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PubMed2000

Performance enhancement of batch aerobic digesters via addition of digested sludge.

The impact of the feed sludge (FS) concentration and addition of digested sludge (DS) to an aerobic digester was evaluated with respect to its capability for removal of the total suspended solids (TSS) and volatile suspended solids (VSS). The aerobic digesters, which operated in a batch mode at constant temperature and mixing rate, were initially filled with FS to 25%, 50%, 75%, and 100% of the reactor's volume. The remaining volume of the reactor was occupied by the DS, having DS/FS ratio of 3, 1, 1/3, and 0. Analysis of the experimental data showed that in the absence of DS, TSS, and VSS destruction rates are very small; however, increasing DS/FS ratio from 1/3 to 3 results in 74-77% increase in VSS and TSS destruction, respectively. The increase of the DS/FS ratio associated with increased ratio of the measured viable biomass (Cc) to VSS concentration (Xv) suggested that DS serves as the source of viable cell mass needed for degradation of organic solids. Assuming pseudo-first-order kinetics, it was shown that while organic solid destruction rate constants (k) are inversely related to initial concentrations of sludge, their values increase with increasing DS/FS ratios.

Bacteria, Aerobic↗
PubMed2004

Relationship between protein deficiency in the ration of rats during early ontogeny and function of enzyme systems of digestive and non-digestive organs in adult life.

Low protein content in the ration of rat pups during transfer from mixed to definitive nutrition (days 21-30 of life) has a negative impact on digestive function of the small intestine and trophic and barrier functions of the large intestine, liver, and kidneys and increases (sucrase, glycyl-L-leucin dipeptidase) or decreases (alkaline phosphatase, aminopeptidase M, glycyl-L-leucine dipeptidase) enzyme activities in these organs in 6-month-old rats. Protein deficiency during the early ontogeny modulates functioning of the enzyme systems in digestive and non-digestive organs in adult life, which can lead to the development of not only gastrointestinal, but other visceral diseases.

Alkaline Phosphatase↗
PubMed1988

Production and Characteristics of Avicel-Digesting and Non-Avicel-Digesting Cellobiohydrolases from Aspergillus ficum.

Two immunologically related cellobiohydrolases, cellobiohydrolase I (CBH I) and cellobiohydrolase II (CBH II), were purified from Aspergillus ficum. The Avicel-adsorbable CBH I (molecular weight, 128,000) digested Avicel, cotton, and cellulose powder to cellobiose, but the Avicel-unadsorbable CBH II (molecular weight, 50,000) could not digest those substrates. Both enzymes hydrolyzed insoluble cellooligosaccharides (DP 25) to cellobiose. High-pressure liquid chromatographic analysis of soluble cellooligosaccharide hydrolysates revealed that both enzymes split off strictly cellobiose units from the nonreducing end of the cellulose chain with an exowise mechanism. CBH I showed glucosyltransferase activity, but CBH II did not. The N-bromosuccinimideoxidized CBH I was completely inactive but retained the ability to adsorb to Avicel. This suggested that CBH I has separate sites for binding to cellulose and for catalyzing cleavage of glycosidic linkages. Cellobiohydrolases were of two types, CBH I and CBH II. The former can adsorb to and digest Avicel, while the latter can do neither.

Journal Article↗
PubMed2006

Implementation of the IWA anaerobic digestion model No.1 (ADM1) for simulating digestion of blackwater from vacuum toilets.

The IWA anaerobic digestion model No.1 (ADM1) is applied to the blackwater anaerobic digestion (BWAD) plant in this work. In order to verify the biochemical kinetics, batch experiments were executed. According to the Monod type kinetics, the maximum uptake rates (km) of butyric acid (HBu), propionic acid (HPr) and acetic acid (HAc) are testified as 18, 14, 13 d(-1), and their half saturation concentrations (Ks) are 110, 120, 160 g COD/m3, respectively. Afterwards, the model was calibrated based on the performance of a laboratory scale BWAD plant (under mesophilic conditions) by three scenario studies, i.e. the reference conditions, different feeding frequencies and high NH4+ concentration. The model successfully simulated three scenarios. The further two virtual scenario studies were achieved based on the calibrated model. First, the performance of BWAD plant was predicted with different hydraulic retention times (HRT); second, the kitchen refuse (KR) was added into the BWAD plant as additional organic loading. The model predicted the perspective of BW plus KR digestion and generated valuable suggestions for the operation of the real BWAD plant.

Anaerobiosis↗
PubMed2006

Parameter analysis of the IWA Anaerobic Digestion Model No. 1 for the anaerobic digestion of blackwater with kitchen refuse.

