Microbial growth at reduced water activities: studies of aw prediction in solutions of compatible solutes

Studies were made of the prediction of intracellular water activity ( a _w) of microorganisms grown at reduced a _w. These included the determination and prediction of a _w of potassium L-glutamate solutions and the prediction of a _w in mixed solutions of various compatible solutes and macromolecules. Compatible solutes studied were L-proline, glycerol, potassium chloride and D-arabitol. The results indicate that a _w predictions of such mixtures may be done with acceptable accuracy by neglecting solute-solute interactions.     

A method for concentrating dilute solutions of macromolecules

A simple, inexpensive acrylate polymer which has a capacity to absorb 170 ml of water per g has been developed. It can be used to concentrate dilute solutions of macromolecules such as proteins, nucleic acids, and carbohydrates. The polymer absorbs only low-molecular-weight substances such as glucose, sucrose, and inorganic salts. It can replace the various conventional concentration methods. No special device or electricity is needed for the concentration. The inexpensive polymer, molded in the form of rods, can be very conveniently used as “disposable concentration sticks.”     

Influence of mixed electrolytes on the adsorption of lysozyme,PEG, and PEGylated lysozyme on a hydrophobic interaction chromatography resin

In a recent work (Werner A and Hasse H in J Chromatogr A 2013;1315:135) the influence of mixed electrolytes on the adsorption of the macromolecules lysozyme, PEG and di‐PEGylated lysozyme on a hydrophobic resin has been studied, but only at one overall ionic strength (3000 mM). The present work, therefore, extends these studies to other ionic strengths (2400 and 2700 mM), and explores the application of a model to predict the entire data set. The adsorbent is Toyopearl PPG‐600M. The solvent is a 25 mM aqueous sodium phosphate buffer at pH 7.0. The studied salts are sodium chloride, sodium sulfate, ammonium chloride and ammonium sulfate. Pure salts as well as binary and ternary mixtures of these salts with varying ratios of the amounts of the salts are studied at 25 °C. The loading of the adsorbent increases with increasing salt concentration for all macromolecules. Synergetic effects of the mixed electrolytes are observed. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1104–1115, 2017     

Interactions of bioactive lipopeptides, iturin A and surfactin from Bacillus subtilis.

The antifungal activity of iturin A and its interaction with erythrocyte membranes were enhanced in the presence of surfactin. The modification of the properties of iturin A was explained by the formation of mixed iturin A-surfactin micelles. Such mixed micelles were easily generated when both lipopeptides were in aqueous solutions in the absence of mineral salts but the formation of these micelles did not occur when the solutions contained a high molarity of mineral cations.     

The influence of kosmotropic and chaotropic salts on the functional properties of Mucuna pruriens protein isolate

The influence of chaotropic and kosmotropic salts on Mucuna pruriens protein isolates was investigated. Protein solubility profile indicated that solubility was minimal at the isoelectric point of the protein isolate (4.0) while the solubility was maximal at pH 10.0 in all salt solutions. Chaotropes (I(-), ClO(4)(-) and SCN(-)) exhibit better protein solubility than the kosmotropes (SO(4)(2-), Cl(-) and Br(-)). Increase in protein solubility follows the Hofmeister series: NaSO(4)相似文献   

Fresh-water fish chemoreceptors responsive to dilute solutions of electrolytes

The existence of the palatal chemoreceptors responding specifically to dilute solutions of salts with monovalent cations was demonstrated in carp. The distilled water effect (a response produced by the application of distilled water after chemoreceptors had been rinsed out with hypertonic salt solutions) was assigned to the activity of the same receptor. Intensity of the response to dilute solutions of salts depended on the valency of the anion: the larger the valency, the greater the response. Positively charged sites of the receptor responsive to dilute salt solutions were suggested by previous treatments with acid and alkali, and dye salts. Increase in the ionic strength of the stimulating solution by the addition of supporting electrolytes caused a depression of response. In particular, strong depression of response was caused by the addition of a supporting electrolyte with a divalent cation. Effects of polarizing current on the chemoreceptor activity were investigated. Based upon the findings in this paper, a hypothesis is presented, which explains mechanisms underlying chemoreceptor responses to dilute solutions of electrolytes in terms of an interfacial electro-kinetic process.     

