Development of a quantitative real-time PCR method to enumerate total bacterial counts in ready-to-eat fruits and vegetables

A newly developed real-time PCR assay rapidly quantifies the total bacterial numbers in contaminated ready-to-eat vegetables and fruits compared with the standard plate count method. Primers targeting the rpoB gene, which encodes for the beta subunit of the bacterial RNA polymerase and which is common to most bacterial species, was used instead of the 16S rRNA gene, which has multiple copies and varies among bacterial species. A primer pair specific for rpoB was confirmed to amplify rpoB in a wide range of bacterial species after we assessed 49 strains isolated from five kinds of fruits and vegetables. We purchased fruits and vegetables from retail shops and enumerated the bacteria associated with them by use of real-time PCR and compared this to the number found by the culture method. We found a high correlation between the threshold PCR cycle number when compared with the plate count culture number. The real-time PCR assay developed in this study can enumerate the dominant bacterial species in ready-to-eat fruits and vegetables.     

Development of a simple bio-hydrogen production system through dark fermentation by using unique microflora

In order to ensure efficient functioning of hydrogen fermentation systems that use Clostridium as the dominant hydrogen producer, energy-intensive process such as heat pretreatment of inoculum and/or substrate, continuous injection, and control of anaerobic conditions are required. Here, we describe a simple hydrogen fermentation system designed using microflora from leaf-litter cattle-waste compost. Hydrogen and volatile fatty acid production was measured at various hydraulic retention times, and bacterial genera were determined by PCR amplification and sequencing. Although hydrogen fermentation yield was approximately one-third of values reported in previous studies, this system requires no additional treatment and thus may be advantageous in terms of cost and operational control. Interestingly, Clostridium was absent from this system. Instead, Megasphaera elsdenii was the dominant hydrogen-producing bacterium, and lactic acid-producing bacteria (LAB) were prevalent. This study is the first to characterize M. elsdenii as a useful hydrogen producer in hydrogen fermentation systems. These results demonstrate that pretreatment is not necessary for stable hydrogen fermentation using food waste.     

Physical Considerations in the Development of Pressure-Sensitive Adhesive Sheets

A pressure-sensitive adhesive sheet is a special kind of paper used in non-impact printers which use a heating process to apply toner to paper. As a result, it needs special characteristics that general pressure-sensitive adhesive paper for labels do not require.

One of these characteristics is that the edge of the folded paper used in non-impact printers must not incline after printing. This was done by making the degree of orientation of the fibers in the face stocks and the release liners low.

The other characteristics are that adhesive must not ooze out from the edges during the slitting or guillotining process and that the labels must not come off of the release liner by themselves during the printing process. Ooze characteristics were found to be related to the adhesive coat weight. An adhesive paper with both a high peel strength and lower adhesive coat weight was developed by studying the dynamic viscoelastic properties of adhesives and release layers. The storage modulus of the release layer concerned with the release force was also found to be related to the self-peeling tendency of the labels.

These points were considered during the development of pressure-sensitive adhesive paper used in non-impact printers which use a heating process to apply toner to paper.     

Dehydration of d-glucose in high temperature water at pressures up to 80 MPa

Reaction of d-glucose in water to yield 5-hydroxymethylfurfural (5-HMF), 1,2,4-benzenetriol (BTO) and furfural was studied at high temperatures (up to 400 °C) and high pressures (up to 80 MPa) using a continuous flow reactor. Maximum temperature and pressure conditions gave maximum furfural yield. Increasing pressure from 40 to 70 and 80 MPa enhanced dehydration reactions to 5-HMF, but also enhanced hydrolysis of 5-HMF leading to the production of BTO and thus lead to lower yields of 5-HMF (below 10%). Remarkably, the dehydration reaction to 5-HMF and the hydrolysis of 5-HMF were both enhanced by the increase in water density at 400 °C.     

