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PubMed1980

Destruction by anaerobic mesophilic and thermophilic digestion of viruses and indicator bacteria indigenous to domestic sludges.

In raw sludges and in mesophilically and thermophilically digested anaerobic sludges, large variations in numbers of viruses occurred over narrow ranges of numbers of fecal coliforms, total coliforms, and fecal streptococci, demonstrating that the bacteria were poor quantitative reflectors of the numbers of the viruses detected. Mesophilic and thermophilic digestion of anaerobic sludges destroyed all three indicator bacteria more rapidly than such digestion destroyed the viruses. The relative rates for the destruction of viruses, fecal coliforms, and fecal streptococci in the digested sludges were consistent over the 17-month study. Fecal coliforms were 7 to 8 times more sensitive than the viruses to mesophilic digestion and 9 to 10 times more sensitive to thermophilic digestion. Total coliforms were even more sensitive. The rates at which fecal streptococci were destroyed by mesophilic and thermophilic digestion of anaerobic sludges approached those at which the viruses were destroyed by those processes; this suggested that the rates at which fecal streptococci in sludges are destroyed by those processes may serve as useful indicators for the rates at which viruses in sludges are destroyed by those processes.

Journal Article↗
PubMed1997

Kinetics of Cellulose Digestion by Fibrobacter succinogenes S85.

Growing cultures of Fibrobacter succinogenes S85 digested cellulose at a rapid rate, but nongrowing cells and cell extracts did not have detectable crystalline cellulase activity. Cells that had been growing exponentially on cellobiose initiated cellulose digestion and succinate production immediately, and cellulose-dependent succinate production could be used as an index of enzyme activity against crystalline cellulose. Cells incubated with cellulose never produced detectable cellobiose, and cells that were preincubated for a short time with thiocellobiose lost their ability to digest cellulose (competitive inhibition [K(infi)] of only 0.2 mg/ml or 0.56 mM). Based on these results, the crystalline cellulases of F. succinogenes were very sensitive to feedback inhibition. Different cellulose sources bound different amounts of Congo red, and the binding capacity was HCl-regenerated cellulose > ball-milled cellulose > Sigmacel > Avicel > filter paper. Congo red binding capacity was highly correlated with the maximum rates of metabolism of cellulose digestion and inversely related to K(infm). Congo red (250 (mu)g/ml) did not inhibit the growth of F. succinogenes S85 on cellobiose, but this concentration of Congo red inhibited the rate of ball-milled cellulose digestion. A Lineweaver-Burk plot of ball-milled cellulose digestion rate versus the amount of cellulose indicated that Congo red was a competitive inhibitor of cellulose digestion (K(infi) was 250 (mu)g/ml).

Journal Article↗
PubMed2000

Use of PCR with universal primers and restriction endonuclease digestions for detection and identification of common bacterial pathogens in cerebrospinal fluid.

We have designed a universal PCR capable of amplifying a portion of the 16S rRNA gene of eubacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Enterococcus faecium, Enterococcus faecalis, Mycobacterium tuberculosis, Legionella pneumophila, Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter baumannii, Proteus mirabilis, Haemophilus influenzae, and Neisseria meningitidis. The sizes of the amplified products from various bacteria were the same (996 bp), but the restriction patterns of most PCR products generated by HaeIII digestion were different. PCR products from S. aureus and S. epidermidis could not be digested by HaeIII but yielded different patterns when they were digested with MnlI. PCR products from S. pneumoniae, E. faecium, and E. faecalis yielded the same HaeIII digestion pattern but could be differentiated by AluI digestion. PCR products from E. coli, K. pneumoniae, S. marcescens, and E. cloacae also had the same HaeIII digestion pattern but had different patterns when digested with DdeI or BstBI. This universal PCR could detect as few as 10 E. coli or 250 S. aureus organisms. Compared with culture, the sensitivity of this universal PCR for detection and identification of bacteria directly from 150 cerebrospinal fluids was 92.3%. These results suggest that this universal PCR coupled with restriction enzyme analysis can be used to detect and identify bacterial pathogens in clinical specimens.

Aged↗
PubMed1984

Barriers to nuclease Bal31 digestion across specific sites in simian virus 40 chromatin.

