Raw milk preservation by hyperbaric storage: Effect on microbial counts, protein structure and technological functionality.

The possibility to apply hyperbaric storage (HS) at room temperature (20 °C) as a sustainable approach for preservation of raw skim milk was studied. Samples were stored at 200 and 150 MPa for up to 6 days. Optimal pressure for milk HS was found to be 150 MPa, since no clotting was detected for up to 6 days. 150 MPa-HS caused the irreversible inactivation of inoculated Escherichia coli (5.13 ± 0.33 logCFU mL-1) and Staphylococcus aureus (5.66 ± 0.93 logCFU mL-1) within 2 and 6 days, respectively. Inactivation of total and faecal coliforms (3.0 log reductions) below the detection limit was achieved after just 2 days, whereas lactic acid bacteria and coagulase-positive Staphylococci were inactivated after 6 days. Pressurized storage also caused an increase in proteose peptones and the release of submicelles from casein micelles. Micelles progressively aggregated with pressure-unfolded ß-Lactoglobulin. These phenomena led to milk presenting up to 4-fold better foaming capacity, probably due to ß-Lactoglobulin unfolding or higher proteose peptones content. This work demonstrated the capability of HS to guarantee milk preservation during storage, and brought attention on the opportunity to consider the technology for milk pasteurization and functionality improvement.

T7-lac promoter vectors spontaneous derepression caused by plant-derived growth media may lead to serious expression problems: a systematic evaluation.

BACKGROUND: The widespread usage of protein expression systems in Escherichia coli (E. coli) is a workhorse of molecular biology research that has practical applications in biotechnology industry, including the production of pharmaceutical drugs. Various factors can strongly affect the successful construction and stable maintenance of clones and the resulting biosynthesis levels. These include an appropriate selection of recombinant hosts, expression systems, regulation of promoters, the repression level at an uninduced state, growth temperature, codon usage, codon context, mRNA secondary structure, translation kinetics, the presence/absence of chaperons and others. However, optimization of the growth medium's composition is often overlooked. We systematically evaluate this factor, which can have a dramatic effect on the expression of recombinant proteins, especially those which are toxic to a recombinant host. RESULTS: Commonly used animal tissue- and plant-based media were evaluated using a series of clones in pET vector, containing expressed Open Reading Frames (ORFs) with a wide spectrum of toxicity to the recombinant E. coli: (i) gfpuv (nontoxic); (ii) tp84_28-which codes for thermophilic endolysin (moderately toxic); and (iii) tthHB27IRM-which codes for thermophilic restriction endonuclease-methyltransferase (REase-MTase)-RM.TthHB27I (very toxic). The use of plant-derived peptones (soy peptone and malt extract) in a culture medium causes the T7-lac expression system to leak. We show that the presence of raffinose and stachyose (galactoside derivatives) in those peptones causes premature and uncontrolled induction of gene expression, which affects the course of the culture, the stability of clones and biosynthesis levels. CONCLUSIONS: The use of plant-derived peptones in a culture medium when using T7-lac hybrid promoter expression systems, such as Tabor-Studier, can lead to uncontrolled production of a recombinant protein. These conclusions also extend to other, lac operator-controlled promoters. In the case of proteins which are toxic to a recombinant host, this can result in mutations or deletions in the expression vector and/or cloned gene, the death of the host or highly decreased expression levels. This phenomenon is caused by the content of certain saccharides in plant peptones, some of which (galactosides) may act as T7-lac promoter inducer by interacting with a Lac repressor. Thus, when attempting to overexpress toxic proteins, it is recommended to either not use plant-derived media or to use them with caution and perform a pilot-scale evaluation of the derepression effect on a case-by-case basis.

Evaluation of the impact of buffered peptone water composition on the discrimination between Salmonella enterica and Escherichia coli by Raman spectroscopy.

