Fusion between protoplasts of Pichia stipitis and isolated filamentous fungi nuclei

Enhancement of phytoremediation of Cd- and Pb-contaminated soils by self-fusion of protoplasts from endophytic fungus Mucor sp. CBRF59

The aim of this study was to isolate protoplasts from endophytic fungi and to carry out self-fusion of protoplasts for their enhancement of metal resistance. Self-fusant CBRF59T3 with resistance to 25 mM Cd(II) was constructed by self-fusion of inactivated protoplasts from Mucor sp. CBRF59. The inoculation of CBRF59 and CBRF59T3 improved significantly the availability of Cd(II) and Pb(II) in the soil. Compared with CBRF59, CBRF59T3 inoculation increased the content of water-soluble Cd(II) by 24%. The dry weight of rape inoculated with CBRF59 and CBRF59T3 was both higher than that of the uninoculation rape. Inoculation of CBRF59T3 further increased the dry weight of rape by 62% than CBRF59 in the higher Cd(II)-+Pb(II)-contaminated soil. Compared with CBRF59, CBRF59T3 inoculation increased the concentration of Cd(II) in rape shoots by 35-189% in Cd(II)- and Cd(II)-+Pb(II)-contaminated soils. The inoculation of CBRF59T3 also enhanced the translocation of Cd(II) from roots to shoots and increased the amount of extracted Cd(II) by rape. The results indicated that the mutants constructed by protoplast fusion is a feasible and efficient method to improve stress tolerance of uncharacterized fungi for phytoremediation of soils contaminated by heavy metals.

Regeneration and molecular characterization of an intergeneric hybrid between Graphium putredinis and Trichoderma harzianum by protoplasmic fusion

The fungal strains Graphium putredinis and Trichoderma harzianum were selected as parents for fusant development. Protoplasts were isolated using the combination of lysing enzymes Novozym 234 and cellulase with 0.6M KCl as osmotic stabilizer. The optimum conditions for release of viable protoplasts from the fungal mycelium viz. age of the mycelium, lytic enzymes, osmotic stabilizers, pH, incubation period and regeneration medium were determined. Intergeneric protoplast fusion was carried out using 50% polyethylene glycol with calcium chloride (CaCl(2)) and glycine buffer and the conditions for effective protoplast fusion, viz. fusogen, osmotic stabilizer, pH, incubation period and regeneration medium were optimized. At optimum conditions, the regeneration frequency of the fused protoplasts on potato dextrose agar (PDA) medium and fusion frequency were calculated. The regeneration frequency on non-selective (PDA) and selective media (PDA amended with starch) was determined for the parental and fusant strains in which, fusant showed a higher rate of regeneration. Fusant formation was confirmed by morphological markers (colony morphology and spore size and shape) and genetical markers like, mycelial protein pattern, restriction digestion pattern and random amplified polymorphic DNA (RAPD) analysis. The efficiency of these parental strains and their intergeneric fusant in the production of hydrolytic enzymes - amylases (treatment plant for sago factory effluent), cellulases (bioethanol), xylanases (bleaching agents for waste paper pulp) and proteases (additives in commercial detergents) - have probable applications in various industrial processes.