The IWA anaerobic digestion model No.1 (ADM1) had been successfully applied to the lab-scale mesophilic blackwater anaerobic digestion (BWAD) plant for cases of only blackwater (BW) feeding and of BW plus kitchen refuse (KR) feeding. In this paper, the simulation results of BW + KR anaerobic digestion are presented and discussed, followed by the analyses and discussion of the critical and important parameters as well as the performance of ADM1 based on these results. The raw BW can contain up to 30% short chain fatty acids (SCFA) which severely impact the performance of the model. The model proved that the disintegration/hydrolysis rate of BW is around 4.5 d(-1), which is about ten times higher than that of KR (Kdis,KR = 0.5 d(-1)). ADM1 is not sensitive to the distribution ratio among carbohydrates, proteins and lipids. For BWAD the C4 metabolism can be integrated in the uptake of LCFA. The uptake delay phenomenon was observed and cannot be simulated by ADM1, but it is tolerable. No unique KI,NH3,ac is found out for all investigated ammonia concentration ranges. Meanwhile, ADM1 is not sensitive to KLa and kp1 so they can easily be set up.

Anaerobiosis↗
PubMed1979

[Retrograde inhibitory effect of continuous reinstillation of digestive juice in temporary artificial and pathological enterostomies on the secretory digestive flow].

The reinstillation of the digestive juice in the lower end of an enterostomy has a retrograde inhibitory effect on the upper digestive secretions (average inhibition of 30,2%) particularly on the intestinal juice during the digestive syndromes associated with one or several interruptions of the continuity of the bovel. It should be noted, however, that the observation has not been made on normal men, but rather on severely ill patients treated in the intensive care unit of a gastro-intestinal disease department.

Crohn Disease↗
PubMed2003

Elucidation mechanism of organic acids production from organic matter (grass) using digested and partially digested cattle feed.

The process of anaerobic digestion is highly influenced by the environmental and operational factors like organic acids concentration and the reactor volume occupied by the feed material. The optimum level of organic acids is commonly assumed to be in the range between 2,500 and 3,500 mg/l for the anaerobic digestion process. It was observed that the production of total organic acids during hydrolysis of grass using cattle dung slurry (CDS) as the inoculum reached up to 4,850 mg/l in 6 days, while on the other hand it reached 5,700 mg/l within 4 days when rumen content was used as inoculum. The organic acids production continued to the 30th day in the case of rumen content, while in the case of CDS it stopped within 10 days because of pH drop. As compared to CDS the anaerobic digestion of grass with rumen content showed better degradation and biogas production with nearly 80% of methane and up to 80 and 95% reduction in chemical oxygen demand and organic acids respectively.

Animal Feed↗
PubMed1989

Micro-quantity tissue digestion for metal measurements by use of a microwave acid-digestion bomb.

We describe a simple and convenient method for processing small amounts of tissue samples for trace-metal measurements by atomic absorption spectrometry, by use of a modified Parr microwave digestion bomb. Digestion proceeds rapidly (less than or equal to 90 s) in a sealed Teflon-lined vessel that eliminates contamination or loss from volatilization. Small quantities of tissue (5-100 mg dry weight) are digested in high-purity nitric acid, yielding concentrations of analyte that can be measured directly without further sample manipulation. We analyzed National Institute of Standards and Technology bovine liver Standard Reference Material to verify the accuracy of the technique. We assessed the applicability of the technique to analysis for aluminum in bone by comparison with a dry ashing procedure.

Aluminum↗
PubMed2006

Fractionation of digestive proteinases from Tenebrio molitor (Coleoptera: Tenebrionidae) larvae and role in protein digestion.

Tenebrio molitor larval digestive proteinases were purified and characterized by gel filtration chromatography combined with activity electrophoresis. Cysteine proteinases, consisting of at least six distinct activities, were found in three chromatographic peaks in anterior and posterior midgut chromatographies. The major activity in the anterior midgut, peak cys II, consisted of cysteine proteinases with Mm of 23 kDa. The predominant peak in the posterior, cys I, was represented by 38 kDa proteinases. The activities of all cysteine proteinases were maximal in buffers from pH 5.0 to 7.0, with 80% stability at pH values from 4.0 to 7.0. In the conditions of the last third of the midgut, the activity and stability of cysteine proteinases was sharply decreased. Trypsin-like activity included a minor peak of "heavy" trypsins with Mm 59 kDa, located mainly in the anterior midgut. An in vitro study of the initial stages of digestion of the main dietary protein, oat 12S globulin, by anterior midgut proteinases revealed that hydrolysis occurred through the formation of intermediate high-Mm products, similar to those formed during oat seed germination. Cysteine proteinases from the cys III peak and heavy trypsins were capable of only limited proteolysis of the protein, whereas incubation with cys II proteinases resulted in substantial hydrolysis of the globulin.

