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PubMed1996

Enhanced intake and production of cows offered ensiled alfalfa with higher neutral detergent fiber digestibility.

The objective of this study was to determine the effect of forage fiber digestibility as part of a total mixed diet on intake and production of cows with intakes that were likely limited by rumen fill, using treatments that were not confounded by fiber source, concentrate, or ratio of forage to concentrate. Two alfalfa silages with similar NDF concentrations (40%) but different NDF digestibilities (40 vs. 45% after 24 h of in vitro fermentation) were harvested, mixed with concentrate to achieve diets containing 35% NDF, and offered to 12 multiparous cows (13 DIM) in a two-period balanced crossover design. Samples taken during silage feeding revealed that diets differed in both NDF digestibility (3 percentage units) and NDF content (1.8 percentage units), making interpretation of results difficult. Nonetheless, milk production (36.3 vs. 38.2 kg/d) and DMI (19.4 vs. 20.4 kg/d) were significantly higher with the higher NDF digestibility diet. Apparent in vivo DM and NDF digestibilities, total rumen VFA after feeding, and molar percentage of propionate were also higher with this diet. Equal NDF intake between diets suggested that higher DMI was due to the lower NDF content in the more digestible NDF diet. Higher NDF digestibility might also increase DMI; further experimentation is necessary with larger unconfounded differences in fiber digestibility at the time of feeding.

Animals↗
PubMed1997

Digestion and passage kinetics of forage fiber in dairy cows as affected by fiber-free concentrate in the diet.

Four ruminally and duodenally cannulated Holstein cows in early lactation were fed alfalfa [47% neutral detergent fiber (NDF)] or timothy silage (49% NDF) for ad libitum intake in a 4 x 4 Latin square experiment. Forages were supplemented with 8 or 12 kg/d of an essentially fiber-free concentrate to study digestion and passage kinetics of forage fiber in high producing dairy cows. Fractional digestion and passage rates of NDF in the rumen were derived from ruminal pool sizes. Alfalfa had a potentially digestible NDF fraction with a faster rate of digestion but a larger indigestible NDF fraction and, consequently, higher physical fill in the rumen than did timothy. However, dry matter intake did not differ between forages, primarily because of the higher fractional passage rates of alfalfa NDF. Although dry matter intake was 23.2 kg/d, fractional passage rates of forage NDF were generally lower than those usually assumed. Fractional rates of NDF digestion decreased equally for both forages as concentrate in the diet increased, but diets with alfalfa forage had the smallest quantitative reduction because of the markedly smaller ruminal pool size of potentially digestible NDF. The fractional passage rate of NDF decreased as concentrate in the diet increased for diets containing alfalfa but did not change for diets containing timothy. Consequently, as concentrate in the diet increased, digestibilities of NDF in the rumen and whole tract increased with alfalfa and decreased with timothy. Results suggest that fiber-free concentrate is useful when digestion and passage kinetics of specific forage fibers are being measured in high producing dairy cows.

Animal Feed↗
PubMed1999

Effects of grain source and enzyme additive on site and extent of nutrient digestion in dairy cows.

Four lactating, cannulated Holstein cows were used in a 4 x 4 Latin square design to investigate the effects of grain source and fibrolytic enzyme supplementation on ruminal fermentation, nutrient digestion in the rumen and in the intestine, and milk production. A 2 x 2 factorial arrangement was used; two grains (barley and hull-less barley) were combined with and without enzyme. The enzyme supplement (Pro-Mote; Biovance Technologies Inc., Omaha, NE) contained primarily cellulase and xylanase activities and was applied daily to the total mixed diet. Dry matter intake was not affected by diet, but starch intake was greatest when hull-less barley was fed. Starch from hull-less barley was more digestible in the rumen and in the total tract than was starch from barley, but opposite results occurred for fiber digestion, indicating that hull-less barley depressed fiber digestion. As a result, cows fed the hull-less barley diets tended to produce more milk with a higher milk lactose content than did cows fed the barley diets. Enzyme supplementation had minimal effects on ruminal digestion but increased nutrient digestibility in the total tract and the proportion of microbial N in nonammonia N. Consequently, cows fed diets supplemented with enzyme had a higher milk protein content and tended to produce more 4% fat-corrected milk than did control cows. These results indicate that the use of hull-less barley rather than barley increased the digestible energy intake of dairy cows, resulting in higher milk production. The use of a fibrolytic enzyme mixture enhanced feed digestibility and milk production.