The detection of Salmonella spp. in food samples is regulated by the ISO 6579:2002 standard, which requires that precise procedures are followed to ensure the reliability of the detection process. This standard requires buffered peptone water as a rich medium for the enrichment of bacteria. However, the effects of different brands of buffered peptone water on the identification of microorganisms by Raman spectroscopy are unknown. In this regard, our study evaluated the discrimination between two bacterial species, Salmonella enterica and Escherichia coli, inoculated and analyzed with six of the most commonly used buffered peptone water brands. The results showed that bacterial cells behaved differently according to the brand used in terms of biomass production and the spectral fingerprint. The identification accuracy of the analyzed strains was between 85% and 100% depending on the given brand. Several batches of two brands were studied to evaluate the classification rates between the analyzed bacterial species. The chemical analysis performed on these brands showed that the nutrient content was slightly different and probably explained the observed effects. On the basis of these results, Raman spectroscopy operators are encouraged to select an adequate culture medium and continue its use throughout the identification process to guarantee optimal recognition of the microorganism of interest.

Single chamber air-cathode microbial fuel cells as biosensors for determination of biodegradable organics.

OBJECTIVES: Single chamber air cathode microbial fuel cells (MFCs) were investigated with sodium-acetate and peptone as test substrates to assess the potential for application as biosensor to determine the concentration of biodegradable organics in water/wastewater samples. RESULTS: MFCs provided well-reproducible performance at high (> 2000 mg COD l-1-Chemical Oxygen Demand) acetate concentration values. Current in the cells proved to be steady from 25 to 35 °C, significant decrease was, however, revealed in the current below 20 °C. Direct calculation of non-toxic biodegradable substrate concentration in water/wastewater from the current in MFCs is possible only in the non-saturated substrate concentration range due to the Monod-like dependence of the current. This range was determined by a fitted and verified Monod-based kinetic model. Half saturation constant (KS) values were calculated at 30 °C applying different external resistance values (100 Ω, 600 Ω and 1000 Ω, respectively). In each case KS remained below 10 mg COD l-1. CONCLUSIONS: Biosensors with this particular MFC design and operation are potentially applicable for detecting as low as 5 mg COD l-1 readily biodegradable substrates, and measuring the concentration of these substances up to ~ 50-70 mg COD l-1.

[Screening, identification and fermentation optimization of a collagenase-producing strain and purification of the collagenase].

Objective: The purpose of this study was to isolate novel strains from the soil nearby meat processing factories to produce collagenase. After the yield of collagenase from the strain improved, the collagenase was purified and used for hydrolyzing collagen. Methods: The strain was identified based on morphological features, physiological and biochemical characteristics and 16S rRNA gene phylogenetic tree analysis. The yield of collagenase was increased by optimizing the fermentation condition, and the collagenase isolated from the fermentation supernatant of the strain was finally purified with strong anion exchange resins. Results: The collagenase-producing strain was identified as Bacillus cereus. The optimized fermentation conditions of the strain were: 2.0% glucose as optimum carbon source, 1.5% tryptone as optimum nitrogen source, 0.005% of Ca2+ as optimum metal ion. The optimum temperature and pH were 37 ℃ and 7.5, respectively. Under the optimum conditions, the enzyme activity of collagenase was (65.81±2.06) U/mL, 1.5-fold increased than that before the optimization. After purified with strong anion exchange resins, a collagenase with the purity higher than 90%, the molecular weight about 100 kDa, and the specific activity of 7615.0±78.7 U/mg was obtained. Conclusion: The activity of Bacillus cereus collagenase was higher than the reported collagenases. Using this novel collagenase, collagen could be degraded into short biological peptides in a short time. Hence, this collagenase has application prospects in many fields, such as food, medical, health care products and cosmetics.

Pressure resistance of cold-shocked Escherichia coli O157:H7 in ground beef, beef gravy and peptone water.

