Search

The suitability of natural hydrogel carriers with probiotic starter culture as whey beverages supplements was examined by assessing their rheological and structural changes during the fermentation and gastrointestinal conditions. Effect of encapsulated cells on the carrier structure is of great importance for the selection of proper material for the preparation of functional supplements. The structural changes of the chitosan-coated alginate/whey carriers were considered based on (1) cell viability and the carrier average volume vs. time (2) the storage and loss modulus vs. time obtained under low oscillator strain conditions, (3) FTIR analysis and (4) SEM cross-sectional observation of the hydrogel carriers. The presence of chitosan coating and fermentation conditions increased cell viability up to 9.01 +/- 0.18 (log CFU/g). According to our results, the encapsulated cells induce weakening of carriers under the gastric conditions but improve their mechanical stability under the intestinal condition. The mechanical behaviour of carriers was also considered in order to formulate the rheological constitutive model equation for describing the irreversible structural changes under the gastric and intestinal conditions. The cell leakage under the gastric condition after the 2 h was less than 5%. Carriers are rapidly degraded under the intestinal condition which ensures the release of cells and provides their beneficial effects on the host health. Our results indicate that this type of coated carrier is suitable to be used for encapsulation of probiotic starter culture in the production of fermented whey-based products.

In-cell NMR enables structural insights at atomic resolution of proteins in their natural environment. To date, very few methods have been developed to study proteins by in-cell NMR in mammalian systems. Here we describe a detailed protocol to conduct in-cell NMR on the intrinsically disordered protein of alpha-Synuclein (αSyn) in mammalian cells. This chapter includes a simplified expression and purification protocol of recombinant αSyn and its delivery into mammalian cells. The chapter also describes how to assess the cell leakage that might occur to the cells, the setup of the instrument, and how to perform basic analyses with the obtained NMR data.

Chilling injury (CI) presents a major problem in postharvest preservation and marketing potential of mango. In this study, tissue breakdown caused by chilling injury was investigated using X-ray computed microtomography (X-ray μCT). This provided a unique insight in 3-D changes in tissue structure and pore networks during chilling injury development. Evidence of cell collapse and cavity formation in severely chill injured fruit was apparent. In addition, microstructural evidence supporting the occurrence of intracellular water leakage was found. Quantitative analysis revealed that chilling injury was associated with, first, a decrease in porosity, pore size and pore connectivity due to cell leakage and tissue breakdown, which was followed by an increase in pore size due to cavity formation. Multivariate statistics identified pore connectivity and Euler number as the most important parameter in relation to chilling injury. The results support the hypothesis that changes in tissue and pore structure in mango fruit contribute significantly to the development of postharvest tissue disorders by drastic changes in tissue aeration and water movement, identical to what has been observed in other fruit species.

Bacterial inactivation by 405 nm light is accredited to the photoexcitation of intracellular porphyrin molecules resulting in energy transfer and the generation of reactive oxygen species that impart cellular oxidative damage. The specific mechanism of cellular damage, however, is not fully understood. Previous work has suggested that destruction of nucleic acids may be responsible for inactivation; however, microscopic imaging has suggested membrane damage as a major constituent of cellular inactivation. This study investigates the membrane integrity of Escherichia coli and Staphylococcus aureus exposed to 405 nm light. Results indicated membrane damage to both species, with loss of salt and bile tolerance by S. aureus and E. coli, respectively, consistent with reduced membrane integrity. Increased nucleic acid release was also demonstrated in 405 nm light-exposed cells, with up to 50 % increase in DNA concentration into the extracellular media in the case of both organisms. SYTOX green fluorometric analysis, however, demonstrated contradictory results between the two test species. With E. coli, increasing permeation of SYTOX green was observed following increased exposure, with >500 % increase in fluorescence, whereas no increase was observed with S. aureus. Overall, this study has provided good evidence that 405 nm light exposure causes loss of bacterial membrane integrity in E. coli, but the results with S. aureus are more difficult to explain. Further work is required to gain greater understanding of the inactivation mechanism in different bacterial species, as there are likely to be other targets within the cell that are also impaired by the oxidative damage from photo-generated reactive oxygen species.

