Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
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Cytotoxic Polyketides with an Oxygen-Bridged Cyclooctadiene Core Skeleton from the Mangrove Endophytic Fungus Phomosis sp. A818
No full textPlant endophytic microorganisms represent a largely untapped resource for new bioactive natural products. Eight polyketide natural products were isolated from a mangrove endophytic fungus Phomosis sp. A818. The structural elucidation of these compounds revealed that they share a distinct feature in their chemical structures, an oxygen-bridged cyclooctadiene core skeleton. The study on their structure–activity relationship showed that the α,β -unsaturated
-lactone moiety, as exemplified in compounds 1 and 2, was critical to the cytotoxic activity of these compounds. In addition, compound 4 might be a potential agonist of AMPK (50-adenosine monophosphate-activated protein kinase)
Effective adsorption of nitroaromatics at the low concentration by a newly-synthesized hypercrosslinked resin. Water Science and Technology.
No full textIn the present study, a series of hypercrosslinked resins (CH series) was prepared in systematically
designed conditions for the adsorption of nitroaromatics from aqueous solution. The newly
synthesized CH-10 possesses a Brunauer–Emmett–Teller (BET) surface area up to 1,329.3 m2/g which
is larger than that of the widely used hypercrosslinked resin H-103 and it exhibits great advantage
over H-103 when subjected to nitrobenzene at low concentrations. The adsorption capacity of CH-10
for nitrobenzene is 1.4 times as much as that of H-103 at the concentration of 100 mg/L. Kinetic
study by film diffusion model and intra-particle diffusion model revealed that its distinctive
mesoporous structure within pore diameters between 2 and 6 nm played significant role in the mass
transfer at low concentrations, and these unique mesopores also resulted in better adsorption
capacity, which was confirmed by adsorption thermodynamics study. Moreover, the CH series
displayed a good affinity to a wide scope of nitroaromatics and exhibited excellent dynamic
adsorption and desorption properties in fixed bed
Improving the production of acetyl-CoA-derived chemicals in Escherichia coliBL21(DE3) through iclR and arcA deletion.
No full textBackground: Acetyl-CoA-derived chemicals are suitable for multiple applications in many industries. The bio-production
of these chemicals has become imperative owing to the economic and environmental problems. However, acetate
overflow is the major drawback for acetyl-CoA-derived chemicals production. Approaches for overcoming acetate
overflow may be beneficial for the production of acetyl-CoA-derived chemicals.
Results: In this study, a transcriptional regulator iclR was knocked out in E.coli BL21(DE3) to overcome acetate overflow
and improve the chemicals production. Two important acetyl-CoA-derived chemicals, phloroglucinol (PG) and
3-hydroxypropionate (3HP) were used to evaluate it. It is revealed that knockout of iclR significantly increased
expressions of aceBAK operon. The cell yields and glucose utilization efficiencies were higher than those of control
strains. The acetate concentrations were decreased by more than 50% and the productions of PG and 3HP were
increased more than twice in iclR mutants. The effects of iclR knockout on cell physiology, cell metabolism and
production of acetyl-CoA-derived chemicals were similar to those of arcA knockout in our previous study. However, the
arcA-iclR double mutants couldn’t gain higher productions of PG and 3HP. The mechanisms are unclear and needed to
be resolved in future.
Conclusions: Knockout of iclR significantly increased gene expression of aceBAK operon and concomitantly activated
glyoxylate pathway. This genetic modification may be a good way to overcome acetate overflow, and improve the
production of a wide range of acetyl-CoA-derived chemicals
Engineering of alkane production in cyanobacteria
No full textAlkanes with defined carbon chain lengths possess
higher energy density, low hygroscopicity and
volatility, and compatibility with existing liquid
fuel infrastructure, which are the predominant
constituents of gasoline, diesel and jet fuels.
