PubMed Health⌕ Search

Biomedical subjects

F M Rombouts

Publications and source records attributed to F M Rombouts.

85 records · Page 5Linked to original sources
PubMed1991

Enzyme-linked immunoassays for the detection of Salmonella spp.: a comparison with other methods.

The first enzyme immunoassay for Salmonella was reported in 1977 and since that time several enzyme-linked immuno assays (ELISAs) have been developed, using either polyclonal or monoclonal antibodies that will detect most Salmonella serotypes. Two of these kits have been declared official first status by the Association of Official Analytical Chemists (AOAC). In comparison with a culture method used in collaborative studies, the total assay time is reduced by 2 days and statistical analysis of the data indicated no significant difference. The main problem related to all methods other than traditional culture methods is the occurrence of false-positive and/or false-negative results. False-positive ELISA results can be eliminated by using (combinations of) highly specific monoclonal antibodies. Good enrichment procedures are very important to be sure that the detection limit of approx. 10(5) cells/ml will be reached. In the future even better limits of detection may be achieved by using enzyme amplification or chemiluminescence to decrease the number of false-negative results.

Enzyme-Linked Immunosorbent Assay↗
PubMed1990

Modeling of the bacterial growth curve.

Several sigmoidal functions (logistic, Gompertz, Richards, Schnute, and Stannard) were compared to describe a bacterial growth curve. They were compared statistically by using the model of Schnute, which is a comprehensive model, encompassing all other models. The t test and the F test were used. With the t test, confidence intervals for parameters can be calculated and can be used to distinguish between models. In the F test, the lack of fit of the models is compared with the measuring error. Moreover, the models were compared with respect to their ease of use. All sigmoidal functions were modified so that they contained biologically relevant parameters. The models of Richards, Schnute, and Stannard appeared to be basically the same equation. In the cases tested, the modified Gompertz equation was statistically sufficient to describe the growth data of Lactobacillus plantarum and was easy to use.

Journal Article↗
PubMed1989

Effect of accelerated natural lactic fermentation of infant food ingredients on some pathogenic microorganisms.

Accelerated natural lactic fermentation in mixtures of water and ground sorghum, millet and pigeon pea was obtained by gradual selection of lactic acid bacteria, through inoculum recycling. Weaning food prepared from ingredients fermented this way, contained approx. 0.7% lactic and 0.05% acetic acids and had a pH of about 3.8. In porridges, a pH of less than or equal to 4.0 was required to cause death of Salmonella typhimurium and Staphylococcus aureus. Several intestinal pathogenic bacteria were inoculated into sour porridge. The most resistant Salmonella sp. died at a rate of 1.2 log cycle/h; the most resistant Shigella sp. at 0.9 log cycle/h; and the most resistant Escherichia coli strain at 0.6 log cycle/h. A yeast, Candida albicans, could grow well in the sour product, whereas a bacteriophage (MS-2) was inactivated at a rate of 0.1 log cycle/h. In the acid-sensitive bacterial cultures, no gradual adaptation to acid environments could be observed. The survival studies were carried out at 30 degrees C.

Bacteria↗
PubMed1988

Effect of environmental conditions during soya-bean fermentation on the growth of Staphylococcus aureus and production and thermal stability of enterotoxins A and B.

During tempe manufacture, Staphylococcus aureus was able to survive in newly started soya-bean soaks (final pH 4.7), whereas it died during soaks with accelerated souring (final pH 4.0). No S. aureus were detected after subsequent heat treatment of soaked beans. S. aureus strain S6 could produce enterotoxins A and B if inoculated on cooked soya-beans. Its growth and enterotoxin production were not influenced by inoculation rate nor by the presence of actively growing Rhizopus oligosporus, the fungus responsible for tempe formation. Enterotoxin levels were highest after 48 h fermentation. Presence of lactobacilli (L. brevis or L. plantarum) during the tempe fermentation did not influence staphylococcal growth, but enterotoxin levels were reduced. Reduced oxygen pressure did not affect staphylococcal growth, but resulted in lower enterotoxin levels after 48 h incubation. The thermal stability of enterotoxin A in tempe was significantly lower than in Brain Heart Infusion broth of comparable pH. Heating of enterotoxin-containing tempe mash reduced enterotoxin A by 99.7% as measured with ELISA and animal feeding methods.

Animals↗
PubMed1987

Purification and properties of extracellular polysaccharide (EPS) antigens produced by different mould species.

Extracellular polysaccharide (EPS) antigens produced by different mould species were purified and partially characterized. Purification included (NH4)2SO4 treatment, Sepharose CL-4B column chromatography and Con A-sepharose chromatography. The EPS of Penicillium digitatum, Mucor racemosus and Cladosporium cladosporioides showed high antigenic capacities. Immunologically the EPS were partially genus-specific, but cross-reactivity was observed. The EPS antigens produced by species of Penicillium, Aspergillus repens and Geotrichum candidum lost their immunological activity upon heating (100 degrees C) at pH 1.8, while the EPS antigen of M. racemosus, Rhizopus oligosporus and C. cladosporioides were stable under the same conditions. The dominant monosaccharides present in the EPS antigen were mannose, galactose and glucose. The EPS obtained from cultures of M. racemosus and R. oligosporus also contained rhamnose. In the EPS produced by Penicillium spp. and A. repens the galactose residues were determined to be immunodominant.