Animals↗
PubMed1990

Effect of oligosaccharide-free soybean meal on true metabolizable energy and fiber digestion in adult roosters.

Adult Leghorn roosters were precision-fed 44% protein soybean meal (SBM) or 80% ethanol-extracted soybean meal (ESBM) to determine nutritional differences due to the removal of oligosaccharides. Dry-matter digestibility and TMEn as well as apparent hemicellulose and cellulose digestion were determined. The transit time, rate of passage, and pH of the cecal contents were also established with roosters that had consumed a .3% chromic-oxide diet that contained SBM or ESBM. The protein content of the SBM and the ESBM was 46.1 and 64.4%, respectively. The true-dry matter digestibility of SBM was 54%. The TMEn of the SBM on a dry-matter basis was 2,794 kcal per kg; and the apparent hemicellulose and cellulose digestibility was 9% and 0%, respectively. The true dry-matter digestibility of the ESBM was 67%. On a dry-matter basis, the TMEn of the ESBM was 3,368 kcal per kg; and the apparent hemicellulose and cellulose digestibility was 62% and 35%, respectively. Oligosaccharide digestion occurred mainly anterior to the ileo-cecal junction. Hemicellulose and cellulose digestion occurred predominantly in the lower gastrointestinal tract. The transit time for the ESBM diet was 115 min, compared to 71 min for the SBM diet. Based on a 16-h collection of excreta, the rate of passage was approximately 50% slower for the ESBM diet than for the SBM diet. The pH of the cecal contents from roosters consuming the ESBM diet was 7.21 versus 6.51 for the SBM diet.

Animal Feed↗
PubMed1996

Effect of microbial phytase on nitrogen and amino acid digestibility and nitrogen retention of turkey poults fed corn-soybean meal diets.

The effect of microbial phytase on N and amino acid (AA) digestibility and N retention was investigated in a 29-d trial using 480 Nicholas Large White Turkey female poults fed corn-soybean meal diets. A 2 x 2 x 2 factorial arrangement of treatments was used with 0.45 and 0.60% nonphytate P (nP), 22.5 and 28.0% CP, and 0 and 750 U of microbial phytase/kg of diet. At 0.45% nP, adding phytase to either 22.5 or 28.0% CP diets increased BW gain (P < 0.01), and percentage (P < 0.01) and weight (P < 0.10) of toe ash; at 0.60% nP, the magnitude of the effect of phytase was less (P > 0.10) than observed for 0.45% nP and inconsistent. Apparent and true ileal digestibility of N and AA was estimated by using chromic oxide as an indicator at Day 24. At 0.45% nP, adding phytase to 22.5% CP diets tended to improve the apparent and true ileal digestibility of N and AA, except cysteine or methionine; adding phytase to 28.0% CP diets increased the digestibility of N and most of the AA (P < 0.001 to 0.10). At 0.60% nP, adding phytase to 22.5% CP diets increased the apparent and true ileal digestibility of N and all the AA (P < 0.001 to 0.10), but did not change digestibilities at 28.0% CP diets. Adding phytase also increased (P < 0.001 to 0.10) apparent ileal digestibility of DM and P at 0.45% nP for both CP diets, but only for 22.5% CP diets at 0.60% nP. The total excreta were collected at Day 27 to 29. Adding phytase to 0.45% nP diets increased apparent utilization of DM (P < 0.01 to 0.10) and retention of N (P < 0.05 to 0.10) at both CP levels; retention of P was only increased (P < 0.10) at 22.5% CP. At 0.60% nP, adding phytase increased utilization of DM (P < 0.05) and retention of N (P < 0.10) only at 22.5% CP; P retention was not affected. In summary, microbial phytase enhanced growth performance, toe ash, ileal N and AA digestibility, and apparent N and P retention.

6-Phytase↗
PubMed1996

Additivity of apparent and true ileal amino acid digestibilities in soybean meal, sunflower meal, and meat and bone meal for broilers.

