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Cleavage of plant cell wall arabinoxylans occurs by the action of ferulic acid esterase (FAE) and acetyl esterase (AE), which cleave feruloyl groups substituted at the 5'-OH group of arabinosyl residues and acetyl groups substituted at O-2/O-3 of the xylan backbone, respectively. In this study, we examined the enzyme profiles of the anaerobic rumen fungus Neocallimastix sp. YQ1 for FAE, AE and polysaccharide hydrolases when grown on corn stover, a lignin-rich waste biomaterial. A 2 × 4 factorial experiment in 10-days pure cultures was used to test glucose addition (G(+) : glucose at 1.0 g/l, G(-) : no glucose) and four N sources (N1: 1.0 g/l yeast extract, 1.0 g/l tryptone and 0.5 g/l (NH(4))(2) SO(4); N2: 2.8 g/l yeast extract and 0.5 g/l (NH(4))(2) SO(4) ; N3: 1.6 g/l tryptone and 0.5 g/l (NH(4))(2) SO(4); N4: 1.4 g/l tryptone and 1.7 g/l yeast extract) in defined media. The optimal combinations of glucose and N sources to promote FAE and AE activity were G(+) N2 and G(+) N4, respectively. The peak activities of FAE and AE occurred on days 9 and 10, respectively. Addition of glucose and an increase in yeast extract and/or tryptone to a Hungate's medium favoured fungal production of volatile fatty acids, which could be just a consequence of more organic matter available to digest. This suggests that enzymatic release of ferulic acid by a synergistic action of lignin hydrolytic esterase and polysaccharide hydrolases may be essential for plant cell wall biodegradation in the rumen., (© 2011 Blackwell Verlag GmbH.)

The effects of phenolic monomers (i.e. rho-coumaric acid, ferulic acid, rho-hydroxybenzaldehyde and vanillin) on the enzymes and fermentation activities of Neocallimastix frontalis B9 grown in ball-milled filter paper and guinea grass media were studied. The enzymes studied were carboxymethylcellulase (CMCase), filterpaperase (FPase), xylanase and beta-glucosidase. At 96 h of incubation, N. frontalis grown in ball-milled filter paper medium produced comparable xylanase and CMCase activities (0.41, 0.5 micromol/min/mg protein) while in guinea grass medium, N. frontalis produced higher xylanase activity than that of CMCase activity (2.35, 0.05 micromol/min/mg protein). The other enzymes activities were low. When N. frontalis was grown in ball-milled filter paper medium, only acetic acid was produced. However, when grown in guinea grass medium, the major end-product was acetate, but propionic, butyric and isovaleric were also produced in lesser amount. Vanillin showed the least inhibitory effects to enzyme activities of N. frontalis B9 grown in both ball-milled filter paper and guinea grass media. For total volatile fatty acid production, all phenolic monomers showed inhibitory effects, but rho-coumaric and ferulic acids were the stronger inhibitors than rho-hydroxybenzaldehyde and vanillin.

Aims: Anaerobic fungi are important members of the fibrolytic community of the rumen. The aim of this study was to study their requirement for aromatic amino acids (AA) and related phenyl acids (phenylpropionic and phenylacetic acids) for optimal xylan fermentation., Methods and Results: Neocallimastix frontalis RE1 and Piromyces communis P were grown in a defined medium containing oat spelts xylan as the sole energy source, plus one of the following N sources: ammonia; ammonia plus a complete mixture of 20 AA commonly found in protein; ammonia plus complete AA mixture minus aromatic AA; ammonia plus phenyl acids; ammonia plus complete AA mixture without aromatic AA plus phenyl acids. Both species grew in all the media, indicating no absolute requirement for AA. The complete AA mixture increased (P<0.05) acetate concentration by 18% and 15%, sugar utilization by 33% and 22% and microbial yield by about 22% and 15% in N. frontalis and P. communis, respectively, in comparison with the treatments that had ammonia as the only N source. Neither the supply of aromatic AA or phenol acids, nor their deletion from the complete AA mixture, affected the fermentation rate, products or yield of either species., Conclusions: AA were not essential for N. frontalis and P. communis, but their growth on xylan was stimulated. The effects could not be explained in terms of aromatic AA alone., Significance and Impact of the Study: Ruminant diets should contain sufficient protein to sustain optimal fibre digestion by ruminal fungi. Aromatic AA or phenyl acids alone cannot replace the complete AA mixture.

The effects of Aspergillus oryzae fermentation extract, Amaferm, on the rumen fungus Neocallimastix frontalis EB188 were studied. The secretion of cellulase was increased by 67% and rhyzoid development was increased 3.8-fold in the presence of extract. Strength of fungal response increased in a dose-dependent manner and demonstrated a positive correlation between cell surface area and enzyme secretion. Above certain concentrations of extract, however, the development of the fungus and enzyme secretions remained at control values or slightly diminished. Supernatant fluid appearance of the intracellular enzyme, malate dehydrogenase, paralleled the secretion of cellulase both in the presence and absence of extract. Ether solubilization of extract demonstrated that the active component(s) possessed a moderately polar value between 2.7 and 2.8. Thin layer chromatography separated extract into inert, inhibitory and intensely stimulating fractions. These results support the idea that by accelerating fungal growth and metabolism, Amaferm increases the rate (or extent) of fibre degradation caused by rumen fungi and that this, in turn, may contribute to enhanced animal performance.