Hongjie An

Effects of ripening stage and cultivar on physicochemical properties and pectin nanostructures of jujubes

Two Chinese jujube (Zizyphus jujuba) cultivars (Huanghua and Zhanhua) at unripe and ripe stages were investigated. During ripening, the weight, pH, hardness, and chewiness of both cultivars decreased while titratable acidity, total soluble solid content, and pectin contents increased. More than 75% pectins of the fruits were water-soluble pectin (WSP). Pectins shared the common major compositions of Gal, Rha and GalUA. For both cultivars, most of the chain widths were between 47 and 70 nm for unripe while less than 40 nm for ripe jujubes. Compared to unripe fruits, all pectins of ripe fruits had less percentage of wide and long pectin chains. All the pectin contents of cultivar Huanghua changed to a degree greater than that of cultivar Zhanhua during ripening. Changes of pectin nanostructure and neutral sugar composition might be responsible for the major physicochemical properties of jujubes.

Nano-Structures of DeBranched Potato Starch Obtained by Isoamylolysis

Starch debranching is fundamental for understanding the structure-function relationships of starch. In this paper, atomic force microscopy (AFM) was used to investigate potato starch by isoamylase [EC 3.2.1.68] debranching at nanometer scale. The hydrolysates were separated by gel-permeation chromatography and the fractions were imaged. In addition to linear structures and branches, coiled structures were revealed in the intermediate hydrolysates. It is concluded that isoamylolysis is very useful for a better understanding of starch structure-property relationships.

Optimization of Enzymatic Hydrolysis of Channel Catfish Bones for Preparing Antimicrobial Agents

The bones of channel catfish (Ictalurus punctatus), a kind of fish processing waste, were hydrolyzed with one of five proteases (alcalase, neutrase, papain, pepsin, and trypsin) in order to generate antibacterial agents. The antibacterial activity of hydrolysates recovered through enzyme hydrolysis was tested by radial diffusion assay (RDA). Pepsin hydrolysate was found to have the greatest antibacterial activity. Thus, the conditions of hydrolysis with pepsin were optimized by response surface methodology (RSM). After screening and optimization, a quadratic model was proposed. The model predicted that the maximum diameter of clear zone, which suggests the optimum antibacterial activity, was around 20.2 mm with a hydrolysis condition of pH 3.5, reaction temperature of 40°C, enzyme-substrate ratio of 1.97/100 (g/g), substrate concentration of 0.15 g/mL, and reaction time of 4 h. Verification experiments under this condition showed a clear zone of 19.8 mm, which agreed well with the models predicted value. This result indicates that RSM is an effective way to optimize the enzymatic hydrolysis of channel catfish bones to increase antibacterial activity, and the bones of channel catfish are promising resources for generating antibacterial components.

Probing starch-iodine interaction by atomic force microscopy.

We explored the interaction of iodine with three crystalline type starches, corn, potato, and sweet potato starches using atomic force microscopy. Results revealed that starch molecules aggregated through interaction with iodine solution as well as iodine vapor. Detailed fine structures such as networks, chains, and super-helical structures were found in iodide solution tests. The nanostructures formed due to iodine adsorption could help to understand the formation and properties of the starch-iodine complex.

Carbon Nanopowder Binds with DNA and May Induce DNA Aggregation

The interaction between nanomaterials and genomes is getting more and more attention. Such studies are getting involved into several fields: environment safety, food safety, nanobiotechnology and drug development. Direct interaction between nanoparticles and DNA in vitro has been reported in several studies, but data for in vivo binding between genomic DNA and nanoparticles are rare. In this study, we presented that carbon nanopowder (CNP) is able to bind with DNA both in vitro and in vivo. Interestingly, CNP binds to DNA with a relatively high density and may induce DNA aggregation.

Analysis of the Chlorophyll a Fluorescence Transient of Spirodela polyrhiza by JIP-Test

Chlorophyll a fluorescence has been used as non-invasive probe for stress physiology and environmental investigation. The changes of photosynthetic apparatus in Spirodela polyrrhiza was studied by using chlorophyll a fluorescence technique and JIP-test. During L-serine-induced senescence, photosynthetic performance index (PI), reaction center (RC) decreased gradually and reached zero on the 8th day of cultivation. However, the oxygen evolving complex (OEC) remained nearly 60% and the capacity of Hill reaction remained about 43%. JIP-test also offers a platform to analyze the energy flux in fronds.