Extent Of Cellulose Digestion Research Articles

Understanding the key factors for enzymatic conversion of pretreated lignocellulose by partial least square analysis

The relationship between the physicochemical properties of lignocellulosic substrates and enzyme digestion is still not well known. After different pretreatments, cellulase hydrolysis and measurements of physicochemical characteristics by column solute exclusion, particle size analysis, X-ray diffraction, Fourier transform infrared spectroscopy and solid state (13)C nuclear magnetic resonance were performed in this study. Partial least squares was then applied to seek the key factors limiting the rate and extent of cellulose digestion. According to the PLS results, the most important factor for cellulose digestion was accessible interior surface area, followed by delignification and the destruction of the hydrogen bonds. The cellulose digestion at 2 and 24 hr were improved with the increased accessibility of interior surface area to the reporter molecules of 5.1-nm diameter. Removal of lignin and breaking of hydrogen bonds were also found to significantly promote cellulose conversion. Other properties, including the breakdown of intramolecular hydrogen bonds, cellulose crystallinity, and hemicellulose content, had less effect on the efficiency of enzymatic hydrolysis.

Effects of a Saccharomyces cerevisiae Culture on Ruminal Bacteria that Utilize Lactate and Digest Cellulose

The objective of this study was to determine the effects of a yeast (Saccharomyces cerevisiae) culture on lactate utilization and cellulose digestion by ruminal bacteria. Growth of Selenomonas ruminantium HD4 in medium that contained 5g/L of DL-lactate, Trypticase, and yeast extract was stimulated 7 and 15% by 1 and 5% (vol/vol) yeast culture filtrate, respectively. The 1 and 5% yeast culture filtrate stimulated growth of Selenomonas ruminantium H18 and Megasphaera elsdenii B159 and T81 on 5g/L of DL-lactate in medium without Trypticase or yeast extract. Growth of Fibrobacter succinogenes S85 and Ruminococcus albus B199 on 6g/L of cellobiose was stimulated by the addition of yeast culture filtrate to medium without Trypticase or yeast extract. The yeast culture filtrate increased the concentrations of acetate and total volatile fatty acids that were produced by Sel. ruminantium HD4 and increased the concentrations of propionate and total volatile fatty acids that were produced by Sel. ruminantium H18 but did not alter end-product formation of M. elsdenii or cellulolytic bacteria. Treatment with yeast culture increased the initial rate but not the extent of cellulose digestion by F. succinogenes S85 and Ruminococcus flavefaciens FD1. Collectively, these results suggest that yeast culture provides soluble growth factors (i.e., organic acids, B vitamins, and amino acids) that stimulate growth of ruminal bacteria that utilize lactate and digest cellulose.

The use of monensin or formaldehyde to control the digestion of the nitrogenous constituents of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) in the rumen of cattle.

Pure swards of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) were harvested daily as primary growth (grass in May, clover in June) or regrowths (clover only in July) and offered, in the long form, to growing cattle at a feeding rate of 22 g dry matter/kg live weight. With each forage, two treatments were compared with the untreated forage (C): monensin (100 g active ingredient/kg, 250 mg/d) addition to the rumen (treatment M) or formaldehyde (30 g/kg crude protein (nitrogen X 6.25] application to the diet (treatment F). The objective of the experiment was to examine means of manipulating N metabolism in the rumen and the duodenal non-ammonia-N (NAN) supply derived from fresh forages. The apparent digestion of ingested organic matter (g/kg) in the rumen was unaffected by treatment M (C 509, M 497) but was significantly (P less than 0.01) reduced by treatment F (443). The extent of cellulose digestion in the rumen was not affected by any of the treatments imposed and the changes in organic matter digestion were due mainly to effects on N digestion and rumen microbial synthesis. On the untreated diets, duodenal NAN supply averaged 0.74 g/g N intake and treatment M caused a small but non-significant increase (M 0.79 g/g N intake). In contrast, the effect of treatment F was much larger (F 0.91 g/g N intake; P less than 0.01). These differences were accompanied by corresponding reductions in rumen NH3 concentrations (mg/l; C 350, M 310, F 220; P less than 0.001). Of the increased flow of NAN to the small intestine observed on the white clover only diets with treatment F, 0.70 was accounted for by an increased net synthesis of microbial N, while treatment M had no effect on microbial N synthesis and a marginal reduction in feed N degradability only with the regrowth white clover diet. Treatment F reduced feed N degradability to a limited extent on both clover diets (C 0.82, M 0.81, F 0.77). No corresponding measurements were made for the ryegrass diets. It is concluded that the extensive loss of N from the reticulo-rumen of cattle fed on fresh forages can be reduced by the use of agents to reduce protein solubility. However, the study demonstrated that treatment F may in some circumstances increase N supply to the small intestine more through enhancing microbial N synthesis within the rumen than through increasing the passage of undegraded feed N to the small intestine.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of structural carbohydrate fermentation by forage phenolics