AIMS: (i) To study the effects of cold shock on Escherichia coli O157:H7 cells. (ii) To determine if cold-shocked E. coli O157:H7 cells at stationary and exponential phases are more pressure-resistant than their non-cold-shocked counterparts. (iii) To investigate the baro-protective role of growth media (0·1% peptone water, beef gravy and ground beef). METHODS AND RESULTS: Quantitative estimates of lethality and sublethal injury were made using the differential plating method. There were no significant differences (P > 0·05) in the number of cells killed; cold-shocked or non-cold-shocked. Cells grown in ground beef (stationary and exponential phases) experienced lowest death compared with peptone water and beef gravy. Cold-shock treatment increased the sublethal injury to cells cultured in peptone water (stationary and exponential phases) and ground beef (exponential phase), but decreased the sublethal injury to cells in beef gravy (stationary phase). CONCLUSIONS: Cold shock did not confer greater resistance to stationary or exponential phase cells pressurized in peptone water, beef gravy or ground beef. Ground beef had the greatest baro-protective effect. SIGNIFICANCE AND IMPACT OF THE STUDY: Real food systems should be used in establishing food safety parameters for high-pressure treatments; micro-organisms are less resistant in model food systems, the use of which may underestimate the organisms' resistance.

Evaluación de la peptona papaínica de corazón de res para el enriquecimiento selectivo de Enterococcus / Evaluation of beef heart papainic peptone for selective enrichment of Enterococcus

Introducción: el control microbiológico de aguas y alimentos ha motivado el desarrollo de medios de cultivo selectivos capaces de detectar Enterococcus, los cuales necesitan de una fuente de energía apropiada para garantizar la recuperación de estos. Objetivos: comparar diferentes bases nutritivas elaboradas a partir de productos y subproductos alimenticios según su capacidad de promoción de crecimiento del género Enterococcus y evaluar la exactitud del medio de cultivo caldo azida dextrosa. Métodos: para el ensayo se seleccionaron 80 cepas de diferentes géneros. Se prepararon dos variantes experimentales del caldo azida dextrosa (una tamponada) y se inocularon los microorganismos seleccionados a una concentración estandarizada. El incremento de la biomasa se determinó midiendo la densidad óptica en un espectrofotómetro a 640 nm cada una hora. La evaluación microbiológica del medio de cultivo se realizó utilizando diferentes géneros microbianos a distintas concentraciones. Se determinó la sensibilidad, especificidad, exactitud diagnóstica y relativa y el índice Kappa del diagnosticador. Como medio de referencia se utilizó el caldo azida glucosa proveniente de la firma comercial Merck (Alemania). ..

Introduction: microbiological control of water and food has motivated the development of selective culture media capable of detecting Enterococcus, which need an appropriate source of energy to ensure the recovery of microorganisms. Objectives: compare different nutrient bases produced from food products and by-products according to their growth promotion capacity for the genus Enterococcus, and evaluate the accuracy of dextrose azide broth culture medium. Methods: eighty strains of different genera were selected for the test. Two experimental variants of dextrose azide broth were prepared (one buffered) and the microorganisms selected were inoculated at a standardized concentration. Biomass increase was determined by measuring optical density in a spectrophotometer at 640 nm every 1 h. Microbiological evaluation of the culture medium was carried out using different microbial genera at different concentrations. Diagnostic and relative sensitivity, specificity and accuracy, and the Kappa index were determined for the culture medium. Glucose azide broth (Merck, Germany)ss production than the other genera...

Evaluación de la peptona papaínica de corazón de res para el enriquecimiento selectivo de Enterococcus / Evaluation of beef heart papainic peptone for selective enrichment of Enterococcus

Introducción: el control microbiológico de aguas y alimentos ha motivado el desarrollo de medios de cultivo selectivos capaces de detectar Enterococcus, los cuales necesitan de una fuente de energía apropiada para garantizar la recuperación de estos. Objetivos: comparar diferentes bases nutritivas elaboradas a partir de productos y subproductos alimenticios según su capacidad de promoción de crecimiento del género Enterococcus y evaluar la exactitud del medio de cultivo caldo azida dextrosa. Métodos: para el ensayo se seleccionaron 80 cepas de diferentes géneros. Se prepararon dos variantes experimentales del caldo azida dextrosa (una tamponada) y se inocularon los microorganismos seleccionados a una concentración estandarizada. El incremento de la biomasa se determinó midiendo la densidad óptica en un espectrofotómetro a 640 nm cada una hora. La evaluación microbiológica del medio de cultivo se realizó utilizando diferentes géneros microbianos a distintas concentraciones. Se determinó la sensibilidad, especificidad, exactitud diagnóstica y relativa y el índice Kappa del diagnosticador. Como medio de referencia se utilizó el caldo azida glucosa proveniente de la firma comercial Merck (Alemania). ..

