Productivity of laccase in solid substrate fermentation of selected agro-residues by Pycnoporus sanguineus

Abstract

A comparative study on solid substrate fermentation (SSF) of sago ‘hampas’, oil palm frond parenchyma tissue (OPFPt) and rubberwood sawdust with Pycnoporus sanguineus for laccase production was carried out. Optimal mycelial growth of Pyc. sanguineus was observed on all the substrates studied over a 21 days time-course fermentation. Laccase productivity was highest during degradation of sago ‘hampas’ and OPFPt and a range from 7.5 to 7.6 U/g substrate on the 11th day of fermentation compared to degradation of rubberwood sawdust with a maximum laccase productivity of 5.7 U/g substrate on day 11 of SSF. Further optimization of laccase production was done by varying the inoculum age, density and nitrogen supplementation. SSF of OPFPt by Pyc. sanguineus gave maximum productivity of laccase of 46.5 U/g substrate on day 6 of fermentation with a 30% (w/w) of 4 weeks old inoculum and 0.92% nitrogen in the form of urea supplemented in the substrate.

The extraction of laccase was also optimized in this study. Recovery of laccase was fourfold higher at 30.6 U/g substrate on day 10 of SSF using unadjusted tap water at pH 8.0 as extraction medium at 25 ± 2 °C compared to laccase recovery of 7.46 U/g substrate using sodium acetate buffer at pH 4.8 at 4 °C. Further optimization showed that laccase recovery was increased by 50% with a value of 46.5 U/g substrate on day 10 of SSF when the extraction medium was tap water adjusted to pH 5.0 at 25 ± 2 °C.