Sol-gel processing of actin to obtain homogeneous glasses at low temperatures

The lethal effects of freezing on cells are currently attributed to the crystallization of extracellular water which leaves concentrated solutions of salts, macromolecules and so forth in the extracellular space. This concentrated fluid establishes a strong osmotic gradient which draws water from the cells. Thus, a cell surrounded by ice can survive only if means can be found for reducing the osmotically driven outflow of cellular water. This is usually attempted through vitrification of the extracellular space, but may also be attained through suitable modifications of cellular plasms. Starting from microscopic observations on early rabbit embryos and related cryotolerance, we investigated purified actin solutions under similar conditions, and found that sol-gel processing could result in the formation of homogeneous glass, and through drying, give rise to monolithic solids, glasses and composites. The first process may be at least partially responsible for the induced cryotolerance of cells, while the second may be representative of new and useful biomaterials.     

Influence of ruminal and plasma osmotic pressure on salivary secretion in sheep

The osmotic pressure of the rumen contents and also of the blood was altered by intraruminal administration of water or hypertonic solutions. It was found that alterations in osmotic pressure were accompanied by inverse changes in the flow rate of mixed saliva. Intravenous infusion of hypertonic solutions, causing elevation of the osmotic pressure of the blood without affecting that of the rumen, also caused a reduction of salivary secretion rate. The flow rates of both parotid and residual saliva were affected. When strongly hypertonic solutions of sodium or potassium salts were infused into the rumen, or sodium salts or urea were infused into the blood, the concentration of those substances increased in the saliva. Other treatments had little effect on salivary composition.     

Thermodynamic aspects of biopolymer functionality in biological systems,foods, and beverages

Molecular mimicry and molecular symbiosis are proposed to be the main factors controlling thermodynamic activity and phase behavior of macromolecular compounds in foods, beverages, and chyme. Molecular mimicry implies a chemical resemblance of hydrophilic surfaces of globular proteins with their chemical information hidden in the hydrophobic interior and low excluded volume of the globules. The molecular mimicry contributes to the efficiency of enzymes. Molecular symbiosis means that interactions attraction or repulsion) between biopolymer molecules greatly differing in conformation (globular and rod-like) favor the biological efficiency of one of them at least. The symbiosis is based on excluded volume effects of macromolecules in mixed solutions. Association-dissociation of rod-like macromolecules can dictate thermodynamic activity of an enzyme in the mixed solution. Thermodynamic incompatibility is typical of food macromolecules, whose denaturation, association, complexing, and chemical modification reduce their mimicry and co-solubility. Foods are normally phase-separated systems with highly volume-occupied phases. The phase-separated nature of the gel-like chyme is important to the efficiency of digestion of mixed diets. Phase separation of biopolymer mixtures, presumably, underlies mechanisms of nonspecific immune defense. The phase behavior-functionality relationships is presented through concrete examples of some foods (such as milk products, low-fat spreads, ice cream, wheat and rye doughs, thermoplastic extrudates, etc.), beverages (tea and coffee), and chyme.     

Changes in hydration, protein and proteoglycan composition of the collagen-keratocyte matrix of the bovine corneal stroma ex vivo in a bicarbonate-mixed salts solution, compared to other solutions

Many solutions have been used to investigate the swelling properties of the mammalian corneal stroma but few of the solutions resemble the expected extracellular matrix fluid of the corneal stroma, and little information is available on whether incubation ex vivo causes significant changes in the gross composition of the stroma. From quality-selected recent post-mortem eyes of adult cattle, stroma preparations were cut from the central part of the cornea. The time-dependent changes in wet mass were assessed over 9 h at 37 degrees C, and the preparations then dried. Various solutions of known pH (6.88-8.32) and osmolality (<50-327 mosmol/kg) were used, and were assayed for protein and proteoglycan after the incubation. The rates and extent of stromal swelling were lowest in a glucose-supplemented mixed salts solution containing 35 mM bicarbonate (0.5% CO2) solution, marginally greater in a mixed salts solution containing 35 mM bicarbonate (5% CO2) or similar non-bicarbonate mixed salts solutions (including BSS), and progressively greater in phosphate-buffered saline (PBS), various phosphate buffers (10-67 mM) and saline solutions (0.025-1%), and greatest in water. The initial rates of swelling ranged from 44 to 451 mg/h and the secondary rates from 9 to 106 mg/h. In all solutions, protein and proteoglycans were detected, but these ranged from around 1 to 10% of the samples with the bicarbonate-buffered solutions, to around 30% with the use of some phosphate buffers or saline.     