A portion of the nucleoprotein containing viral DNA extracted from cells infected by simian virus (SV40) is preferentially cleaved by endonucleases in a region of the genome encompassing the origin of replication and early and late promoters. To explore this nuclease-sensitive structure, we cleaved SV40 chromatin molecules with restriction enzymes and digested the exposed termini with nuclease Bal31. Digestion proceeded only a short distance in the late direction from the MspI site, but some molecules were degraded 400 to 500 base pairs in the early direction. By comparison, BglI-cleaved chromatin was digested for only a short distance in the early direction, but some molecules were degraded 400 to 450 base pairs in the late direction. These barriers to Bal31 digestion (bracketing the BglI and the MspI sites) define the borders of the same open region in SV40 chromatin that is preferentially digested by DNase I and other endonucleases. In a portion of the SV40 chromatin, Bal31 could not digest through the nuclease-sensitive region and reached barriers after digesting only 50 to 100 base pairs from one end or the other. Chromatin molecules that contain barriers in the BglI to MspI region are physically distinct from molecules that are open in this region as evidenced by partial separation of the two populations on sucrose density gradients.

Chromatin↗
PubMed1982

Digests of protein augment acid-induced canine pancreatic secretion.

To study interactions between intraluminal acid and protein digests, six dogs with chronic gastric and pancreatic fistulas received three sets of intestinal perfusates. The first set contained HCl (1, 2, or 4 mmol/50 ml) and 64 mM D- or L-phenylalanine. The second set contained HCl plus either intact or pepsin-digested bovine serum albumin (BSA); the BSA and HCl were varied so that each 50 ml contained 1, 2, or 4 meq of acid titratable from an initial pH of 2.0 to an end-point pH of 4.5. The third set was identical to the second set except for an initial pH of 3.5. All perfusates were adjusted to 300 mosM and randomly infused at 200 ml/h. L-Phenylalanine enhanced acid-induced bicarbonate and protein outputs, as did pH 2.0 BSA digests. At pH 3.5, only acid-induced protein output was augmented by BSA digests. In additional studies, undigested or digested BSA at pH 7.0 was infused with secretin (82 pmol.kg-1.h-1). Only digested BSA enhanced secretin-induced pancreatic secretion. We conclude that there is an important, albeit complex, interaction between the intestinal acid stimulus and the protein digest stimulus on pancreatic secretion.

Animals↗
PubMed2006

Sucralfate protects blood clots from peptic digestion by gastric juice in vitro.

OBJECTIVE: To test in vitro the ability of sucralfate to protect a blood clot from peptic digestion by gastric juice. MATERIAL AND METHODS: Blood clots adhering to the bottom of plastic tubes were exposed to native acidic gastric juice or gastric juice to which Al-Mg antacids, sucralfate or alkali had been added. The tubes were tilted regularly at room temperature and clot digestion monitored by measuring the diameters of the clots. After 15 h, the liquids, but not the adherent clots, were poured out and the tubes refilled with native acidic gastric juice. Further clot digestion was measured, as before. RESULTS: Native gastric juice digested the clots completely during approximately 7 h, while in neutralized gastric juice or in gastric juice containing antacids or sucralfate no digestion was seen. In the second experiment, native gastric juice completely digested all remaining clots, except those previously exposed to sucralfate. A dose-response study indicated that gastric juice containing 3% or more of sucralfate had this long-lasting, clot-protective effect. CONCLUSIONS: In vitro, sucralfate adheres to and protects blood clots from digestion by gastric juice pepsin. This unique effect of sucralfate may be of clinical relevance in the treatment of bleeding peptic ulcers.

Anti-Ulcer Agents↗
PubMed1973

Metabolic effects of plasmin digests of human growth hormone in the rat and man.

As a first step in our study of structure-function relationships among primate and non-primate growth hormones, human growth hormone (hGH) was subjected to the limited digestive activity of human plasmin. The lyophilized whole digest, containing less than 2% of unchanged hormone, had an average of 2.3 new amino-terminal groups per mole. The digest had the same potency as the native hormone (a) in causing weight gain in hypophysectomized rats; (b) in stimulating somatomedin production in hypophysectomized rats; (c) in stimulating upake of [(3)H]leucine into isolated diaphragm of hypophysectomized rats; (d) in accelerating transport of [(14)C]alpha-aminoisobutyric acid into isolated diaphragm of hypophysectomized rats; (e) in stimulating uptake of [3-0-methyl-(14)C]glucose by isolated adipose tissue of hypophysectomized rats; (f) in accelerating conversion of [(14)C]glucose to (14)CO(2) by isolated epididymal adipose tissue of hypophysectomized rats. The digest also caused glucosuria in partially pancreatectomized rats treated with dexamethasone. These metabolic actions of plasmin-digested hGH in the array of animal tests were confirmed by comparable effects elicited in 11 human subjects (nine pituitary-deficient children and adolescents and two nondeficient adults). A single injection of the plasmin digest caused an increase in plasma free fatty acids and a fall in plasma amino acids. Seven daily injections caused positive balances of nitrogen, phosphorous, sodium, and potassium, gain in body weight, and in two of three subjects impairment of glucose tolerance. The potency of the plasmin digest in producing these metabolic effects in man was comparable to that of native hGH.Thus, 2-3 bonds in the hGH molecule can be cleaved by plasmin without impairing the hormone's growthpromoting, anabolic, diabetogenic, and adipokinetic actions for rat and man.

