6-04: Genome shuffling of Penicillium decumbens to improve its cellulase production

Genome shuffling is an efficient approach for the rapid improvement of important industrial microorganisms. The cellulase production of P. decumbens was improved by genome shuffling of an industrial catabolite-repression-resistant strain JU-A10 with its mutants. The mutants were obtained by UV-EMS mutation or N⁺ ions implanting of JU-A10, and prepared for protoplasts fusion. Six improved fusant strains were selected as parents for the second genome shuffling. Three fusants, GS2-15, GS2-21 and GS2-22, were selected based on their capacity to show clear hydrolysis halo on the two-layer plate containing 2% glucose and 5% ball-milled microcrystalline cellulose. The fusants showed 100%, 109% and 94% increase in filter paper activity, respectively. The cellulase production of the fusants on various substrates, such as corn stover, wheat straw, bagasse and the corncob residue from xylitol production, were studied.  It was obvious that the three fusants could produce abundant cellulase much earlier than the parental strain JU-A10, the maximum volumetric productivity of GS2-15, GS2-21 and GS2-22 was 92.15, 102.63, and 92.35 FPU/L/h respectively when fermented with the corncob residue at 44 h, which was 117%, 142%, 118% higher than that of JU-A10 (42.44 FPU/L/h at 90 h).  Higher glucose yield from the corncob residue were also observed by using the fermented broth of the fusants as crude cellulase.  The improved cellulase production of the fusants was proposed to be mainly due to their increased growth rates and enhanced secretion of extracellular proteins.