Changes in hydration,protein and proteoglycan composition of the collagen–keratocyte matrix of the bovine corneal stroma ex vivo in a bicarbonate–mixed salts solution,compared to other solutions

Many solutions have been used to investigate the swelling properties of the mammalian corneal stroma but few of the solutions resemble the expected extracellular matrix fluid of the corneal stroma, and little information is available on whether incubation ex vivo causes significant changes in the gross composition of the stroma. From quality-selected recent post-mortem eyes of adult cattle, stroma preparations were cut from the central part of the cornea. The time-dependent changes in wet mass were assessed over 9 h at 37°C, and the preparations then dried. Various solutions of known pH (6.88–8.32) and osmolality (<50–327 mosmol/kg) were used, and were assayed for protein and proteoglycan after the incubation. The rates and extent of stromal swelling were lowest in a glucose-supplemented mixed salts solution containing 35 mM bicarbonate (0.5% CO₂) solution, marginally greater in a mixed salts solution containing 35 mM bicarbonate (5% CO₂) or similar non-bicarbonate mixed salts solutions (including BSS), and progressively greater in phosphate-buffered saline (PBS), various phosphate buffers (10–67 mM) and saline solutions (0.025–1%), and greatest in water. The initial rates of swelling ranged from 44 to 451 mg/h and the secondary rates from 9 to 106 mg/h. In all solutions, protein and proteoglycans were detected, but these ranged from around 1 to 10% of the samples with the bicarbonate-buffered solutions, to around 30% with the use of some phosphate buffers or saline.     

Thermodynamic Aspects of Biopolymer Functionality in Biological Systems,Foods, and Beverages

ABSTRACT:?

Molecular mimicry and molecular symbiosis are proposed to be the main factors controlling thermodynamic activity and phase behavior of macromolecular compounds in foods, beverages, and chyme. Molecular mimicry implies a chemical resemblance of hydrophilic surfaces of globular proteins with their chemical information hidden in the hydrophobic interior and low excluded volume of the globules. The molecular mimicry contributes to the efficiency of enzymes. Molecular symbiosis means that interactions attraction or repulsion) between biopolymer molecules greatly differing in conformation (globular and rod-like) favor the biological efficiency of one of them at least. The symbiosis is based on excluded volume effects of macromolecules in mixed solutions. Association-dissociation of rod-like macromolecules can dictate thermodynamic activity of an enzyme in the mixed solution. Thermodynamic incompatibility is typical of food macromolecules, whose denaturation, association, complexing, and chemical modification reduce their mimicry and co-solubility. Foods are normally phase-separated systems with highly volume-occupied phases. The phase-separated nature of the gel-like chyme is important to the efficiency of digestion of mixed diets. Phase separation of biopolymer mixtures, presumably, underlies mechanisms of nonspecific immune defense. The phase behavior-functionality relationships is presented through concrete examples of some foods (such as milk products, low-fat spreads, ice cream, wheat and rye doughs, thermoplastic extrudates, etc.), beverages (tea and coffee), and chyme.     

Heat Resistance of Bacillus subtilis Spores at Various Water Activities

S ummary : The heat resistance of spores of Bacillus subtilis was determined in water vapour and in aqueous solutions of NaCl, LiCl, glucose and glycerol at various water activities. In water vapour and in glycerol solutions, maximal resistance appeared at low, but not zero water activity. In NaCl and glucose solutions only small variations in heat resistance occurred with decreasing water activity although a small increase was observed at the highest concentrations tested. With increasing concentrations of LiCl, heat resistance at first decreased but increased at water activities below 0·5. The possible interaction of compounds controlling water activity and water activity per se on heat resistance is discussed.     