An experiment was conducted to determine the additivity of apparent and true ileal amino acid digestibility values in soybean meal (SBM), sunflower meal (SFM), and meat and bone meal (MBM). A total of 63 individually caged 5-wk-old broilers were assigned to seven groups and given semi-purified diets containing SBM, SFM, MBM, and their combinations. True digestibilities were estimated by using the homoarginine in guanidinated proteins as the marker. Additivity was tested by comparing the differences between the observed digestibilities of ingredient combinations and the predicted values from measurements with individual ingredients. In general, for both apparent and true digestibilities, there were no significant differences (P > 0.05) between the observed and predicted values in ingredient combinations. The only exception was SBM + MBM combination, in which the observed values for apparent digestibilities of aspartic acid, serine, glutamic acid, isoleucine, and tyrosine were significantly higher (P < 0.05) than the predicted values. Overall, the present results indicate that amino acid digestibility values are additive and that digestible amino acid supply in a complete diet can be predicted from amino acid digestibilities of individual ingredients.

Amino Acids↗
PubMed1996

Digestible threonine requirement of broiler chickens during the period three to six and six to eight weeks posthatching.

Four experiments were conducted to determine the digestible Thr requirement of commercial broiler chickens (Ross x Hubbard) during the period 3 to 6 and 6 to 8 wk posthatching. Threonine-deficient corn-peanut meal basal diets (3,200 MEn/kg) contained 20% CP and 0.50% Thr for 3- to 6-wk-old birds, and 18.3% CP and 0.50% Thr for 6- to 8-wk-old birds. True digestibility assessment using cecectomized roosters indicated that Thr was 81% digestible in both basal diets. Thus, both diets contained 0.40% digestible Thr. Growth rate and feed efficiency of chicks fed the corn-peanut meal basal diets supplemented with surfeit Thr was equal to that of chicks fed a 20% CP Met-fortified corn-soybean meal diet. Graded doses of Thr produced marked responses (P < 0.05) in weight gain and feed efficiency in birds of both age groups. Maximal feed efficiency was achieved at 0.61% digestible Thr in 3- to 6-wk-old birds and at 0.52% digestible Thr in 6- to 8-wk-old birds. Extrapolating these digestible Thr requirements to total requirements for chicks consuming corn-soybean meal diets (Thr digestibility = 87%) results in estimates of 0.70 and 0.60% for broiler chickens during the growth periods 3 to 6 and 6 to 8 wk posthatching, respectively. These estimates are lower than those of NRC (1994) but are in close agreement with those obtained from ideal protein calculations, i.e., Thr requirements should be 70% of lysine requirements for chicks 3 to 8 wk of age.

Aging↗
PubMed1995

The influence of the period of adaptation on the digestibility of diets containing different types of indigestible polysaccharides in rats.

In balanced experiments with rats the influence of the period of adaptation on nutrient digestibility in diets containing cellulose (CEL), guar gum (GG), pectin (PEC) or retrograded high amylose maize starch (RS) was studied. Inclusion level was 80 g/kg diet DM except for the retrograded high-amylose maize starch, where the level was 316 g/kg diet DM. A diet containing normal maize starch only acted as a control diet (FF). The apparent digestibilities of DM, NSP, starch and protein were determined after adaptation periods of 4 d and 2, 4, 6 and 8 weeks. The digestibility of nutrients was affected by diet (P < 0.001) as well as by the period of adaptation (P < 0.001). The digestibilities of DM, NSP and starch increased asymptotically during the course of the experiment. The asymptotic progress over time was most pronounced for the GG, PEC and RS diets. The estimated periods of adaptation required for stable DM digestibility were approximately 1 week for the GG, PEC and RS diets and < 4 d for the FF and CEL diets. The digestibility of NSP in the GG and PEC diets was also stable after approximately 1 week, while it was stable from < 4 d for the CEL diet. However, PEC increased the faecal content of uronic acids for at least 2 weeks. A stable starch digestibility required 1 month in the case of RS and 3-10 d for the other diets. The high faecal content of glucose for the RS diet decreased during all 8 weeks but was still high at the close of the experiment. The apparent protein digestibility changed over time in a parabolic rather than an asymptotic fashion. The GG, PEC and RS diets increased the amount of N excreted by the faecal route.

Adaptation, Physiological↗
PubMedDate not supplied

[Current concepts of digestion and absorption of carbohydrates].