Higher-order structures and mechanical properties of stereocomplex-type poly(lactic acid) melt spun fibers

Equimolar blend of poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was melt spun into fibers and the relations among the processing conditions, crystalline structures, thermal properties, and mechanical properties were investigated. Drawing and annealing were performed in order to obtain fiber mainly consisting of the stereocomplex crystal phase. Fibers drawn at various temperatures exhibited either amorphous, highly oriented homo crystal, or the mixture of homo and stereocomplex with a fairly low orientation depending on the drawing temperature. Annealing of the drawn fibers at an elevated temperature higher than the melting temperature of homo crystal increased the stereocomplex content significantly. The fractions of the homo and the stereocomplex crystals strongly depended on the higher-order structure of the drawn fibers and the annealing temperature.     

Syntheses and characterization of xylan esters

A series of low-molecular weight and high-molecular weight xylan esters with different alkyl chain lengths (C2–C12) were synthesized by heterogeneous and homogeneous reactions, respectively. Structure elucidation of these xylan esters was obtained by NMR analysis. The solubility of xylan in CHCl₃ improved after esterification. DSC results did not show a melting peak for all samples. However, WAXD diffractograms show the presence of diffraction peaks. The proposed structural model for xylan ester films is presented. TGA suggested that the thermal stability of xylan increased after esterification. Xylan esters with longer alkyl chains had higher decomposition temperatures. The mechanical properties of the xylan esters were dependent on the alkyl chain length. The tensile strength and elongation at break of these xylan esters ranged from 8 to 29 MPa and from 19 to 44%, respectively. Xylan esters in HFIP can be electrospun into nanofibers.     

Mixed Lubrication with C18 Fatty Acids: Effect of Unsaturation

In this paper, the lubrication mechanism of fatty acids is revisited with a new approach combining experimental and computational chemistry studies. The lubricating properties of single and mixtures of stearic, oleic and linoleic acids in a synthetic Poly-Alpha-Olefin base oil (PAO4) on iron oxide surface are investigated under mixed boundary regime with temperatures from 50 °C up to 150 °C. Low friction coefficient (about 0.055) with no visible wear is reported in the presence of single stearic acid at high temperature. This lubricating behavior is inhibited in the presence of unsaturated fatty acids highlighting an anti-synergic effect of a saturated/unsaturated mixture, especially at 150 °C. To understand the anti-synergic effect and the adsorption mechanism of these molecules, molecular dynamic (MD) and quantum chemistry simulations are performed to evaluate their diffusion coefficient in PAO4 and their adsorption mechanism on iron oxide at different temperatures. MD simulation results show a faster diffusion toward the surface for unsaturated fatty acids than for saturated fatty acid at all the studied temperatures. This means that unsaturated molecules arrive and mainly adsorb before stearic acid on the surface leading to a tribological behavior of the mixture characteristic of the unsaturated molecule. Computational chemistry suggests that all fatty acids (saturated and unsaturated) adsorption mechanism is due to the chemisorption of the carboxylic group on iron oxide surface with no desorption up to 150 °C.     

Sol–Gel‐Derived High‐Performance Stacked Transparent Conductive Oxide Thin Films

Single‐ and multi‐layer transparent conductive oxide (TCO) thin films exhibiting high performance, good packing density and low surface/interface roughness are deposited on silica glass substrates by the sol–gel method. The crystal and microstructural properties of the TCO thin films are evaluated as an alternate to films prepared by ultra‐high vacuum deposition. Tin‐doped indium oxide (ITO) thin films produced using a two‐step drying process showed low surface roughness because of dense packing structure not only horizontal but also vertical directions. As a result, electrical conductivity, carrier concentration, carrier mobility, and optical transmittance of 2.3 × 10³ S/cm, 8 × 10²⁰ cm^?3, 18 cm²/Vs, and over 98% at 500 nm, respectively, were achieved. A multilayer ZnO/ITO stacked structure was also fabricated using the sol–gel process. Our findings suggest that solution‐based methods show promise as an alternative to existing ultra‐high vacuum methods to fabricate TCO thin films.