Animals↗
PubMed1994

Mean retention time in digestive tract and digestion of fresh perennial ryegrass by lactating dairy cows: influence of grass maturity and comparison with a maize silage diet.

The effects of grass maturity on the mean retention time of liquid and particles, digestibility and duodenal nutrient flows were measured by feeding second cuts of perennial ryegrass to 3 fistulated lactating dairy cows over 2 successive periods (late June and mid-July, 28 and 49 d regrowth, respectively). Fresh forage was given ad libitum with 12% (dry matter (DM) basis) concentrate. The increase in maturity lowered grass nitrogen content, organic matter (OM) digestibility and non-ammoniacal nitrogen flow into the duodenum, but did not affect OM intake (13.2 kg/d). Neither the fractional outflow rate of liquid in the rumen (FOR; 17.3%/h) nor the concentrate total mean retention time (TMRT; 32.9 h) were affected. With maturity forage TMRT tended to increase (43.0-48.8 h), certainly because of the longer comminution time of coarse particles. These results were compared with data obtained 2 months earlier with the same cows fed on a maize silage diet (25% DM basis of the same concentrate) ad libitum (17.4 kg OM/d). Despite a lower total OM intake, FOR was much higher with the grass than with the maize silage diet (12.1%/h) and this may explain the lower retention time in the rumen of the small particles when grass diets were given (19.0 vs 24.3 h for maize silage diet).

Animal Feed↗
PubMed1981

[Nutritional physiology studies in pigs on the evaluation of modified proteins. 1. Results of the estimation of N-turnover, apparent and true digestibility of proteins in addition to apparent and true absorption of amino acids in the entire digestive tract].

Sulfuric acid-casein (A), spray dried isolated Vicia faba protein (B), Vicia faba protein/casein (1 : 1) protein fibres-untreated (C), treated with dialdehyde starch (D) or aluminum chloride (E) and meal of Vicia faba (F) were studied as sole protein sources in semisynthetic feed mixtures on 13 female pigs (40 to 45 kg body weight). Total utilization of nitrogen (b-value, PNu) and intermediate utilization (BW) were highest in A, followed by C. Protein C was superior to D. Protein E showed a drastic drop in protein quality compared with D because of a high decrease in S-containing amino acids content, however, their efficiency (bc-1-value) was not limited. Despite of a higher apparent digestibility by approximately 17 units in protein B, proteins B and F showed a similar quality. The true absorption of cystine (estimated by the balance of digestive tract) was corresponding to the protein quality of the respective step of treatment of protein C and was used for the correction of the gross content is S-containing amino acids.

Amino Acids↗
PubMed1983

[Protein and amino acid digestibility in various sections of the digestive tract of swine. 2. Protein sources of plant origin].

Growing pigs provided with ileocaecal re-entrant cannulae were fed three rations containing plant protein sources and two N-free rations. The crude protein and amino acid flow in the digestive tract as well as the apparent and true digestibility of the crude protein and the amino acids for the individual sections of the intestines are explained. It shows that relating the calculation of metabolic faecal amino acids to live weight results in more realistic values than relating it to feed intake.

Amino Acids↗
PubMed1985

Effects of calcium source and level on site of digestion and calcium levels in the digestive tract of cattle fed high-concentrate diets.

The effect of calcium (Ca) source and level on site of digestion of an 88% concentrate diet was tested with four 431-kg, intestine-cannulated steers in a 4 X 4 Latin square experiment. Diets, limit-fed at 1.3% of body weight, contained .25% Ca with no supplemental Ca (B), .40 or .48% Ca from addition of either .95% CaCl2-2H2O (Cl) or .65% CaCO3 (LL), or 1.11% Ca from addition of 2.5% CaCO3 (HL). No effects of source of Ca (CaCl2-2H2O vs CaCO3) were observed, although ruminal pH and ruminal ammonia-nitrogen (N) concentrations tended to be lower with Cl. Ruminal fluid dilution rate increased linearly (P less than .05) with the addition of Ca to the diet. Ruminal fluid dilution rate and volume were negatively related (r = -.72; P less than .01). Organic matter (OM) and starch digestibilities in the rumen tended to decline with the addition of Ca to the diet, while postruminal OM and starch disappearance increased (P less than .05) to compensate. Flow of N to the duodenum decreased (P greater than .05) with addition of Ca to the diet. Concentrations of soluble Ca found in ruminal and duodenal fluid increased linearly (P less than .05) with dietary Ca intake. Intestinal Ca disappearance increased linearly and quadratically (P less than .05) with increasing dietary Ca and exceeded 80% of Ca entering the small intestine. In a second experiment, the rate of in situ dry matter (DM) disappearance of rolled corn was not greatly altered by addition of Ca to the diet.

