JBB : Journal of Bioscience and Bioengineering

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Journal of Bioscience and Bioengineering vol.119 cover

Journal of Bioscience and Bioengineering – Recent Articles

  • Characterization of glycerophosphoethanolamine ethanolaminephosphodiesterase from Streptomyces sanglieri
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Shingo Mineta , Kazutaka Murayama , Daisuke Sugimori

    Streptomyces sanglieri extracellularly produces a glycerophosphoethanolamine ethanolaminephosphodiesterase (GPE-EP). The gene encoding the enzyme was found to consist of a 2124-bp ORF, which codes for an N-terminal 48 residue signal peptide required for secretion and a 660 amino acid mature protein with a calculated molecular mass of 72,918 Da. The maximum activity for sn-glycero-3-phosphoethanolamine (GPE) was found at pH 8.4 and 65°C in the presence of 0.1% (w/v) Triton X-100. The enzyme was activated in the presence of 2 mM EDTA; however, Zn2+ remarkably inhibited activity. During the hydrolysis of GPE at 65°C and pH 8.4, the apparent V max, turnover number (k cat) and K m were determined to be 0.430 mmol min−1 mg-protein−1, 522 s−1 and 0.785 mM, respectively. The enzyme exhibited specificity toward GPE and hydrolyzed ethanolamine-type substrates such as 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine, lysophosphatidylethanolamine and ethanolamine lysoplasmalogen, but not 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine. Moreover, the enzyme showed no activity toward other phospholipids, such as glycerophospholipids and plasmalogens, and sn-glycero-3-phosphodiesters except for sn-glycero-3-phosphoglycerol, suggesting that GPE-EP is not a phospholipase C (PLC). However, the amino acid sequence of GPE-EP shows 86% identity to that of PLC from Streptomyces sp. SirexAA-E (UniProt accession no. G2NFN1). Recombinant GPE-EP was functionally expressed in Escherichia coli using pET-24a(+). GPE hydrolysis by GPE-EP may represent a new pathway for phosphatidylethanolamine metabolism.





  • Improvement of glycosylation structure by suppression of β-N-acetylglucosaminidases in silkworm
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Tsuyoshi Nomura , Masatoshi Suganuma , Yukiko Higa , Yukiko Kataoka , Shunsuke Funaguma , Hironobu Okazaki , Takeo Suzuki , Isao Kobayashi , Hideki Sezutsu , Kazuhito Fujiyama

    The baculovirus-silkworm recombinant protein expression system is an excellent method for achieving high-level expression and post-translational modifications, especially glycosylation. However, the presence of paucimannosidic-type N-glycan in glycoproteins restricts their clinical use. Paucimannosidic-type N-glycan is produced by insect-specific membrane-binding-type β-N-acetylglucosaminidase (GlcNAcase). In the silkworm, BmGlcNAcase1, BmGlcNAcase2, and BmFDL are membrane-binding-type GlcNAcases. We investigated the localization of these GlcNAcases and found that BmFDL and BmGlcNAcase2 were mainly located in the fat body and hemolymph, respectively. The fat body is the main tissue of recombinant protein expression by baculovirus, and many glycoproteins are secreted into the hemolymph. These results suggest that inhibition of BmFDL and BmGlcNAcase2 could increase GlcNAc-type N-glycan levels. We therefore injected a GlcNAcase inhibitor into silkworms to investigate changes in the N-glycan structure of the glycoprotein expressed by baculovirus; modest levels of GlcNAc-type N-glycan were observed (0.8% of total N-glycan). Next, we generated a transgenic silkworm in which RNA interference (RNAi) reduced the BmFDL transcript level and enzyme activity to 25% and 50%, respectively, of that of the control silkworm. The proportion of GlcNAc-type N-glycan increased to 4.3% in the RNAi-transgenic silkworm. We conclude that the structure of N-glycan can be changed by inhibiting the GlcNAcases in silkworm.





  • In vitro selection of a photoresponsive peptide aptamer to glutathione-immobilized microbeads
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Seiichi Tada , Qingmin Zang , Wei Wang , Masuki Kawamoto , Mingzhe Liu , Michiru Iwashita , Takanori Uzawa , Daisuke Kiga , Masayuki Yamamura , Yoshihiro Ito

    Photoresponsive peptide aptamer to glutathione-immobilized microbeads was in vitro selected using ribosome display incorporated with tRNA carrying an amino acid coupled with an azobenzene.





