Jixian Gong

Genome shuffling: Progress and applications for phenotype improvement

Although rational method and global technique have been successfully applied in strain improvement respectively, the demand for engineering complex phenotypes required combinatorial approach. The technology of genome shuffling has been presented as a novel whole genome engineering approach for the rapid improvement of cellular phenotypes. This approach using recursive protoplast fusion with multi-parental strains offers the advantage of recombination throughout the entire genome without the necessity for genome sequence data or network information. Genome shuffling has been demonstrated as an effective method, which is not only for producing improved strain but also for providing information on complex phenotype. In this review we attempt to present the advantage of genome shuffling, introduce the procedure of this technology, summarize the applications of this approach for phenotype improvement and then give perspective on the development of this method in the future.

Femtosecond laser-induced cell fusion

Femtosecond laser was employed to induce cell fusion. The interface between two protoplasts of Phaffia rhodozyma in contact was irradiated by femtosecond laser pulses with 1.38×104W for 0.25s. After about 20min, the fusion of cells became visible and finally two cells merged into one larger cell within 160min. Fusion rate at this power level was 80%. The experiments suggested the existence of threshold power for cell fusion induced by femtosecond laser. Regarding femtosecond laser pulses as a trigger, we present a hypothetical model for femtosecond laser-induced cell fusion.

Preparation and properties of EDC/NHS mediated crosslinking poly (gamma-glutamic acid)/epsilon-polylysine hydrogels

In this paper, a novel pH-sensitive poly (amino acid) hydrogel based on poly γ-glutamic acid (γ-PGA) and ε-polylysine (ε-PL) was prepared by carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mediated polymerization. The influence of PGA/PL molar ratio and EDC/NHS concentration on the structure and properties was studied. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved that hydrogels were crosslinked through amide bond linkage, and the conversion rate of a carboxyl group could reach 96%. Scanning electron microscopy (SEM) results showed a regularly porous structure with 20 μm pore size in average. The gelation time in the crosslink process of PGA/PL hydrogels was within less than 5 min. PGA/PL hydrogels had excellent optical performance that was evaluated by a novel optotype method. Furthermore, PGA/PL hydrogels were found to be pH-sensitive, which could be adjusted to the pH of swelling media intelligently. The terminal pH of swelling medium could be controlled at 5 ± 1 after equilibrium when the initial pH was within 3-11. The swelling kinetics was found to follow a Voigt model in deionized water but a pseudo-second-order model in normal saline and phosphate buffer solution, respectively. The differential swelling degrees were attributed to the swelling theory based on the different ratio of -COOH/-NH2 and pore size in hydrogels. The results of mechanical property indicated that PGA/PL hydrogels were soft and elastic. Moreover, PGA/PL hydrogels exhibited excellent biocompatibility by cell proliferation experiment. PGA/PL hydrogels could be degraded in PBS solution and the degradation rate was decreased with the increase of the molar ratio of PL. Considering the simple preparation process and pH-sensitive property, these PGA/PL hydrogels might have high potential for use in medical and clinical fields.

Preparation of γ-PGA hydrogels and swelling behaviors in salt solutions with different ionic valence numbers

In this paper, a novel poly γ-glutamic acid (γ-PGA) hydrogel was successfully synthesized by solution polymerization and ethylene glycol diglycidyl ether (EGDE) was used as crosslinker. The structure and morphology of the γ-PGA was investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The influence of ionic (Na+, Ca2+ and Fe3+) concentrations, temperature and pH on the swelling degree of γ-PGA hydrogels was studied. The results revealed that the swelling capacity is enhanced with increasing pH, but decreased with increasing ionic concentration. The swelling kinetics study indicated that γ-PGA hydrogels were ion-sensitive and presented more limited swelling kinetics in metal ion solutions with higher ionic valence numbers. The results showed that the pseudo-second-order adsorption kinetics were predominant. Maximum swelling degrees were obtained for γ-PGA hydrogels with 21.03 g g−1 in 0.154 mol L−1 NaCl solution, 8.5 g g−1 in 0.154 mol L−1 CaCl2 solution and 12.8 g g−1 in 0.154 mol L−1 FeCl3 solution. Considering the simple preparation process, the ionic- and pH-sensitive properties, this γ-PGA hydrogel might have high potential to be used in medical and other fields.

