Production of organic acids from kitchen wastes

This study involves the production of short-chain organic acids from kitchen wastes as intermediates for the production of biodegradable plastics. Flasks, without mixing were used for the anaerobic conversion of the organic fraction of kitchen wastes into short-chain organic acids. The influence of pH, temperature and addition of sludge cake on the rate of organic acids production and yield were evaluated. Fermentations were carried out in an incubator at different temperatures controlled at 30 degrees C. 40 degrees C, 50 degrees C, 60 degrees C and uncontrolled at room temperature. The pH was also varied at pH 5, 6, 7, and uncontrolled pH. 1.0 M phosphate buffer was used for pH control, and 1.0 M HCl and 1.0 M NaOH were added when necessary. Sludge cake addition enhanced the rate of maximum acids production from 4 days to 1 day. The organic acids produced were maximum at pH 7 and 50 degrees C i.e., 39.84 g/l on the fourth day of fermentation with a yield of 0.87 g/g soluble COD consumed, and 0.84 g/g TVS. The main organic acid produced was lactic acid (65-85%), with small amounts of acetic (10-30%), propionic (5-10%), and butyric (5-20%) acids. The results of this study showed that kitchen wastes could be fermented to high concentration of organic acids, which could be used as substrates for the production of biodegradable plastics.     

The composition of natural latex fromHevea brasiliensis

Hevea brasiliensis latex collected by tapping can be considered as cytoplasm, in spite of the absence of nucleus and mitochondrial material. It possesses the complexity of cytoplasm both in its subcellular organization and the diversity of the constituent molecules. Its essential characteristic is the high rubber content. Rubber is a very long chaincis-polyisoprene polymer synthesized in the cytosol compartment. Rubber forms 90% of latex dry weight and 40% of fresh weight, which underlines the astonishing dominance of this anabolic pathway in the laticiferous metabolism. However, the preparation of dry rubber or concentrated latex as used in industry removes a fairly large proportion of the mineral and organic solutes from fresh latex. Latex processing conditions in plantation factories can considerably modify the technological properties of rubber after vulcanization through the influence of the nature and proportion of the residual nonrubber substances. Some of these give natural rubber properties that are still better than those of syntheticcis-polyisoprene. In contrast, it appears to have been clearly demonstrated that the proteins extracted from latex or from rubber tree leaves containing latex display allergenic properties (46,47). Turjanmaa et al. (48) observed that allergenic proteins extracted from latex gloves have molecular weights of between 2 and 30 kDa and are thus similar to various allergens, including those of pollen. It has been mentioned that large quantities of proteins with low molecular weights are found in latex.     

Gastric emptying of organic acids in the dog.

Test meals of 300 ml. of six different organic acids were instilled into the stomach of six healthy mongrel dogs. Citric, acetic, propionic, lactic, tartaric and succinic acid were given in 50, 100, 150, and 200 mN concentrations. 2. During the emptying process, the gastric contents were aspirated and immediately re-instilled at 10 min intervals, and the following parameters were recorded: volume, concentration of the organic anion, pH, hydrogen ion concentration and osmolarity. 3. By multiple stepwise regression analysis, the combination of parameters which most effectively determines gastric emptying rate was found to be: concentration of the organic anion, followed by intragastric volume and number of previous test meals given on the same day. These three parameters appear in the equation for gastric emptying rate in which the individual characteristic of each acid is expressed by a constant. 4. Among the various acids, inhibition of emptying rate increases with rising number of carboxylic groups of the acid and its molecular weight. 5. After proximal gastric vagotomy, emptying rate of organic acids is independent of volume, and emptying approaches an exponential pattern. 6. A model for gastric emptying of organic acids with at least three different receptors is proposed: one for the structure of the organic acid, one for concentration and one for intragastric volume.     