  • Isolation and characterization of awamori yeast mutants with l-leucine accumulation that overproduce isoamyl alcohol
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Hiroshi Takagi , Keisuke Hashida , Daisuke Watanabe , Ryo Nasuno , Masataka Ohashi , Tomoya Iha , Maiko Nezuo , Masatoshi Tsukahara

    Awamori shochu is a traditional distilled alcoholic beverage made from steamed rice in Okinawa, Japan. Although it has a unique aroma that is distinguishable from that of other types of shochu, no studies have been reported on the breeding of awamori yeasts. In yeast, isoamyl alcohol (i-AmOH), known as the key flavor of bread, is mainly produced from α-ketoisocaproate in the pathway of l-leucine biosynthesis, which is regulated by end-product inhibition of α-isopropylmalate synthase (IPMS). Here, we isolated mutants resistant to the l-leucine analog 5,5,5-trifluoro-dl-leucine (TFL) derived from diploid awamori yeast of Saccharomyces cerevisiae. Some of the mutants accumulated a greater amount of intracellular l-leucine, and among them, one mutant overproduced i-AmOH in awamori brewing. This mutant carried an allele of the LEU4 gene encoding the Ser542Phe/Ala551Val variant IPMS, which is less sensitive to feedback inhibition by l-leucine. Interestingly, we found that either of the constituent mutations (LEU4 S542F and LEU4 A551V) resulted in the TFL tolerance of yeast cells and desensitization to l-leucine feedback inhibition of IPMS, leading to intracellular l-leucine accumulation. Homology modeling also suggested that l-leucine binding was drastically inhibited in the Ser542Phe, Ala551Val, and Ser542Phe/Ala551Val variants due to steric hindrance in the cavity of IPMS. As we expected, awamori yeast cells expressing LEU4 S542F, LEU4 A551V, and LEU4 S542F/A551V showed a prominent increase in extracellular i-AmOH production, compared with that of cells carrying the vector only. The approach described here could be a practical method for the breeding of novel awamori yeasts to expand the diversity of awamori taste and flavor.





  • Two transaldolase isogenes from Moniliella megachiliensis behave in a different way depending on the stress class
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Hisashi Iwata , Daiki Mizushima , Yosuke Kobayashi , Tetsuya Ookura , Jun Ogihara , Jun Kato , Takafumi Kasumi

    We cloned and sequenced two transaldolase genes from Moniliella megachiliensis, a microorganism known to produce a significant amount of erythritol under hyper-osmotic stress. The amino acid sequences encoded by these two genes (MmTAL1, MmTAL2) showed 72% homology to each other. An AP-1 (ap response element) associated with oxidative stress was found in the promoter region of MmTAL1, while four STREs (stress response element) associated with osmotic stress were found in the promoter region of MmTAL2. In early-stage cultivation (up to 2 h), MmTAL1 was specifically expressed in response to oxidative stress generated by the presence of 0.15 mM menadione; expression level 3-fold higher than before stress loading. MmTAL2 was expressed in response to osmotic stress caused by 1.2 M NaCl; expression level was 21-fold higher than stress-free control. Erythritol accumulated intracellularly under osmotic and oxidative stress, approximately 30-fold and 35-fold, respectively. We therefore concluded that M. megachiliensis selectively uses two isogenes and produces erythritol during early-stage response to stress, depending on the type of environmental stress.





  • Fed-batch fermentation for enhanced lactic acid production from glucose/xylose mixture without carbon catabolite repression
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Mohamed Ali Abdel-Rahman , Yaotian Xiao , Yukihiro Tashiro , Ying Wang , Takeshi Zendo , Kenji Sakai , Kenji Sonomoto

    There has been tremendous growth in the production of optically pure l-lactic acid from lignocellulose-derived sugars. In this study, Enterococcus mundtii QU 25 was used to ferment a glucose/xylose mixture to l-lactic acid. Maintenance of the xylose concentration at greater than 10 g/L achieved homo-lactic acid fermentation and reduced the formation of byproducts. Furthermore, carbon catabolite repression (CCR) was avoided by maintaining the glucose concentration below 25 g/L; therefore, initial concentrations of 25 g/L glucose and 50 g/L xylose were selected. Supplementation with 5 g/L yeast extract enhanced the maximum xylose consumption rate and consequently increased lactic acid production and productivity. Finally, a 129 g/L lactic acid without byproducts was obtained with a maximum lactic acid productivity of 5.60 g/(L·h) in fed-batch fermentation with feeding a glucose/xylose mixture using ammonium hydroxide as the neutralizing agent. These results indicate a potential for lactic acid production from glucose and xylose as the main components of lignocellulosic biomasses.





