THE BIOCHEMISTRY OF RUMEN PROTOZOA. 7. THE CARBOHYDRASES OF POLYPLASTRON MULTIVESICULATUM (DOGIEL & FEDOROWA)

Isolation and Characterization of Ruminal Yeast Strain with Probiotic Potential and Its Effects on Growth Performance, Nutrients Digestibility, Rumen Fermentation and Microbiota of Hu Sheep

Yeast strains are widely used in ruminant production. However, knowledge about the effects of rumen native yeasts on ruminants is limited. Therefore, this study aimed to obtain a rumen native yeast isolate and investigate its effects on growth performance, nutrient digestibility, rumen fermentation and microbiota in Hu sheep. Yeasts were isolated by picking up colonies from agar plates, and identified by sequencing the ITS sequences. One isolate belonging to Pichia kudriavzevii had the highest optical density among these isolates obtained. This isolate was prepared to perform an animal feeding trial. A randomized block design was used for the animal trial. Sixteen Hu sheep were randomly assigned to the control (CON, fed basal diet, n = 8) and treatment group (LPK, fed basal diet plus P. kudriavzevii, CFU = 8 × 10⁹ head/d, n = 8). Sheep were housed individually and treated for 4 weeks. Compared to CON, LPK increased final body weight, nutrient digestibility and rumen acetate concentration and acetate-to-propionate ratio in sheep. The results of Illumina MiSeq PE 300 sequencing showed that LPK increased the relative abundance of lipolytic bacteria (Anaerovibrio spp. and Pseudomonas spp.) and probiotic bacteria (Faecalibacterium spp. and Bifidobacterium spp.). For rumen eukaryotes, LPK increased the genera associated with fiber degradation, including protozoan Polyplastron and fungus Pichia. Our results discovered that rumen native yeast isolate P. kudriavzevii might promote the digestion of fibers and lipids by modulating specific microbial populations with enhancing acetate-type fermentation.

CARBOHYDRASES OF THE RUMEN CILIATE EPIDINIUM ECAUDATUM (CRAWLEY). HYDROLYSIS OF PLANT HEMICELLULOSE FRACTIONS AND BETA-LINKED GLUCOSE POLYMERS

1. Cell-free extracts from Epidinium ecaudatum (Crawley) hydrolysed the three hemicellulose fractions of pasture plants, but at different rates. 2. All of the constituent monosaccharides are released from the hemicellulose fractions, galactose and uronic acids being liberated at much slower rates than pentoses. 3. An arabinofuranosidase, which removes arabinose from highly branched arabinoxylan before the xylan chain can be hydrolysed, was isolated free from other pentosanases. 4. A xylanase hydrolysing xylan (by random cleavage) and xylodextrins of degree of polymerization (D.P.) > 3 to xylotriose and xylobiose was isolated free from other pentosanases. 5. A separate xylodextrinase hydrolysing (by random cleavage) xylodextrins of D.P. > 2 to xylobiose and xylose was also obtained; this enzyme did not hydrolyse xylan or xylobiose and the original extracts themselves possessed very weak xylobiase activity. 6. The epidinial extracts hydrolysed laminaribiose, laminarin, lichenin and cellodextrins of D.P. < 7 rapidly, cellobiose and gentiobiose slowly but cellulose not at all. 7. Polysaccharide glucose associated with plant linear B hemicellulose was liberated with cellobiose and possibly laminaribiose as intermediates. 8. The cellodextrinase hydrolysed cellopentaose initially to cellobiose plus cellotriose and is a distinctly different enzyme from the xylanase and xylodextrinase. 9. Extracts from Entodinium species and Eremoplastron bovis also hydrolysed all three types of plant hemicellose.