Influence of intestinal anaerobes and organic acids on the growth of enterohaemorrhagic Escherichia coli O157:H7

A suspension of human faeces (FS) and its anaerobic culture (FC), bacterial metabolic products and organic acids were examined for inhibitory effects on growth and verotoxin 2 (VT2) production of Escherichia coli O157:H7 in vitro. FS and FC showed a marked inhibitory activity to growth and production of VT2 by E. coli O157:H7 under anaerobic conditions. They may have both bacteriostatic and bactericidal effects on E. coli O157. The growth of E. coli O157 was markedly suppressed by acetic, propionic and butyric acids compared with hydrochloric acid and lactic acid at concentrations between 25 mM and 40 mM, being proportional to the pH values. At pH 5.5, 40 mM of short-chain fatty acids (SCFAs) almost completely inhibited the growth of E. coli O157. SCFAs markedly inhibited the growth of E. coli O157 at pH 6.0 rather than pH 7.0. Propionic acid is likely to be more suppressive to E. coli than acetic and butyric acids. The production of VT2 was approximately proportional to the growth of E. coli O157. However, incubation for 24 h in vitro showed that the growth and VT2 production of E. coli O157 decreased but were not completely inhibited at pH 6.5 and 7.0 in a mixture of acetic, propionic and butyric acids at a physiological concentration (110 mM, 60:25:25, respectively, in molar ratio). It is probable that the colonic microflora could contribute to a reduction of E. coli O157:H7 infections via the activation of intestinal fermentation by dietary manipulation or something similar to give pH 6.0 or <6.0 and that factors such as age, chemical therapy and body condition, which have effects on the balance of the intestinal microflora, would be associated with the incidence rates of E. coli O157 infections.     

Biosynthesis of vitamin B12 by Propionibacterium shermanii IV. Vitamin B12 and porphyrin synthesis in relation to the metabolic activities of the bacterium

The bacterial cell pool contains 16 amino acids. No qualitative change appeared in the amino acid pool at different stages of growth. No amino acids were liberated from the cell pool into the culture medium. Pyruvic and α-ketoglutaric acids were detected in the culture medium and cell pool of Propionibacterium shermanii. Bacterial growth, vitamin B₁₂, and coproporphyrin III synthesis increased with increasing age of the culture. A part of the synthesized porphyrin is released into the culture medium. Glucose, the total nitrogen content of the culture medium, ammonia nitrogen, amino acid nitrogen, methionine and glycine decreased gradually with the increase in the age and the bacterial dry weight of the culture. Succinic acid appeared on the 4^th day and increased with age. Acetic and propionic acids were the only detectable volatile acids. The ratio of propionic to acetic acid was about 3:1 (w/w).     

Rapid presumptive identification of anaerobes in blood cultures by gas-liquid chromatography.

Production of volatile and nonvolatile metabolic acids in blood culture broths by aerobic, facultative anaerobic, and obligate anaerobic bacteria was analyzed by gas-liquid chromatography. Anaerobic blood culture isolates were presumptively identified by the qualitative analysis of volatile fatty acids. Isolates, with a characteristic Gram stain reaction and cellular morphology, were identified by the following acid patterns: Bacteriodes fragilis group with acetic and propionic acids; Fusobacterium with acetic, butyric, and usually propionic acids; Veillonella with acetic and propionic acids; gram-positive cocci with acetic and butyric acids; and Clostridium with acetic and butyric acids.     

The effects of pH on colonic bacteria grown in continuous culture

A model of the proximal colon was used to investigate the effects of pH on fermentation by colonic bacteria in vitro. Twelve continuous anaerobic cultures of human faecal bacteria were maintained at constant pH in a medium simulating ileostomy effluent. Five cultures were maintained at pH 7, five at pH 6, and two at pH 5. The pH of each of three further cultures was altered after they had reached steady state, either from 7 to 6 and then to 5, or from 5 to 6 to 7. Both experimental designs showed that the pH exerted an important effect on bacterial metabolism without causing major changes in bacterial populations. Osmolality was lower in cultures run at a low pH. Total volatile fatty acid concentration was decreased at pH 5, and the production of propionic acid rather than acetic acid was favoured at pH 6. Changing the pH had no significant influence on the production of ammonia in these systems.     

