Production parameter optimization for laccases by Aspergillus niger

Dialysis

Pellet was dissolved in 0.01 M phosphate buffer with pH-7 and was dialysed

against the same buffer overnight at 4ºC.

Estimation of protein content of partially purified laccases

Protein content of the sample was measured by Lowry’s method and bovine serum

albumin (BSA) was used as standard (Lowery et al., 1951).

Results and Discussion

Optimization of culture conditions for laccase production

Effect of temperature on laccase activity

Highest laccase activity was observed at 30ºC(0.0356 U/ml) (Fig: 1). Similar

kind of study was conducted by Adejoye and Fasidi, (2009) in which effect

of temperature on laccase activity was studied and reported maximum laccase

activity (51.5 ± 2.21 U/ml) at 28°C.Rajeshwari and Parvantham, (2011) reported

maximum laccase production at 40°C.Incubation temperature plays an important

role in the metabolic activities of microorganisms. The optimal temperature of

laccase differs greatly from one strain to another.It has been found that 25°C is

the optimal temperature for laccase production in presence of light, but, in case of

dark, the optimal temperature is 30°C.Increase and decrease in temperature lead

to the gradual decrease in protein products. In the present in investigation there

was a gradual increase in enzyme activity from 20-40°C and at 50°C the enzyme

activity decreases.

Fig: 1 Effect of temperatureon laccase activity by Aspergillus niger

Effect of pH on laccase activity

Highest laccase activity was observed at pH 7 (0.0341 U/ml), while lowest

laccase activity was observed at pH 12 (0.0287 U/ml). (Fig:2).Similar kind of

study conducted Sivakumar et al. (2010) and the maximum release of laccase

activity of 0.24 U/ml was reported at pH 6.0 by Ganoderma sp. Study conducted

by Adejoye and Fasidi, (2009) in which the highest laccase activity of (2.86

U/min) was recorded at pH 5.5.Rajeshwari and Parvantham, (2011) reported

maximum laccase production at pH 5. pH is one of the important factor for the

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