  • Influence of ofloxacin on photosystems I and II activities of Microcystis aeruginosa and the potential role of cyclic electron flow
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Chunnuan Deng , Xiangliang Pan , Daoyong Zhang

    Pollution with antibiotics poses a great risk to aquatic ecosystems. Although some toxic effects of antibiotics on photosystem II (PSII) have been documented, their toxicity to photosystem I (PSI) is still unclear. In this study, effects of ofloxacin on activities of both PSI and PSII of Microcystis aeruginosa (Kützing) Kützing were investigated. Exposure to 0.1 mg L 1 ofloxacin led to increases in contents of chlorophyll a and carotenoids and photosynthetic activity of M. aeruginosa. PSI activity and its electron transport were not affected by 0.1 mg L 1 ofloxacin. When M. aeruginosa was exposed to ≥10 mg L 1 ofloxacin, the electron transport rates of PSI and PSII, the yield of cyclic electron flow (CEF) and the contribution of linear electron flow (LEF) to PSI decreased whereas Y(NA) (limitation of donor side of PSI) and Y(NO) (the quantum yield of non-regulated energy dissipation in PSII) significantly increased. CEF had a significant contribution to alleviating the inhibitory effect of ofloxacin on PSI of M. aeruginosa treated with low concentrations of ofloxacin. The protective role CEF for tolerance of PSI to the toxicity of ofloxacin decreased with increasing ofloxacin concentration.





  • Production of squalene by squalene synthases and their truncated mutants in Escherichia coli
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Akinori Katabami , Ling Li , Miki Iwasaki , Maiko Furubayashi , Kyoichi Saito , Daisuke Umeno

    Squalene is a precursor of thousands of bioactive triterpenoids and also has industrial value as a lubricant, health-promoting agent, and/or drop-in biofuel. To establish an efficient Escherichia coli-based system for squalene production, we tested two different squalene synthases and their mutants in combination with precursor pathways. By co-expressing a chimeric mevalonate pathway with human or Thermosynechococcus squalene synthase, E. coli accumulated squalene up to 230 mg/L or 55 mg/g-DCW in flask culture. We also determined that a significant truncation of squalene synthase at the C-terminus retains partial cellular activity. The squalene-producing strain described herein represents a convenient platform for gene discovery and the construction of the pathway toward natural and non-natural hopanoids/steroids.





  • Trehalose accumulation enhances tolerance of Saccharomyces cerevisiae to acetic acid
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Yoko Yoshiyama , Koichi Tanaka , Kohei Yoshiyama , Makoto Hibi , Jun Ogawa , Jun Shima

    Trehalose confers protection against various environmental stresses on yeast cells. In this study, trehalase gene deletion mutants that accumulate trehalose at high levels showed significant stress tolerance to acetic acid. The enhancement of trehalose accumulation can thus be considered a target in the breeding of acetic acid-tolerant yeast strains.





  • Enhancement of l-cysteine production by disruption of yciW in Escherichia coli
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Yusuke Kawano , Iwao Ohtsu , Kazuhiro Takumi , Ai Tamakoshi , Gen Nonaka , Eri Funahashi , Masaki Ihara , Hiroshi Takagi

    Using in silico analysis, the yciW gene of Escherichia coli was identified as a novel l-cysteine regulon that may be regulated by the transcriptional activator CysB for sulfur metabolic genes. We found that overexpression of yciW conferred tolerance to l-cysteine, but disruption of yciW increased l-cysteine production in E. coli.