Application of Terahertz Time‐Domain Spectroscopy in Intracellular Metabolite Detection

Using terahertz time-domain spectroscopy (THz-TDS), we have investigated the THz spectra of astaxanthin and riboflavin and the spectra of two kinds of cell, haenatcoccus plusivalis and bacillus subtilis, which could produce astaxanthin and riboflavin, respectively, during their metabolite process. Riboflavin was found to be much more absorptive to THz radiation and have richer spectral characteristics than astaxanthin. As an intracellular metabolite, riboflavin could be distinguished from the cells by using THz-TDS. The technique has potential applications in high-throughput screening of industrial strains.

pH-Mediated Antibacterial Dyeing of Cotton with Prodigiosins Nanomicelles Produced by Microbial Fermentation

This study developed a novel pH-mediated antimicrobial dyeing process of cotton with prodigiosins nanomicelles produced by microbial fermentation. The average diameter of the pigment nanomicelles was 223.8 nm (range of 92.4–510.2 nm), and the pigment concentration was 76.46 mg/L. It was found that the superior dyeing effect of cotton fabric was achieved by adjusting the dye bath pH. When the pH was three, dyed cotton under 90 °C for 60 min exhibited the greatest color strength with good rubbing, washing and perspiration color fastness. By the breaking strength test and XRD analysis, it was concluded that the cotton dyed under the optimum condition almost suffered no damage. In addition, due to the presence of prodigiosins, dyed cotton fabric under the optimal process showed outstanding bacteriostatic rates of 99.2% and 85.5% against Staphylococcus aureus and Escherichia coli, respectively. This research provided an eco-friendly and widely-applicable approach for antimicrobial intracellular pigments with the property of pH-sensitive solubility in water to endow cellulose fabric with color and antibacterial activity.

Sensing Textile Fibers by THz Time-Domain Spectroscopy

Along with the booming development of multi-component blending fabrics, the accurate detection of component of fabrics has become a major goal in textile testing. Terahertz sensing technology provides a new way for detecting the materials. THz time-domain spectroscopy (THz-TDS) is a novel spectroscopic technique which measures the electric field of the radiation through a sample and provides the phase and amplitude changes of the radiation, which can provide information unavailable through conventional methods such as microwave and X-ray techniques. In this investigation, THz-TDS technology was introduced into the textile differentiation. Three kinds of cellulose textile fibers, cotton fiber, bamboo fiber and viscose fiber, were prepared as the sample and detected by THz-TDS at room temperature in the absence of vapor. The temporal and frequency signals of the fibers were obtained. In the THz absorption spectrum, the characteristic absorption peaks of textile fibers in THz wave band were found, which can be used to recognize the fibers. This approach provides a novel non-contact examine method for fiber identification in complicated textiles.

Preparation of Biocolorant and Eco-Dyeing Derived from Polyphenols Based on Laccase-Catalyzed Oxidative Polymerization

Natural products have been believed to be a promising source to obtain ecological dyes and pigments. Plant polyphenol is a kind of significant natural compound, and tea provides a rich source of polyphenols. In this study, biocolorant derived from phenolic compounds was generated based on laccase-catalyzed oxidative polymerization, and eco-dyeing of silk and wool fabrics with pigments derived from tea was investigated under the influence of pH variation. This work demonstrated that the dyeing property was better under acidic conditions compared to alkalinity, and fixation rate was the best when pH value was 3. Furthermore, breaking strength of dyed fabrics sharply reduced under the condition of pH 11. Eventually, the dyeing method was an eco-friendly process, which was based on bioconversion, and no mordant was added during the process of dyeing.

Rheological Properties and Microstructures of Hydroxyethyl Cellulose/Poly(Acrylic Acid) Blend Hydrogels

A simple in-situ method was introduced to prepare hydroxyethyl cellulose/poly(acrylic acid) (HEC/PAA) blend hydrogels by forming an interpenetrating network (IPN). Storage modulus (G′) and loss modulus (G″) were improved dramatically compared to HEC. To prove that hydrogen bonds and chemical crosslinking played major roles in improving the hydrogel strength and toughening, and to optimize the components of HEC/PAA blend hydrogels, a series of blend hydrogels with different ratios of HEC to PAA were designed and the corresponding Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), rheological tests, and swelling properties were compared. Crosslinked HEC/PAA blend hydrogel (mol/mol = 1:1) showed the best properties appropriate for opening up biomedical applications of the hydrogel.

Hydrophilic Finishing of Polyester Fiber with Finishing Agents Based on Poly(γ-glutamic acid)

The work is aimed to investigate the suitability of poly (γ-glutamic acid) (γ-PGA) for the hydrophilic finishing of polyester fiber. γ-PGA hydrogel was successfully synthesized by a simple mixture process in the aqueous solution. A novel hydrophilic finishing agent was prepared by γ-PGA hydrogel. The rheology behavior study indicated that γ-PGA solution and hydrophilic finishing agent performed pseudoplastic fluid and approximately Newtonian behavior, respectively. The particle diameter determined that particles in hydrophilic finishing agent reached micro-nanograde. Furthermore, polyester fiber was treated with γ-PGA solution and hydrophilic finishing agent. Moisture regain was evaluated as a key performance, results shown the hydrophilicity of polyester fiber was greatly enhanced by γ-PGA finishing.