Aims: To test the anaerobic fungus, Piromyces sp. FNG5, for its tolerance to phenolic monomers released in the rumen by degradation of lignocellulosic poor-quality feeds. Methods and Results: Effects of phenolic monomers on biomass and fibrolytic enzyme activities of a pure culture of lignocellulolytic anaerobic fungus (Piromyces sp. FNG5) isolated from faeces of wild nil gai (blue bull, Baselophus tragocamelus) were evaluated. There was a reduction in fungal biomass at 1 mM M concentration of catechol with complete inhibition at 10 mM M. p-Coumaric acid caused a reduction in biomass at 10 mM M and no growth was observed above 20 mM M concentration. The fungal isolate could tolerate up to 5 mM M of ferulic acid without any reduction in biomass level, and was able to grow to some extent up to the highest level of ferulic acid tested (20 mM M). Vanillic acid had no effect on biomass of the fungus even up to 50 mM M level. The phenolic monomers varied in their potential to inhibit the secretion of carboxymethyl cellulase, xylanase, b-glucosidase and acetyl esterase activities with catechol being the most inhibitory and vanillic acid being the least inhibitory. After 14 days of incubation, 38AE49-65AE14% p-Coumaric acid, 65AE22-74AE10% ferulic acid and 34AE13-66AE78% vanillic acid disappeared from the medium under anaerobic conditions. Conclusions, Significance and Impact of the Study: It is concluded that the anaerobic fungus Piromyces sp. FNG5 is tolerant to phenolic monomers and has ability to degrade them. Therefore, such anaerobic fungi may play an important role in fibre degradation in the rumen.

-Five strains of anaerobic fungi isolated from the faeces of wild (hog deer, Cervus porcinus; blackbuck, Antelope cervicapra; spotted deer, Axis axis; nilgai, Baselophus tragocamelus) and rumen liquor of domestic (sheep, Ovies aries) ruminants showing high fibrolytic enzyme producing ability were added to mixed rumen microflora of buffalo to study their effect on the digestibility of lignocellulosic feed (wheat straw and wheat bran in the ratio of 80:20), enzyme production and fermentation end products in in vitro conditions. Among the 5 isolates studied, FNG5 (isolated from nilgai) showed the highest stimulating effect on apparent digestibility (35.31 ± 1.61% vs. 28.61 ± 1.55%; P < 0.05), true digestibility (43.64 ± 1.73% vs. 35.37 ± 1.65%; P < 0. 01), neutral detergent fiber digestibility (29.30 ± 2.58% vs. 18.47 ± 2.12; P < 0.01) of feed 24 h after inoculation compared to the control group. The production of carboxymethyl cellulase, xylanase, acetyl esterase and β-glucosidase was significantly (P < 0.05) higher in the FNG5 inoculated incubation medium. There was no improvement in the digestibility and enzyme production on the addition of the other 4 isolates. Total volatile fatty acid levels as well as the concentration of acetate, propionate, isobutyrate and valerate were significantly higher in the FNG5 added group as compared to the control group. The fungal isolate FNG5 from nilgai, a wild ruminant, was found to be superior to the other isolates tested and appears to have a potential to be used as a feed additive for improving fiber degradation in domestic ruminants. rumen fungus / digestion / wild animals / enzyme / buffalo / rumen microflora / Piromyces sp.

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Fermentative characteristics and fibrolytic enzyme activities of anaerobic gut fungi from wild (17 isolates) and domestic ruminants (15 isolates) were examined. In a medium containing 0.5% wheat straw and 0.02% cellobiose as energy source, activities of carboxymethyl cellulase (CMCase), avicelase, xylanase, acetyl esterase and protease produced by the fungal isolates were investigated. Average activity of CMCase (17.4 vs. 8.25 mIU ml(-1)), acetyl esterase (134 vs. 57 mIU ml(-1)) and protease (4400 vs. 1683 mIU ml(-1)) were significantly higher in isolates from wild ruminants than those from domestic ruminants. Xylanase and avicelase activities were comparable. When compared irrespective of source, fungal isolates having monocentric growth pattern produced more fibrolytic enzymes than isolates having polycentric growth pattern. CMCase, xylanase, avicelase activities were highest in Neocallimastix isolates. Acetyl esterase activity was highest in Piromyces and Neocallimastix isolates. Protease activity was highest in Piromyces isolates followed closely by Neocallimastix isolates. Between isolates from wild and domestic ruminants few differences were observed in pattern of carbohydrate utilisation and end products of fermentation. Inter-strain differences in the end product formation were apparent. All of the isolates produced acetate, lactate and formate; only a few isolates produced succinate. For isolation of superior fibrolytic isolates of anaerobic fungi, greater emphasis should be given to the screening of enzyme activities of isolates of genera Neocallimastix and Piromyces.