Water‐Soluble Polyurethane Resins as Emulsifiers in Emulsion Polymerization of Styrene: Nucleation and Particle Growth

Polystyrene/polyurethane hybrid latex particles were synthesized by employing water‐soluble (or dispersible) polyurethane resins which had been prepared from isophorone diisocyanate (IPDI), poly(1,2‐propylene glycols) (PPG‐750 and PPG‐2000), and 2,2‐bis(hydroxymethyl)propionic acid (DMPA). Two kinds of polyurethane resin were used as emulsifiers and their effect on emulsion kinetics was investigated by measuring the rate of polymerization, the particle size distribution, the number of particles, and the average number of radicals per particle. Effects of the resin concentration on the rate of polymerization and the number of particles were found have a somewhat similar kinetic behavior with exponents in the range of 0.25–0.30 and 0.60–0.70, respectively. The average particle sizes, however, were very small (ca. 40–60 nm) and the particle size distribution showed a broad distribution. The particle nucleation period continued even over 0.7–0.8 fractional conversion of styrene. Moreover, the initial latex particle size was very large in comparison with the final particle size. Characteristic behavior of the particle nucleation and growth was mainly attributed to superior solubilizing ability and high internal viscosity of the polyurethane resin aggregates.     

The effect of organic acids on phytohaemagglutinin-activated proliferation of human lymphocytes in vitro

The present study assesses the effects of 25 organic acids on in vitro proliferation of human peripheral lymphocyte stimulated with phytohaemagglutinin (PHA). Lymphocytes were cultured in flat-bottomed 96-well microplates at 37°C for 96 h in the presence of the mitogen and of one acid. The concentrations of organic acids tested in the cultures were from 1 to 5 mM, corresponding to those usually found in the blood of patients with organic acidaemias. Cellular growth was measured by the incorporation of 6[³H]-thymidine into cellular DNA. We observed that tiglic (2-methylcrotonic), α-keto-β-methylvaleric, aminoadipic, sebacic and alpha-ketoisocaproic acids strongly inhibited lymphocyte DNA synthesis, whereas α-ketoisovaleric, propionic, α-hydroxy-β-methylvaleric, α-methylbutyric and isobutyric acids moderately suppressed DNA synthesis. Lactic and ethylmalonic acids, however, stimulated DNA synthesis. The most inhibitory acids were added to cultures at different times after the beginning of the incubation period. Except for tiglic acid, whose action persisted even after 48 h from the onset of cultures, the others acted only when added during the first 24 h. The present study demonstrated that organic acids modulate DNA synthesis in mitogen-stimulated human lymphocytes.     

Latex allergy--Part I

Natural rubber latex (NRL), is a resin sap produced in the cells of caoutchouc plants. It is a water dispersion of cis-1,4-polisopren (caoutchouc)--35%, stabilized with little amounts of proteins, sugar, alcohol, fatty acids and salts. The concentration of all solid substances is about 40%, the rest is water. Immunogenicity of latex depends on the proteins it contains. For many years we read in medical papers about the cases of contact urticaria, asthma, rhinitis, and anaphylaxis after contacting with latex products. It turns out that medical staff is the group of high occupational risk, because of exposure to gloves and other latex products. It is connected with the fact of high gloves usage caused by the danger of virus infections: HIV, HBV, HCV. Latex allergy is one of the reasons of dramatic complications after surgical operations. People who are allergic to latex may have cross reactions to allergens not connected with occupational environment. These are: food and houseplants (Ficus benjamina). The frequency of latex allergy is about 0.1% of the population. In the groups of high risk the frequency rises sharply. It is 17% among medical staff and it reaches 60% among children with spina bifida.     

