Lihui Gan

Identification of a genomic region containing a novel promoter resistant to glucose repression and over-expression of β-glucosidase gene in Hypocrea orientalis EU7-22.

A high concentration of glucose in the medium could greatly inhibit the expression of cellulase in filamentous fungi. The aspartic protease from fungus Hypocrea orientalis EU7-22 could efficiently express under both induction condition and glucose repression condition. Based on the sequence of structure gene of aspartic protease, the upstream sequence harboring the putative promoter proA for driving the expression of aspartic protease was obtained by genome walking. The upstream sequence contained the typical promoter motifs “TATA” and “CAAT”. The β-glucosidase gene (Bgl1) from H. orientalis was cloned and recombined with promoter proA and terminator trpC. The expression cassette was ligated to the binary vector to form pUR5750-Bgl1, and then transferred into the host strain EU7-22 via Agrobacterium tumefaciens mediated transformation (ATMT), using hygromycin B resistance gene as the screening marker. Four transformants Bgl-1, Bgl-2, Bgl-3 and Bgl-4 were screened. Compared with the host strain EU7-22, the enzyme activities of filter paper (FPA) and β-glucosidase (BG) of transformant Bgl-2 increased by 10.6% and 19.1% under induction condition, respectively. The FPA and BG activities were enhanced by 22.2% and 700% under 2% glucose repression condition, respectively, compared with the host strain. The results showed that the putative promoter proA has successfully driven the over-expression of Bgl1 gene in H. orientalis under glucose repression condition.

Controllable synthesis of mesoporous titanosilicates for styrene oxidization using a nanocellulose template strategy

In this work, mesoporous titanosilicates with tunable pore size were successfully synthesized using green and cheap bio-templates (nanocellulose). A series of samples was systematically prepared, characterized and used as catalysts for styrene oxidation by H2O2. The results demonstrated that the nanocellulose template strategy reported here was a feasible and effective method. The as-prepared titanosilicates presented high specific surface areas (450–500 m2 g−1) and their mesopore sizes could be tuned from 2 to 8 nm by varying the addition amount of templates in the synthesis process. Active tetrahedral Ti species were efficiently incorporated in the mesoporous silica. Meanwhile, strong acid sites of the samples were confirmed using NH3-TPD. The catalytic results revealed that the optimal catalysts (Si/Ti = 20 mol ratio) showed high catalytic activity and product selectivity can be adjusted through changing the mesopore size of the catalysts. The recycling tests indicated that as-prepared catalysts exhibited low catalytic deactivation. In addition, the oxidation mechanism over this catalyst was proposed. Thus, the present novel, sustainable and controllable method showed potential practical applications.

Rational Design of Si@SiO2/C Composites Using Sustainable Cellulose as a Carbon Resource for Anodes in Lithium-Ion Batteries

In this work, we propose a novel and facile route for the rational design of Si@SiO2/C anode materials by using sustainable and environment-friendly cellulose as a carbon resource. To simultaneously obtain a SiO2 layer and a carbon scaffold, a specially designed homogeneous cellulose solution and commercial Si nanopowder are used as the starting materials, and the cellulose/Si composite is directly assembled by an in situ regenerating method. Subsequently, Si@SiO2/C composite is obtained after carbonization. As expected, Si@SiO2 is homogeneously encapsulated in the cellulose-derived carbon network. The obtained Si@SiO2/C composite shows a high reversible capacity of 1071 mA h g-1 at a current density of 420 mA g-1 and 70% capacity retention after 200 cycles. This novel, sustainable, and effective design is a promising approach to obtain high-performance and cost-effective composite anodes for practical applications.