  • Autotrophic denitrification performance and bacterial community at biocathodes of bioelectrochemical systems with either abiotic or biotic anodes
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Van Khanh Nguyen , Sungsug Hong , Younghyun Park , Kyungmin Jo , Taeho Lee

    Two-chamber bioelectrochemical systems (BESs) have recently been developed for nitrate removal from nitrate-contaminated water. In this study, we compared the nitrate removal performance of biocathodes of BESs when using abiotic and biotic anodes. Acetate was used as electron donor in BESs with biotic anode, whereas a direct current power supply was used as energy source in BESs with abiotic anode. The nitrogen removal efficiency increased from 18.1% to 43.0% when the voltage supplied to the BES with abiotic anode increased from 0.7 V to 0.9 V, whereas no higher removal efficiency was obtained at a higher supplied voltage (1.1 V). The highest efficiency (78.0%) of autotrophic nitrogen removal was achieved when electron transfer from the biotic anode chamber of BESs was used. Unexpectedly, control of the cathode potential did not enhance nitrate removal in BESs with biotic anode. Special attention was paid to elucidate the differences of bacterial communities catalysing autotrophic denitrification in the biocathodes of BESs with abiotic and biotic anodes. Data from denaturing gradient gel electrophoresis and phylogenetic analysis suggested that denitrification in BESs with abiotic anode could be attributed to Nitratireductor sp., Shinella sp., and Dyella sp., whereas the dominant bacterial denitrifiers in BESs with biotic anode were found to be Pseudomonas sp., Curtobacterium sp., and Aeromonas sp. These results implied that biocathodes of BESs with biotic anode are more efficient than those of BESs with abiotic anode for nitrate removal from nitrate-contaminated water in practical applications.





  • Humin as an electron donor for enhancement of multiple microbial reduction reactions with different redox potentials in a consortium
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Dongdong Zhang , Chunfang Zhang , Zhixing Xiao , Daisuke Suzuki , Arata Katayama

    A solid-phase humin, acting as an electron donor, was able to enhance multiple reductive biotransformations, including dechlorination of pentachlorophenol (PCP), dissimilatory reduction of amorphous Fe (III) oxide (FeOOH), and reduction of nitrate, in a consortium. Humin that was chemically reduced by NaBH4 served as an electron donor for these microbial reducing reactions, with electron donating capacities of 0.013 mmol e/g for PCP dechlorination, 0.15 mmol e/g for iron reduction, and 0.30 mmol e/g for nitrate reduction. Two pairs of oxidation and reduction peaks within the humin were detected by cyclic voltammetry analysis. 16S rRNA gene sequencing-based microbial community analysis of the consortium incubated with different terminal electron acceptors, suggested that Dehalobacter sp., Bacteroides sp., and Sulfurospirillum sp. were involved in the PCP dechlorination, dissimilatory iron reduction, and nitrate reduction, respectively. These findings suggested that humin functioned as a versatile redox mediator, donating electrons for multiple respiration reactions with different redox potentials.





  • Reflectometric interference spectroscopy-based immunosensing using immobilized antibody via His-tagged recombinant protein A
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Hyung Woo Choi , Yasuhiko Sakata , Tooru Ooya , Toshifumi Takeuchi

    The proposed approach demonstrated in this study provides an immunosensing system based on reflectometric interference spectroscopy (RIfS) in combination with an antibody immobilization method using histidine-tagged recombinant protein A. Carboxymethyldextran (CMD) was immobilized on a 3-aminopropyltriethoxysilane-treated a silicon nitride-coated silicon wafer, followed by chelating histidine-tagged recombinant protein A with copper (II) ions. The CMD-layer was found to be advantageous in terms of not only immobilization of histidine-tagged recombinant protein A-mediated an antibody against myoglobin (anti-Myo) but also prevention of non-specific binding of myoglobin. Myoglobin was repeatedly detected, and the apparent detection limit was 0.1 μg mL−1. The proposed RIfS-based protein sensing system, in conjunction with the easy preparation of silicon-based inexpensive immunosensing chips, is expected to be applicable for label-free optical detection for other proteins in various fields.