Atmospheric cold plasma (ACP) is a promising nonthermal technology effective against a wide range of pathogenic microorganisms. Reactive oxygen species (ROS) play a crucial inactivation role when air or other oxygen-containing gases are used. With strong oxidative stress, cells can be damaged by lipid peroxidation, enzyme inactivation, and DNA cleavage. Identification of ROS and an understanding of their role are important for advancing ACP applications for a range of complex microbiological issues. In this study, the inactivation efficacy of in-package high-voltage (80 kV [root mean square]) ACP (HVACP) and the role of intracellular ROS were investigated. Two mechanisms of inactivation were observed in which reactive species were found to either react primarily with the cell envelope or damage intracellular components. Escherichia coli was inactivated mainly by cell leakage and low-level DNA damage. Conversely, Staphylococcus aureus was mainly inactivated by intracellular damage, with significantly higher levels of intracellular ROS observed and little envelope damage. However, for both bacteria studied, increasing treatment time had a positive effect on the intracellular ROS levels generated.

In a conventional three-dimensional (3D) cell culture system based on microencapsulation, the calcium alginate microcapsules tend to rupture within 7 days of culture, causing unwanted cell leakage. The microencapsulation based on flicking model of calcium-alginate-polyethylene glycol (Ca-alg-PEG) was proposed to rectify this problem. An analytical model to simulate the flicking process based on the deflection of a needle cantilever was also successfully developed and used to predict the size of the microbeads. The size of the microbeads were ranged from 300 to 500 μm and it is controlled by varying the liquid flow rate from 4.8 to 366 μL/min and flicking speed from 70 to 120 rpm. Under a flicking force of 0.58 N, uniform sized and spherical shaped Ca-alginate-PEG microbeads were produced at a liquid flow rate of 40 μL/min and a flicking rate of 100 rpm. The microbeads were characterized by Field Emission Scanning Microscopy, Atomic Force Microscopy, Raman Spectroscopy and Nanoindentation, and the results indicated improved bio-physical properties of the ca-alginate microbeads after added with PEG. The cell viability test demonstrated that Ca-alginate-PEG microbeads were able to support the growth of viable HeLa cells into spheroids. Resilient calcium-alginate-polyethylene glycol (Ca-alg-PEG) microbeads were found to be able to last up to 15 days before rupturing and greatly reduced the cell leakage problem.