Adipose Tissue↗
PubMedDate not supplied

Novel method for isolation of adult porcine pancreatic islets with two-stage digestion procedure.

It is particularly difficult to isolate porcine islets (PI). Experience suggests that the success rate of porcine islet isolation (PII) is probably considerably influenced by the distension and digestion of the pancreas. In this study, we divided the digestion procedure into two stages and developed a new enzyme solution to improve both the distension and digestion procedures. As a result, we established a novel and stable method of large-scale adult porcine islet isolation (APII). The harvested pancreata of 2-year-old pigs weighing over 200 kg (n = 18) were distended by introducing our new enzyme solution gently and slowly through the pancreatic ducts. Two-stage digestion (cold, then warm) was then performed by first placing the distended pancreata on ice for 2 h to cause diffusion of the enzyme solution around the islets, and then by incubating the pancreata in a water bath at 37 degrees C for 45 min without shaking. The islets were purified by a COBE 2991 cell processor on dextran T70 discontinuous density gradients. Histological study was performed on porcine pancreata sampled after 0, 15, 30, and 45 min of the second stage, and stained with H&E stain. Next, islet equivalent was calculated. Static incubation study was performed by stimulating the islets with 3.3 and 16.7 mM glucose in Krebs' Ringer bicarbonate buffer (KRBB) solution at 37 degrees C for 1 h, and finally the insulin released was measured. The dilated acinar cells septa around the islets were observed at time 0. Destruction of the acinar cells around the islets by warm digestion was recognized at 15 and 30 min, and destroyed and separated acinar cells present around the islets at 45 min. During the entire course of the warm digestion, the islets remained intact. The number of isolated islets was 291,667 +/- 240,452 IEQ/pancreas (n = 14) and 3,294 +/- 2199 IEQ/g of pancreatic tissue. The purity of recovered porcine islets was over 90%. The concentration of the insulin secreted by 10,000 IEQ islets selected at random was 83.9 +/- 13.4 microU/dish/h in response to 3.3 mM glucose and 104.1 +/- 12.9 microU/dish/h in response to 16.7 mM glucose (n = 20). A success rate of approximately 80% was attained with APII. We demonstrated that this increase in the success rate was due to the improved distension and digestion provided by this method. This two-stage APII method with its new enzyme solution may facilitate the future use of porcine islets in clinical xenotransplantation trials.

Animals↗
PubMed2006

The pH of the digestive vacuole of Plasmodium falciparum is not associated with chloroquine resistance.

Chloroquine resistance in the human malaria parasite, Plasmodium falciparum, arises from decreased accumulation of the drug in the ;digestive vacuole' of the parasite, an acidic compartment in which chloroquine exerts its primary toxic effect. It has been proposed that changes in the pH of the digestive vacuole might underlie the decreased accumulation of chloroquine by chloroquine-resistant parasites. In this study we have investigated the digestive vacuole pH of a chloroquine-sensitive and a chloroquine-resistant strain of P. falciparum, using a range of dextran-linked pH-sensitive fluorescent dyes. The estimated digestive vacuole pH varied with the concentration and pK(a) of the dye, ranging from approximately 3.7-6.5. However, at low dye concentrations the estimated digestive vacuole pH of both the chloroquine-resistant and chloroquine-sensitive strains converged in the range 4.5-4.9. The results suggest that there is no significant difference in digestive vacuole pH of chloroquine-sensitive and chloroquine-resistant parasites, and that digestive vacuole pH does not play a primary role in chloroquine resistance.

Animals↗
PubMed2006

Rice protein digestion by sake koji enzymes: comparison between steamed rice grains and isolated protein bodies from rice endosperm.

The digestion of proteins in steamed rice grains by sake koji enzymes under simulated sake mash conditions was analyzed by comparing the hydrolysis of steamed rice grains and heat-treated protein bodies (PBs) isolated from seven rice samples including four endosperm-storage protein mutants. The disappearance of peptides in the digest of isolated PBs was faster than that of steamed rice grains; however, more insoluble proteins formed in the case of isolated PBs. Not all of the hydrolyzed PB proteins were immediately solubilized in the digestion tests. High-molecular-weight peptides were more abundant in the solubilized digest of steamed rice grains than in that of isolated PBs. Variance in Ile, Ser, Glu, and Gly levels in the digest of steamed rice grains was relatively high among the seven samples, but was not found to be high in digests of isolated PBs. These results indicate that factors that may be derived from the steamed rice grains profoundly affect the digestion of proteins in steamed rice grains by sake koji enzymes.