  • Molecularly imprinted protein recognition thin films constructed by controlled/living radical polymerization
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Shogo Sasaki , Tooru Ooya , Yukiya Kitayama , Toshifumi Takeuchi

    We demonstrated the synthesis of molecularly imprinted polymers (MIPs) with binding affinity toward a target protein, ribonuclease A (RNase) by atom transfer radical polymerization (ATRP) of acrylic acid, acrylamide, and N,N′-methylenebisacrylamide in the presence of RNase. The binding activity of the MIPs was evaluated by surface plasmon resonance (SPR) of the MIP thin layers prepared on the gold-coated sensor chips. The MIPs prepared by ATRP (MIP-ATRP) had a binding affinity toward RNase with larger binding amount compared to MIPs prepared by conventional free radical polymerization methods (MIP-RP). Moreover, protein selectivity was evaluated using reference proteins (cytochrome c, myoglobin, and α-lactalbumin) and was confirmed in MIP-ATRP of optimum film thickness determined experimentally to be 15–30 nm; however, protein selectivity was not achieved in all MIP-RP. We have shown that ATRP is powerful technique for preparing protein recognition materials by molecular imprinting.





  • Simultaneous recovery and purification of rice protein and phosphorus compounds from full-fat and defatted rice bran with organic solvent-free process
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Masanori Watanabe , Isamu Maeda , Masahiro Koyama , Kozo Nakamura , Kazuo Sasano

    We studied a process that enables simultaneous recovery of protein and phosphorus compounds from rice bran. Phosphorus substances in full-fat and defatted rice bran such as phytic acid and inorganic ions were solubilized under acidic conditions in the first step. After that, inorganic and/or organic phosphate salts were recovered in insoluble form under weak alkaline conditions. Furthermore, protein fractions obtained after phosphorus compounds had been removed were solubilized under alkaline conditions. After solubilization, protein fractions with high content were recovered by isoelectric precipitation (IP) followed by electrolyzed water treatment (EWT). The highest protein content (52.3 w/w%) was attained when machine defatted rice bran was treated through the process. Energy-dispersive X-ray spectroscopy (EDX) and inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses demonstrated efficient desalting from the protein fractions by EWT and higher phosphorus contents (15.1–16.4 w/w% P) in the phosphorus fractions compared with commercial phosphate rock. In addition, no heavy metal ions in either protein or phosphorus fractions were detected. These results suggest that the newly developed process is suitable for practical recovery of highly concentrated protein and phosphorus compounds from rice bran without enzymes or chemicals such as organic solvents, buffering agents, and surfactants.





  • Microfluidic devices for construction of contractile skeletal muscle microtissues
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Kazunori Shimizu , Hiroyuki Araki , Kohei Sakata , Wataru Tonomura , Mitsuru Hashida , Satoshi Konishi

    Cell-culture microchips mimicking tissue/organ-specific functions are required as alternatives to animal testing for drug discovery and disease models. Although three-dimensional (3D) cell culture microfluidic devices can create more biologically relevant cellular microenvironments and higher throughput analysis platforms of cell behavior than conventional techniques, devices for skeletal muscle cells have not been developed. In the present study, we aimed to develop microfluidic devices for 3D cultures of skeletal muscle cells. Skeletal muscle cells mixed with a collagen type-I solution was introduced into the microchannel for cells (MC-C) and was gelated. Then, the medium was introduced into the microchannel for medium (MC-M). During this process, connecting microchannels (Con-MCs) prevented leakage of the collagen solution mixed with cells from MC-C to MC-M and supplied the nutrients from the medium in MC-M to the cells in MC-C. Skeletal muscle microtissues cultured in the microchannel for a week consisted of myotubes were confirmed by histological analysis and immunofluorescence staining. The skeletal muscle microtissues in the microchannel contracted in response to externally applied electrical stimulation (1 and 50 Hz). These results indicate that the functional skeletal muscle microtissues were constructed in the microchannel. Thus, the microfluidic device for culturing 3D skeletal muscle microtissues presented in this study has a potential to be used for drug discovery and toxicological tests.





  • Gamma-cross-linked nonfibrillar collagen gel as a scaffold for osteogenic differentiation of mesenchymal stem cells
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Takako Takitoh , Masahiko Bessho , Motohiro Hirose , Hajime Ohgushi , Hideki Mori , Masayuki Hara

    We fabricated a transparent nonfibrillar collagen gel using gamma irradiation (5 kGy) and cultured rat mesenchymal stem cells (MSCs) on both the gamma-irradiated collagen gel and on unirradiated fibrillar collagen gel. Cells attached well and proliferated with high viability on the surface of both gels. The cells cultured on the gamma-irradiated nonfibrillar gel had a unique elongated shape and adhered to each other in culture. After 21 days of culture in dexamethasone-containing culture medium, the contents of bone-specific osteocalcin and calcium on the gamma-irradiated nonfibrillar gel were 1.4 and 1.9 times higher than those on fibrillar collagen gel, respectively. These data show that osteogenic differentiation of MSCs was promoted more efficiently on the gamma-cross-linked nonfibrillar gel than on the fibrillar gel and demonstrate the potential of the gamma-irradiated collagen gel for use in bone tissue engineering.





