gelatinolytic and cellulolytic activity, the fungus Paecilomyces
variotii is capable of biodegradation of some aromatic
volatile organic compounds (VOC) like toluene 21 , formaldehyde
22 and alkylbenzenes 23 . In addition, recent reports
showed that Paecilomyces variotii could be use in cadmium
biosorption 24 and for bioremediation of aflatoxine 25 . Previous
mycoremediation studies indicated that different fungal
cultures have capability of MTBE biodegradation 15,16 .
The results of investigation shown that Paecilomyces
variotii mycelia can grow in the presence of different MTBE
concentration. MTBE degradation rate is lowest in the latest
phase of incubation period. This conclusion is in accordance
with previous MTBE studies 14 , where the MTBE degradation
rate progressively declined during the mycelia incubation
with MTBE alone. Our experiments showed that the
degradation rate was lower than in previous studies 14 , but the
initial MTBE concentration was lower than in our investigation.
The slower degradation rate was also possibly due to
presence of methanol, which was solvent for MTBE. Other
authors 15 also reported similar conclusion.
The low degradation rate and yield of mycelia indicates
that MTBE may be a poor substrate and energy source
and/or that an intermediate during degradation may inhibit
the microbial growth 12 . During the MTBE degradation, intermediates
concentrations increased, while concentration of
MTBE was decreased 26 . This conclusion confirms the MTBE
degradation by microbial pure cultures. The results showed
that ether bonds could be cleavage by certain microorganisms,
although some investigations showed that this bond
is not biodegradable or resistant to biodegradation 27 . According
to this conclusion is a result of yield of Paecilomyces
variotii mycelia, which was comparatively low. The low
yield of microbial cultures in the presence of MTBE was also
reported in earlier studies 28 , probably because this compound
is metabolic and electron transport inhibitor 9 .