AbstractThe benzoic and cinnamic acids found in forages were tested for their inhibitory effects on digestion of cellulose and hemicellulose by mixed cultures of rumen microorganisms in vitro. Rate and extent of cellulose digestion with the addition of cinnamic acids were determined. The benzoic acids and aldehydes were also compared for their inhibitory potential. Of the benzoic acid derivatives, only the parent compound (benzoic acid) inhibited in vitro dry matter disappearance (IVDMD) of cellulose after 48 h, whereas most of the cinnamic acids were inhibitory. None of these compounds depressed IVDMD of hemicellulose. Extent of cellulose digestion was unaffected by cinnamic acids, but rate of digestion was significantly reduced. The ranking of compounds for inhibitory potential was essentially reversed between 48 and 168 h of fermentation as compared with the ranking for 0 to 48 h of fermentation. There were also shifts in the molar proportions of volatile fatty acids produced between these times. The rapid reduction in concentration of cinnamic acids by microbial fermentation may explain these shifts. Benzoic aldehydes were more inhibitory of structural carbohydrate fermentation than were acids. No clear relationship existed between addition of hydroxyl or methoxyl groups to benzoic or cinnamic acids and their depressing effects on IVDMD. Cinnamic acids, which are more abundant in forages, were more inhibitory than the benzoic acids; but for all compounds, it appeared that hemicellulolytic bacteria were generally more tolerant of these compounds than the cellulolytic bacteria.

Effect of pH on cellulose distion under in vitro conditions.

AbstractThe extent of cellulose digestion by rumen micro‐organisms in vitro is dependent on the pH of the medium. Digestion is greatly reduced at pH values similar to those found within the rumen of sheep fed with diets rich in readily digestible carbohydrates.It is suggested that this may be one of the reasons for reduced digestion of the fibre component of forages when carbohydrate supplements are fed.

Extent of Cellulose and Hemicellulose Digestion in Various Forages by Pure Cultures of Rumen Bacteria

The ability of nine pure strains of rumen bacteria to digest the cellulose and hemicellulose portions of an intact forage was investigated. Using a limiting level of substrate, the extent of digestion of these components was measured in varying maturity stages of both grasses and alfalfa. Bacteroides succinogenes strains were able to digest significantly greater amounts of cellulose from forages than were the other species. Two of the four strains of Ruminococcus flavefaciens had a markedly reduced ability to digest cellulose from alfalfa. Of the seven cellulolytic strains, only three were able to digest forage hemicelluloses. These three strains, all ruminococci, digested considerable amounts of hemicellulose from bromegrass, but had a very limited ability to digest alfalfa hemicellulose. Opposite results were obtained with Bacteroides ruminicola. Butyrivibrio fibrisolvens digested appreciable amounts of hemicellulose from both types of forage. Across all organisms and forages, the extent of both cellulose and hemicellulose digestion decreased with forage maturity. Studies on the possible synergistic effect of combining two cultures in a single fermentation were conducted with four cellulolytic strains and one noncellulolytic strain. All possible combinations of two were used, and a significant increase in the extent of cellulose digestion was consistently observed when the noncellulolytic organism, B. ruminicola, was combined with any of the four cellulolytic strains.