An alternative approach to the regeneration of coenzymes is described here using immobilized microorganisms possessing “NADH-oxidase”
function. Bacteria containing NADH-oxidase activity are immobilized by microencapsulation within artificial cells. In this
form, the microencapsulated bacteria can recycle NADH back to NAD in the presence of molecular oxygen as an electron acceptor.
The only byproduct of the recycling reaction is water. In order to perform the biological regeneration of NAD, the activity
of NADH-oxidase was investigated in 13 strains of aerobic bacteria and yeast. The NADH-oxidizing bacteriaLeuconostoc mesenteroides exhibited the highest activity among the microorganisms tested. The permeabilized bacteria showed 10% of their initial activity
after microencapsulation. Light and electron microscopy studies of bacteria loaded microcapsules have been done. Enzymatic
properties of microcapsule-immobilized bacteria were investigated in comparison with those of the free enzyme complex.Leuconostoc mesenteroides, containing NADH-oxidase, has been microencapsulated together with 3α-hydroxysteroid dehydrogenase (3α-HSDH) for stereospecific
steroid oxidation.
In a batch reactor, 2 mg of NAD, with recycling, allowed the same substrate consumption as 4.4 mg of NAD without recycling.
The microencapsulated system can be used repeatedly. The system is functional for 10 h, during which time each molecule of
NAD has been used 7.6 times. 相似文献
This report describes our studies on the optimal conditions for the complex coacervation of an acid-precusor gelatin with
an isoelectric point of pH 8.3 at high colloid concentration (5%). The following factors were studied: the amount of gelatin
deposited and the electrical behavior of colloids. 相似文献
Schistosomiasis is among the top five diseases in the world in terms of morbidity, affecting perhaps 200 million people in
tropical and subtropical countries. Antischistosomal drugs are toxic and rapidly metabolized. Hence, they must be given in
a number of spaced doses. In spite of this there are severe side effects leading to poor patient compliance. This is an ideal
situation for the application of sustained drug release to avoid the toxic peak concentration of drug.
This study was carried out using Astiban acid, an antimonial drug that is effective againstS. mansoni. Unfortunately, the drug is sufficiently soluble that 50 mg will dissolve in 100 mL water in less than a minute. To permit
sustained release of intramuscularly injected drug, microcapsules of astiban acid in poly(d,l-lactic acid) were formed by coacervation.
Release studies show that an appreciable fraction of the drug is available at the surface for rapid solution. After this surface
drug dissolves, the remaining drug is released slowly with half-times of many hours. After the initial burst, the release
of drug follows Higuchi’s equation up to approximately 80% release, with exponentially decreasing release rates thereafter. 相似文献
A coacervation technique for microencapsulation using Eudragit Retard polymers [poly(methyl methacrylates) substituted by
quaternary ammonium groups] as wall material is described, based upon phase separation using a cold chloroform-cyclohexane
mixture together with polyisobutylene as a stabilizer. The effect of various parameters on the nature and properties of the
microcapsules of potassium dichromate and paracetamol has been studied, in particular the alteration in wall content and structure
and release rate of contents. The microcapsules are discrete, their properties are reproducible, and various degrees of sustained
release are obtained. 相似文献
A new medical device called Thermascan has been developed based on heat-sensitive microencapsulated liquid crystals. This
thermographic device assists in early detection of breast abnormalities that are characterized by minor changes in tissue
temperature and displayed by the color changes in the device. This liquid crystal device is used to screen patients who fall
into the average to high risk category. The value of this diagnostic device is that it will detect minute temperature changes
that occur in the breast from very small heat-producing cancers. 相似文献
The thermal degradation of linalool-chemotype Cinnamomum osmophloeum leaf essential oil and the stability effect of microencapsulation of leaf essential oil with β-cyclodextrin were studied. After thermal degradation of linalool-chemotype leaf essential oil, degraded compounds including β-myrcene, cis-ocimene and trans-ocimene, were formed through the dehydroxylation of linalool; and ene cyclization also occurs to linalool and its dehydroxylated products to form the compounds such as limonene, terpinolene and α-terpinene. The optimal microencapsulation conditions of leaf essential oil microcapsules were at a leaf essential oil to the β-cyclodextrin ratio of 15:85 and with a solvent ratio (ethanol to water) of 1:5. The maximum yield of leaf essential oil microencapsulated with β-cyclodextrin was 96.5%. According to results from the accelerated dry-heat aging test, β-cyclodextrin was fairly stable at 105 °C, and microencapsulation with β-cyclodextrin can efficiently slow down the emission of linalool-chemotype C. osmophloeum leaf essential oil. 相似文献
In many industrial applications, inadequate cell attachment can be a limitation, especially when serum‐free media are used. Nitrogen‐rich plasma‐polymerised ethylene (PPE:N) exhibits high concentrations of polar groups that can help to promote the attachment of weakly adherent cell types. Tissue plasminogen activator‐producing Chinese hamster ovary (CHO) cells, adapted to suspension, were grown in the presence PPE:N flakes and were found to adhere to them. The growth rate was reduced, but cell viability was enhanced and their metabolism was more efficient, with generally higher recombinant protein productivity. Finally, cell adhesion on PPE:N surfaces was found to be independent of integrins, and was probably mediated by certain non‐specific interactions with the PPE:N surface.
