Exploring the Substrate Specificity and Enantioselectivity of a Baeyer–Villiger Monooxygenase from Dietzia sp. D5: Oxidation of Sulfides and Aldehydes

Baeyer–Villiger monooxygenases (BVMOs) are valuable enzymes for specific oxyfunctionalization chemistry. They catalyze the oxidation of ketones to esters, but are also capable of oxidizing other chemical functions, namely aldehydes and heteroatoms such as sulfur, nitrogen, selenium and boron. The oxidation specificity and enantioselectivity of a newly characterized BVMO (BVMO4) from a strain of Dietzia towards sulfide- and aldehyde substrates have been studied. BVMO4 could react with sulfides containing an aromatic group. The presence of a substituent on the aromatic group was tolerated when they were in the meta- and para position and the oxidations yielded predominantly the (R)-sulfoxides. Similarly, BVMO4 displayed a higher activity for aldehydes containing a phenyl group, but long aliphatic aldehydes, namely octanal and decanal, were also accepted as substrate by this enzyme. The major oxidation products of the aldehyde substrates were the respective carboxylic acids in contrast to formate ester that was obtained in most of the previous reports. The Baeyer–Villiger oxidation of the substrate 2-phenylpropionaldehyde was studied in further detail and the corresponding acid product was obtained with good regio- and enantioselectivity. This is a unique feature for BVMO4 and is of great interest for further exploration of an alternative biocatalytic process.     

The effect of increased interrogation zone,reader antenna polarization and application factors in the performance of UHF RFID tag detection on modified atmosphere packaged meat

The effect of conveyor speed, test sample size, antenna to sample distance, antenna polarization and ideal tag location in relation to the coupling capabilities of ultra‐high frequency radio frequency identification on optimal reader antenna placement were studied. The influence of each individual factor and its interaction was determined using the general linear model analysis of variance. In decreasing order of significance of the variables tested were sample type (F = 4174.40, p < 0.0005), smaller samples preferred for coupling; distance (F = 863.83, p < 0.0005), where distance between sample and antenna should be kept to a minimum; inlay design (F = 167.82, p < 0.0005), where AD‐612 preformed best due to its large antenna area; and reader antenna polarization (F = 149.64, p < 0.0005), where circular polarization preformed better yet comparative advantage decreased with distance. A reader antenna offset of 95 mm, while not significant, (F = 1.73, p = 0.188) tended to decrease coupling capabilities of the system despite increasing the zone of influence. Ideal tag location on sample was found to be on the right, back and front face with y‐orientation proving superior than either x or z. A 190‐mm centre–to‐centre reader antenna offset resulted in a decrease in the average tag detection rate from 62 to 49% highlighting the importance of optimal reader antenna placement which needs to be confirmed if a similar result is to be obtained when a large number of tags are interrogated simultaneously. Copyright © 2010 John Wiley & Sons, Ltd.     

The effects of item composition,tag inlay design,reader antenna polarization,power and transponder orientation on the dynamic coupling efficiency of backscatter ultra‐high frequency radio frequency identification

The effects of packaged content, packaging material, transponder inlay design, reader antenna polarization, interrogation power and transponder orientation on the detection rate of ultra‐high frequency radio frequency identification (UHF RFID) passive transponders were studied. The influence of individual factors and their interactions were determined using general linear model analysis of variance. Influences originated in order of importance, from sample type, antenna polarization, power and inlay design. Important interactions in decreasing order of significance exist between: power and antenna polarization; sample type and antenna polarization; sample type and inlay design; inlay design and antenna polarization; sample type, power and antenna polarization; sample type and power; inlay design and power; sample type, inlay design and power. It was also observed that random orientation of tags did not cause a statistically significant variation in tag detection rate. It can be concluded that the use of UHF RFID for item level of food requires multi‐parameter assessment before hand. Copyright © 2009 John Wiley & Sons, Ltd.     