Svrha ovog rada je odrediti utjecaj hladne plazme na stanice kvasca Saccharomyces cerevisiae S288C. Uzorci kvasca su tretirani različitim protocima plina argona (1, 1.5 i 2 L/min) uz različito vremensko trajanje tretmana (1, 3, 5 i 20 min). Uzorcima je prije i nakon tretmana mjerena temperatura, pH, provodljivost, apsorbancija pri 600 nm za određivanje broja stanica te apsorbancija pri 260 i 280 nm za određivanje istjecanja staničnog sadržaja. Rezultati su analizirani metodom odzivne površine (RSM) korištenjem programa STATGRAPHICS Centurion. Iz rezultata je vidljivo da nije došlo do inaktivacije stanica kvasca jer nije uočena razlika u broju živih stanica prije i nakon tretmana. Najveće stanično istjecanje DNA postignuto je u uzorku tretiranom 5 min protokom plina od 2 L/min gdje je došlo do porasta apsorbancije za 0.591, a najveće stanično istjecanje proteina postignuto je u uzorku tretiranom 1 min protokom plina od 1 L/min gdje je zabilježen porast apsorbancije za 0.635. The aim of this study is to determine the effect of cold plasma on Saccharomyces cerevisiae S288C. Yeast samples were treated with different argon gas flow rates (1, 1.5 and 2 L/ min) with varying duration of treatment (1, 3, 5 and 20 minutes). Before and after treatment, samples were measured for pH, conductivity, absorbance at 600 nm for cell count and absorbance at 260 and 280 nm for determination of cellular leakage. The results were analyzed by the reaction surface method (RSM) using STATGRAPHICS Centurion program. The results showed that there was no cell inactivation because no difference in the number of live cells before and after treatment was shown. The highest cellular DNA leakage was achieved in a sample treated 5 minutes with a gas flow rate of 2 L/min where absorbance was increased by 0.591. The highest cellular protein leakage was achieved in a sample treated 1 minute with a gas flow rate of 1 L/min where absorbance was increased by 0.635.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major problem in clinical settings, and because it is resistant to most antimicrobial agents, MRSA infections are difficult to treat. We previously reported that synthetic macrocyclic bis(bibenzyl) derivatives, which were originally discovered in liverworts, had anti-MRSA activity. However, the action mechanism responsible was unclear. In the present study, we elucidated the action mechanism of macrocyclic bis(bibenzyl) RC-112 and its partial structure, IDPO-9 (2-phenoxyphenol). Survival experiments demonstrated that RC-112 had a bactericidal effect on MRSA, whereas IDPO-9 had bacteriostatic effects. IDPO-9-resistant mutants exhibited cross-resistance to triclosan, but not to RC-112. The mutation was identified in the fabI, enoyl-acyl carrier protein reductase gene, a target of triclosan. We have not yet isolated the RC-112-resistant mutant. On the other hand, the addition of RC-112, unlike IDPO-9, caused the inflow of ethidium and propidium into S. aureus cells. RC-112-dependent ethidium outflow was observed in ethidium-loaded S. aureus cells. Transmission electron microscopy also revealed that S. aureus cells treated with RC-112 had intracellular lamellar mesosomal-like structures. Intracellular Na+ and K+ concentrations were significantly changed by the RC-112 treatment. These results indicated that RC-112 increased membrane permeability to ethidium, propidium, Na+, and K+, and also that the action mechanism of IDPO-9 was different from those of the other compounds.

UNLABELLED This study evaluated the effect of soy lecithin on the bile resistance of Lactobacillus plantarum. Six strains were cultured in MRS broth supplemented with soy lecithin at different concentrations. The strains incubated in MRS broth with 1·0% soy lecithin showed no inhibitory effect on cell growth. After culturing in MRS broth with 0·2-1·0% soy lecithin, the survival rate of harvested cells increased significantly (P < 0·05) in the 0·3% bile challenge compared with the no added soy lecithin group. The cells incubated with 0·6% soy lecithin were able to grow in an MRS broth with a higher bile salt content. The surface hydrophobicity and cell leakage in the bile challenge were assessed to reveal the physical changes caused by the addition of soy lecithin. The cell surface hydrophobicity was enhanced and the membrane integrity in the bile challenge increased after culturing with soy lecithin. A shift in the fatty acid composition was also observed, illustrating the cell membrane change in the soy lecithin culture. SIGNIFICANCE AND IMPACT OF THE STUDY In this study, we report for the first time the beneficial effect of adding soy lecithin to an MRS broth on subsequent bile tolerance of Lactobacillus plantarum. Soy lecithin had no inhibitory effect on strain viability but significantly enhanced bile resistance. Surface hydrophobicity and cell integrity increased in strains cultured with soy lecithin. The observed shift in the cell fatty acid composition indicated changes to the cell membrane. As soy lecithin is safe for use in the food industry, its protective effects can be harnessed for the development of bile-sensitive strains with health-benefit functions for use in probiotic products.