A solid-state, diffuse reflectance-based fiberoptic sensor is described for quantifying ammonia. This sensor is constructed
by immobilizing chlorophenol red, a weak acid chromophoric indicator dye, in a microporous polypropylene membrane. A flow-injection
analysis system is used to carry a 10-μL aliquot of the sample across the treated membrane. Ammonia in the sample diffuses
through the air-filled pores within the membrane structure before reacting with the indicator dye. A reversible acid-base
reaction between ammonia and chlorophenol red results in a measurable change in the reflectance at 560 nm. Response characteristics
include a peak response within 20 s, a limit of detection of 0.2 ± 0.1 mM ammonia, and a dynamic range of up to 60 mM ammonia.
The analytical utility of this sensor is demonstrated by measuring ammonia levels in 48 individual samples collected during
the growth of PC3 human prostate cancer cells in a typical serum-containing growth medium. Accuracy of the proposed sensor
is verified by a comparison of results from this sensor to those from a conventional enzyme assay. 相似文献
Scientific evidence in the prevention and treatment of various disorders is accumulating regarding probiotics. The health
benefits supported by adequate clinical data include increased resistance to infectious disease, decreased duration of diarrhea,
management of inflammatory bowel disease, reduction of serum cholesterol, prevention of allergy, modulation of cytokine gene
expression, and suppression of carcinogen production. Recent ventures in metabolic engineering and heterologous protein expression
have enhanced the enzymatic and immunomodulatory effects of probiotics and, with time, may allow more active intervention
among critical care patients. In addition, a number of approaches are currently being explored, including the physical and
chemical protection of cells, to increase probiotic viability and its health benefits. Traditional immobilization of probiotics
in gel matrices, most notably calcium alginate and κ-carrageenan, has frequently been employed, with noted improvements in
viability during freezing and storage. Conflicting reports exist, however, on the protection offered by immobilization from
harsh physiologic environments. An alternative approach, microencapsulation in “artificial cells,” builds on immobilization
technologies by combining enhanced mechanical stability of the capsule membrane with improved mass transport, increased cell
loading, and greater control of parameters. This review summarizes the current clinical status of probiotics, examines the
promises and challenges of current immobilization technologies, and presents the concept of artificial cells for effective
delivery of therapeutic bacterial cells. 相似文献
The proteinoid cells are assembled of thermal polymers of amino acids. Typically, an appropriate mixture of amino acids containing
aspartic or glutamic acid is heated at 190°C for 6 h, stirred with water for 2 h, dialyzed during 2 d, and lyophilized. Spheroidal
cells are made from such polymer by dissolving it in the water by boiling, and then cooling. Many of them can be made by sonication
at room temperature.
These artificial cells, ranging from microns to tens of microns in diameter (depending on composition and preparation), have
double membranes and various internal compositions. The spherules can microencapsulate dyes, oxidant-reductant compounds or
acceptor-donor substances, and can be packed together.
Such spherules display electrical polarization and electrical discharges and respond to intra- and extracellular ionic and
electric influence upon membrane and action potential. These properties arise from the double membrane structure, asymmetric
membrane permeability, and channeling phenomena.
Such features as exponential dependence of the steady-state conductance and capacitance as well as negative resistance of
the membrane seem to be responsible for the flip-flop alternations of the membrane polarization, rhythmic electric oscillations,
and all-or-none action potentials.
The presence of such chromophores as pteridine and flavin in polymers constituting these cells is responsible for their photosensitivity. 相似文献
Whole cells ofBrevibacterium flavum having fumarase activity were immobilized using K-carrageenan. The stabilities of fumarase activity in the immobilized cells
against external factors, including heat, pH, organic solvents, and protein denaturing reagents, were compared with those
of free cells and native enzyme. The stabilities of fumarase activity in immobillized cells against external factors were
highest, and those of native enzyme were lowest. In the “gel-state,” K-carrageenan-immobilized cells showed a much higher
stabilization effect for external factors than “sol-state” immobilized cells. 相似文献
Microgel particles can be fabricated with great control by droplet‐based microfluidics; however, to this end, their shape is intrinsically limited to be spherical. Existing approaches to circumvent this limitation rely on the rapid interception of transient non‐spherical preparticle shapes, greatly limiting their versatility. This paper presents a facile microfluidic approach that overcomes this limitation. The method utilizes the injection of scaffolding microgel particles into droplets that have insufficient volumes to host the microgels in a spherical shell. As a result, the drops adopt non‐spherical equilibrium shapes that serve to template non‐spherical soft supraparticles by slow and gentle chemical reactions. 相似文献
Probiotics and probiotic therapy have been rapidly developing in recent years due to an increasing number of people suffering from digestive system disorders and diseases related to intestinal dysbiosis. Owing to their activity in the intestines, including the production of short-chain fatty acids, probiotic strains of lactic acid bacteria can have a significant therapeutic effect. The activity of probiotic strains is likely reduced by their loss of viability during gastrointestinal transit. To overcome this drawback, researchers have proposed the process of microencapsulation, which increases the resistance of bacterial cells to external conditions. Various types of coatings have been used for microencapsulation, but the most popular ones are carbohydrate and protein microcapsules. Microencapsulating probiotics with vegetable proteins is an innovative approach that can increase the health value of the final product. This review describes the different types of envelope materials that have been used so far for encapsulating bacterial biomass and improving the survival of bacterial cells. The use of a microenvelope has initiated the controlled release of bacterial cells and an increase in their activity in the large intestine, which is the target site of probiotic strains. 相似文献