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At least 1,423 records · Page 79Linked to original sources
PubMed1993

Microbial delignification with white rot fungi improves forage digestibility.

Three wild-type white rot fungi and two cellulase-less mutants developed from Phanerochaete chrysosporium K-3 (formerly Sporotrichum pulverulentum) were tested for their ability to delignify grass cell walls and improve biodegradation by rumen microorganisms. Fungal-treated and control stems of Bermuda grass were analyzed for their content of ester- and ether-linked aromatics by using alkali extraction and gas chromatography, for in vitro dry weight digestion and production of volatile fatty acids in in vitro fermentations with mixed ruminal microorganisms, for loss of lignin and other aromatics from specific cell wall types by using microspectrophotometry, and for structural changes before and after in vitro degradation by rumen microorganisms by using transmission electron microscopy. P. chrysosporium K-3 and Ceriporiopsis subvermispora FP 90031-sp produced the greatest losses in lignin and improved the biodegradation of Bermuda grass over that of untreated control substrate. However, C. subvermispora removed the most lignin and significantly improved biodegradation over all other treatments. Phellinus pini RAB-83-19 and cellulase-less mutants 3113 and 85118 developed from P. chrysosporium K-3 did not improve the biodegradation of Bermuda grass lignocellulose. Results indicated that C. subvermispora extensively removed ester-linked p-coumaric and ferulic acids and also removed the greatest amount of non-ester-linked aromatics from plant cell walls. Microscopic observations further indicated that C. subvermispora removed esters from parenchyma cell walls as well as esters and lignin from the more recalcitrant cell walls (i.e., sclerenchyma and vascular tissues). C. subvermispora improved in vitro digestion and volatile fatty acid production by ruminal microorganisms by about 80%, while dry matter loss due to fungi was about 20% greater than loss in untreated control stems. The chemical and structural studies used identified sites of specific fungal attack and suggested mechanisms whereby improvement occurred.

Journal Article↗
PubMed1994

Patterns of Reactivity between a Panel of Monoclonal Antibodies and Forage Rhizobium Strains.

A panel of 11 monoclonal antibodies raised against vegetative cells of Rhizobium leguminosarum biovar trifolii or Rhizobium meliloti was tested by enzyme-linked immunosorbent assay for reactivity with 47 strains of R. leguminosarum biovar trifolii and 60 strains of R. meliloti. The goal of the study was to define the degree of specificity associated with each antibody and to gain an understanding of the amount of antigenic diversity found among the strains and between the species. Each antibody was tested against each Rhizobium strain in four forms: washed steamed cells, washed unsteamed cells, cell-free culture broth, and nodule squash material. Each antibody showed a different pattern of reactivity among the 107 strains. One of each of the antibodies developed against R. meliloti and R. leguminosarum biovar trifolii reacted in a highly specific manner with cells or antigen from the immunogenic strain only. Nine of the antibodies recognized secreted as well as cellular antigen from many of the strains. Analysis of patterns of reactivity between the 107 strains and the 11 antibodies separated the strains into 28 groups of which 12 were represented by one strain only.

Journal Article↗
PubMed1997

Amino acid use by the gastrointestinal tract of sheep given lucerne forage.

Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-13C-labeled amino acid or (1-13C]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer 13C-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer 13C-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45-0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25-0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.

Amino Acids, Essential↗