Construction of cellulase hyperproducing strains derived from polyploids of Trichoderma reesei

The mycelial mat of Trichoderma reesei strain QM 6a was treated with 0.1% (w/v) colchicine solution for 14 days and designated M14. The cellulase productivity of strain M14 was not much higher than that of the original strain. When conidia of M14 were treated with ethylmethane sulphonate (EMS) solution, the cellulase hyperproducers, M14-1 and M14-2, were isolated using a selection medium containing Avicel. The DNA content of M14-1 and M14-2 was higher than that of the original strain. Cellulase productivity per mycelium of these strains increased and was higher than that of the original strain. The cellulase productivity did not change through ten generations when these strains were cultivated successively on a medium containing Avicel. It was concluded that cellulase hyperproducers, whose cellulase productivity per mycelium increased, could be obtained when the conidia of strain M14 were treated with EMS.