• The Korean Journal of Mycology
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• v.21 no.3
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• pp.195-199
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• 1993

This experiments was designed for development of Fusarium oxysporum strains with enhanced activity of polygalacturonase by means of mutants and protoplasts fusion. Six auxotrophic mutants of F. oxysporum were induced by treatment of MNNG. Protoplasts from mutants were formed from early exoponential mycelium after treatment with driselase(10 mg/ml) using 0.6 M KCl as osmotic stabilizer. Fusion experiments between protoplasts of several auxotrophic mutants were done using polyethyleneglycol 8,000 and $CaCl_2$. The frequency of fusion was $5.0{\times}10^{-3}$ as determined from several experiments. Activity of polygalacturonase was determined by the methods of modified DNS. Consequently, the polygalacturonase activities of mutants and fusant derived F. oxysporum were 1.4 to 3.5 times greater than that of the parental strain, and mutant Fx-2 seemed to be the best strain. Thus, the method we used seemed to be favorable for the improvement of strains.

• Microbiology and Biotechnology Letters
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• v.14 no.4
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• pp.305-310
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• 1986

To improve the starch fermentation ability of yeast, hybrids were introduced by protoplast fusion of S. cerevisiae and S. diastaticus. The protoplasts of parental auxotrophic cells were fused in the presence of 10 mM CaCl$_2$and 30% of polyethyleneglycol (M.W 4, 000). The frequencies of fusant formation varied depending upon the strains used and were 3.51$\times$10$^{-4}$ to 5.04$\times$10$^{-4}$ for the regenerated protoplasts. The strains capable of extensive starch hydrolysis produce only 10% to total fusants. The 4 strains were finally selected by the results of starch fermentation and genetic stability test. The DNA content and cell volume of the fusants were greater than those of the parental strains.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.133-137
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• 1994

Functional properties of packaging films prepared with cellulose derivatives were measured. As a presolvation treatments of celluloses, 95% ethanol solution for methylcellulose (MC), hydroxypropyl-methylcellulose (HPMC) and ethylcellulose (EC) and water for hydroxypropyl cellulose (HPC) were used. For film sheeting, the ethanol concentration of final cellulose solution should exceed 50% for MC, HPMC and HPC and 80% for EC. Thickness and functionalities of the prepared films were varied by type, molecular weight and viscosity of the cellulose and kind of plasticizer used. Tensile strength of MC, HPMC and HPC films were $67.7{\sim}275.4\;MPa$, $124.6{\sim}260.0\;MPa$, and $14.8{\sim}29.4\;MPa$, respectively. The strength of MC and HPMC films was higher than that of low density polyethylene (LDPE) films $(13.1{\sim}27.6\;MPa)$. Solubility of the cellulose films varied widely by plasticizer used and the films containing polyethyleneglycol (PEG) as a plasticizer was more soluble than the films by glycerol. Maximum water vapor permeability and oxygen permeability of the cellulose films was more than 1,000 folds and less than one-twelfth of the LDPE film, respectively.