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Journal of Applied Genetics 45(1), 2004, pp. 37-48

Intensification of lipase biosynthesis as a result of electrofusion of Rhizopus cohnii protoplasts

Regina SAWICKA-ZUKOWSKA, Danuta JUSZCZAKIEWICZ, Anna MISIEWICZ, Andrzej KRAKOWIAK, Barbara JEDRYCHOWSKA


Abstract: Our objective was to obtain products of fusion of the filamentous fungus Rhizopus cohnii Rh.c./1 with an increased capacity for lipase biosynthesis in comparison with the original strain. Protoplasts of auxotrophic mutants of the parent strain Rh.c./1 obtained after UV irradiation of the spores were subjected to electrofusion. We found that the largest number of electrofusion products could be obtained with the use of the following process parameters: 1 or 2 impulses immediately following one another with a field intensity of 200 V/cm and an exposition time of 1000 ms at the stage of dielectrophoresis, 1 impulse with a field intensity of 500 V/cm and an exposition time of 10 ms or 20 ms at the stage of fusion, regulated temperature of 4oC before and after the process, rounding time of ca 20 min. Electrofusion of protoplasts of auxotrophic mutants of the Rh.c./1 strain produced 19 fusion products whose lipase biosynthesis capacity in a liquid medium culture was higher than that of the parent strains. The fusion product labelled XIII-21 was selected as the best strain. Lipase activity obtained after its culture in the liquid medium was ca 3.5 times higher than that obtained after the culture of the original strain Rh.c./1.

Key words: electrofusion, lipase-producing capacity, Rhizopus cohnii.

Correspondence: D. JUSZCZAKIEWICZ, Department of Industrial Microbiology and Biochemistry, Institute of Agricultural and Food Biotechnology, ul. Rakowiecka 36, 02-532 Warszawa, Poland; e-mail: juszczakiewicz@ibprs.pl

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