International Journal of Medicinal Mushrooms

ISSN for PRINT: 1521-9437

For Online Access

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2002, Volume4

Issue 1

80 pages

Issue price - $128.00

Limor-Leibovitz Persky
Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, P. 0. Box 12, Rehovot 76100, Israel

Zohar Kerem
Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, P. 0. Box 12, Rehovot 76100, Israel; Fax: 972-8-9468785

Elisha Tel-Or
Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, P. 0. Box 12, Rehovot 76100, Israel; Fax: 972-8-9468785

Yitzhak Hadar
Department of Plant Pathology and Microbiology, Faculty of Agricultural and Environmental Quality Sciences, the Hebrew University, Rehovot 76100, Israel

Degradation oflignin requires a complex enzymatic system that includes oxidases, peroxidases, and H₂O₂-producing enzymes. A time-course study of extracellular catalase and glyoxal oxidase (GLOX) activity in liquid cultures of the edible and medicinal mushroom Pleurotus ostreatus (Jacq.: Fr.) Kumm. was performed. Activity levels of GLOX increased, reaching maximal activity at 6.9 mM H₂O₂/min on the 7th day of growth. Catalase activity followed the pattern of GLOX activity, and was highest on the 8th day of growth (1.49 mM H₂O₂ reduced/min). The patterns of GLOX and catalase activity under conditions of solid-state fermentation (SSF) resembled those in liquid culture, with both activities reaching their highest levels on day 13 of growth. This trend was also observed in Trametes versicolor (L.: Fr.) Lloyd but not in the non-lignin-degrading basidiomycete Sclerotium rolfsii Sacc. The enzymes superoxide dismutase (SOD) and fumarase were selected as intracellular markers, as their activities were apparent only in the intracellular sample. On the basis of these results, we suggest that the catalase activity was indeed extracellular. The addition ofl H₂O₂ (3.3 mM, 6.6 mM) to P. ostreatus cultures caused increases in catalase activity at 15 and 30 minutes, but a decrease at 45 minutes. The addition of glucose to 5-day-old P. ostreatus cultures induced low GLOX activity, but no catalase activity was detected. Extracellular catalase in lignin-degrading fungi may play two roles: it may protect the fungus from oxidative damage and it may protect ligninolytic peroxidases from inactivation which might be caused by H₂O₂ accumulation.

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