Time and energy-efficient homogeneous transesterification of cellulose under mild reaction conditions

In this research, cellulose aliphatic esters (CEs) were synthesized efficiently in an N, N-dimethylacetamide/lithium chloride system (DMAc/LiCl) with vinyl esters (VEs, number of carbon atoms ranging from 4 to 12) as acylation reagent and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as catalyst. The structures and properties of the products have been characterized by various analytical techniques. The key concept in this cellulose modification was the achievement the degree of substitution (DS) >2.75 at much milder temperature and shorter reaction time (under 30°C within 15min-30min), other than previous research. Generally, the DS of obtained CEs showed a reverse trend with the length of the aliphatic chain increasing. The priority of reactions in three positions of the CEs followed the same order of C6>C2>C3 for a homogeneous conversion. There was no decrease of molecule weight under this mild reaction. This research provides a novel homogeneous technology to synthesize various CEs efficiently.

Enhanced stability of antimicrobial bamboo fiber by launching ultra fine silver particles in a sodium dodecyl sulfate microemulsion system

Currently, the antimicrobial textile market is emerging and has rapidly developed to meet the inherent demands placed on public hygiene. Silver (Ag) is an efficient antimicrobial due to its direct function with the cellular membrane of probe samples. The application of Ag in the textile industry is limited due to its poor stability in repeatedly washing. In this study we synthesized a kind of novel antibacterial fiber containing nano-size silver particles in a reversed emulsion reaction system. The Ag nano-particles are incorporated onto the bamboo fibers solidly through primitive oxidation by sodium periodate. The identification, dependent on Staphylococcus aureus, was implemented to check the influence of the reaction conditions on the antimicrobial property. Meanwhile, reactive oxygen species and the leakage of cytoplasmic contents were focused on investigating the antimicrobial mechanism. The antimicrobial assay suggested that samples from inversed micelle and aqueous system own the comparative antibacterial activity. However, samples from an emulsion system could maintain a better bactericidal property than samples from an aqueous system. Meanwhile, the reactive oxygen species and ultraviolet absorption show the same trend consistent with the antibacterial result. This result might be explained by the morphology and size of Ag particles attached on cellulose surface, which was proved by scanning electron microscopy and energy dispersive spectroscopy. It was revealed that the surface-to-volume ratio of Ag particles played a more crucial role in achieving higher antimicrobial activity than the mass. This approach will provide a practical solution for the synthesis of wash-durable antimicrobial substances.

Commentary on the Development and Application of Chitosan in Immunochemistry

Chitosan has attracted much interest due to its special physical and chemical properties related to immunochemistry. The aim of this commentary is to appraise chitosan as an attractive functional polymer for medicine applications, which contributes to the development of chitosan for the immunochemistry. As reported, Chitosan has been used for immunochemistry purpose, such as functional food for enhancement of immune ability, immunostimulant and bio-remediating agent, nanoparticles antigen delivery systems, coating or gel vehicle for drug delivery, composites for intracellular delivery, wound healing medicine, enhance immune responses to virus, as well as other immunochemical materials. The further chemical modifications in chitosan will further assist the scientists for reaching new applications in immunochemistry based on chitosan.

Purification, characterization, gene cloning and sequencing of a new β-glucosidase from Aspergillus niger BE-2

The cDNA gene (BgL1), encoding GH3 family β-glucosidase (EC 3.2.1.21) from Aspergillus niger BE-2 (abbreviated to BgL1), was amplified and inserted into the yeast expression pPIC9K vector at the site of Bln I (Avr II) and NotI. The recombinant expression vector, designated as pPIC9K-BgL1, was transformed into Pichia pastoris GS115. The transformants were screened on minimal dextrose plates, which inoculated on geneticin G418-containing yeast extract-peptone-dextrose plates. The transformants expressed the high β-glucosidase activity of 22.6 U/mL. SDS-PAGE demonstrated that the BgL1 was extracellularly expressed with an apparent molecular weight of 90.0 kDa. The purified BgL1 displayed the maximum activity at pH 6.0 and 60°C. It was highly stable at a broad pH range of 4.0–7.5 and temperature of 60°C. The BgL1 displayed high similarity to the β-glucosidases of A. niger FN430671 and A. niger DQ655704, the members of the GH3 family. Its three-dimensional structure was predicted using http://swiss-model.expasy.org/ on-line programs based on the crystal structure of Aspergillus aculeatus β-glucosidase.