Random mutagenesis and genetic diversity of white rot fungus (Phellinus igniarius) by physical mutagens

Phellinus spp. a fungus that induces white-rot owing to the unique ability to break down lignin, has been widely exploited for laccase synthesis. In this study, medicinal mushroom Ph. igniarius, was exposed to pulsed light and pulsed magnetic field to develop high laccase producing mutants. Pulsed light showed a higher lethality rate (treatment condition 8.5 cm, only 3 pulses at the intensity of 100 J/pulse, the protoplast lethality rate achieved 82%) than the pulsed magnetic field around 70% (even treated at a higher magnetic field 9 T). The pulsed light treatment yielded QB72, while the pulsed magnetic field treatment yielded 13c-j and 7c-a. Initially, the colony was white; later it developed a yellowish-cream coloration and grew dense and compact; the advancing zone was composed of elevated, short, even hyphae, and clamp connections were plainly obvious in all strains. All the three mutants showed a higher growth speed on the plate. However, QB72 had superior fermentation mycelia (23.997 g/L); superior ABTS radical scavenging ability (58.87%); and superior FRAP value (0.330). Strains obtained through physical treatment altered the protein (esterase isoenzyme protein analysis) and DNA polymorphisms (TRAP-PCR of the laccase target genes). The pulsed light and pulsed magnetic field could be a mutagenesis method applied to treat the Ph. igniarius protoplast for higher growth and laccase strains.