Alkane biosynthesis is ubiquitous and biosynthetic
pathways have been identified in cyanobacteria,
photosynthetic microbes, which opens a door to
engineer alkane production with high efficiency
in cyanobacteria. Firstly, redirecting the carbon
flux to fatty acids or acyl-acyl carrier proteins
can provide larger precursor pools for further
conversion to alkanes. In combination with the
overexpression of alkane biosynthesis genes,
alkane production can be significantly improved
in engineered strains. Protein engineering for key
enzymes in alkane biosynthesis pathways will
further enhance the yield of alkanes. Secondly,
systems biology research on cyanobacteria will
increase our knowledge about the metabolism
in cyanobacteria and lead to significant
improvements in strain modification for alkane
production. Convenient and effective molecular
tools for genetic engineering of cyanobacteria will
expand the ability to engineer cyanobacteria for
alkane production. It is significant and promising
to directly utilize solar energy and convert carbon
dioxide into alkanes, drop-in biofuels, in cyanobacteria
A Simple Strategy to Achieve Mussel-Inspired Highly Effective Antibacterial Coating
No full textAlthough significant progress has been made in the preparation of musselinspired antibacterial coatings, continual challenges still remain in pursuing more facile and simpler fabrication methods to construct more robust and effective coatings. In this study, quaternized catechol (QCat), which is synthesized via a simple quaternization reaction from two commercially available materials, 2-chloro-3′,4′-dihydroxyacetophenone and N,N-dimethyldodecylamine, is used as a reactive antimicrobial agent to fabricate musselinspired antibacterial coatings. Specifically, QCat reacts with branched polyethyleneimine (PEI) in Tris-HCl solution through a cross-linking reaction between amino and catechol groups to form a homogeneous coating on various substrates via a simple co-deposition process. The formed PEI/QCat coating exhibits highly effective antimicrobial activity against both Staphylococcus aureus and Escherichia coli and good adhesion on glass, metal, and plastic substrates. Such a simple fabrication process makes it a potential candidate for industrial and medical applications
材料工程
No full textA variety of biomaterials in living systems rely on hierarchical hybridization of bio-macromolecular with different natural inorganic/organic nanomaterials for incredible mechanical property, optic and biological functions, such as collagen with apatite in bone and cellulose with lignin in wood. These hybridization strategies have inspired to design various functional composites of bio-macromolecules for biomimetic structural hierarchies and desired properties. In particular, silk fibroin has drawn researchers’ attention as advanced materials for its widely available raw material, excellent mechanical property, perfect biocompatibility and controllable biodegradability. To further improve its mechanical properties, many synthetic/natural inorganic nanomaterials with high moduli have been hybridized into regenerated silk fibroin to compete with its strongest analogues, especially biological nanofibrils which were incorporated into silk fibroin for biomimetic structures and higher properties. However, broad applications of these biologic nanofibrils were hindered by their complicated production procedures, limited starting materials and poor intermolecular interaction with bulk filk fibroin. Herein we proposed a biomimetic nanofibrous strategy to incorporate aramid nanofibril (ANF) into silk fibroin for unprecedented properties and discussed the microstructure, mechanical properties and applications of ANF hybridized silk fibroin materias.
Following the biomimetic inspiration, commercial Kevlar fibers were first liquid-exfoliated into ANF via deprotonation of amide groups in the solvent of dimethyl sulfoxide (DMSO) saturated with KOH. In order to improve its surface hydrophilicity and adhesion for hybridization of silk, ANF was hydrothermally treated under acidic conditions to introduce functional groups. By optimizing the hydrothermal treating condition and hybridizing compositions of ANF in the final composites of silk fibroin, the fracture strength and elastic moduli ultimate stress could reach to 210.43 MPa, 6.25 GPa for SF/ANF2 composite film, which has enchanced by 184.1% and 184.3% as those of pure silk fibroin.
Besides strengthen SF films, ANF could be used to enhance the mechanical properties of regenerated silk nanofibrils (RSF) membranes. Generally, SF molecules self-assemble into elongated RSF through incubating in 7 vol.% ethanol at pH 9.5. And acid treated ANF for 2h, named as ANF2, was used as additives to RSF to enhance the interaction between ANF2 and RSF. The addition of 20 wt% ANF2 is enough to convert the weak and poor pure RSF into free-standing membranes with ultimate stress reached to 52.4 MPa, the strain to 1.76% and Young’s modulus to 2.27 GPa.
The free-standing porous RSF/ANF2 membranes with good mechanical properties and stability showed hopeful application in pressure-driven filtration. Additionally, due to the outstanding biocompatibility and biodegradability of silk fibrion, pore size of the composite membranes could be tuned to some extent by enzymatic degradation of silk I and noncrystalline regions in SF. And the separation performance of the RSF/ANF2 membranes could be adjusted through changing the ratio between RSF and ANF2, by varying the membrane thickness.