Removal of cyanobacteria from the water column using a coagulant and a ballast compound is a promising technique to mitigate nuisance. As coagulant the organic, biodegradable polymer chitosan has been promoted. Results in this study show that elevated pH, as may be common during cyanobacterial blooms, as well as high alkalinity may hamper the coagulation of chitosan and thus impair its ability to effectively remove positively buoyant cyanobacteria from the water column. The underlying mechanism is likely a shielding of the protonated groups by anions. Inasmuch as there are many chitosan formulations, thorough testing of each chitosan prior to its application is essential. Results obtained in glass tubes were similar to those from standard jar tests demonstrating that glass tube tests can be used for testing effects of coagulants and ballasts in cyanobacteria removal whilst allowing far more replicates. There was no relation between zeta potential and precipitated cyanobacteria. Given the well-known antibacterial activity of chitosan and recent findings of anti-cyanobacterial effects, pre-application tests are needed to decipher if chitosan may cause cell leakage of cyanotoxins. Efficiency- and side-effect testing are crucial for water managers to determine if the selected approach can be used in tailor-made interventions to control cyanobacterial blooms and to mitigate eutrophication.

Chemical encapsulation of microbes in threedimensional polymeric microcapsules promises various applications, such as cell therapy and biosensors, and provides a basic platform for studying microbial communications. However, the cytoprotection of microbes in the microcapsules against external aggressors has been a major challenge in the field of microbial microencapsulation, because ionotropic hydrogels widely used for microencapsulation swell uncontrollably, and are physicochemically labile. Herein, we developed a simple polydopamine coating for obtaining cytoprotective capability of the alginate capsule that encapsulated Saccharomyces cerevisiae. The resulting alginate/ polydopamine core/shell capsule was mechanically tough, prevented gel swelling and cell leakage, and increased resistance against enzymatic attack and UV-C irradiation. We believe that this multifunctional core/shell structure will provide a practical tool for manipulating microorganisms inside the microcapsules.

This paper presents an efficient approach to statistical leakage analysis (SLA) that can estimate the arbitrary n-sigma leakage currents of the VLSI system for the probability density function (PDF) of a lognormal distribution. Unlike existing SLA approaches, the proposed method uses deterministic cell leakage models and gate-level deterministic leakage analysis, and thus, provides significantly reduced analysis complexity. Providing the n-sigma chip leakage current for the PDF of WM-based SLA with a computational complexity of O(N), where N is the number of cells in a chip, the proposed approach is a promising candidate for the analysis of recent technology (comprising billions of logic cells in a chip) to address the high-complexity of conventional approaches to SLA. Compared to conventional WM-based SLA, when the value of n was 5.1803, 3.6022, and 2.8191, the average absolute errors of n-sigma chip leakage current exhibited by the proposed approach were 5.08%, 4.73%, and 4.45%, respectively.

International audience; This paper presents for the first time a TFET/CMOS hybrid CAM architecture designed to address the requirements for ULP (Ultra-Low Power) applications like the IoT (Internet of Things). Proposed design is low power, area efficient and re-configurable i.e. can either be used as CAM or normal SRAM or as a combination of both. The simulation extractions for power and speed are done including wiring and device parasitic capacitances from 16Kb CAM designed in 28nm FDSOI CMOS process using MOSFETs and Tunnel FETs (TFETs). The proposed CAM architecture supports voltage scaling and allows application of performance boosting techniques without impacting cell leakage. Less than 5 fA/bit memory array leakage current is achieved at 1V supply voltage, showing up-to 106× improvement compared with state-of-the-art CMOS SRAM and CAM bitcells, respectively. Minimum write access pulse for CAM and SRAM mode is 1.37ns evaluated at 1V supply voltage. Evaluated access pulse is 1.39ns and 1.03ns for CAM and SRAM mode reads, respectively at 1V.