The aim of this paper is to review recent aspects of digestion and absorption of carbohydrates that are the main source of energy in human diets. Recent researches have found that starch is not largely hydrolysed and absorbed in the small bowel but one part of it is resistant to digestion. Several food factors may be responsible for digestion and absorption velocity and totality of carbohydrates. Therefore, carbohydrate classification must be based not only on molecular size to express the real carbohydrates utilization as an energy source by humans. In agreement with molecular size of carbohydrate, its classification can be: a) monosaccharides; b) disaccharides; c) oligosaccharides; d) polysaccharides. In agreement with carbohydrate digestibility or availability, its classification can be: a) digestible carbohydrates; b) undigestable carbohydrates (NSP). Carbohydrate digestibility can be altered by several factors like: Intrinsic factors: a) physical structure; b) molecular physical distribution; c) physical state of food; d) food antinutrients. Extrinsics factors: a) chewing; b) transit time of food; c) amount of starch present; d) diet antinutrients. Under influence of this factors, process of digestion happen by enzymatic activity a long the gastrointestinal tract. Salivary and pancreatic amylase; glycosidases of the duodenal enterocyte brush border (lactase, sacarase and maltase), whose activity happen by close interaction of digestive breakdown with transport. The summarized pathways of the absorptive process: 1. movement from the bulk phase of the lumenal or mucosal fluid to enterocyte surface; 2. movement across the brush border membrane through specific transporters: a) SGLT1; b) GLUT 5; c) passive diffusion. 3. movement across the basolateral membrane by the GLUT 2.

Carbohydrate Metabolism↗
PubMed1998

[Descriptive study of digestive functional symptoms in the French general population].

UNLABELLED: To study the prevalence of "reported" functional digestive symptoms (FDS) in terms easily understood by the general population without resorting to predefined concepts of functional syndromes, and to assess FDS impact on public health, a sample survey has been carried out between September and December 1995. METHODS: Four thousand eight hundred and seventeen subjects representative of the French general population aged 15 years or more filled in a questionnaire describing their digestive disorders. RESULTS: Seventy percent of the subjects had digestive complaints, 9% being related to a presumably organic disease, and 61% attributed to FDS. Twenty-seven % of the subjects claimed to be inconvenienced by their FDS, whereas 34% seemed not to feel any inconvenience. Among FDS, gas emission was the most frequent symptom (59%), followed by stomach ache and/or digestive pain (48%), flatulence (47%), bad digestion sensations (40%), constipation (35%), aerophagia (29%), bad breath (22%), incomplete evacuation of stools (19%). FDS had lasted from 6 months to 5 years in 38%, and over 5 years in 52%. In the subgroup of subjects inconvenienced by FDS (27%), 9% consulted and 18% did not, whereas in the subgroup not inconvenienced, 3% consulted and 31% did not. Altogether, 26% of the subjects followed a prescription or self medication treatment; 35% were not treated. Some explanatory variables appeared to be associated with the onset of inconvenience: the associations pain and bad digestion, flatulence and aerophagia, incomplete evacuation and nervous or presumably organic origin of FDS, age, stress, FDS frequency. Duration of symptoms, age above 65 years, digestive pain, presumably organic origin, and FDS frequency were associated with the need to consult. This descriptive, pragmatic survey shows the widespread prevalence of FDS, affecting 28 million French people. Functional digestive disorders in the "academic" meaning constitute only a limited subset. FDS lead to major health care consumption. Their impact on public health is undoubtedly greater than the estimates derived from studies designed in accordance with conventional nosological categories.

Adolescent↗
PubMed1998

Methanogenic population dynamics during start-up of anaerobic digesters treating municipal solid waste and biosolids.

An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m3/day and the retention time was 20 days. Ribosomal RNA-targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start-up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start-up period (20 days), stable performance was observed with high gas production rates (1.52 m3/m3/day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start-up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start-up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester.

Anaerobiosis↗
PubMedDate not supplied

Optimization of microwave digestion for mercury determination in marine biological samples by cold vapour atomic absorption spectrometry.

Optimization of acid digestion method for mercury determination in marine biological samples (dolphin liver, fish and mussel tissues) using a closed vessel microwave sample preparation is presented. Five digestion procedures with different acid mixtures were investigated: the best results were obtained when the microwave-assisted digestion was based on sample dissolution with HNO3-H2SO4-K2Cr2O7 mixture. A comparison between microwave digestion and conventional reflux digestion shows there are considerable losses of mercury in the open digestion system. The microwave digestion method has been tested satisfactorily using two certified reference materials. Analytical results show a good agreement with certified values. The microwave digestion proved to be a reliable and rapid method for decomposition of biological samples in mercury determination.

Animals↗
PubMed2004

Microbial population dynamics during start-up and overload conditions of anaerobic digesters treating municipal solid waste and sewage sludge.