Development of a monoclonal antibody-based sandwich ELISA for detection of the latex allergen Hev b 1

BACKGROUND: Natural rubber latex (NRL) products are complex mixtures consisting of different allergenic components. Among them, Hev b 1 belongs to the important and well-characterized ones. To quantify the relevant allergen Hev b 1 in NRL products, a two-site monoclonal antibody (mAb)-based assay was developed. METHODS: Two Hev b 1-specific mAbs with different epitope recognition and ability to bind simultaneously to an Hev b 1 molecule were used in the study. Both mAbs (II4F9 and II4G9) were enriched by in vitro production in a modular minifermenter and affinity purified. Wells of micro-ELISA plates coated with captured mAb II4G9 were incubated with samples containing Hev b 1. Bound Hev b 1 was detected by a combination of biotinylated mAb II4F9 as detection antibody and peroxidase-labeled avidin. RESULTS: The optimized sandwich ELISA was highly reproducible in the linear range of the standard curve and Hev b 1 concentrations ranging from 12.5 to 400 ng/100 microl could be detected. The assay was suitable for the detection of Hev b 1 concentrations in latex sap and latex products, e.g. gloves, with a detection limit of 1.25 microg of Hev b 1/g of rubber. In a preliminary study with five different brands of latex gloves, Hev b 1 concentrations were found to be in the range of 18-40 microg per gram of rubber material, corresponding to 2-4% of the total extractable protein content in latex glove extracts. Conclusions: A sensitive sandwich assay was developed to quantify the latex allergen Hev b 1. This assay can be used to standardize latex extracts with regard to the content of the major allergen Hev b 1.     

Odor masking in the rat

A computer controlled behavioral apparatus and olfactometer were used to determine the olfactory threshold of rats for propionic acid and to determine their ability to discriminate propionic acid in binary mixtures that contained the dissimilar odorants, limonene or carvone, or a similar odorant, acetic acid. The concentration of propionic acid that rats required to discriminate this substance from the other odorants was substantially above that of the threshold concentration, the increase being greatest with acetic acid. The increased levels of propionic acid needed for detection of this odorant in mixtures is attributed to masking by the other components. This study represents the first time behavioral methods have been used to demonstrate masking with odor mixtures in a rodent. The results indicate that it should be possible to use behavioral methods to define conditions for odor masking in animals so that physiological studies of the underlying mechanisms can be achieved.     

Development of an improved technique for the perfusion of the isolated caudal lobe of sheep liver

The study was designed to develop an improved technique for perfusing the isolated caudal lobe of sheep liver. Twenty caudal lobes were perfused for 3-4 h, in a non-recirculating mode, with Krebs-Henseleit bicarbonate buffer. The perfusion system was designed to give a constant flow. The hepatic viability and functional normality of the perfused lobe were assessed by measuring the perfusion flow rate, pH, K+ efflux, O2 uptake, substrate uptake, gluconeogenesis from propionate and amino acids, and ureagenesis from ammonia and amino acids. Liver tissue was sampled for histological examination, as well as for the determination of liver glycogen and wet : dry weight ratio. The perfusion flow rate and pH were both stable throughout the perfusion. The potassium concentration in the effluent perfusate did not increase during the perfusion, suggesting that there was no loss of viability or hypoxia. The perfused lobe extracted more than 50% of the O2 supply. The rate of oxygen consumption was comparable to the rate reported in vivo. The initial glycogen content was reduced by about 40% after 4 h perfusion. The wet : dry weight ratio was 3.6, consistent with the absence of tissue oedema. Urea production was stimulated when NH4Cl (0.3 mM) was added to the medium but there was no significant increase in urea release when alanine (0.15 mM), glutamine (0.2 mM) or lysine (0.2 mM) was added. Urea production, however, increased by about 171% when a physiological mixture of amino acids was added. Propionate (0.5 mM), alanine and glutamine stimulated glucose production but not lysine or the complete amino acid mixture. Glutamine release was lower than that reported in the rat liver. Changing the direction of flow also revealed an apparent difference between livers from sheep and rats in their metabolism of ammonia. The improved technique offers a simple practical and inexpensive approach to many problems in ruminant physiology and nutritional biochemistry.     

Role of volatile fatty acids in colonization resistance to Clostridium difficile.

