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Biochemical Engineering Journal (v.48, #3)
Organic solvent-tolerant enzymes by Noriyuki Doukyu; Hiroyasu Ogino (pp. 270-282).
The use of organic solvents as reaction media for enzymatic reactions provides numerous industrially attractive advantages compared to traditional aqueous reaction systems. Despite the advantages, native enzymes almost universally exhibit low activities and/or stabilities in the presence of organic solvents. This inactivation of the enzymes by organic solvents results in significant limitation of the enzymatic reaction process. Numerous attempts have been made to improve enzyme activity and stability in the presence of organic solvents using methods based on protein engineering and chemical or physical modification. Most enzymes used in these studies did not originally exhibit high activity and stability in the presence of organic solvents because they were not screened as organic solvent-tolerant enzymes. Recently, various attempts have been made to screen enzymes that naturally possess organic solvent-tolerance form various microorganisms including organic solvent-tolerant bacteria, thermophiles, halophiles and mesophiles. These organic solvent-tolerant enzymes are expected to have potential for applications in industrial chemical processes.
Keywords: Organic solvent-tolerant; Organic solvent-stable; Enzymes; Non-aqueous; Extremophiles
Engineering cytokine receptors to control cellular functions by Masahiro Kawahara; Hiroshi Ueda; Teruyuki Nagamune (pp. 283-294).
Cytokine receptors function as an interface between a cell and the extracellular milieu, and play a pivotal role in cell fate, because they recognize specific ligands via their extracellular domain and trigger signal transduction via their intracellular domain. Recent advances in unraveling the mechanism of cytokine receptor-mediated signal transduction have allowed us to engineer cytokine receptors with distinct functions, which have a potential for use in biotechnology. This paper reviews the history and current topics of receptor engineering.
Keywords: Chimeric protein; Cytokine; Growth factor; Receptor; Signal transduction
Recent advances of enzymatic reactions in ionic liquids by Muhammad Moniruzzaman; Kazunori Nakashima; Noriho Kamiya; Masahiro Goto (pp. 295-314).
The tremendous potential of room temperature ionic liquids as an alternative to environmentally harmful ordinary organic solvents is well recognized. Ionic liquids, having no measurable vapor pressure, are an interesting class of tunable and designer solvents, and they have been used extensively in a wide range of applications including enzymatic biotransformation. In fact, ionic liquids can be designed with different cation and anion combinations, which allow the possibility of tailoring reaction solvents with specific desired properties, and these unconventional solvent properties of ionic liquids provide the opportunity to carry out many important biocatalytic reactions that are impossible in traditional solvents. As compared to those observed in conventional organic solvents, the use of enzymes in ionic liquids has presented many advantages such as high conversion rates, high enantioselectivity, better enzyme stability, as well as better recoverability and recyclability. To date, a wide range of pronounced approaches have been taken to further improve the performance of enzymes in ionic liquids. This review presents the recent technological developments in which the advantages of ionic liquids as a medium for enzymes have been gradually realized.
Keywords: Biocatalysis; Biotransformation; Bioprocesses; Enzymes stability; Ionic liquids; Water-in-ionic liquid microemulsions
New function and application of the cysteine synthase from archaea by Kazuhiko Ishikawa; Koshiki Mino; Takashi Nakamura (pp. 315-322).
Proposal of the archaea as a discrete domain shed new light on the central problems of early evolution of life and prokaryotic systematics. Recently new amino acid synthesis pathways and new amino acid synthases have been found in archaea from its genome database. The cysteine biosynthesis of many organisms has been studied well and seems to be a crucial metabolic pathway supplying a building block for de novo protein synthesis. The pathway of cysteine biosynthesis of archaea remains to be elucidated. From the characterization of cysteine synthase of hyperthermophilic archaea Aeropyrum pernix, new enzyme O-phosphoserine sulfhydrylase (OPSS; EC 2.5.1.65) which catalyzes the new reaction of synthesis of cysteine from O-phospho-l-serine and sulfide was found. From the finding of OPSS, new pathway for cysteine synthesis was pointed out in archaea and its application has been expected. The unique substrate specificity and characteristics of OPSS seem to be applicable for many fields. In this review, the application of the enzyme and new cysteine synthesis pathway are discussed together with structural study.