HYDROLYSIS OF FIBROUS COTTON AND REPRECIPITATED CELLULOSE BY CELLULOLYTIC ENZYMES FROM SOIL MICRO-ORGANISMS

1. The action of cell-free filtrates from Trichoderma koningii was examined on undegraded cellulose in the form of cotton fibres, on degraded cellulose in the form of cellulose powder reprecipitated from phosphoric acid and on the soluble cellulose derivative CM-cellulose. 2. The cell-free filtrates compare favourably with intact cellulolytic micro-organisms in producing complete solubilization of undegraded as well as of degraded types of cellulose. Enzymic solubilization of cotton fibres gives quantitative conversion into glucose. Cellobiase is present. 3. The early enzymic breakdown of cotton fibres is characterized by the formation of very short fibres that increase to a maximum and disappear gradually by conversion into glucose. Disintegration of cotton fibres to short fibres is assisted by shaking, and within 20hr. the enzyme converts a minor fraction (up to 16%) of substrate into soluble products and a major portion (80%) into insoluble short fibres. 4. Maximum enzymic activity on cotton fibres occurs at about pH5.0, measured by the formation of short fibres, and at about pH3.8 on reprecipitated cellulose, measured by solubilization of the substrate. 5. Gluconolactone, glucose and cellobiose fail to produce marked inhibition of the enzymic hydrolysis of cotton fibres to short fibres or of the solubilization of reprecipitated cellulose unless present in amounts comparable with or greater than the initial weight of these two forms of cellulose. 6. The heavy-metal ions Cu(2+), Hg(2+) and Fe(3+) at 2mm concentration give 80-100% decrease in the enzymic breakdown of cotton fibres, measured by the formation of short fibres. At the same concentration Hg(2+) and Fe(3+) but not Cu(2+) also produce 70-100% inhibition of the solubilization of reprecipitated cellulose. 7. The ability to hydrolyse cotton fibres to short fibres and CM-cellulose to sugars is completely lost after heating enzyme preparations for 10min. at 71 degrees .

[The nitrogen metabolism in the large intestine of ruminants. 8. Metabolism of intracecally infused 15N-urea with a supplement of pectin in heifers]

Three heifers with live weights of 255, 261 and 300 kg were supplied with ileo-caecal re-entrant cannulas, jugular vena catheters and bladder catheters. The ration consisted of 4 kg maize silage and 4 kg wheat straw pellets. In a previous period 50% of the digesta flow was collected over 12 h/d on 5 consecutive days and stored in a deep-freeze. During the main period the re-entrant cannulas were disrupted and the flowing digesta was quantitatively collected. Precollected digesta and pectin were infused into the distal part of cannula hourly for about 30 hours. During the first 24 hours the digesta was also supplemented with 15N-labelled urea. The amount of pectin corresponded to about 10% of digesta dry mater. An analysis of urine, faeces, digesta and blood plasma were carried out. The application of pectin increased the 15N-incorporation in the bacterial protein of faeces from 4.7% (without supplementation in an earlier experiment) to 10.5% of the introduced 15N. The ammonia-fraction of faeces was markedly higher than the bacterial fraction. The 15N-utilization of urea by the microbes of large intestine was lower in the actual trial evident than with supplementation of starch in the anterior experiment. During the pectin administration the amount of urine increased in comparison with earlier experiments and according to the literature to about the 4.5 fold. The amount of passage of 15N at the ileum cannula (recycled 15N) was 3.8% of the 15N intake. It is the same amount as in experiments in which starch was applied.

Influence of CO2 and low concentrations of O2 on fermentative metabolism of the ruminal ciliate Polyplastron multivesiculatum

The effects of ruminal concentrations of CO2 and oxygen on the end products of endogenous metabolism and fermentation of D-glucose by the ruminal entodiniomorphid ciliate Polyplastron multivesiculatum were investigated. The principal metabolic products were butyric, acetic, and lactic acids, H2, and CO2. 13C nuclear magnetic resonance spectroscopy identified glycerol as a previously unknown major product of D-[1-13C]glucose fermentation by this protozoan. Metabolite formation rates were clearly influenced by the headspace gas composition. In the presence of 1 to 3 microM O2, acetate, H2, and CO2 formation was partially depressed. A gas headspace with a high CO2 content (66 kPa) was found to suppress hydrogenosomal pathways and to favor butyrate accumulation. Cytochromes were not detected (less than 2 pmol/mg of protein) in P. multivesiculatum; protozoal suspensions, however, consumed O2 for up to 3 h at 1 kPa of O2. Under gas phases of greater than 2.6 kPa of O2, the organisms rapidly became vacuolate and the cilia became inactive. The results suggest that fermentative pathways in P. multivesiculatum are influenced by the O2 and CO2 concentrations that prevail in situ in the rumen.