The in vitro inhibition of Clostridium difficile by volatile fatty acids was correlated with the pH and concentrations of volatile fatty acids in the ceca of hamsters of different ages. The concentrations of cecal volatile fatty acids increased with the age of the animals. Maximum concentrations of individual volatile fatty acids were attained when the animals were ca. 19 days old, with acetic, propionic, and butyric acids occurring in the highest concentrations (72, 16, and 32 microequivalents/g of cecum, respectively). The cecal pH was approximately the same in hamsters of all ages (pH 6.6 to 7.0). Only butyric acid reached a concentration in the ceca of hamsters which was inhibitory to the in vitro multiplication of C. difficile. This inhibitory concentration was attained when the animals were ca. 19 days of age. When mixtures of volatile fatty acids were prepared at concentrations equal to those present in the ceca of hamsters, there was a direct correlation between the in vitro inhibitory activity of the volatile fatty acids and the susceptibility of hamsters 4 days of age or older to C. difficile intestinal colonization. The resistance of hamsters less than 4 days of age to C. difficile intestinal colonization appears to be due to factors other than volatile fatty acids.     

Characterization of a bovine synovial fluid lubricating factor. I. Chemical,Surface activity and lubricating properties

A lubricating glycoprotein (PSLF) with an apparent molecular weight of 280 kDa was purified from bovine synovial fluid by anion exchange, molecular sieve chromatography, and density gradient centrifugation. Lubrication was measured under boundary conditions as lowering of the coefficient of friction (μ) between oscillating natural latex and polished glass. Lubricating ability was first observed at a concentration of 200 μg/ml and became maximal at 260 μg/ml. Hydrophobic interfacial tension measurements indicated that at the former concentration, monolayers of PSLF formed. Sugar digestions showed that lubricating ability depends upon the terminal galactose of the molecule. PSLF is similar if not identical to lubricin. It is proposed that a repulsive hydration force is the molecular mechanism for lubricating activity.     

Effect of acetic acid on xylose fermentation to xylitol by Candida guilliermondii

The effect of acetic acid concentration on xylose fermentation to xylitol by Candida guilliermondii FTI 20037 was evaluated in semisynthetic medium containing different concentrations of the acid. Increasing acetic acid concentration up to 1.0 g/1 favored xylitol yield and productivity, with maximum values of 0.82 g/g and 0.57 g/.h1, respectively. The presence of acetic acid reduced cell production at all concentration. Furthermore, acetic acid was assimilated by the yeast together with the sugars and was depleted from the medium at concentrations of less than 3.0 g/1. The ability of this yeast to assimilate acetic acid suggests that these cells act as agents of medium detoxification. This behavior may lead to a viable microbiological process of xylitol production by C. guilliermondii FTI 20037 using xylose-rich lignocel-lulosic hydrolysates in which acetic acid is commonly present, causing inhibition of fermentative activity.     

The Influence of the Rubber Carboxyl Functionality on the Processability and Properties of Solid Rubber Modified Epoxy Mixtures

Summary: A high molecular weight, carboxyl functionalised solid rubber was added to an epoxy resin‐aromatic amino system developed for autoclave curing of honeycomb core composite structures. The achievement of an optimal balance of viscous flow and viscoelasticity of the resin, by controlling the nature and extent of cross‐linking of the functionalised rubber, was proposed as a route to void‐free honeycomb skins. The aim of the present investigation is to understand how the concentration of carboxylic groups of the rubber, prereacted with one of the epoxy monomers, affects the matrix resin flow properties. The concentration of carboxyl groups was changed by reacting them with a monofunctional epoxy resin. Dynamic shear viscosity profiles varying frequency, temperature and as function of time during isothermal cure have been determined for blends with differently functionalised rubbers. Carbon fibre wettability and laminate consolidation quality have been evaluated, making composite samples according to conventional prepregging and autoclave curing processes, through electron microscopy of fracture surfaces from transverse flexural strength tests.

Loss factor and storage modulus from dynamic‐mechanical torsion analysis for PWE0 blend. Loss factor and storage modulus for Nipol 1072 are reported for comparison.     

Cloning, expression, and characterization of recombinant Hev b 3, a Hevea brasiliensis protein associated with latex allergy in patients with spina bifida.