Microbial population dynamics were investigated during start-up and during periods of overload conditions in anaerobic co-digesters treating municipal solid waste and sewage sludge. Changes in community structure were monitored using ribosomal RNA-based oligonucleotide probe hybridization to measure the abundance of syntrophic propionate-oxidizing bacteria (SPOB), saturated fatty acid-beta-oxidizing syntrophs (SFAS), and methanogens. These changes were linked to traditional performance parameters such as biogas production and volatile fatty acid (VFA) concentrations. Digesters with high levels of Archaea started up successfully. Methanosaeta concilii was the dominant aceticlastic methanogen in these systems. In contrast, digesters that experienced a difficult start-up period had lower levels of Archaea with proportionally more abundant Methanosarcina spp. Syntrophic propionate-oxidizing bacteria and saturated fatty acid-beta-oxidizing syntrophs were present at low levels in all digesters, and SPOB appeared to play a role in stabilizing propionate levels during start-up of one digester. Digesters with a history of poor performance tolerated a severe organic overload event better than digesters that had previously performed well. It is hypothesized that higher levels of SPOB and SFAS and their methanogenic partners in previously unstable digesters are responsible for this behavior.

Adaptation, Physiological↗
PubMed1993

Improved DNA content histograms from formalin-fixed, paraffin-embedded liver tissue by proteinase K digestion.

An improved method for the enzymatic digestion of formalin-fixed, paraffin-embedded liver tissue for DNA content analysis by flow cytometry is presented. Forty samples of histologically normal liver were alternately digested by the traditional pepsin method or a new method utilizing proteinase K and heat. Sixteen (40%) of the pepsin-digested samples had apparent DNA aneuploid peaks by flow cytometry. False DNA aneuploid peaks were not present in any of the histograms obtained after proteinase K digestion. Microscopy showed that the pepsin-digested samples had residual cytoplasmic remnants which contained fluorescent material. Samples digested with proteinase K had few cytoplasmic remnants. The average G0/G1 coefficient of variation after proteinase K treatment was lower (41%) and the fluorescent intensity higher (128%) than the pepsin-treated samples. The apparent mean S-phase (a combination of S-phase cells and underlying debris) after proteinase K digestion was 35% of the pepsin-treated samples. Primary and secondary tumors of the liver that were DNA aneuploid after pepsin treatment were also DNA aneuploid after proteinase K treatment. A modified digestion protocol utilizing proteinase K and heat can provide superior results for DNA content analysis of formalin-fixed, paraffin-embedded liver tissue.

Aneuploidy↗
PubMed1983

Cytophysiological aspects of digestion and storage in the liver of a scorpion, Androctonus australis (Arachnida).

The liver of a scorpion, Androctonus australis (Arachnida), was examined electron-microscopically and cytochemically, emphasizing correlations between structure, cytochemistry and physiology. The liver consists of digestive diverticula and interstitial tissue. Digestive diverticula are composed of basophilic cells and digestive cells. Basophilic cells produce exoenzymes. Digestive cells ensure intracellular digestion of nutrients absorbed by pinocytosis and store glycogen, lipids and mineral salts; the wastes of the digestive process (guanine, uric acid, mineral elements, pigments) are concentrated in "brown body vacuoles" which are ejected into the lumen of the diverticula. The interstitial tissue stores glycogen and lipids; it contains many lysosome-like organelles rich in iron. Fasting induces a decrease of the ratio of the volume of the diverticula to that of the interstitial tissue, a slow disappearance of the reserves in both diverticula and interstitial tissue, an increase of synthesis in the basophilic cells, and a decrease of the number of vacuoles in the digestive cells. The digestive mode of the scorpions associates a primitive intracellular process with an advanced extracellular process. The interstitial tissue can be considered as homologous to the adipose tissue of insects and myriapods, although it is devoid of urate cells. The excretion of guanine and uric acid has a peculiar meaning, because these purine wastes do not come from endogenous catabolism.

Animals↗
PubMed1995

In vitro mucosal digestion of synthetic gliadin-derived peptides in celiac disease.