Animal Feed↗
PubMed1991

Regional distribution and substrate specificity of digestive enzymes involved in terminal digestion in Musca domestica hind-midguts.

One membrane-bound alpha-glucosidase and two soluble alpha-glucosidases were isolated from homogenates of the hind-midgut, the main digestive region in Musca domestica larvae. The membrane-bound alpha-glucosidase and the low-Mr soluble alpha-glucosidase hydrolyze maltopentaose better than maltose, maltotriose, and maltotetraose, the reverse being true for the high-Mr soluble alpha-glucosidase. A membrane-bound glucoamylase previously described in Musca domestica midgut was shown by gradient centrifugation and dialysis against EDTA to result from the combined action of an amylase and an alpha-glucosidase. The determination of amylase, alpha-glucosidases, soluble and membrane-bound carboxypeptidase A, membrane-bound aminopeptidase and dipeptidase along the tissue and luminal contents of the hind-midgut is described. The data support a proposal concerned with how starch and protein are digested in Musca domestica larval hind-midguts and where and how midgut glycosidases and peptidases are secreted.

Animals↗
PubMed1990

Physical-chemical behavior of dietary and biliary lipids during intestinal digestion and absorption. 2. Phase analysis and aggregation states of luminal lipids during duodenal fat digestion in healthy adult human beings.

Following the feeding of a triacylglycerol-rich meal to healthy adult human beings, duodenal contents were aspirated for ex vivo chemical and physical-chemical analyses. The aspirates were collected during established lipid digestion and absorption into a "cocktail" of chemical inhibitors that rapidly inhibited ex vivo lipolysis. Following ultracentrifugation, the lipids separated into a floating oil layer, several interfacial layers, a "clear" or turbid "subphase", and a precipitated "pellet". By chemical and phase analyses, the floating layer was composed of oil-in-water emulsion particles with cores of triacylglycerol (TG), diacylglycerols (DG), and cholesteryl esters (CE) emulsified with a surface coat of partially ionized fatty acids (FA), monoacylglycerols (MG), diacylphosphatidylcholine (PL), and bile salts (BS). The interfacial layers contained similar emulsion particles dispersed among excess emulsifier which adopted a lamellar liquid-crystalline structure. Precipitated pellets were composed principally of emulsifying lipids, with smaller amounts of crystalline calcium soaps and BS. Relative lipid compositions of all but three subphases fell within a two-phase region of the condensed ternary phase diagram (Staggers et al., 1990, companion paper) where saturated mixed micelles composed of BS, FA "acid-soaps", MG, PL, cholesterol (Ch), and traces of DG (and TG) coexisted with unilamellar liquid-crystalline vesicles composed of the same lipids. Attempts to achieve clean separation of vesicles from micelles by repeat ultracentrifugation failed. Compared with the structure and sizes of lipid particles in equilibrated model systems (Staggers et al., 1990), quasielastic light scattering (QLS) analysis revealed that ex vivo micellar sizes (mean hydrodynamic radii, Rh) were similar (less than or equal to 40 A), whereas unilamellar vesicle sizes (Rh = 200-600 A) were appreciably smaller. Two-component QLS analysis of the subphases showed that much larger proportions of lipids were solubilized by micelles than were dispersed as unilamellar vesicles. When followed as functions of time, vesicles frequently dissolved spontaneously into mixed micelles, indicating that, in the nonequilibrium in vivo conditions, the constituent micellar phase was often unsaturated with lipids. These results are consistent with the hypothesis that, during hydrolysis of emulsified DG and TG by luminal lipases, unilamellar vesicles originate in lamellar liquid crystals that form at emulsion-water interfaces in the upper small intestine. In a BS-replete environment, unilamellar vesicles probably represent the primary dispersed product phase of human fat digestion and facilitate the dissolution of lipolytic products into unsaturated mixed micelles.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

A controlled trial in intensive care units of selective decontamination of the digestive tract with nonabsorbable antibiotics. The French Study Group on Selective Decontamination of the Digestive Tract.