Keywords: Cysteine; Synthase; Archaea; Phosphoserine; Sulfhydrylase; Thermophile
Hair follicular cell/organ culture in tissue engineering and regenerative medicine by Bo-Young Yoo; Youn-Ho Shin; Hee-Hoon Yoon; Young-Kwon Seo; Jung-Keug Park (pp. 323-331).
Hair follicles are complex organs composed of the dermal papilla (DP), dermal sheath (DS), outer root sheath (ORS), inner root sheath (IRS) and hair shaft. Development of hair follicles begins towards the end of the first trimester of pregnancy and is controlled by epidermal–mesenchymal interaction (EMI), which is a signaling cascade between epidermal and mesenchymal cell populations. Hair grows in cycles of various phases. Specifically, anagen is the growth phase, catagen is the involuting or regressing phase and telogen is the resting or quiescent phase. Alopecia is not life threatening, but alopecia often causes severe mental stress. In addition, the number of individuals afflicted by alopecia patients has been increasing steadily. Currently there are two methods employed to treat alopecia, drug or natural substance therapy and human hair transplantation. Although drug or natural substance therapy may retard the progress of alopecia or prevent future hair loss, it may also accelerate hair loss when the medication is stopped after prolonged use. Conversely, the transplantation of human hair involves taking plugs of natural hair from areas in which occipital hair is growing and transplanting them to bald areas. However, the number of hairs that can be transplanted is limited in that only three such operations can generally be performed. To overcome such problems, many researchers have attempted to revive hair follicles by culturing hair follicle cells or mesenchymal cells in vitro and then implanting them in the treatment area.
Keywords: Mesenchymal stem cell; Dermal papilla; Outer root sheath; Hair
Practical and functional culture technologies for primary hepatocytes by Hiroyuki Ijima (pp. 332-336).
The liver is a central organ for metabolism in the body, and it is therefore important to develop effective culture methods for the expression of liver-specific functions. The development of effective primary hepatocyte culture methods for the expression of these functions has been attempted by focusing on cell–cell and cell–matrix interactions. Two-dimensional organoid culture methods using substrata with the immobilized arginine–glycine–aspartic acid sequence, a well-known cell-adhesive sequence, have been developed. Furthermore, a drug metabolism simulator and a hybrid-type blood purification system as applications of this type of two-dimensional organoid culture method have been developed. On the other hand, growth factor/heparin-immobilized culture substrata and cell-embedded hydrogels in extracellular matrix-filled biocompatible macroporous scaffold culture systems for liver tissue engineering have been developed. Promotion of organoid formation and high expression of the liver-specific functions of primary rat hepatocytes will be realized by using these substrata and culture systems.
Keywords: Animal cell culture; Biomedical; Bioreactor; Hepatocyte; Immobilization; Liver tissue engineering
Tissue transplantation by stealth—Coherent alginate microcapsules for immunoisolation by Andy Leung; Lars K. Nielsen; Matt Trau; Nicholas E. Timmins (pp. 337-347).
Several of today's most prominent diseases arise as a result of aberrant secretory or enzymatic function, or loss of the corresponding tissue. While an obvious approach to treating these diseases is to simply replace the malfunctioning, damaged, or lost tissue, the need to immunosuppress recipients places them at increased risk of pathogenic infection and development of cancer. Limited availability of donor tissue is also problematic, and while xenogenic tissue could be used in some instances, immunosuppression alone is insufficient to prevent rejection. As an alternative, a physical barrier could be employed to mask the implanted tissue from immune surveillance at a local level, without the need for systemic immunosuppression. This approach is embodied through tissue microencapsulation. We review the underlying rationale of alginate based tissue microencapsulation technologies, current challenges, and possible solutions to these challenges in the form of a simple emulsion coating system incorporating functionalized alginate for local immunomodulation.