We propose FinFETs with unequal source and drain doping concentrations [asymmetrically doped (AD) FinFETs] for low-power robust SRAMs. The effect of asymmetric source/drain doping on the device characteristics is extensively analyzed, and the key differences between conventional and AD FinFETs are clearly shown. We show that asymmetry in the device structure leads to unequal currents for positive and negative drain biases, which is exploited to achieve mitigation of read-write conflict in 6T SRAMs. The proposed device exhibits superior short-channel characteristics compared to a conventional FinFET due to reduced electric fields from the terminal that has a lower doping. This results in significantly lower cell leakage in AD-FinFET-based 6T SRAM. Compared to the conventional FinFET-based 6T SRAM, AD-FinFET SRAM shows 5.2%-8.3% improvement in read static noise margin (SNM), 4.1%-10.2% higher write margin, 4.1%-8.8% lower write time, 1.3%-3.5% higher hold SNM, and 2.1-2.5 lower cell leakage at the cost of 20%-23% higher access time. There is no area penalty associated with the proposed technique.

In nano-like or nano-regime trench DRAM products, the product yield usually determines the marketing competition. Due to active area (AA) layer shift in lithography process, the cell leakage and the contact resistance at the source terminal of a cell transistor are increased. These factors will deteriorate the cell integrity in charging and access functions. To monitor this inferiority from lithography deviation, an improved Kelvin measurement and a novel pattern design were recommended. The yield improvement with this technology was really conspicuous.

Dialkyl-alginate biosurfactant is an amphifilik rhamnolipid biosurfactant that has the potential to be developed into an antibacterial agent. The purpose of this study was to prove that the biosurfactant of dialkyl alginate both before and after creams has antibacterial activity especially against Staphylococcus aureus and Pseudomonas aeruginosa . Test of antibacterial activity of biosurfactant dialkyl alginate at concentrations of 5%, 10% and 20% to Staphylococcus aureus and Pseudomonas aeruginosa using Hammond, et al (2011) modified quantitative method. Enbatic® 1% is used as a positive control and sterile aquadest as a negative control. Determination of antibacterial activity of dialkyl alginate biosurfactant followed by analysis of leakage of protein and nucleic acids using UV-vis Spectrophotometry and leakage of Ca 2 + and K + metal ions using Atomic Absorption Spetrophotometry (AAS). The most active concentration was formulated into cream and then performed physical evaluation (organoleptic, pH, adhesion, spreading and viscosity) and tested antibacterial activity using the well method. The test results showed that the biosurfactants of dialkyl-alginate before and after the cream was treated as antibacterial activity. The concentration of 10% was the most active concentration having activity which did not differ significantly to positive control with p value of 0,05

In this study agarose-alginate scaffolds are synthesized using cryogelation technology in different formats like monolith, sheet, discs, and beads, and show amiable mechanical strength like soft tissue properties and high interconnected macroporous degradable architecture. In cell-material interactions, fibroblast (NIH-3T3) cells showed good adherence and proliferation on these scaffolds presenting its potential application in soft tissue engineering. The application of cryogel beads and monoliths was also examined by the efficient immobilization of bacterial cells (BL21) on these matrices revealing their use for recovery of product from continuous fermentation systems without cell leakage. These scaffolds also showed potential as a filter for repeated recovery of heavy metal binding, such as copper and nickel from the waste water. The cryogels prepared herein do have a number of unique features that make them an important class of soft materials for developing multi-featured scaffolds as a novel carrier for bioengineering applications.

Enterobacter sakazakii is an emerging opportunistic pathogen associated with life-threatening illnesses in infants, with infant formula serving as the principal mode of transmission. In the present study, C. sakazakii (formely E. sakazakii) BCRC 13988 was subjected to various heat shock treatments (42-48 degrees C for 5-15 min). Its subsequent survival at 51 degrees C and the leakage of intracellular materials was investigated. It was found that 47 degrees C was the maximum growth temperature of the test organism. In addition, heat shock enhanced the thermal tolerance of C. sakazakii BCRC 13988. Within heat shock temperatures between 42 and 47 degrees C, the thermal tolerance enhancing effect increased as the length or temperature of the heat shock treatment was increased. However, increasing the heat shock temperature to 48 degrees C reduced the thermal tolerance enhancing effect. Among the various heat shocked cells examined, the 47 degrees C-15 min-heat shocked C. sakazakii exhibited the highest thermal tolerance. Moreover, electron micrograph analysis showed that heat shock treatment caused damage and disruption in C. sakazakii cells. There was a significant increase (P

