Aqueous counter collision using paired water jets as a novel means of preparing bio-nanofibers.

This study involved a detailed investigation of a novel approach to reducing naturally occurring cellulose fibers into nanofibers solely by the use of aqueous counter collision (ACC) without any chemical modification. In this process, equivalent aqueous suspensions of cellulose are ejected from dual nozzles and collide at high speed and pressure. Even a few repetitions of the collision process are sufficient to produce nano-sized fibers dispersed in water. This work compared the ACC nano-pulverization of stable Iß-rich and meta-stable Iα-rich cellulose samples. The ACC method is applicable to various kinds of polymeric materials with hierarchical structures, either natural or synthetic, as a means of preparing aqueous dispersions of nano-sized structures.

Autonomous bottom-up fabrication of three-dimensional nano/microcellulose honeycomb structures, directed by bacterial nanobuilder.

We investigated the autonomous bottom-up fabrication of three-dimensional honeycomb cellulose structures, using Gluconacetobacter xylinus as a bacterial nanoengine, on cellulose honeycomb templates prepared by casting water-in-oil emulsions on glass substrates (Kasai and Kondo, Macromol. Biosci., 4, 17-21, 2004). The template film had a unique molecular orientation state along the honeycomb frames, but was non-crystalline. When G. xylinus, used as a nanofiber-producing bacterium, was incubated on the honeycomb scaffold in a culture medium, it secreted cellulose nanofibers only on the upper surface of the honeycomb frame. The movement was regulated by a selective interaction between the synthesized nanofiber and the surface of the honeycomb frames of the template. The relationship between directed deposition of synthesized nanofibers and ordered fabrication from the nano- to the micro-scale could provide a novel bottom-up methodology, using bacteria, for the design of three-dimensional honeycomb structures as functional materials with nano/micro hierarchical structures, with low energy consumption.

Regioselective modification of a xyloglucan hemicellulose for high-performance biopolymer barrier films.

Biobased polymers such as starch and hemicelluloses from wood are of interest for packaging applications, but suffer from limitations in performance under moist conditions. Xyloglucan from industrial tamarind seed waste offers potential, but its Tg is too high for thermal processing applications. Regioselective modification is therefore performed using an approach involving periodate oxidation followed by reduction. The resulting polymer structures are characterized using MALDI-TOF-MS, size-exclusion chromatography, FTIR and carbohydrate analysis. Films are cast from water and characterized by thermogravimetry, dynamic mechanical thermal analysis, dynamic water vapor sorption, oxygen transmission and tensile tests. Property changes are interpreted from structural changes. These new polymers show much superior performance to current petroleum-based polymers in industrial use. Furthermore, this regioselective modification can be carefully controlled, and results in a new type of cellulose derivatives with preserved cellulose backbone without the need for harmful solvents.

Regulated patterns of bacterial movements based on their secreted cellulose nanofibers interacting interfacially with ordered chitin templates.

Gluconacetobacter xylinus, a gram-negative bacterium that synthesizes and extrudes a cellulose nanofiber in SH media moves in random manners, resulting in 3D-network structure of the secreted nanofibers termed a pellicle. In this study, the bacterial movement was successfully regulated to be in a waving manner when cultured on ordered templates made of chitin. Interestingly, by addition of more cellulose into the chitin ordered templates, the waving pattern was getting close to a linear or straight manner. Real time video analysis and other visualization techniques clarified that the regulation of the moving manners was due to the interfacial interaction between the secreted nanofibers and the template surfaces. Furthermore, the changing of the pattern due to the cellulose content in the ordered templates appeared to depend on the magnitude of the interaction between the template and nanofibers. This regulated autonomous deposition of the fibers will build patterned 3D-structure with unique properties on the surface of the templates, leading to a novel type of nanotechnology using biological systems with biomolecular nano-templates to design 3D-structures.

"Nanocellulose" as a single nanofiber prepared from pellicle secreted by Gluconacetobacter xylinus using aqueous counter collision.

This study attempted to prepare a single cellulose nanofiber, "nanocellulose", dispersed in water from 3D networks of nanofibers in microbial cellulose pellicle using aqueous counter collision (ACC), which allows biobased materials to be down-sized into nano-objects only using water jets without chemical modification. The nanocellulose thus prepared exhibited unique morphological properties. In particular, the width of the nanocellulose, which could be controlled as desired on nanoscales, was smaller than that of just secreted cellulose nanofiber, resulting in larger specific surface areas. Moreover, ACC treatment transformed cellulose I(α) crystalline phase into cellulose I(ß) phase with the crystallinity kept >70%. In this way, ACC method depending on the treatment condition could provide the desired fiber width at the nanoscale and the different ratios of the two crystalline allomorphs between cellulose I(α) versus I(ß), which thus opens further pathways into versatile applications as biodegradable single nanofibers.