Alcoholic Beverages↗
PubMed1993

[Digestion method for detection of ferruginous bodies in human tissues from autopsy cases].

We compared three sodium hypochlorite digestion methods and two potassium hydroxide digestion methods for detection of ferruginous bodies in human tissues. The following results were obtained. 1. Methods using sodium hypochlorite were effective for digestion of lung tissue samples, but only in part for greater omentum tissue samples. The potassium hydroxide digestion method worked well for preparation of lung and greater omentum tissue samples. 2. Results obtained by the different digestion methods were compared by Kruskal-Wallis test and Mann-Whitney U-test. No significant difference was detected in concentrations of ferruginous bodies and naked fibers in samples of lung, and tumor and normal tissues of the greater omentum among the digestion methods. 3. A more simplified procedure for sample processing with potassium hydroxide digestion was recommended for detection of ferruginous bodies in human tissues.

Humans↗
PubMed1995

Role of the carbohydrate moiety of a glucoamylase from Aspergillus awamori var. kawachi in the digestion of raw starch.

The digestion of raw starch by a glucoamylase (GA MU-H) from a mutant strain of Aspergillus awamori var. kawachi was closely correlated with mannoside chains O-linked to the Gp-I region (A470-V514), but not sugar chains N-linked to catalytic GAI' domain of GA MU-H. The partial replacement of mannose residues by glucose residues led to a significant decrease raw starch digestion. By the substitution of D2O for H2O in the reaction mixture, the raw starch digestion of GA MU-H decreased to 80% of that at 30 degrees C, although the rate of hydrolysis of soluble starch by and the ability to bind beta-cyclodextrin of GA MU-H were unchanged. Glycerol, known as an antichaotropic reagent, decreased the raw starch digestion of GA MU-H significantly. However, it did not have any effect on the enzymatic activity for soluble starch when soluble starch was the substrate. The efficient digestion of raw starch with raw starch-digesting glucoamylase needed the mannoside chains O-linked to the Gp-I region, which were suggested to contribute to digestion of raw starch through the interaction with water.

Amidohydrolases↗
PubMed2004

Enhancement of enzymatic digestibility of recycled newspaper by addition of surfactant in ammonia-hydrogen peroxide pretreatment.

The effect of surfactant on enzymatic digestibility was investigated during the pretreatment stage. Newspaper was pretreated with an ammonia-hydrogen peroxide mixture on a shaking bath at 40 degrees C and 130 strokes/min for 3 h. Two kinds of nonionic surfactants, NP series and Tween series, were utilized. The effect of hydrophile-lipophile balance (HLB) value of both series surfactants on digestibility was found to be negligible, even though de-inking efficiency was improved as HLB value was increased. The effect of surfactant loading on digestibility was small, below 0.5 wt%, and negligible above 0.5 wt% at 60 international filter paper units (IFPU). The percentage improvement in digestibility increased as enzyme loading decreased. Digestibility of NP-5-added sample relative to control sample, increased significantly at an enzyme loading <60 IFPU, i.e., 19 and 13% at 15 and 30 IFPU, respectively. Such an increase in digestibility was not explained clearly from the experimental results. It was also found that ink removal before enzymatic hydrolysis is very important to enhance digestibility.

Ammonia↗
PubMed2001

Comparison of different digestion methods for total decomposition of siliceous and organic environmental samples.

A comparison was made of different digestion methods for the total decomposition of siliceous and organically environmental samples prior to their analysis by inductively coupled plasma optical emission spectrometry (ICP-OES). In the present study, three different digestion methods, including microwave-assisted, hot plate heating and pressurized digestion (pressure bomb), were employed for the determination of nine heavy metals, i.e. Ag, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in sediment, soil, sludge and oil. The investigation of different combinations of acids through their analytical performance demonstrated that HCl plays a vital role in the determination of silver. The combination of HNO3 and HCl possesses more reactive ability in oxidizing organic matter. The recoveries of all elements of interest in sediment (NIST 2704) obtained by different digestion methods were found to be 86% to 113%, while microwave assisted digestion with various combinations of HNO3-HCl-HF and HNO3-HClO4-HF was considered to be a viable alternative to the conventional digestion systems because of its more intensive reaction conditions. The analytical results of four certified reference materials with different matrices, including sediment (GBW 07305), soil (GBW 07411), sludge (BCR R-143) and oil (NIST 1085a), by the microwave-assisted acid digestion method indicated that the recoveries of all elements of interest were more than 85% and the throughput of applied analytical method could be elevated significantly.