Keywords: Encapsulation; Alginate; Transplant; Cell therapy; Emulsion; Membranes
Toward engineering of vascularized three-dimensional liver tissue equivalents possessing a clinically significant mass by Yasuyuki Sakai; Hongyun Huang; Sanshiro Hanada; Toshiki Niino (pp. 348-361).
In this review, we focus on how to develop and rear liver tissue equivalents that can be finally used as liver tissues as a substitute for the original liver. The size should be over 500cm3 and its per-volume-based functionalities should be those comparable to the in vivo liver. As can easily be imagined, it will necessitate continuous efforts and we cannot predict when it becomes feasible at present. However, we need to set up an appropriate road map based on the latest knowledge concerning various related areas and to make efficient and integrative efforts to address the issues. The efforts that are currently required include design and fabrication of scaffolds, procurement of large mass of mature hepatocytes, rearing of the liver tissue equivalents in vitro and proof-of-concept studies in large animals such as pigs. Through the establishment of fundamental methodologies in such preclinical studies, we will know whether we can proceed to human clinical trials of such tissue equivalents. According to the possible road map, we summarized latest related approaches, with consistently stressing the two important but sometimes conflicting standpoints, that is, optimization of oxygenation supply to the cells in both micro- and macro-scale and three-dimensional (3D) culture of hepatocyte progenitors or stem cells toward hepatic lineages. In addition, we tried to clear up the remaining issues and the clues to overcome them.
Keywords: Liver tissue engineering; Vascularization; Three-dimensional (3D) culture; Hepatic differentiation; Stem/progenitor cell; Oxygen carrier
Recent progress in lentiviral vector mass production by Sven Ansorge; Olivier Henry; Amine Kamen (pp. 362-377).
Lentiviral vectors (LV) are promising tools for gene and cell therapy. They are presently used in several clinical trials as in vivo or ex vivo gene delivery vectors. However their mass production remains a challenge and might limit their potential therapeutic use. New robust and scalable processes are required for industrial production of these vectors.In this review, we focus on the assessment of current LV production methods and evaluate the most critical limitations with a focus on scalability. The key properties of LV are described and their inherent advantages and disadvantages discussed. A brief overview of the quantification methods generally used to characterize vector production is also provided as well as indications on downstream processing and basic regulatory aspects.The recent developments in the field including production in serum-free suspension cell cultures indicate that LV production is now amenable to industrial manufacturing using reliable large-scale processes.
Keywords: Abbreviations; Ampho; MLV 4070A envelope; AZT; azidothymidine; BBS; N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES) buffered saline; BIV; bovine immunodeficiency virus; BR; stirred tank bioreactor; cGMP; current good manufacturing practice; CMV; cytomegalovirus; COS-1; COS-1 African green monkey kidney cells; COS-7; COS-7 African green monkey kidney cells; (c)PPT; (central) polypurine tract; CTS; central termination sequence; CV-1; CV-1 African green monkey kidney cells; DMEM; Dulbecco's modified Eagle's medium; DMEM-0; DMEM without serum; DMEM-10; DMEM; +; 10% FBS; dox; doxycycline, tetracycline analog; dpt; days post-transfection; Ecd-on; ecdysone/ponasterone A-response system; EIAV; equine infectious anaemia virus; EMEA; European Medicines Agency; EYFP; enhanced yellow fluorescent protein; FIV; feline immunodeficiency virus; FDA; Food and Drug Administration; G418; geneticin; GALV; gibbon ape leukemia virus; GFP; green fluorescent protein; GFP+; quantification of GFP-positive cells; HBS; HEPES buffered saline; HEK293; human embryonic kidney cell line; HIV; human immunodeficiency virus; HOS; human osteosarcoma cells; hpt; hours post-transfection; HT1080; human fibrosarcoma cell line; HyQ; HyClone SFM4Transfx-293™, commercial serum-free medium formulation; ICH; International