Antibodies, Fungal↗
PubMed1985

Polysaccharides and food processing.

The rôle of polysaccharides during processing and for the quality of foods is discussed. Starch is the most important energy source for man. Most other polysaccharides are not metabolized for energy, but play an important rôle as dietary fibres. Pectins, alginates, carrageenans, and galactomannans are discussed as functional food additives in relation to their structure and their rheological behaviour, stability and interactions. Endogenous polysaccharides of fruits and vegetables and in products derived from them are responsible for such phenomena as texture (changes), press yields, ease of filtration and clarification, cloud stability, and mouth feel. To achieve desirable properties, the action of endogenous enzymes on polysaccharides must be inactivated and/or exogenous enzymes added as processing aids. This is also true for overcoming haze phenomena in clear juices or to break down undesirable microbial polysaccharides. Dough properties for bread baking can be improved by enzymic breakdown of a restrictive pentoglycan network. Network formation may come about by oxidative coupling of phenol rings of ferulic acid bound to hemicelluloses by ester links. Gels may be made by inducing oxidative coupling in natural or synthetic systems. Stagnation in development of new polysaccharide food additives is ascribed to difficulties in obtaining government approval for food use.

Carbohydrate Conformation↗
PubMed1985

The cellulase of Trichoderma viride. Purification, characterization and comparison of all detectable endoglucanases, exoglucanases and beta-glucosidases.

Six endoglucanases (Endo I; II; III; IV; V; VI), three exoglucanases (Exo I; II; III) and a beta-glucosidase (beta-gluc I) were isolated from a commercial cellulase preparation derived from Trichoderma viride, using gel filtration on Bio-Gel, anion exchange on DEAE-Bio-Gel A, cation exchange on SE-Sephadex and affinity chromatography on crystalline cellulose. Molecular masses were determined by polyacrylamide gel electrophoresis. One group of endoglucanases (Endo I, Endo II and Endo IV) with Mr of 50 000, 45 000 and 23 500 were more random in their attack on carboxymethylcellulose than another group (Endo III, Endo V and Endo VI) showing Mr of 58 000, 57 000 and 53 000 respectively. Endo III was identified as a new type of endoglucanase with relatively high activity on crystalline cellulose and moderate activity on carboxymethylcellulose. Exo II and Exo III with Mr of 60 500 and 62 000 respectively showed distinct adsorption affinities on a column of crystalline cellulose and could be eluted by a pH gradient to alkaline regions. These enzymes were cellobiohydrolases as judged by high-pressure liquid chromatography of the products obtained from incubation with H3PO4-swollen cellulose. It was concluded that these exoglucanases are primarily active on newly generated chain ends. Exo I was essentially another type of exoglucanase which in the first instance was able to split off a cellobiose molecule from a chain end and then hydrolyse this molecule in a second step to two glucose units beta-Gluc I was a new type of aryl-beta-D-glucosidase which had no activity on cellobiose. The enzyme had a Mr of 76 000 and was moderately active on CM-cellulose, crystalline cellulose and xylan and highly active on p-nitrophenyl-beta-D-glucose and p-nitrophenyl-beta-D-xylose.

Cellulase↗
PubMed1976

Lysis of yeast cell walls. Lytic beta-(1 leads to 6)-glucanase from Bacillus circulans WL-12.

When grown in a mineral medium with yeast cell walls or yeast glucan as the sole carbon source, Bacillus circulans WL-12 produces wall-lytic enzymes in addition to non-lytic beta-(1 leads to 3) and beta-(1 leads to 6)-glucananases. The lytic enzymes were isolated from the culture liquid by adsorption on insoluble yeast glucan in batch operation. After digestion of the glucan, the mixture of enzymes was chromatographed on hydroxylapatite on which the lytic activity could be resolved into one lytic beta-(1 leads to 6)glucanase and two lytic beta-(1 leads to 3)-glucanase was further purified by chromatography over diethylamino-ehtyl-agarose and carboxymethyl cellulose. Its specific activity on pustulan was 6.2 units per mg of protein. The enzyme moved as a single protein with a molecular weight of 54000 during sodium dodecylsulphate electrophoresis in slab gels. Hydrolysis of pustulan went thorugh a series of oligosaccharides, leading to a mixture of gentiotriose, gentiobiose and glucose. The enzyme also produced small amounts of gentiobiose from laminarin and pachyman and on this basis its lytic activity on yeast cell walls,was attribut beta-(1 leads to 3)-linked oligosaccharides were not detected. The lytic beta-(1 leads to 6)-glucanase has an optimum pH of 6.0. Pustulan hydrolysis followed Michaelis-Menten kinetics. A Km of 0.29 mg pustulan per ml and a V of 9.1 micro-equivalents of glucose released/min per mg of enzyme were calculated. The enzyme has no metal ion requirement. The lytic beta-(1 leads to 6)-glucanase differs in essence from the non-lytic beta-(1 leads to 6)-glucanase of the same organism by its positive action on yeast cell walls and yeast glucan and its much lower specific activity on soluble pustulan.