Effects of Antibiotics on Induction, Viability, and Reversion Potential of L-Forms of Haemophilus influenzae

The physical interactions between Serratia marcescens and solutions of NaCl, CaCl(2), CaI(2), NaI, and Na(2)HPO(4) plus NaH(2)PO(4) were examined. Dilute (0.017 n) salt solutions did not cause cells to lose water, as evidenced by the unchanged weight of centrifugally packed cells. The cells preferentially adsorbed the cations and repelled the anions of most salts in these solutions. Concentrated (1.71 n) salt solutions markedly reduced the weight and water content of centrifugally packed cells, although these cells took up considerable amounts of salts. More than 90% of the water in the packed-cell pellets was available for the solution of NaCl at 4.2 to 4.4% concentration. The observation that salts apparently penetrated the cells freely and yet caused extensive dehydration was not readily compatible with conventional concepts of solute-induced plasmolysis. Alternative hypotheses to explain the data included the following. First, the cells lost weight and water to concentrated salt solutions through a nonosmotic competitive dehydration, causing a shrinkage of the protoplasmic gel. The shrinkage of the cell wall was limited because of the rigidity of its mucopeptide layer; therefore, a space appeared between the cell wall and the cell membrane. Second, cells may have equilibrated their water activity with that of their environment by two mechanisms: (i) the loss of water by plasmolysis or competitive dehydration, and (ii) alterations in cell permeability that admitted previously excluded solutes to the cell interior. Possibly, the correct explanation of the observations reported here involves elements of all three hypotheses, plasmolysis, competitive dehydration, and permeability alterations.     

Activation of tyrosine hydroxylase by polyanions and salts. An electrostatic effect.

The activity of a partially purified preparation of tyrosine hydroxylase (EC 1.14.16.2) from the bovine caudate nucleus was increased by heparin, chondroitin sulfate, phosphatidylserine, polyacrylic acid, polyvinyl sulfuric acid and both poly-D-, and poly-L-glutamic acids, all polyanions. A variety of salts both activated the enzyme and prevented the activation by the polyanions. The observations that activity is increased when the enzyme interacts with salts and with macromolecules of high negative charge density are used to infer a model for these interactions and for the structural change in the enzyme that accompanies activation.     

The action of chromium(III) in fixation of animal tissues

Summary Chromic salts have been studied as fixatives of mammalian tissues for light microscopy, and the binding of the metal has been examined histochemically. Tissues bind chromium(III) from aqueous solutions less acid than pH 2.5; the metal attaches mainly to collagen and basement membranes. Solutions containing chromium(III) as the only active ingredient cannot be used as fixatives because they destroy cytoplasm and cause great structural distortion. When mixed with other fixative agents, however, chromic salts can bring about considerable improvement in structural preservation. In aqueous mixtures more acid than pH 2, and in aqueous-methanolic solutions in the pH range 4.0–5.3, a chromic salt provides only a nonspecific osmotic effect: little or no metal is bound to the tissue, and an aluminium or a sodium salt can be effectively substituted. In less acid (pH 2.3–3.2) aqueous mixtures, the beneficial action of chromium(III) cannot be imitated by aluminium or sodium ions.Chromium(III) forms coordinate bonds that cross-link ionized carboxyl groups of macromolecules. The reaction occurs so slowly that such cross-links can internally strengthen a tissue only after the structure has been stabilized by rapidly acting fixative agents. Thus, a valuable future use of chromic salts may be in a post-fixation treatment to protect specimens against the adverse effects of embedding in paraffin wax. Chromium(III) might also be useful for enhancing the opacity of collagen fibrils in electron microscopy.Address until 30 June 1986: Department of Anatomy and Cell Biology, University of Sheffield, Sheffield, S10 2TN, UK     

Activity coefficients of salts in highly concentrated protein solutions: I. Alkali chlorides in isoionic bovine serum albumin solutions

