Extracellular enzyme production by freshwater ascomycetes

Thirty species of freshwater ascomycetes isolated from woody and/or herbaceous substrates were screened for their ability to produce extracellular degradative enzymes on solid media. Enzymes tested included: amylase, endoglucanase, endoxylanase, beta -glucosidase, laccase, lipase, pectinase, peroxidase, polygalacturonase, polyphenoloxidase, protease, tyrosinase and beta -xylosidase. All species were positive for cellulase and endoxylanase/ beta -xylosidase. Two species, Chaetomastia typhicola (herbicolous) and Massarina sp. A25 (lignicolous) tested positive for all enzyme assays. Submersisphaeria aquatica (lignicolous) was positive for all enzymes except tyrosinase and Jahnula sp. A322 (lignicolous) was positive for all enzymes except polyphenoloxidase. Generally, the species which were isolated from herbaceous substrates and woody/herbaceous substrates had good growth rates on different types of enzyme media used (such as, peptone. yeast extract, glucose agar, etc.). Fifty percent of the lignicolous species produced pectin degrading enzymes, compared to about 80% for herbicolous and woody/herbicolous species, suggesting that there may be some specialization in the types of enzymes produced within substrate groups. The greatest differences among species occurred in the production of enzymes associated with detection of lignin degradation. Laccase and peroxidase detection depended on the assay technique used. Freshwater ascomycetes, as a group, produce many of the extracellular enzymes important in the decomposition of plant structural materials thereby supporting the idea that they play an imnortant role in recycling in aquatic habitats.