Bacillus↗
PubMed1976

Lysis of yeast cell walls. Lytic beta-(1 leads to 3)-glucanases from Bacillus circulans WL-12.

Bacillus circulans WL-12 when grown in a mineral medium with yeast cell walls or yeast glucan as the soli carbon source, produced five beta-glucanases. Two beta-(1 leads to 3)-glucanases (I and II), which are lytic to yeast cell walls, were isolated from the culture liquid by batch adsorption on yeast glucan, and separated by chromatography on hydroxylapatite. Lytic beta-(1 leads to 3)-glucanase I was further purified by carboxymethylcellulose chromatography. The specific activity of lytic beta-(1 leads to 3)-glucanase I on laminarin was 4.1 U per mg of protein. The enzyme moved as a single protein with a molecular weight of 40000 during sodium dodecylsulfate electrophoresis in slab gels. It was specific for the beta-(1 leads to 3)-glucosidic bond but the enzyme did not hydrolyze laminaribiose. Hydrolysis of laminarin went through a series of oligosaccharides, and laminaribiose and glucose accumulated till the end of the reaction. A small amount of gentibiose was also produced from laminarin. Products from yeast cell walls and yeast glucan included laminaripentaose, laminaritriose, laminaribiose, glucose and gentiobiose, but no laminaritetraose was detected. This glucanase has an optimum pH of 5.5.

Bacillus↗
PubMedDate not supplied

Glucose and sucrose fermenting capacity of homofermentative lactic acid bacteria used as starters in fermented salads.

Salads, i.e., vegetables and/or meat in an oil-in-water emulsion with a low pH due to the addition of acids, are popular in western countries. The shelf life of these salads is influenced mainly by storage temperature and the use of preservatives, i.e., sorbic and benzoic acid. Lactic acid fermentation could be an interesting novel approach to salad preparation. As part of an investigation on fermented salads, lactic acid bacteria from the genera Lactobacillus, Pediococcus and Streptococcus were screened for their capacity to ferment glucose and sucrose in a model system and in a standard salad. The temperature optimum of these strains was in the range of 34-48 degrees C. Most of these strains produced about equal amounts of L(+)- and D(-)-lactic acid. To determine the specific sugar fermenting capacity (mmol lactic acid produced per min per g dry weight) of non-growing cells of lactic acid bacteria, a semi-automated model system was used, based on monitoring the pH decrease in a phosphate buffer during conversion of sugars to lactic acid. The strains tested showed acid production rates on glucose varying between 0.03 and 0.39 mmol of acid produced per min per g dry weight (average 0.23). These glucose-grown cells showed varying, but lower fermentation rates on sucrose (0-0.25 mmol/min/g d.w., average 0.04) than sucrose-grown cells (0-0.33 mmol/min/g d.w., average 0.19). Results obtained with the model system were in good agreement with those of fermentation tests, carried out with a standard salad. Inhibition of spoilage bacteria in the standard salad could be achieved by using starter cultures with high fermenting capacity.

Animals↗
PubMedDate not supplied

Campylobacter jejuni non-culturable coccoid cells.

The behaviour of Campylobacter jejuni in the environment is poorly documented. Rapid loss of viability on culture media is reported. This phenomenon is associated with the development of so-called coccoid cells. It has been suggested that these cells can be infective to animals and man. Results obtained with ATP-measurements of coccoid cells and Direct Viable Count (DVC) support this hypothesis. Introduction of coccoid cells into simulated gastric, ileal and colon environments did not result in the presence of culturable cells. Oral administration to laboratory animals and volunteers caused no typical symptoms of campylobacteriosis. Until 30 days after uptake of the cells antibodies against C. jejuni could not be detected in the blood, and the presence of this microorganism in stool samples could not be demonstrated.

Adenosine Triphosphate↗
PubMedDate not supplied

Fumonisin B1 in maize for food production imported in The Netherlands.

Sixty-two samples of maize imported in The Netherlands and intended for human consumption were screened for the presence and concentration of fumonisin B1. Sixty-one of those samples contained fumonisin B1 with concentrations ranging from 30 to 3350 micrograms kg-1, 11 maize samples contained > 1000 micrograms kg-1. The average fumonisin B1 concentration was 640 micrograms kg-1 for the positive samples and 620 micrograms kg-1 for all samples. Medians were 600 micrograms kg-1 and 550 micrograms kg-1 for positive and all samples, respectively. The results obtained were comparable to results from other studies in maize from various countries.

Carboxylic Acids↗