Conference on Harmonisation; IEX; anion exchange chromatography purification; lacZ(co); (codon-optimized) bacterial lacZ; LCR; locus control region; LTR; long terminal repeat; LV; lentiviral vectors; MT4; human T cell lymphotropic virus-I (HTLV-I) carrying human T cell line; n.a.; not available; nlacZ; nuclear localized β-galactosidase enzyme; PB; Polybrene; PEI; polyethylenimine; UC; UltraCULTURE™, commercial serum-free medium formulation; YFP; +; quantification of YFP-positive cells; IMDM; Iscove's modified Dulbeccos's medium; MLV; Moloney Leukemia virus; PB; Polybrene; ®; RCL; replication-competent lentiviruses; RD114; feline endogenous virus RD114 envelope; RNA; ribonucleic acid; RRE; rev; responsive element; RRV; Ross River virus; RV; retroviral vectors; SEC; size exclusion chromatography; SFV; Semliki Forest virus; SIN; self-inactivating; SIV; simian immunodeficiency virus; spec.prod.; specific productivity (tu/cell), based on cell density at transfection; Tet; tetracycline; Tet-off; tet-inducible system: tet/dox removal required for induction/transcription; Tet-on; tet-inducible system: tet/dox addition required for induction/transcription; tu; transducing units; vif; virus infectivity factor; vpr; viral protein R; VSV-G; vesicular stomatitis virus glycoprotein G; WHO; World Health Organization; WPRE; woodchuck hepatitis virus post-transcriptional regulatory elementAnimal and insect cell culture engineering; Virus production; Viral vectors; Lentiviral vectors; Scalable processes; Large-scale production
Development of scalable culture systems for human embryonic stem cells by Samira M. Azarin; Sean P. Palecek (pp. 378-384).
The use of human pluripotent stem cells, including embryonic and induced pluripotent stem cells, in therapeutic applications will require the development of robust, scalable culture technologies for undifferentiated cells. Advances made in large-scale cultures of other mammalian cells will facilitate expansion of undifferentiated human embryonic stem cells (hESCs), but challenges specific to hESCs will also have to be addressed, including development of defined, humanized culture media and substrates, monitoring spontaneous differentiation and heterogeneity in the cultures, and maintaining karyotypic integrity in the cells. This review will describe our current understanding of environmental factors that regulate hESC self-renewal and efforts to provide these cues in various scalable bioreactor culture systems.
Keywords: Human embryonic stem cells; Culture scale-up; Bioreactors
Application of flow cytometry to industrial microbial bioprocesses by Mario Díaz; Mónica Herrero; Luis A. García; Covadonga Quirós (pp. 385-407).
Flow cytometry (FC) is a powerful technique for the rapid analysis of single cells in a mixture, by means of light-scattering and fluorescence measurements. In biotechnology, the power of this method lies both in the possibility of determining a wide range of cell parameters at single cell level, and in the ability to obtain information about their distribution within cell populations, providing valuable information for bioprocess design and control. The first part of this review will be devoted to describe the basic aspects of multicolour FC, the different strategies used for cell detection, and the cellular target sites and fluorescent probes which are currently used in cell assays. Next, a deep revision concerning the most recent FC applications related to cell analysis and quantification (especially both bacteria and yeast) in food, drink and pharmaceutical industries and in natural environment and water systems is presented. This review seeks to highlight the advantages of this technique in microbial fermentations monitoring and control, as well as in the development of more accurate kinetic models directed to bioprocesses optimization. Finally, an overview of some commercial FC devices is presented along with a discussion of the progress and advantages of the method for bioprocesses on-line monitoring.
Keywords: Flow cytometry; Instrumentation; Cell parameters; Bioprocesses control; Optimization; Kinetic modelling
Molecular simulation of adsorption and its implications to protein chromatography: A review by Lin Zhang; Yan Sun (pp. 408-415).