With CO2 and N2 as the pressure media, the effects of the moderate pressure (0.1–1.0MPa) and the holding time on the conductivities of the cell suspension of Saccharomyces cerevisiae CICC1447 and Saccharomyces cerevisiae CICC1339, as well as the absorbances of the supernatant (after centrifuged) at 280 nm (A280) and 260 nm (A260) were determined. The membrane permeability of Saccharomyces cerevisiae CICC1447 increased significantly and the cell leakage was aggravated with the pressure increase. For Saccharomyces cerevisiae CICC1339, the conductivity of the cell suspension, A280 and A260 of the supernatant fluctuated with the pressure increase; as a whole, they increased with pressure. Different from high pressure, a moderate pressure not only remarkably improved the permeability of the yeast cell membrane, but also kept yeast cell viability; moreover, the integrity of the yeast cell membrane could be maintained.

The purpose of the present study was to provide further insights on the applicability of microencapsulation using emulsification method, to immobilise Clostridium acetobutylicum ATCC 824 spores, for biobutanol production. The encapsulated spores were revived using heat shock treatment and the fermentation efficiency of the resultant encapsulated cells was compared with that of the free (non-encapsulated) cells. The microspheres were easily recovered from the fermentation medium by filtration and reused up to five cycles of fermentation. In contrast, the free (non-encapsulated) cells could be reused for two cycles only. The microspheres remained intact throughout repeated use. Although significant cell leakage was observed during the course of fermentation, the microspheres could be reused with relatively high butanol yield, demonstrating their role as microbial cell nurseries. Both encapsulated and liberated cells contributed to butanol production.

An ultralow-standby-power technology has been developed in both 0.18-µm and 0.13-µm lithography nodes for embedded and standalone SRAM applications. The ultralow-leakage six-transistor (6T) SRAM cell sizes are 4.81 µm2 and 2.34 µm2, corresponding respectively to the 0.18-µm and 0.13-µm design dimensions. The measured array standby leakage is equal to an average cell leakage current of less than 50 fA per cell at 1.5 V, 25°C and is less than 400 fA per cell at 1.5 V, 85°C. Dual gate oxides of 2.9 nm and 5.2 nm provide optimized cell leakage, I/O compatibility, and performance. Analyses of the critical parasitic leakage components and paths within the 6T SRAM cell are reviewed in this paper. In addition to the well-known gate-oxide leakage limitation for ULP technologies, three additional limits facing future scaled ULP technologies are discussed.

A negative wordline bias scheme is utilized to reduce the subthreshold leakage of deep submicron DRAM cell transistors. With excessive negative wordline bias, gate-induced drain leakage (GIDL) could dominate cell leakage and degrade product retention time performance. The dependence of retention time on negative wordline bias for a 256-Mbit DRAM with 0.14/spl mu/m ground rule is investigated. The retention fail bit count in the tail distribution increases as wordline bias goes more negative and as temperature increases. A cell array with a density of 1.14M is also characterized for the device leakage behavior. The negative wordline bias and temperature dependent GIDL is believed to be due to band to defect tunneling. Hence, elimination of traps near the oxide/silicon interface in the gate to drain overlap region during the DRAM fabrication process is important for the negative wordline scheme.