Journal Article↗
PubMed2004

Restriction digestion monitors facilitate plasmid construction and PCR cloning.

Plasmid construction by "forced" or "directional" ligation of fragments digested with two different restriction enzymes is highly efficient, except when inhibited digestion of one site favors vector recircularization. Such failures often result because incomplete double digestion is undetected in vector polylinkers or at terminal cloning sites on a PCR fragment. To test cleavage efficiency indirectly, a "monitor" plasmid is added to the digest. In a suitable monitor, the two test sites are separated by enough DNA (approximately 20% of full length) to distinguish the double digest from the failed single digest. To make this applicable to combinations of 32 popular cloning enzymes, we constructed a set of 4 monitors (pDM1, pDM2, pDM3, and pDM4). Each contains three polylinkers separated by stuffer segments of approximately 1 kb. The 32 sites are distributed in the polylinkers such that at least one plasmid in the set is diagnostic for each enzyme pair. The set is designed to be extended to up to 81 sites. A linearized version of the monitor allows for the determination of which of the two enzymes has failed in an incomplete double digest and is also useful when the target DNA is close to the size of the pDM backbone. The plasmids also serve as versatile self-monitoring cloning vectors for any site combination.

Cloning, Molecular↗
PubMed2006

Enhanced biogas recovery by applying post-digestion in large-scale centralized biogas plants.

The main objective of this study was to investigate the degradation efficiency of centralized biogas plants and provide guidance for the design of more efficient digester and post-digestion systems. These centralized biogas plants in Denmark digest manure together with organic waste from the food industry to generate biogas, which is used for electricity and thermal energy. A total of 20 such plants are currently active in Denmark, most of which were included in the investigation. From the plants, samples were obtained from various steps of the process. Samples were analysed and the residual biogas potential determined by batch post-digestion at various temperature levels. Results were correlated with plant characteristics and production statistics in order to judge the efficiency of various digestion concepts. A simplified model based on a two-step biogas production process was developed and experimental data were used to determine kinetic constants. Experimental results and analysis combined with model simulations showed that the residual biogas potential in the main digestion step effluent is originating mainly from undegraded particulate matter in the biomass. For thermophilic plants 93% of the residual biogas potential was originating from particulate matter and 88% for the mesophilic biogas plants. This indicates that the residual biogas potential is mainly due to insufficient retention time in the main digestion step for hydrolysis of particulate material and that the hydrolysis step is the methane yield limiting factor, while conversion of soluble material such as VFA is the rate limiting factor critical for achieving a stable process.

Denmark↗
PubMed2006

Influence of staging, mean cell residence time, and thermophilic temperature on the thermophilic anaerobic digestion process.

As Class B biosolids land application has become less acceptable to many local jurisdictions, low-cost processes to achieve Class A standards have become more popular. Prominent among these low-cost processes is thermophilic anaerobic digestion. As a result, thermophilic anaerobic digestion is now a popular topic in wastewater treatment literature, but quantifiable methods for selecting a particular thermophilic process have not been offered. To provide for this need, an empirical model was developed from data collected in thermophilic anaerobic digestion studies conducted using East Bay Municipal Utility District's (Oakland, California) primary and waste activated sludge to feed both bench- and full-scale digesters. The model predicts at which thermophilic temperature and mean cell residence time (MCRT) one process will outperform or equal another, with respect to fecal coliform reduction. The different disinfection efficiencies in the different thermophilic processes might be explained by the presence or absence of high volatile acid and/or un-ionized ammonia levels in the processes' digested sludges. Data from these studies also show an apparent relationship between increased thermophilic temperatures and volatile solids destruction, and between increased temperatures and specific volatile acids production, for digesters operating at a 13-day MCRT and higher, but not for digesters operating at a 2-day MCRT.

Anaerobiosis↗
PubMed2006

Pretreatment of sludge with microwaves for pathogen destruction and improved anaerobic digestion performance.

A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory-scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450-MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65 degrees C for primary sludge and anaerobic digester sludge and at 85 degrees C for waste activated sludge when sludge was irradiated with 2450-MHz microwaves. During the bench-scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave-pretreated sludge (> or = 2.66 log removal). The anaerobic digester fed with microwave-irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench-scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave-irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65 degrees C.

Anaerobiosis↗