Trans-fernloyl and trans-p-coumaroyl esterases were found in the culture filtrates of two monocentric (Piromyces MC-1, Neocallimastix MC-2) and three polycentric (Orpinomyces PC-2, Orpinomyces PC-3, and PC-l, an unnamed genus with uniflagellated zoospores) isolates of anaerobic rumen fungi. Treatment of cell walls of Coastal berrnudagrass shoots with the filtrates released the trans isomers of ferulic and pcoumaric acids; results of microscopic observations indicated that fungal isolates degraded primarily unlignified cell walls in leaf blades and stems. A greater proportion of ferulic than p-coumaric acid was released by this treatment when compared with the amounts of the acids released by saponification of the walls with 1 M NaOH. The filtrates also showed esterase activities against the trans isomers of methyl ferulate and methyl p-coumarate, with ferulic acid being released at a faster rate than p-coumaric acid. Assays for other cell-walldegrading enzymes (xylanase, fl-xylosidase, a-L-arabinosidase, cellulase, fl-glucosidase) indicated that only fl-xylosidase correlated with ferulate and p-coumarate esterase activities. The monocentric isolate MC-2 had the highest esterase activity against both the plant cell wall and methyl ester substrates and the highest specific activities of acetyl esterase, fl-xylosidase, a-I~-arabinosidase, cellulase and fl-glucosidase. Isolate MC-2 produced substantially greater amounts of feruloyl and p-coumaroyl esterase when the growth substrate contained higher levels of saponifiable fernlic and p-coumaric acids.
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