Introduction: microbiological control of water and food has motivated the development of selective culture media capable of detecting Enterococcus, which need an appropriate source of energy to ensure the recovery of microorganisms. Objectives: compare different nutrient bases produced from food products and by-products according to their growth promotion capacity for the genus Enterococcus, and evaluate the accuracy of dextrose azide broth culture medium. Methods: eighty strains of different genera were selected for the test. Two experimental variants of dextrose azide broth were prepared (one buffered) and the microorganisms selected were inoculated at a standardized concentration. Biomass increase was determined by measuring optical density in a spectrophotometer at 640 nm every 1 h. Microbiological evaluation of the culture medium was carried out using different microbial genera at different concentrations. Diagnostic and relative sensitivity, specificity and accuracy, and the Kappa index were determined for the culture medium. Glucose azide broth (Merck, Germany)ss production than the other genera...

Amylase production by endophytic fungi Cylindrocephalum sp. isolated from medicinal plant Alpinia calcarata (Haw.) Roscoe

Amylases are among the most important enzymes used in modern biotechnology particularly in the process involving starch hydrolysis. Fungal amylase has large applications in food and pharmaceutical industries. Considering these facts, endophytic fungi isolated from the plant Alpinia calcarata (Haw.) Roscoe were screened for amylolytic activity on glucose yeast extract peptone agar (GYP) medium. Among thirty isolates of endophytic fungi, isolate number seven identified as Cylindrocephalum sp. (Ac-7) showed highest amylolytic activity and was taken for further study. Influence of various physical and chemical factors such as pH, temperature, carbon and nitrogen sources on amylase production in liquid media were studied. The maximal amylase production was found to be at 30ºC and at pH 7.0 of the growth medium. Among the various carbon and nitrogen sources tested, maltose at 1.5% and Sodium nitrate at 0.3% respectively gave optimum amylase production.

Production of cellulase by Aspergillus niger under submerged and solid state fermentation using coir waste as a substrate

Aspergillus niger was used for cellulase production in submerged (SmF) and solid state fermentation (SSF). The maximum production of cellulase was obtained after 72 h of incubation in SSF and 96 h in Smf. The CMCase and FPase activities recorded in SSF were 8.89 and 3.56 U per g of dry mycelial bran (DBM), respectively. Where as in Smf the CMase & FPase activities were found to be 3.29 and 2.3 U per ml culture broth, respectively. The productivity of extracellular cellulase in SSF was 14.6 fold higher than in SmF. The physical and nutritional parameters of fermentation like pH, temperature, substrate, carbon and nitrogen sources were optimized. The optimal conditions for maximum biosynthesis of cellulase by A. niger were shown to be at pH 6, temperature 30 ºC. The additives like lactose, peptone and coir waste as substrate increased the productivity both in SmF and SSF. The moisture ratio of 1:2 (w/v) was observed for optimum production of cellulase in SSF.

Acidibility established as a characteristic of high strength organic wastewater quality.

Acidification processes of the alcohol wastewater on molasses and the sugar-peptone manual make-up water were studied to determine their acidification capability. The two types of wastewater were both diluted into serial gradient dilutions and acidified separately. The volatile fatty acids (VFAs) and were detected daily until acidification reached a maximum state. The degraded COD in each dilution, which were considered as degraded VFAs and analyzed. The ratio of the sum of produced VFAs and degraded VFAs to the initial COD of dilutions was defined as acidibility (V/C). It showed that within a large concentration extent, the V/C values were consistent for different dilutions of each wastewater. Thus acidibility becomes a characteristic of high strength organic wastewater quality. The acidibility of the alcohol wastewater on molasses was analyzed to be 0.71, and the acidibility of sugar-peptone manual make-up water was 0.76. In a practicable view, it is meaningful to set up acidibility as a new water quality index, which can be used to guide the design of acidification technique in various high concentration organic wastewater treatment practices.

Sorption of organic contaminants by carbon nanotubes: influence of adsorbed organic matter.