Degradation of hemicellulose and pectin by horse caecum contents

1. Polysaccharide depolymerases and glycoside hydrolases involved in the breakdown of plant structural polysaccharides (hemicellulose and pectins) were monitored in three fractions of the liquid phase of horse caecum digesta: acellular fluid (AF), bacteria (B) and protozoa plus bacteria (PB). 2. Both bacteria and protozoa were found to be involved in the decomposition of pectic substances, with two enzymic activities: depolymerase (polygalacturonase, EC 3.2.1.15; and pectin lyase, EC 4.2.2.10) and esterase (pectinesterase, EC 3.1.1.11). The activity of the PB fraction was higher than that of B. 3. With hemicellulosic substrates, all three fractions showed a significant xylan endo-1,3-beta-xylosidase (EC 3.2.1.32) activity. Mannan was hardly broken down. 4. Galactomannan and arabinogalactan were broken down more extensively by the PB fraction than by the B fraction. Glycosidase activities (xylan 1,4-beta-xylosidase, EC 3.2.1.37 and alpha-L-arabinofuranosidase, EC 3.2.1.55) were also observed.

Effects of diet on the protozoa population in permeable continuous cultures of rumen contents

1. Responses of the protozoa population to the composition and the components of the diet were studied in permeable continuous cultures of rumen contents. 2. In Expt 1 a study was made of responses to diets containing different combinations of rice straw, lucerne meal and mixed concentrates given to the cow supplying inocula for cultures. It was found that (1) when a diet devoid of concentrates was fed, entodiniomorphs decreased in numbers; (2) their numbers increased with the increase in the amount of concentrates; (3) holtrich numbers were hardly affected by the type of diet; (4) rice straw and lucerne meal were not essential for protozoa to survive in culture medium. 3. In Expt 2 responses were determined to diets containing different combinations of maize, maize starch, sugars (glucose-sucrose (1:1, w/w)), soya-bean meal and isolated soya-bean protein. The results suggested the following relationship between dietary component and protozoa population. (1) The diet rich in both starch and sugars sustains the increased numbers of protozoa on the whole. (2) The diet rich in starch and deficient in sugars decreases selectively Dasytricha and small species of Entodinium such as Entodinium minimum and E. nanellum. The other species of protozoa, especially large entodiniomorphs such as Ophyroscolex and Polyplastron, are maintained at relatively high levels. (3) The diet deficient in starch and abundant in sugars decreases general entodiniomorphs except small species, while the numbers of Holotrichs are kept at relatively high levels.

Purification, properties, and mode of action of hemicellulase I produced by Ceratocystis paradoxa

A culture isolate (CP2) of the fungal plant pathogen Ceratocystis paradoxa produces at least five extra-cellular hemicellulases when grown on a medium containing a commercial hemicellulose as inducer. One of the five enzymes, hemicellulase I (HC-I), was purified by ammonium sulphate preceipitation, ion-exchange chromatography (DEAE-Sephadex and then Cellex-CM), and iso-electric focusing at pH 3-10 and 8-10. HC-I behaves as a single protein on a electrophoresis at pH 6.0 and 8.4. The enzyme degrades hemicellulose B (an arabino-4-O-methylglucurono-xylan) and arabinoxylanto arabinose, xylose, xylobiose (Xyl2; beta-D-Xylp-(1 leads to 4)-D-Xyl), and a mixture of arabinose-xylose and xylose oligosaccharides (AraXyln and Xyln, where n=3, 4, or 5). The enzyme is deduced to be an endo-enzyme. Xylotetraose (Xyl4) was the lowest homologue of the xylose oligosaccharides attacked, yielding xylobiose and xylotriose (Xyl3) only. A mechanism is postulated for this reaction. AraXyl5 were slowly hydrolysed to arabinose and the respective xylose saccharide (Xyl2-Xyl5), and thence to Xyl2 and Xyl3. Hydrolysis of the arabinofuranosyl linkage probably does not occur at the same active site as for the xylose oligosaccharides. Hemicellulose B fractions from different sources appeared to be degraded by HC-I. The enzyme showed optimum activity at pH 5.5 and 40 degrees, and Km was 4.24 mg of hemicellulose/ml.

