Page 27 - Volume 6, Issue 2, July 2013

Biodegradation of diazinon by epiphytic yeasts

75

trient medium prevents the assimilation or

the metabolism of another substance from

the cells of the yeast until the depletion of

the levels of glucose. In the case of

Rh. rubra

,

the addition of glucose in the nutrient medi-

um as an extra source of carbon did not af-

fect its ability to degrade diazinon. Biodeg-

radation was observed from the beginning

of the trials in both media (Figure 2) and in

particular the medium supplemented with

glucose gave higher biodegradation rates,

1.67 μg/mL/day and 2.5 μg/mL/day com-

paring to 1.25 μg/mL/day and 2.08 μg/mL/

day on the medium without glucose for 10

μg/mL and 25 μg/mL diazinon, respectively.

By the end of the experiment diazinon was

fully degraded in both media. This has also

been reported by Cycon

et al.

(2009) during

the degradation of diazinon by the bacteria

Pseudomonas

sp.,

Serratia liquefaciens

and

Serratia marcescens

and by Sethunathan and

MacRae (1969), who reported that

Strepto-

myces

sp., isolated from soil of rice fields, de-

grade diazinon only under the presence of

Figure 2.

Biodegradation of 10 and 25 μg/mL diazinon by the yeasts

Rhodotorula glutinis

and

Rhodotorula rubra

in miner-

al salts nutrient medium with and without glucose. Each value is the mean of three replicates with error bars representing

the standard deviation of the mean.