BACKGROUND: Two natural rubber latex proteins, Hev b 1 and Hev b 3, have been described in spina bifida (SB)-associated latex allergy. OBJECTIVE: The aim of this study was to clone and express Hev b 3 and to obtain the immunologic active and soluble recombinant allergen for diagnosis of SB-associated latex allergy. METHODS: A complementary DNA (cDNA) coding for Hev b 3 was amplified from RNA of fresh latex collected from Malaysian rubber trees (Hevea brasiliensis). PCR primers were designed according to sequences of internal peptide fragments of natural (n) Hev b 3. The 5'-end sequence was obtained by specific amplification of cDNA ends. The recombinant (r) Hev b 3 was produced in Escherichia coli as a 6xHis tagged protein. Immunoblotting and inhibition assays were performed to characterize the recombinant allergen. RESULTS: An Hev b 3 cDNA clone of 922 bp encoding a protein of 204 amino acid residues corresponding to a molecular weight of 22.3 kd was obtained. In immunoblots 29/35, latex-allergic patients with SB revealed IgE binding to rHev b 3, as did 4 of 15 of the latex-sensitized group. The presence of all IgE epitopes on rHev b 3 was shown by its ability to abolish all IgE binding to nHev b 3. Hev b 3 is related to Hev b 1 by a sequence identity of 47%. Cross-reactivity between these 2 latex allergens was illustrated by the large extent of inhibition of IgE binding to nHev b 1 by rHev b 3. CONCLUSION: rHev b 3 constitutes a suitable in vitro reagent for the diagnosis of latex allergy in patients with SB. The determination of the full sequence of Hev b 3 and the production of the recombinant allergen will allow the epitope mapping and improve diagnostic reagents for latex allergy.     

Acid production in normal and foot- and- mouth disease virus infected bovine kidney culture cells

Summary Bovine kidney culture cells were examined for acid production by known chromatographic procedures. Lactic acid was the major acidic component, accounting for 86 to 90 per cent of the total acidity, while acetic and pyruvic acids accounted for 7 to 9 per cent and 3 to 6 per cent, respectively. Cells infected with FMDV produced greater quantities of lactic acid than uninfected cultures, with probable increases in the only other acids produced, acetic and pyruvic. No other acids of the tricarboxylic acid cycle were detected in either infected or uninfected cells. Studies with cultures partially depleted of endogenous nutrients and exposed to a defined medium containing glucose as the only organic substrate indicated that acetic and pyruvic acids may be derived from an endogenous substrate other than glucose. The contribution of lactic acid to the total acidity increased with increasing glucose concentrations in the medium.     

Crossreactivity between allergens in natural rubber latex and banana studied by immunoblot inhibition

Background An association between allergic reactions to natural rubber latex and to banana has been reported but the immunochemical properties of the putative crossreacting allergens remain unknown. Obfective To study extracts of banana and natural rubber latex and sera from latex-allergic patients for possible crossreacting allergens and IgE antibodies. Methods Sera from 22 latex-allergic patients and 22 control subjects with no evidence of allergy to latex or to banana were studied. All patients had positive and controls negative reactions in skin-prick testing using an eluate of latex gloves. IgE antibodies to natural rubber latex and to banana were evaluated by immunoblotting and by radioailergosorbent test (RAST) and crossreactivity between allergens in banana and natural rubber latex by immunoblot inhibition. Skin-prick testing was used to examine in vivo reactivity to banana. Results Ten of the 22 (45%) latex-allergic patients sera recognized altogether 14 allergens in banana by immunoblotting. The most frequently identified banana allergens were 23, 32, 36, 39 and 47kDa proteins. The banana skin-prick test was positive in 14 of 18 (78%) latex-allergic patients studied and banana RAST in 12 of 14 patient sera tested. Fourteen of 21 interviewed patients reported symptoms from eating or handling bananas. In immunoblot inhibition studies a dose-dependent inhibition of IgE binding to banana extract with natural rubber latex proteins was observed in all five patient sera tested and, likewise, the binding of IgE to natural rubber latex extract was inhibited with banana proteins in four of the five patient sera. Conclusions The present results confirm the existence of crossreacting allergens in natural rubber latex and banana and provide new information on the immunochemical nature and heterogeneity of these allergens.