[Efficacy of a community-based weight reduction program to improve exercise and diet behavior in overweight adults].

OBJECTIVE: The study was a non-randomized, parallel-group comparison to evaluate the efficacy of a community-based weight reduction program with exercise and diet modification for overweight adults using existing community health services. METHODS: The study population consisted of 1,115 community-dwelling people who underwent annual health checkups in 2002 and were screened by exclusion criteria (age> 65, body mass index (BMI) < 24.2). They received a mail request to select one of two courses; a usual single-session health instruction course (control group) or a 9-month weight management course (intervention group). Forty six patients registered in the intervention group, and fifty patients in the control group. The analyzed sample consisted of 76 participants (9 males and 67 females) excluding dropouts from November 2002 to July 2003. Intervention included monthly classes (2 hours per class, 9 classes) consisting of an individual support program for behavioral change and a community support program for continuation after the class. The control group participants received conventional instructions based on their health status. RESULTS: No significant inter-group differences were observed at baseline, except in age and height of females. The mean BMI decreased from 27.2 (SD = 2.8) kg m(-2) to 25.3(3.1) kg m(-2) in the intervention group, and 26.4 (1.7) kg m(-2) to 26.1(1.7) kg m(-2) in the control group. Repeated measures analysis of variance showed significant time and group interaction adjusted for gender and age. The proportion showing maintenance and action in stage of exercise behavior increased in the intervention group (31% to 60%), but remained stable in the control group (45% to 48%) . The proportion showing maintenance and action in stage of diet behavior increased in the intervention group (24% to 80%), but remained stable in the control group (29% to 26%). CONCLUSION: Community-based weight reduction programs may be effective to facilitate change in exercise and diet behavior for body weight reduction in overweight adults.

Compression behavior of Langmuir-Blodgett monolayers of regioselectively substituted cellulose ethers with long alkyl side chains.

Regioselectively substituted alkylcellulose ethers having long alkyl side chains, 6-O- (6C18), 2,3-di-O- (23C18), and tri-O-octadecyl-cellulose (triC18) were successfully synthesized. The key step of these syntheses was removal of the residual alkylation reagent by an isothermal crystallization procedure to isolate and purify the compounds, since a physical entanglement between the long alkyl side chains in the cellulose derivatives and the reagent had caused difficulty in obtaining the purified derivatives. After the monolayers from these cellulose ethers were fabricated on a water surface, they were deposited on substrates by a vertical dipping method to be Langmuir-Blodgett (LB) monolayers. During the compression process of each monolayer, a surface pressure (pi)-area (A) isotherm behaved in a different way. Atomic force microscopy (AFM) was employed to interpret changes of the surface topography of the obtained LB monolayers depending on the surface pressure. The compressed 23C18 LB monolayer was observed to be more homogeneous than other samples. On the basis of the LB monolayer thickness estimated by AFM as well as X-ray reflection measurements, the 23C18 LB monolayer was assumed to possibly possess the vertical arrangement of an up-ordering of all the alkyl side chains on the individual glucose ring against the water surface. In other words, with increase in the surface pressure, the usual conformation of a 2(1) screw of cellulose backbone may be changed into an unusual conformation with a certain phi-psi dihedral angle resulting in 1-fold axis without a symmetry element. These results suggest that the formation of such compressed LB monolayers was strongly influenced by the hydrophobic interaction among the distribution of the long alkyl side chains in the anhydroglucose unit and further lack of inter- and/or intramolecular hydrogen bonds engaged in cellulose ethers, and as a result, those effects may even change the main chain conformation.

Fabrication of honeycomb-patterned cellulose films.

This paper reports for the first time on the fabrication of honeycomb-patterned cellulose films by casting water in oil emulsion of cellulose acetate onto a glass substrate and subsequent deacetylation treatment. The honeycomb pore size could be controlled from 1 to 100 microm under a saturated water vapor condition. Both cellulose and cellulose acetate films with honeycomb-pattern are expected to be a two-dimensional model of plant cell walls as well as of micro-wells for single cell cultivation. Surface topographic image of a honeycomb-patterned cellulose film (scalebar: 50 microm).