Two celiac-active synthetic peptides derived from the A-gliadin structure corresponding to residues 8-19 (LQPQNPSQQQPQ) and to 11-19 were digested in vitro with small intestinal mucosa from children with celiac disease in remission and from normal children. The products of digestion were separated into two fractions on the basis of M(r) < 400 and M(r) > 400 by gel permeation chromatography and subjected to amino acid analysis. After digestion of the dodecapeptide with celiac mucosa, 71 +/- 14% (molar) of the total digestion products remained in the M(r) > 400 fraction. Glutamine, proline, serine, and asparagine were the major amino acids present. Glutamine, proline, and leucine were the major amino acids in the M(r) < 400 fraction. The M(r) > 400 fraction from the celiac mucosal digestion of the nonapeptide was of similar composition to the corresponding fraction from the dodecapeptide and represented 78 +/- 15% of the total products. Digestion of the two peptides with normal mucosa gave lower amounts of products in the M(r) > 400 fraction, but they were of similar composition to the corresponding fractions from the celiac mucosal digestion. Peptides such as NPSQQP and QNPSQQQ may be present in the M(r) > 400 fractions since glutamine and proline are present in the approximate ratio of 2:1, respectively. The results indicate a defect in the mucosal digestion of peptides which are active in an animal model of celiac disease.

Amino Acid Sequence↗
PubMed2004

Monitoring the degradation and solubilisation of butyltin compounds during in vitro gastrointestinal digestion using "triple spike" isotope dilution GC-ICP-MS.

An in vitro gastrointestinal digestion approach in combination with species-specific isotope dilution analysis has been employed for the first time to study the transformation reactions as well as the solubilisation of butyltin species throughout a simulated human digestion. Different sample preparation procedures were assayed in order to avoid problems derived from lack of isotope equilibration between the endogenous and the isotopically-enriched added species. A "triple spike" approach, which can be used to calculate the corrected concentrations of mono-, di-, and tributyltin (MBT, DBT and TBT, respectively), as well as six interconversions, was employed throughout this work. In order to calculate and compare the species degradation factors, a triple spike solution containing each butyltin species enriched in a different isotope was added to the simulated gastric and intestinal fluids before the digestion procedures in the presence and in the absence of a solid biological matrix (commercial mussel tissue). Additionally, by analysing the soluble and insoluble fractions resulting from the simulated digestion of a commercial mussel tissue (gastric and gastric plus intestinal digestion), total mass balances for each butyltin compound could be derived. For this purpose, the isotopically-enriched species were added after the enzymatic digestions in order to avoid problems derived from lack of isotope equilibration. The mass balances provided information not only about the solubilisation but also about the degradation of the butyltin species during the digestion procedures. Good agreement between the degradation factors calculated under all experiments performed in this work and between those reported in previous works were obtained. The most serious degradation observed was that of DBT to produce MBT, whereas slight degradations of TBT and MBT were detected. Moreover, a worrying 61% of the original total butyltin content present in a commercial mussel tissue was found to be solubilised after complete simulated gastrointestinal digestion, with minimal degradation of TBT.

Gas Chromatography-Mass Spectrometry↗
PubMed1990

Cloning and expression of raw-starch-digesting alpha-amylase gene from Bacillus circulans F-2 in Escherichia coli.

The raw potato-starch-digesting alpha-amylase gene of Bacillus circulans F-2 was cloned for the first time in Escherichia coli C600, using plasmid pYEJ001. The recombinant plasmid, named pYKA3, has a 5.4 kb insert from a chromosome of the donor bacterium. Subcloning of this amylase gene gave plasmid pHA300 which carried 3.15 kb of the inserted DNA. The transformed bacterium, E. coli C600 (pYKA3), produced the amylase in the periplasmic space, whereas it is secreted outside the cell in the donor bacterium. The cloned raw-starch-digesting alpha-amylase has a molecular weight of 93,000 on SDS-PAGE, and its action pattern was absolutely the same as that of the potent raw-starch-digestible amylase produced by B. circulans F-2. The periplasmic amylase produced by the transformed E. coli (pHA300) could digest raw starch granules such as potato, corn and barley raw starch granules, indicating that the raw-starch-digesting amylase is active in E. coli. Furthermore, this amylase crossreacted with the rabbit antiserum raised against the raw potato-digesting alpha-amylase of B. circulans F-2. From these results it was concluded that the cloned amylase is the same amylase protein as B. circulans F-2 amylase, which has a potent raw-starch digestibility. Thus, this paper is to our knowledge the first describing the molecular cloning of raw-starch-digesting alpha-amylase from Bacillus species and its successful expression in E. coli.

Bacillus↗