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Improvement of pectinase production by interspecific hybrids of Aspergillus strains

Protoplast fusion induced by polyethylene glycol and Ca2+, was performed between auxotrophic mutants of pectinolytic fungi Aspergillus sp. CH‐Y‐1043 (A13) ade− and Aspergillus flavipes ATCC‐16795 (F7) lys−. Prototrophic colonies were developed on minimal medium with a fusion frequency of 1·0×10−2. The reversion frequency of the mutation in spores and protoplasts was low and ranged from 2·0 to 4·0×10−7. Four prototrophic hybrids (HH, HE, HF and HJ) exhibited enhanced production of endo‐pectinase and pectin‐lyase. The highest production was observed in HJ ; maximum activities were 150 and 160% respectively, whereas the exo‐pectinase production was similar to the wild‐type strain Aspergillus sp. CH‐Y‐1043. Hybrid HJ showed the greatest growth ; nevertheless, specific endo‐pectinase and pectin‐lyase activities were higher in all hybrids than those produced by the wild‐type strains.