Adsorption on solid surface is of fundamental importance in the research and development of chromatographic science and technology. Due to the limitation of the currently available experimental approaches, molecular simulation, a research tool with sufficiently small scales in both time and space, has been used to explore the molecular insights into adsorption phenomena. This article offers an overview of the molecular simulation studies of adsorption on solid surfaces. First of all, various models of adsorbents used in different chromatographic modes are reviewed, including coarse-grained models and all-atom models, depending on the description precision required and the computational power provided. In the adsorbent models, the surface morphology is visualized using Monte Carlo simulation or molecular dynamics simulation. Then, studies on the adsorption and retention behaviors of small molecules by these models and methods are summarized. Finally, emphases are focused on the application of molecular simulation to protein adsorption, including protein–surface interaction, protein orientation and conformational transition on solid surfaces. In these studies, the effects of ligand parameters, including the ligand composition, ligand length, bonding density, ligand distribution have been examined. Meanwhile, chromatographic parameters, including the mobile phase composition and temperature, have also been investigated. Based on the successful applications reviewed herein, it is concluded that molecular simulation studies have contributed to the development of adsorption and chromatography in bioseparations. Moreover, it is suggested that molecular simulation combined with computational quantum chemistry and experiments would provide more comprehensive understanding of adsorption phenomena in the future.
Keywords: Bioseparation; Adsorption; Chromatography; Molecular simulation; Retention behavior; Conformational transition
Potential uses of titanium dioxide in conjunction with ultrasound for improved disinfection by Nobuaki Shimizu; Kazuaki Ninomiya; Chiaki Ogino; Mohammad Mizanur Rahman (pp. 416-423).
The inactivation of hazardous microorganisms is an important subject for water treatment. While the most widely used methods in water treatment systems are chlorination, ozonation, and ultraviolet ray irradiation, the drawbacks of these techniques surpass their efficacy. The potential formation of carcinogenic chemical byproducts has been reported as a drawback of chemical disinfection methods, hence there is a need to develop some alternate disinfection techniques. Ultrasonic (US) irradiation is well known as a useful technique for microbial inactivation due to its chemical and physical factors. Our recent studies indicated that the presence of titanium dioxide (TiO2), known as a photocatalyst, accelerates the generation of hydroxyl (OH) radicals during US irradiation, and that the process is mediated through the induction of cavitation bubbles in irradiating solutions. This review describes a disinfection method that utilizes US irradiation of contaminated solution in the presence of TiO2, a so-called “sonocatalytic disinfection” method. The significant role of OH radicals in the mechanism of cell-killing is discussed.
Keywords: Disinfection; Titanium dioxide; Ultrasonic irradiation; Hydroxyl radical; Cavitation
Bacterial adhesion: From mechanism to control by Katsutoshi Hori; Shinya Matsumoto (pp. 424-434).
Bacterial adhesion is the initial step in colonization and biofilm formation. Biofilms can, on the one hand, be detrimental to both human life and industrial processes, for example, causing infection, pathogen contamination, and slime formation, while on the other hand, be beneficial in environmental technologies and bioprocesses. For control and utilization of bacterial adhesion and biofilms, adhesion mechanisms must be elucidated. Conventional physicochemical approaches based on Lifshitz-van der Waals, electrostatic and acid–base interactions provide important models of bacterial adhesion but have a limited capacity to provide a complete understanding of the complex adhesion process of real bacterial cells. In conventional approaches, bacterial cells, whose surfaces are structurally and chemically heterogeneous, are often described from the viewpoint of their overall cellular properties. Cell appendages such as polysaccharide chains and proteinous nanofibers have an important function bridging between cells and the substratum in conventional adhesion models, but sometimes cause deviation from the models of cell adhesion. In reality, cell appendages are responsible for specific and nonspecific cell adhesion to biotic and abiotic surfaces. This paper reviews conventional physicochemical models and cell appendage-mediated cell adhesion. State-of-the-art technologies for controlling microbial adhesion and biofilm formation are also described. These technologies are based on the adhesion mechanisms.
Keywords: Adhesion; Biofilm; DLVO theory; Surface potential; Bacterial nanofiber; Polysaccharide