BACKGROUND: Selective decontamination of the digestive tract with topical nonabsorbable antibiotics has been reported to prevent nosocomial infections in patients receiving mechanical ventilation, and the procedure is used widely in Europe. However, it is unclear whether selective decontamination improves survival. METHODS: We conducted a randomized, double-blind multicenter study in which 445 patients receiving mechanical ventilation in 15 intensive care units were given either prophylactic nonabsorbable antibiotics (n = 220) or a placebo (n = 225). Topical antibiotics (tobramycin, colistin sulfate, and amphotericin B) or a placebo was administered through a nasogastric tube and applied to the oropharynx throughout the period of ventilation. The main end points were the mortality rate in the intensive care unit and within 60 days of randomization. RESULTS: A total of 142 patients died in the intensive care unit; 75 (34 percent) in the treatment group and 67 (30 percent) in the placebo group (P = 0.37). Mortality within 60 days of randomization was similar in the two groups (P = 0.40), even after adjustment for factors that were either unbalanced or individually predictive of survival in the two groups (P = 0.70). Pneumonia developed in 59 patients (13 percent) in the intensive care unit within 30 days of enrollment in the study (33 in the placebo group and 26 in the treatment group, P = 0.42). Pneumonia acquired in the intensive care unit and due to gram-negative bacilli was less frequent (P = 0.01) in the treatment group than in the placebo group. The total charges for antibiotics were 2.2 times higher in the treatment group. CONCLUSIONS: Selective decontamination of the digestive tract does not improve survival among patients receiving mechanical ventilation in the intensive care unit, although it substantially increases the cost of their care.

Administration, Topical↗
PubMed1978

Studies on digestion and absorption in the intestines of growing pigs. 3. Net movements of mineral nutrients in the digestive tract.

1. Pigs growing from 20 to 60 kg live weight were given diets based on barley, weatings and fish meal, or starch, sucrose and groundnut meal or starch, sucrose and casein. Seventeen pigs were fitted with single re-entrant cannulas in the duodenum (posterior to entry of bile and pancreatic ducts), jejunum or terminal ileum and twenty-four non-cannulated pigs were used in a conventional digestibility trial. 2. The amounts of calcium, phosphorus, magnesium, sodium and potassium passing through the re-entrant cannulas and amounts excreted in the faeces were measured. These values were used to calculate the direction and extent of net movements of the five elements through the walls of the four parts of the digestive tract anterior to the collection sites. 3. The small intestine was the principal site of Ca and P absorption but there were differences between the diets in the relative importance of the regions anterior and posterior to the mid-jejunum. 4. Secretion of small amounts of Mg occurred in the anterior small intestine; the ileum and large intestine were the principal sites of net absorption. 5. There was a large net secretion of Na anterior to the duodenal cannulas and further secretion into the anterior small intestine with each diet. There were marked differences between diets in the amounts secreted but the ileal Na concentration was the same in each instance. Absorption occurred in the ileum and large intestine. 6. Secretion of small amounts of K was evident anterior to the duodenal cannulas and net absorption occurred in both parts of the small intestine with each diet.

Animals↗
PubMed1984

The effect of protein quality and fibre level in the diet and microbial activity in the digestive tract on protein utilization and energy digestibility in rats.

Two nitrogen-balance experiments were performed with growing rats to test the effect of dietary fibre level, protein quality and antibiotic inclusion on microbial activity, N excretion patterns and energy digestibility. Each experiments involved eight dietary treatments in a 2 X 2 X 2 factorial design, with five rats per treatment. The eight treatments resulted from a combination of two protein treatments, two fibre treatments and two antibiotic treatments. In Expt 1 the protein was provided as barley, or barley plus 2 g L-lysine hydrochloride/kg dry matter (DM) (at 15 g N/kg DM) and in Expt 2 as soya-bean meal or soya-bean meal plus 2 g DL-methionine/kg DM (at 15 g N/kg DM). In both experiments the basal diet was provided with or without additional fibre as 100 g barley husk/kg DM and with or without antibiotic as 7 g Nebacitin/kg DM. With both barley and soya-bean meal, true protein digestibility (TD) was improved with the addition of amino acids. Only with the soya-bean meal diets was TD increased with Nebacitin treatment, with the effect of Nebacitin and methionine being additive. Barley husk slightly reduced the TD of soya-bean meal. The effect of treatments on biological value (BV) was considerable. Lysine increased BV of the barley diet from 0.741 to 0.815 whereas Nebacitin reduced BV from 0.799 to 0.757. Methionine increased the BV of soya-bean meal from 0.754 to 0.911 while BV was reduced by Nebacitin from 0.843 to 0.821 and by barley husk from 0.845 to 0.820.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