Screening and production of a potential extracellular fungal laccase from Penicillium chrysogenum: Media optimization by response surface methodology (RSM) and central composite rotatable design (CCRD)

Abstract

This paper describes the isolation of potent extracellular-laccase producing white-rot fungus, identified by 18 s-rRNA as Penicillium-chrysogenum and its medium optimization by central-composite-rotatable-design using RSM. The optimum laccase-activity of 6.0 U ml-1 was obtained and maximum activity of 7.9 U ml-1 was achieved by statistical-optimization of the medium at 32 °C for 5 days. The molecular-weight of the laccase was found to be 67 kDa. UV-visible absorption-spectrum analysis shows peak at 600 nm and 325 nm corresponding to the type-I Cu(II) & type-III binuclear Cu(II) pair respectively confirming presence of laccase. The sharp endothermic peak at 150 °C and three-phases of protein denaturation was observed by DSC and TGA analysis for enzyme protein. The FT-IR analysis of laccase shows band at 1405cm-1, 1656 cm-1 &3400cm-1 corresponding to amide-I band, amide-II band and amino-acid group respectively. Results of the study show the enzyme is capable of carrying-out hydrolytic-cleavage of chemical-pollutants from the industrial waste-water for providing sustainable-greener environment Keywords: Laccase, Penicillium chrysogenum, RSM, redox potential, UV-vis spec, DSC and FT-IR