Prajapati et al.

is depicted in figure 5. The linear relationship between

concentration thereafter. However, the isolate AGYP-1

incubation temperature and color removal was observed in

was quite stable and exhibited 74.34% decolorization at

the temperature range of 15 to 30 o C. The isolate exhibited

500 mg l -1 Reactive Red M5B concentration. Moreover,

maximum decolorization of the dye (91.34±4.5%) along

the decolorization rate increased from 7.68 to 30.97 mg

with 237.17±11.3 U ml -1 and 68.13±5.4 U ml -1 activities

dye day -1 with an increase in initial dye concentration from

of laccase and MnP respectively at 30 o C. The dye was

100 to 500 mg l -1 explaining a typical Monod-type profile.

decolorized 84.32±3.9% at 37 o C, and the color removal

Under experimental conditions, the correlation between

activity of the isolate was severely reduced at 50 o C.

decolorization rate (R _D ) and initial dye concentration

The fungal growth was highest (0.258±0.04 g) at 30 o C

([RRM5B]) was obtained by Michaelis-Menten double

indicating an optimum temperature for the growth, enzyme

reciprocal model ( R

D max

[RRM5B] / (K m + [RRM5B]).

production and decolorization activity of the isolate

The values of an apparent maximum decolorization rate

AGYP-1. Different fungi grow at different optimum

( R

D max

) and Michaelis constant (K m ) were 128.20 mg dye

temperatures, with most of them growing at 25-35 o C (Fu

day -1 and 166.66 mg l -1 respectively. Above results thus

and Vararaghavan 2001). Similar results were reported

demonstrate a good capability of the isolate AGYP-1 for

by Gahlout et al . (2013), stating that the decolorization

the decolorization of higher concentration of the dye. The

of Reactive Violet 1 was maximum at 30 o C and lesser

effect of Malachite Green concentration on decolorization

decolorization was observed at 45 o C using Ganoderma

capacity of white rot fungus Dichomitus squalens has

cupreum AG-1. Beyond the optimum temperature, the

been studied; wherein the dye at 50 mg l -1 concentration

slower growth and deactivation of enzymes responsible

inhibited the fungal growth (Eichlerova et al ., 2006).

for degradation are main reasons for decreased degradation

activities of the microorganisms (Ali, 2010).

Figure 5: Effect of incubation temperature on

decolorization of Reactive Red M5B by isolate AGYP-1

Figure 4: Effect of pH on decolorization of Reactive Red

M5B by isolate AGYP-1

3.4.5 Effect of co-substrate

3.4.4 Effect of initial dye concentration

In general, dyes are deficient in carbon content and their

degradation without any extra carbon and nitrogen source

The decolorization capability of the isolate AGYP-1 was

is found to be very difficult (Stolz, 2001). In order to

studied by varying initial dye concentration (100-500 mg

evaluate the effect of co-substrate, the decolorization of

l -1 ) under shaking condition. Maximum decolorization of

Reactive Red M5B by isolate AGYP-1 was monitored in

Reactive Red M5B (92.18±2.2%) was observed at 100

the presence of various carbon sources. Variable results

mg l -1 concentration (Fig. 6). A marginal reduction in

of decolorization of the dye were obtained with different

decolorization efficiency of the isolate was observed at

co-substrates tested (Table 2). The decolorization

200 mg l -1 concentration (86.45±4.5%). The decolorization

performance of the isolate AGYP-1 was better in the

of the dye was decreased with increase in initial dye

presence of maltose (96.11±2.7%) with maximum laccase

506