2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology<br />
of sampling. After 19 days of incubation, the degradation of<br />
initial middle (34.34) and high (83.15) MTBE concentration<br />
stopped, while the degradation of lowest MTBE concentration<br />
(10.85) continued after incubation period (Table I).<br />
Table I<br />
The decreasing of MTBE concentration (ppm) caused by fungal<br />
strain Paecilomyces variotii isolate 129b<br />
MTBE [ppm] 5th day 12 th day 15 th day 19 th day<br />
10.85 6.6 6.08 <strong>2.</strong>45 1.55<br />
34.34 33.5 23.34 19.19 20.2<br />
83.15 74.3 46.92 38.25 40.7<br />
Moreover, even different pattern of degradation the fungal<br />
strain of Paecilomyces variotii, isolate 129b, decreased<br />
MTBE concentration in all treatments used (Table II). The<br />
highest degradation rate (<strong>2.</strong>23 ppm per day) was in the treatment<br />
with the highest concentration used, (from 83.15 to<br />
40.70). In the middle treatment, the degradation rate decreased<br />
to 0.744 ppm per day and in lowest concentration the<br />
degradation rate further decrees to 0.490 ppm per day. However,<br />
the total MTBE degraded by fungi is to be in highest<br />
concentration used (4<strong>2.</strong>7 ppm for 19 days). From the Table III<br />
it can be seen that there is no substantial change in the fungus<br />
yields (mg/ml) compared treatments and control.<br />
Table II<br />
The MTBE degradation rate [%] caused by fungal strain<br />
Paecilomyces variotii isolate 129b<br />
MTBE 5th day 12 th day 15 th day 19 th day<br />
[ppm] [%] [%] [%] [%]<br />
10.85 39.2 44.0 77.4 85.7<br />
34.34 <strong>2.</strong>4 3<strong>2.</strong>0 44.1 41.2<br />
83.15 10.6 43.6 54.0 51.1<br />
The highest yield of Paecilomyces variotii mycelia was<br />
noticed at lowest initial MTBE concentration. The addition of<br />
MTBE slightly affects mycelia yield and is similar to control.<br />
The results of mycelia yield is in correlation with degradation<br />
results, because the highest mycelia yield is noticed in variant<br />
with lowest concentration used, but even that the difference<br />
among treatments are not statistically significant.<br />
Table III<br />
Paecilomyces variotii mycelia biomass after 19 days of<br />
MTBE treatments<br />
MTBE initial<br />
concentration<br />
repeats [mg ml –1 ]<br />
[ppm] I II III<br />
average<br />
[mg ml –1 ]<br />
10.85 0.010 0.026 0.037 0.024<br />
34.34 0.019 0.022 0.012 0.018<br />
83.15 0.018 0.025 0.014 0.019<br />
control 0.013 0.022 0.016 0.017<br />
s407<br />
The results of experiments showed that the fungal strain<br />
Paecilomyces variotii isolate 129b, is capable of MTBE utilization<br />
as sole source of carbon and energy to support growth.<br />
The highest MTBE degradation rate was at the lowest initial<br />
MTBE concentration. The addition of MTBE had a negative<br />
effect on degradation rate but total MTBE degraded was<br />
higher.<br />
Discussion<br />
Fungi are highly successful in survival because of their<br />
great physiological versatility. Their ability to produce extracellular<br />
enzymes is of great survival value. Fungi are involved<br />
in the biodegradation processes of undesirable materials<br />
(waste, pesticides, detergents, oil spills etc.) into harmless<br />
products 19 . The utilization of filamentous fungi for bioremediation<br />
processes has been limited compared with bacteria.<br />
Because of enzyme production in different environmental<br />
conditions, the fungi perform the degradation of broad<br />
spectrum of pollutants 20 . One of enzyme that is responsible<br />
for MTBE degradation is alcohol dehydrogenase 14 , who affects<br />
the TBF formation during the MTBE oxidation. Because<br />
of its gelatinolytic and cellulolytic activity, the fungus Paecilomyces<br />
variotii is capable of biodegradation of some aromatic<br />
volatile organic compounds (VOC) like toluene 21 , formaldehyde<br />
22 and alkylbenzenes 23 . In addition, recent reports<br />
showed that Paecilomyces variotii could be use in cadmium<br />
biosorption 24 and for bioremediation of aflatoxine 25 . Previous<br />
mycoremediation studies indicated that different fungal<br />
cultures have capability of MTBE biodegradation 15,16 .<br />
The results of investigation shown that Paecilomyces<br />
variotii mycelia can grow in the presence of different MTBE<br />
concentration. MTBE degradation rate is lowest in the latest<br />
phase of incubation period. This conclusion is in accordance<br />
with previous MTBE studies 14 , where the MTBE degradation<br />
rate progressively declined during the mycelia incubation<br />
with MTBE alone. Our experiments showed that the<br />
degradation rate was lower than in previous studies 14 , but the<br />
initial MTBE concentration was lower than in our investigation.<br />
The slower degradation rate was also possibly due to<br />
presence of methanol, which was solvent for MTBE. Other<br />
authors 15 also reported similar conclusion.<br />
The low degradation rate and yield of mycelia indicates<br />
that MTBE may be a poor substrate and energy source<br />
and/or that an intermediate during degradation may inhibit<br />
the microbial growth 12 . During the MTBE degradation, intermediates<br />
concentrations increased, while concentration of<br />
MTBE was decreased 26 . This conclusion confirms the MTBE<br />
degradation by microbial pure cultures. The results showed<br />
that ether bonds could be cleavage by certain microorganisms,<br />
although some investigations showed that this bond<br />
is not biodegradable or resistant to biodegradation 27 . According<br />
to this conclusion is a result of yield of Paecilomyces<br />
variotii mycelia, which was comparatively low. The low<br />
yield of microbial cultures in the presence of MTBE was also<br />
reported in earlier studies 28 , probably because this compound<br />
is metabolic and electron transport inhibitor 9 .