Sorption of three types of dissolved organic matter (DOM; i.e., humic acid, peptone and alpha-phenylalanine) by a mutiwalled carbon nanotube (MWNT40) and sorption of phenanthrene (Phen), naphthalene (Naph), and 1-naphthol (1-Naph) by the original and DOM-coated MWNT40 were examined. Sorption data of Phen, Naph, and 1-Naph by all sorbents were fitted with Freundlich and Polanyi models. MWNT40 had nonlinear isotherms for all DOMs examined. Sorption of DOMs by MWNT40 followed the order peptone > humic acid > alpha-phenylalanine. The humic acid used in this study had much lower sorption for Phen, Naph, and 1-Naph than MWNT40, but its coating did not make striking changes on sorption of these compounds by MWNT40, suggesting that humic acid coating dramatically altered the physical form and surface properties of MWNT40. Peptone coating made the strongest suppression on sorption of Phen, Naph, and 1-Naph by MWNT40 among the three DOMs used, due to its highest sorption on MWNT40, thus causing a great reduction in accessibility of sorption sites. Polanyi modeling results showed that reduction in the maximum volume sorption capacity (Q0) of MWNT40 induced by DOM coating followed the order Phen < Naph < 1-Naph. 1-Naph was less hydrophobic than Phen and Naph but it had much higher sorbed volume (V(m)) than Phen and Naph at individual RT In(S(w)/C(e))/V(s)points for all sorbents. The correlation curve for the Polanyi model was applicable for sorption of aromatic compounds of similar structure by the original and DOM-coated carbon nanotubes.

Menstrum for culture preservation and medium for seed preparation in a tetanus toxin production process containing no animal or dairy products.

AIMS: To completely eliminate animal and dairy products from the lyophilization menstrum and the seed medium used to produce tetanus toxin with Clostridium tetani. METHODS AND RESULTS: Tetanus toxin production in a recently developed fermentation medium lacking animal and dairy products was studied with different seed media. It was found that soy peptone could completely replace the beef heart infusion plus animal peptone previously used as seed medium. In addition, we found that cells lyophilized in soy milk could replace the usual type of cells lyophilized in cow's milk. CONCLUSIONS: We have now developed a complete tetanus toxin production process containing no animal and dairy products. SIGNIFICANCE AND IMPACT OF THE STUDY: Toxoid preparations made from toxin produced with animal and dairy products can contain undesirable contaminants such as the prion causing bovine spongiform encephalopathy (Mad Cow's Disease) or antigenic peptides that stimulate anaphylactic reactions and other undesirable immune reactions in immunized hosts. The new vegetable-based process described here avoids such unfortunate possibilities.

Sugarcane molasses and yeast powder used in the Fructooligosaccharides production by Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611.

Different concentrations of sucrose (3-25% w/v) and peptone (2-5% w/v) were studied in the formulation of media during the cultivation of Aspergillus japonicus-FCL 119T and Aspergillus niger ATCC 20611. Moreover, cane molasses (3.5-17.5% w/v total sugar) and yeast powder (1.5-5% w/v) were used as alternative nutrients for both strains' cultivation. These media were formulated for analysis of cellular growth, beta-Fructosyltransferase and Fructooligosaccharides (FOS) production. Transfructosylating activity (U ( t )) and FOS production were analyzed by HPLC. The highest enzyme production by both the strains was 3% (w/v) sucrose and 3% (w/v) peptone, or 3.5% (w/v) total sugars present in cane molasses and 1.5% (w/v) yeast powder. Cane molasses and yeast powder were as good as sucrose and peptone in the enzyme and FOS (around 60% w/w) production by studied strains.

Molecular characterization of thermostable direct haemolysin-related haemolysin (TRH)-positive Vibrio parahaemolyticus from oysters in Mangalore, India.