  • Hydrocortisone and triiodothyronine regulate hyaluronate synthesis in a tissue-engineered human dermal equivalent through independent pathways
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Madhura Deshpande , Suzanne Papp , Lana Schaffer , Tara Pouyani

    Hydrocortisone (HC) and triiodothyronine (T3) have both been shown to be capable of independently inhibiting hyaluronate (HA, hyaluronic acid) synthesis in a self-assembled human dermal equivalent (human dermal matrix). We sought to investigate the action of these two hormones in concert on extracellular matrix formation and HA inhibition in the tissue engineered human dermal matrix. To this end, neonatal human dermal fibroblasts were cultured in defined serum-free medium for 21 days in the presence of each hormone alone, or in combination, in varying concentrations. Through a process of self-assembly, a substantial dermal extracellular matrix formed that was characterized. The results of these studies demonstrate that combinations of the hormones T3 and hydrocortisone showed significantly higher levels of hyaluronate inhibition as compared to each hormone alone in the human dermal matrix. In order to gain preliminary insight into the genes regulating HA synthesis in this system, a differential gene array analysis was conducted in which the construct prepared in the presence of 200 μg/mL HC and 0.2 nM T3 was compared to the normal construct (0.4 μg/mL HC and 20 pM T3). Using a GLYCOv4 gene chip containing approximately 1260 human genes, we observed differential expression of 131 genes. These data suggest that when these two hormones are used in concert a different mechanism of inhibition prevails and a combination of degradation and inhibition of HA synthesis may be responsible for HA regulation in the human dermal matrix.





  • Relative charge density model on chitosan–fucoidan electrostatic interaction: Qualitative approach with element analysis
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Eun Ju Lee , Kwang-Hee Lim

    This paper proposes a relative charge density model of prepared chitosan-fucoidan nanoparticles (CFNs) to provide insight into an analysis of the ionic interactions in terms of polyelectrolyte complexes. Using the relative charge density model, the extent of the ionic interactions is predicted in terms of the pH (2 through 6) and used fucoidan to chitosan mass ratio (FCMR) (1:0.05 through 1:1), through which the formation of CFNs can be controlled to be ranked qualitatively according to size and stability. It was confirmed by the measurements of their zeta potentials and sizes and by the analysis of their decay with time. Moreover, the relative charge density model was validated to predict the isoelectric condition of a polyelectrolyte complexed suspension of CFNs. Elemental analysis with a proper mass-conversion showed that the ratio of the stoichiometric coefficients of sulfate groups to amino groups in CFNs formed were almost consistent to that of the sulfate groups to amino groups in a chitosan solution mixed with a fucoidan solution prior to the occurrence of polyelectrolyte complexation. In a pH 2-environment, there were locally intensive electrostatic interactions with a low yield to form sulfate group-rich CFNs. In contrast, in a pH 6-environment, extensive electrostatic interactions occurred to form sulfate group-poor CFNs with a high yield. In addition to the chitosan-amide groups, the separate yield-distribution of loaded chitosan indicated the possible involvement of positively charged amino groups in the electrostatic interactions among chitosan molecules.





  • Simple and reliable urea assay based on a signal accumulation type of ion-sensitive field-effect transistor
    Publication date: February 2015
    Source:Journal of Bioscience and Bioengineering, Volume 119, Issue 2

    Author(s): Naohiro Tomari , Asako Kawasaki , Yoshihiro Yamamoto , Yoshiaki Nishiya

    A simple urea assay was developed using a signal accumulation type of ion-sensitive field-effect transistor (SA-ISFET). Decreases in proton concentration resulting from urease-catalyzed hydrolysis of urea are detected by SA-ISFET as a change in potential. The method exhibits high sensitivity, linearity, and reproducibility when potential signals are accumulated 10-fold.