Mead is an alcoholic drink known since ancient times, produced by yeast fermenting diluted honey. However, the production of mead has suffered in recent years, partially owing to the lack of scientific progress in this field. In this study, two strains of Saccharomyces cerevisiae, QA23 and ICVD47, were immobilized in 2 or 4% (w/v) alginate beads to assess the most effective alginate concentration for yeast immobilization to produce mead. Neither of the alginate concentrations was able to prevent cell leakage from the beads. The fermentation length was 120 h for both yeast strains. In all cases, at the end of the fermentation, the number of cells entrapped in the beads was higher than the number of free cells, and the total 4% alginate bead wet weight was significantly higher than the 2% alginate bead wet weight. In addition, the evaluation of mead quality showed that the yeast strain had significantly more influence on the physicochemical characteristics than the alginate concentration. Although the yeasts immobilized in the two alginate concentrations were able to perform the fermentation, further research is needed in order to understand the evolution of the yeast population inside the beads throughout the fermentative process. Copyright © 2014 The Institute of Brewing & Distilling

Mead is an alcoholic drink known since ancient times, produced by yeast fermenting diluted honey. However, the production of mead has suffered in recent years, partially owing to the lack of scientific progress in this field. In this study, two strains of Saccharomyces cerevisiae, QA23 and ICVD47, were immobilized in 2 or 4% (w/v) alginate beads to assess the most effective alginate concentration for yeast immobilization to produce mead. Neither of the alginate concentrations was able to prevent cell leakage from the beads. The fermentation length was 120h for both yeast strains. In all cases, at the end of the fermentation, the number of cells entrapped in the beads was higher than the number of free cells, and the total 4% alginate bead wet weight was significantly higher than the 2% alginate bead wet weight. In addition, the evaluation of mead quality showed that the yeast strain had significantly more influence on the physicochemical characteristics than the alginate concentration. Although the yeasts immobilized in the two alginate concentrations were able to perform the fermentation, further research is needed in order to understand the evolution of the yeast population inside the beads throughout the fermentative process. The research presented in this paper was partially funded by the Fundação para a Ciência e Tecnologia, and by the PTDC project (contract PTDC/AGR-ALI/68284/2006). A.P.P. is the recipient of a PhD grant from FCT (SFRH/BD/45820/2008). info:eu-repo/semantics/publishedVersion

A cell immobilization technique to prevent cell leakage from the matrix in a very common system, alginate-Saccharomyces cerevisiae, was investigated. A double coating of immobilized cell beads prev...

Immobilized Nicotiona tabacum cells in calcium alginate gel beads were prepared under various conditions and then were cultivated. The effects of different conditions of preparation, in relation to concentration of calcium ions (Ca2+), on intraparticle cell growth and cell leakage from beads were investigated experimentally. As the amount of Ca2+ incorporated into the beads increased, the numbers of cells leaked from the beads into the medium decreased. However, cell growth was inhibited by high Ca2+ concentrations in the beads. Optimal conditions existed, which prevented cell leakage without inhibiting intraparticle cell growth. The effect of adding CaCl2 to the culture medium was also studied. The Ca2+, used for the alginate crosslinking, gradually leached from the beads with increasing cultivation time, such that the beads gradually became brittle and fragile. The addition of CaCl2 was effective in preventing Ca2+ loss from the beads and cell leakage. © 2000 Society of Chemical Industry

In this study, we investigated the immobilization of loofa sponge as a carrier for plant cells using a novel immobilization reactor, namely, a two-way bubble circular (TBC) reactor, for analyzing the effects of medium flow pattern, A TBC reactor, in which two-way circular flow prevailed and was controlled by bubble flow and sparger adjustment, was developed as a suitable system for plant cell immobilization using loofa sponge. In this system, relatively small aggregates of cultured plant cells could be immobilized, and the entrapped cells grew quickly, avoiding cell leakage from the sponge throughout 31 days of incubation. The optimum immobilization conditions and immobilization mechanism in this system were investigated using Coffea arabica cells as a model cell line. By changing the flow direction of culture medium in the circular reactor periodically between downflow and up-flow, cell immobilization efficiency of the loofa sponge was improved as compared with reactors using one-directional flows. The specific respiration activity of cells immobilized in loofa sponge was also studied. Uniform distribution of cell density and specific respiration activity were obtained along the axial direction of the loofa sponge. In the same reactor system, loofa sponge exhibited high immobilized cell concentration and specific respiration activity not less than those of polyurethane foam.