In order to understand the thermodynamic state of simple salts in living cells, the mean activity coefficients of LiCl, NaCl, KC1, RbCl, CsCl were determined in concentrated isoionic bovine serum albumin (BSA) solutions by use of the EMF method with ion exchange membrane electrodes. The protein concentration range extended up to 22 wt %, whereas the salt concentration was kept constant at 0.1 mole per kilogram water. These solutions may be regarded as crude but appropriate model systems for the cytoplasm of cells as far as type and magnitude of the macromolecular component influence on the chemical potential of the salts is concerned. The mean stoichiometric activity coefficients of the alkali chlorides in the isoionic BSA solutions decreased linearly with the protein molality; this decrease, however, did not exceed ca. 10% compared with the pure 0.1 molal salt solutions. Only very small differences in the behaviour of the different alkali chlorides were observed. The results may be interpreted by the superposition of the effects of specific Cl^? ion binding to BSA and BSA bound “non-solvent” water with probably electrostatic long range interactions of the BSA(Cl^?)_v polyions with the salt ions in solution. The resulting mean activity coefficients, corrected for ion binding and non-solvent water, showed a very slight linear dependence on the protein concentration. The departure from the value in the pure 0.1 molal salt solutions did not exceed ± 2%.     

Activity coefficients of salts in highly concentrated protein solutions. II. Potassium salts in isoionic bovine serum albumin solutions

Mean activity coefficients of different potassium salts KX (X = F-, Cl-, Br-, I-, NO3-, SCN-) have been measured in concentrated isoionic bovine serum albumin (BSA) solutions, by use of the EMF method with ion-exchange membrane electrodes. These solutions may be regarded as simple model systems for the cytoplasm of living cells as far as the influence of the macromolecular component on the activity coefficients of the salts is concerned. Two series of measurements have been carried out: (a) varying the amount of salt from 0.01 to 0.5 molal and maintaining the BSA concentration constant at 20 wt% and (b) varying the protein concentration up to 25 wt% and keeping the salt concentration constant at 0.1 molal. For all salts studied, the mean activity coefficients in the protein-salt solutions increase as the salt concentration rises, when the protein concentration is maintained constant. In the series of measurements (b) the activity coefficients of all salts change linearly with the protein concentration. Marked qualitative differences, however, were observed depending on the anion species, which could be interpreted in terms of specific ion binding of X- to the protein molecule. By taking into account BSA-bound 'non-solvent' water, the results were analyzed in terms of numbers of anions bound per BSA molecule. Comparison with the results of Scatchard, obtained at low protein concentrations, showed only a very small electrostatic effect of the BSA-(X-)v polyions on the activity coefficient of the salts at higher protein and salt concentrations.     

Effect of salts and organic solvents on the activity of Halobacterium cutirubrum catalase

Catalase in extracts of the extreme halophile Halobacterium cutirubrum exhibits up to threefold stimulation by 0.5 to 1.5 m monovalent salts and by 0.1 m divalent salts. Above these concentrations, inhibition of enzyme activity is observed. The inhibitory effect, and to some extent the stimulation, is salt-specific; the effectiveness of a salt in inhibiting enzyme activity depends on both cation and anion. Thus, the order of effectiveness is MgCl(2) > LiCl > NaCl > KCl > NH(4)Cl, and LiCl > LiNO(3) > Li(2)SO(4). The magnitude of enzyme inhibition for the salts tested is positively correlated with their molar vapor pressure depression in aqueous solution. Stimulation of enzyme activity was observed when one salt was added at its optimal concentration in the presence of inhibiting concentrations of another salt, indicating that the effect on the enzyme is not due to changing water activity but probably to enzyme-salt interaction. Aqueous solutions of ethylene glycol, glycerol, and dimethyl sulfoxide containing no ions influence enzyme activity in the same manner as do salts.     

Purification of Penicillin G Amidase using Quaternary Ammonium Salts and effect on the activity of the immobilised enzymes

This paper describes the purification of Penicillin G Amidase (EC 3.5.1.11) using quaternary ammonium salts with the aim of increasing the activity of immobilised enzymes prepared from the purified solutions. Two different quaternary ammonium salts were tested with different solutions of the enzyme. It was concluded that the quaternary ammonium salts used selectively precipitated the non-enzymatic protein leaving in solution practically all the enzyme resulting in a high yield of purification. Optimal conditions for purification using the two types of quaternary ammonium salts were determined. Immobilisation studies were performed from various purified enzyme solutions, using different amounts of a quaternary ammonium salt. The immobilised enzymes so obtained showed a much higher activity than the immobilised enzyme obtained from non-purified enzyme solutions.