Solubilization of native and derived forms of cellulose by cell-free microbial enzymes

1. Cell-free enzymes from Myrothecium verrucaria and Trichoderma koningii hydrolyse native undegraded cellulose, as found in cotton fibres, in a random manner to short insoluble fibres and to minor amounts of soluble products. 2. Enzyme preparations from M. verrucaria fail to attack the short fibres whereas preparations from T. koningii solubilize them completely to sugars at an optimum pH4.2-4.6. 3. The mode of hydrolysis of cotton cellulose by preparations from T. koningii involves from the earliest stages the formation of reducing sugars, followed closely by the appearance of short fibres, until the insoluble and soluble products each constitute about 40-50% of the weight of the initial substrate. After this stage the quantity of sugars increases at the expense of the insoluble short fibres. 4. Depending upon the method of preparation, derived forms of cellulose may be hydrolysed more slowly, much more rapidly, or at the same rate as cotton fibres by enzyme preparations from T. koningii.

EFFECT OF ABSENCE OF CILIATE PROTOZOA FROM THE RUMEN ON MICROBIAL ACTIVITY AND GROWTH OF LAMBS

A survey of the components of the rumen ciliate population in a series of adult sheep, raised in the Faculty of Agriculture, University of Alexandria, has shown that a mixture of Entodinium, Isotricha, Ophryoscolex, Diplodinium, and Polyplastron species was found in the rumen contents of Egyptian sheep; no Epidinium and a negligible number of Dasytricha ruminantium were also observed. The microbial population, reducing sugars, ammonia, volatile fatty acids (VFA) production, and growth rate of 14 lambs inoculated with whole rumen contents from a mature sheep were compared over a 6-month period with those of 13 lambs maintained under the same conditions, except that they were strictly isolated from other ruminants. Certain large oval organisms and large numbers of flagellates and Oscillospira were frequently observed in the rumen contents of the isolated lambs. The reducing sugars, ammonia, and VFA levels, measured before and at intervals after feeding, in the inoculated lambs showed a pronounced rise above the values found in the ciliate-free animals. The propionic acid-acetic acid ratio in the rumen contents of the faunated lambs was considerably higher than in the nonfaunated controls. The inoculated lambs grew faster than the isolated lambs. Differences in weight gain which ranged from 15 to 17% were statistically significant. The inoculated animals impressed the observers by their good appearance which was superior to that of the ciliate-free lambs. It was, therefore, concluded that the rumen ciliate protozoa are essential for the metabolism and growth of young lambs.

Effect of Absence of Ciliate Protozoa From the Rumen on Microbial Activity and Growth of Lambs

A survey of the components of the rumen ciliate population in a series of adult sheep, raised in the Faculty of Agriculture, University of Alexandria, has shown that a mixture of Entodinium, Isotricha, Ophryoscolex, Diplodinium , and Polyplastron species was found in the rumen contents of Egyptian sheep; no Epidinium and a negligible number of Dasytricha ruminantium were also observed. The microbial population, reducing sugars, ammonia, volatile fatty acids (VFA) production, and growth rate of 14 lambs inoculated with whole rumen contents from a mature sheep were compared over a 6-month period with those of 13 lambs maintained under the same conditions, except that they were strictly isolated from other ruminants. Certain large oval organisms and large numbers of flagellates and Oscillospira were frequently observed in the rumen contents of the isolated lambs. The reducing sugars, ammonia, and VFA levels, measured before and at intervals after feeding, in the inoculated lambs showed a pronounced rise above the values found in the ciliate-free animals. The propionic acid-acetic acid ratio in the rumen contents of the faunated lambs was considerably higher than in the nonfaunated controls. The inoculated lambs grew faster than the isolated lambs. Differences in weight gain which ranged from 15 to 17% were statistically significant. The inoculated animals impressed the observers by their good appearance which was superior to that of the ciliate-free lambs. It was, therefore, concluded that the rumen ciliate protozoa are essential for the metabolism and growth of young lambs.