Pathogenic Vibrio parahaemolyticus strains producing either or both of a thermostable direct haemolysin (TDH) and a TDH-related haemolysin (TRH) encoded by tdh and trh genes, respectively, are isolated at a low rate from the environment. However, recently we observed that a considerable percentage of APW (alkaline peptone water) enrichment broths of oysters collected off Mangalore India, were trh(+), rather than tdh(+) by PCR. In order to further investigate the prevalence and genetic diversity of trh bearing V. parahaemolyticus in our coast, we attempted to isolate and characterize trh(+)V. parahaemolyticus from oysters. A total of 27 trh(+) strains were isolated during the period between March 2002 and February 2004, of which nine were also tdh(+). All the trh(+) isolates were positive for urease phenotype. The isolates belonged to diverse phenotypes. In order to explore the possible presence of heterogeneity in the trh gene region among trh(+)V. parahaemolyticus, a 1.5 kb region around trh gene was PCR amplified and restriction digested using selected restriction enzymes. The whole genome comparison of strains was performed by randomly amplified polymorphic DNA PCR (RAPD PCR). The PCR-RFLP results revealed fairly well conserved nature of the trh gene region studied in different serotypes. Though 11 strains were positive by PCR for a genomic fragment that has been reported to be amplified in pandemic strains, all strains were negative by group-specific PCR (GS-PCR), orf8 PCR and showed a different RAPD pattern compared with pandemic strains. The results suggest that genetically diverse V. parahaemolyticus carrying virulence genes are associated with the aquatic environment in this region.

Antibacterial activity of pepsin-digested lactoferrin on foodborne pathogens in buffered broth systems and ultra-high temperature milk with EDTA.

AIMS: To evaluate the antimicrobial activity in peptone yeast extract glucose (PYG) broth and ultra-high temperature (UHT) milk of bovine lactoferrin hydrolysate (LFH) with pepsin against the foodborne pathogens Salmonella Stanley, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. METHODS AND RESULTS: The LFH was suspended in PYG and the minimum inhibitory concentration for each pathogen determined. The LFH was also suspended in UHT milk adjusted to pH 4 or 7, samples incubated at 4 or 35 degrees C and the change in bacterial cell population determined. Experiments in UHT milk were conducted using L. monocytogenes and E. coli O157:H7. At pH 4 LFH reduced the population of E. coli O157:H7 and L. monocytogenes by approx. 2 log; however, only E. coli O157:H7 was inhibited in samples adjusted to pH 7. The addition of EDTA (10 mg ml(-1)) to UHT milk supplemented with LFH did not markedly influence the growth of E. coli O157:H7 or L. monocytogenes. CONCLUSIONS: The results suggest that, under low pH and refrigeration conditions, LFH can limit the growth or reduce the population of pathogenic bacteria in a dairy product. SIGNIFICANCE AND IMPACT OF THE STUDY: Natural preservatives that are active against Gram-negative and Gram-positive bacteria are desirable to the food industry. This study demonstrates that LFH is effective in a complex food system. Moreover, the LFH used was not purified, making its use by industry more attractive.

A comparison of human dental plaque microcosm biofilms grown in an undefined medium and a chemically defined artificial saliva.

The growth and pathogenic properties of dental plaque result from interactions between the microbiota and the oral environment and have been studied in laboratory experimental systems ranging from single or a few species (such as in chemostats) to dental plaque microcosms. Microcosm plaque is an in vitro version of natural plaque and has been explored as a microflora model because it is sited a more manipulable and controllable environment. It is obtained as microcosm biofilms in an 'artificial mouth' plaque culture system by culturing the bacteria in natural plaque-enriched saliva (i.e. salivary bacteria where a whole-saliva donor has abstained from oral hygiene for 24 h to increase the plaque bacteria in the saliva). The aim here was to examine whether a new, chemically defined analogue of saliva (defined medium mucin, DMM) could substitute for a previously used, chemically undefined medium (basal medium mucin, BMM) as an analogue of saliva for large-scale biofilm culturing. DMM contains various ions, mucin, amino acids, vitamins and growth factors at concentrations generally similar to those in saliva, whereas BMM contains yeast extract, peptones and mucin. To model the nutrient functions of salivary proteins, amino acids equivalent to 5 g/l casein were also included in DMM. In earlier studies, BMM-grown plaques were similar to natural plaques in structure, composition, growth rate and pH response to substrates. Their doubling-time patterns over a 20-day period were similar, except that the DMM-grown plaques showed biphasic growth patterns that were more pronounced than with BMM. Variation in enzyme profiles between BMM- and DMM-grown plaque, measured using the API-ZYM technique, provided evidence of nutritional effects on plaque composition. It was concluded that realistic growth rates and patterns are generated in microcosm plaque biofilms by supplying both DMM and BMM. However, the use of DMM enables specific modifications to be made to nutrient conditions during large-scale culture in our 'artificial mouth' biofilm system.