Visual Quantitative Detection of Circulating Tumor Cells with Single‐Cell Sensitivity Using a Portable Microfluidic Device

Immunocytological technologies, molecular technologies, and functional assays are widely used for detecting circulating tumor cells (CTCs) after enrichment from patients' blood sample. Unfortunately, accessibility to these technologies is limited due to the need for sophisticated instrumentation and skilled operators. Portable microfluidic devices have become attractive tools for expanding the access and efficiency of detection beyond hospitals to sites near the patient. Herein, a volumetric bar chart chip (V‐Chip) is developed as a portable platform for CTC detection. The target CTCs are labeled with aptamer‐conjugated nanoparticles (ACNPs) and analyzed by V‐Chip through quantifying the byproduct (oxygen) of the catalytic reaction between ACNPs and hydrogen peroxide, which results in the movement of an ink bar to a concentration‐dependent distance for visual quantitative readout. Thus, the CTC number is decoded into visually quantifiable information and a linear correlation can be found between the distance moved by the ink and number of cells in the sample. This method is sensitive enough that a single cell can be detected. Furthermore, the clinical capabilities of this system are demonstrated for quantitative CTC detection in the presence of a high leukocyte background. This portable detection method shows great potential for quantification of rare cells with single‐cell sensitivity for various applications.     

Recycling of cotton and polyester fibers to produce nonwoven fabric for functional sound absorption material

Recycled fibers are commonly used in dissimilar applications and one of the most important applications is sound absorption. Recycled fiber nonwovens currently are in greater demands in industries because of their advantages such as low cost, biodegradability, acceptable mechanical and physical properties, and so on. Sound absorption materials, renewable, and eco-friendly nonwovens have been developed using recycled cotton and polyester fibers. This research provides a contribution to the body of knowledge on the sound absorption properties of nonwovens using recycled fibers which contain cotton and polyester by means of spun-laid technique and provides a better understanding of the effects of a number of manufacturing processes on nonwovens noise control performance and also contributes to the wider adoption of nonwovens as sound absorbers. The sound absorption coefficients were measured according to ASTM E 1050 by an impedance tube method. The results revealed that the average of the sound absorption coefficients increased with the thickness of the nonwovens, but decreased with the nonwoven fabric density.     

Baeyer–Villiger Oxidation of Cyclohexanone in Aqueous Medium with In Situ Generation of Peracid Catalyzed by Perhydrolase CLEA

A perhydrolase, immobilized as a cross linked enzyme aggregate (CLEA), was employed to catalyze the in situ formation of peracetic acid (PAA) from ethylene glycol diacetate (EGDA) and hydrogen peroxide. The produced PAA was used for the Baeyer–Villiger oxidation of cyclohexanone, which afforded caprolactone in 63 % yield. The effect of type and amount of acyl donor, solvent, pH, temperature and ratio of cyclohexanone to hydrogen peroxide on the production of caprolactone was studied. The highest caprolactone yield was obtained with 100 mM EGDA as the acyl donor at pH 6 and room temperature using a ratio of cyclohexanone to hydrogen peroxide ratio of 1:4. Interestingly, the perhydrolase CLEA exhibited the highest activity in aqueous medium in contrast to the well studied lipase B from Candida antarctica. The perhydrolase CLEA proved to be a very efficient catalyst; the K _m and V_max values were 118 mM and 56.3 μmol min^?1, respectively.     

Antimicrobial Protein Candidates from the Thermophilic Geobacillus sp. Strain ZGt-1: Production,Proteomics, and Bioinformatics Analysis

A thermophilic bacterial strain, Geobacillus sp. ZGt-1, isolated from Zara hot spring in Jordan, was capable of inhibiting the growth of the thermophilic G. stearothermophilus and the mesophilic Bacillus subtilis and Salmonella typhimurium on a solid cultivation medium. Antibacterial activity was not observed when ZGt-1 was cultivated in a liquid medium; however, immobilization of the cells in agar beads that were subjected to sequential batch cultivation in the liquid medium at 60 °C showed increasing antibacterial activity up to 14 cycles. The antibacterial activity was lost on protease treatment of the culture supernatant. Concentration of the protein fraction by ammonium sulphate precipitation followed by denaturing polyacrylamide gel electrophoresis separation and analysis of the gel for antibacterial activity against G. stearothermophilus showed a distinct inhibition zone in 15–20 kDa range, suggesting that the active molecule(s) are resistant to denaturation by SDS. Mass spectrometric analysis of the protein bands around the active region resulted in identification of 22 proteins with molecular weight in the range of interest, three of which were new and are here proposed as potential antimicrobial protein candidates by in silico analysis of their amino acid sequences. Mass spectrometric analysis also indicated the presence of partial sequences of antimicrobial enzymes, amidase and dd-carboxypeptidase.