Furthermore, considering their good mechanical property, the RSF/ANF2 composite membranes can also be constructed to flexible electronic devices. Large-size single gold crystal platelets were synthesized with the help of RSF, and the gold nanoplatelets were deposited onto the surface of RSF/ANF2 composite membranes through vacuum filtration with a patterned mold, and showed excellent conductivity as flexible electronic devices.中
生物工程
No full textPlant cell walls contain abundant cellulose and hemicellulose that are important sources for producing bioenergy and forage. However, the presence of lignin in cell walls negatively impacts the bioconversion of these polysaccharides, and thereby increases the cost of biofuels and fodders. Switchgrass（Panicum virgatum L.）is a gramineous forage and energy grass. Lignin polymers of switchgrass mainly comprise three types of lignin monomers with different extent of methoxylation, which are designated as hydroxyl phenyl propane (H), guaiacyl propane (G) and syringyl propane (S). Large amounts of G and S monomers are deposited in switchgrass cell walls compared with a trace of H monomers. The methoxylation of G and S precursors is catalyzed by caffeoyl COA-O-METHYLTRANSFERASE (CCoAOMT) and CAFFEIC ACID-O-METHYLTRANSFERASE (COMT). Their methyl donors are provided by S-adenosyl methionine (SAM). Previous studies have shown that downregulation of COMT in switchgrass can result in significant changes in lignin composition and content, and therefore increase the efficiency of cell wall saccharification and the production of bioethanol. Additionally, recent studies in our lab indicate that downregulation of CCoAOMT in switchgrass has no effects on the biosynthesis of lignin monomers. Thus, the present work focused on two genes, namely S-ADENOSYL HOMOCYSTEINE HYDROLASE (SAHH) and S-ADENOSYL METHIONINE SYNTHETASE (SAMS), which are involved in the biosynthesis of SAM and its demethylation product S-adenosyl homocysteine (SAH), respectively. We genetically regulated the expression levels of SAMS and SAHH in switchgrass to aim at simultaneous inhibition of the turn-over efficiency of both CCoAOMT and COMT in vivo.
Our results showed that downregulation of PvSAHH in switchgrass resulted in a dramatic increase in SAH content, and thereby led to a 46.9%-72.8% decrease in the ratio of SAM/SAH. In contrast, overexpression of PvSAHH1 in switchgrass had various influences on SAH accumulation. We suspected that other biosynthetic pathways might compensate for the loss of SAH due to SAHH overexpression in switchgrass. Further analysis showed that overexpression of PvSAHH1 was able to reduce the ratio of SAM/SAH as well. Previous studies in animals and microorganisms have shown that SAH is a competitive inhibitor of O-methyltranferases. Therefore, the turn-over efficiency of O-methyltransferases depends on the ratio of SAM/SAH rather than the content of SAM in cells. To test this hypothesis in switchgrass, we measured the enzyme activity of crude enzyme extracts of COMT prepared from wild type switchgrass plants. We found that COMT activities in vitro were declined accompanying the decrease of SAM/SAH ration. Thus, our results suggest that both downregulation and upregulation of PvSAHH in switchgrass can inhibit the enzyme activity of methyltransferases in lignin biosynthetic pathway, and ultimately reduce the accumulation of G and S monomers simultaneously. Lignin composition analysis of PvSAHH-RNAi and -OE transgenic switchgrass lines revealed a substantial decrease in both G and S monomers which further confirmed our hypothesis. Moreover, total lignin contents of the above transgenic switchgrass lines were reduced by 17%-28%, and their saccharification efficiency were improved by 4.2%-11.2%.
In addition, genetic regulation of SAMS in switchgrass was fulfilled in the present work. We generated PvSAMS1RNAi transgenic switchgrass lines in which expression levels of SAMS were significantly altered. AcBr lignin content analysis showed that downregulation of SAMS in switchgrass was able to reduce total lignin contents by 7%-25%.
In summary, previous studies in lignin genetic engineering have been focused on the lignin biosynthetic pathway, which limited the number of target genes. In this study, genetic regulation of SAHH and SAMS were successfully performed in switchgrass. The results indicate that alternation of SAM and SAH accumulation can reduce the biosynthesis of both G and S monomers in switchgrass cell walls, and change the structure and content of lignin. Although the lignin biosynthesis was dramatically suppressed, the transgenic switchgrass plants were similar in growth with wild type plants. Due to lignin reduction, the cell wall digestibilities were significantly elevated in transgenic switchgrass plants. Therefore future researches will focus on the effects of other one-carbon genes on lignin biosynthesis in switchgrass, which can improve our understanding for the regulation mechanism of lignin biosynthesis, but also can increase the number of target genes in lignin engineering. Moreover, the target genes including SAMS and SAHH have potential to be employed as molecular markers for developing the cultivars of bioenergy and forage grass with high cell wall quality.中