Efectividad de clorogenos destinadosa agua de consumo / Efectiveness of chlorogenic products destinated to drinking waters

Se propone una metodología para la evaluación de productos clorógenos destinados a la desinfección de aguas para consumo, utilizando materia orgánica para simular el consumo de cloro que tienen las aguas no tratadas. Se evaluó el comportamiento de suspensión de levadura de cerveza, peptona y extracto de levadura frente a dosis usuales (10 mg/L, como cloro total) de comprimidos de la sal disódica de la dicloro-S-triazina-triona. Como comparación se utilizó agua de río.Se determinó la concentración de cada sustancia orgánica que despues de 30 minutos dejó 0,1 mg/L de cloro libre en la solución de ensayo. Posteriormente se ensayó microbiologicamente la efectividad del clorógeno en presencia de dichas sustancias según metodología AFNOR (AU)

Simultaneous separation and quantitation of the major bovine whey proteins including proteose peptone and caseinomacropeptide by reversed-phase high-performance liquid chromatography on polystyrene-divinylbenzene.

A precise, sensitive and reliable RP-HPLC method was developed to enable not only unequivocal determination of alpha-lactalbumin and beta-lactoglobulin in bovine whey samples, but also simultaneous measurement of proteose peptone, caseinomacropeptide, bovine serum albumin and immunoglobulin G. The optimised method on the Resource RPC column allowed separation of the proteins in 30 min and could be applied to the analysis of soluble proteins in a variety of commercial and laboratory whey products. Furthermore, some qualitative information on protein heterogeneity and quality could be derived from the RP-HPLC analyses with additional data available from on-line electrospray mass spectrometry. Within- and between-day repeatability over a wide range of concentrations was excellent (RSD< or =5%) for all proteins except immunoglobulin G and bovine serum albumin where RSD was 7-10%. Analysis of grouped data from whey protein concentrate and whey protein isolate samples gave a limit of detection of < or =0.3% powder mass and a limit of quantitation of < or =1.0% powder mass for all proteins except immunoglobulin G. Limits of detection and quantitation were 0.6% and 2.0%, respectively, for this protein. Quantitative data obtained by the RP-HPLC method compared very favourably with data obtained by alternative methods of whey protein analysis.

Comparison of nitrogen-15 and purines as microbial markers in continuous culture.

Eight dual-flow continuous-culture fermenters were used in four replicated periods to compare the effects of diet and microbial marker on estimates of N metabolism in continuous culture of ruminal microorganisms. A basal diet was supplemented with urea and tryptone, soybean meal (SBM), lignosulfonate-treated SBM, corn gluten meal, blood meal (BM), hydrolyzed feather meal, fish meal (FM), or meat and bone meal (MBM). Microbial protein flow and protein degradation in fermenters were estimated using purines, purine N, and 15N in bacteria obtained from fermenter flasks or from the effluent. The ratio of purine N to total N in bacteria averaged .083 and was not affected (P > .05) by treatment. Dietary purine content (percentage of DM) ranged from .033 in BM to .084 in FM. Escape of feed purine N (percentage of total purine N flow) averaged 1.7% (SE = 2.9) and was not different (P > .05) among treatments. Bacterial N flows obtained using purines were more variable than estimates obtained using 15N. Bacterial N flows calculated using 15N in bacteria isolated from fermenters were more variable than those obtained using bacteria isolated from the effluent. The use of purines as a microbial marker resulted in lower estimates of protein degradation and smaller differences among treatments compared with use of 15N. Data suggest that escape of feed purine N seems to be a minor factor affecting calculation of bacterial N flow and that the use of 15N in effluent bacteria may be a more accurate procedure when using continuous-culture fermenters.