Cellulose Synthase Mutants Distinctively Affect Cell Growth and Cell Wall Integrity for Plant Biomass Production in Arabidopsis.

Cellulose is the most characteristic component of plant cell walls, and plays a central role in plant mechanical strength and morphogenesis. Despite the fact that cellulose synthase (CesA) mutants exhibit a reduction in cellulose level, much remains unknown about their impacts on cell growth (elongation and division) and cell wall integrity that fundamentally determine plant growth. Here, we examined three major types of AtCesA mutants (rsw1, an AtCesA1 mutant; prc1-1 and cesa6, AtCesA6-null mutants; and IRX3, an AtCesA7 mutant) and transgenic mutants that overexpressed AtCesA genes in the background of AtCesA6-null mutants. We found that AtCesA6-null mutants showed a reduced cell elongation of young seedlings with little impact on cell division, which consequently affected cell wall integrity and biomass yield of mature plants. In comparison, rsw1 seedlings exhibited a strong defect in both cell elongation and division at restrictive temperature, whereas the IRX3 mutant showed normal seedling growth. Analyses of transgenic mutants indicated that primary wall AtCesA2, AtCesA3, AtCesA5 and AtCesA9 genes played a partial role in restoration of seedling growth. However, co-overexpression of AtCesA2 and AtCesA5 in AtCesA6-null mutants could greatly enhance cell division and fully restore wall integrity, leading to a significant increase in secondary wall thickness and biomass production in mature plants. Hence, this study has demonstrated distinct functions of AtCesA genes in plant cell growth and cell wall deposition for biomass production, which helps to expalin our recent finding that only three AtCesA6-like genes, rather than other AtCesA genes of the AtCesA family, could greatly enhance biomass production in transgenic Arabidopsis plants.

Identification and characterization of a new acid-stable endoglucanase from a metagenomic library.

A new endoglucanase gene cel124 was cloned from a metagenomic library and expressed in Escherichiacoli. Catalytic triad analysis showed that the catalytic triad sites were different from the known endoglucanases. Cel124, a 34 kDa protein, exhibited a specific activity (29.08 U mg(-1)) toward 1% of sodium carboxymethyl cellulose and was stable at 50 °C for 30 min. The optimal temperature and pH for its catalytic activity were 50 °C and pH 5.5 respectively. Cel124 could hydrolyze soluble cellulose, but not insoluble cellulose or other polysaccharides. The kinetic parameters (5.63 mg ml(-1) for Km and 0.0397 mmol min(-1) mg(-1) for Vmax) were measured. 3M NaCl in the system could increase its activity by 2 fold. Site-directed mutation and circular dichroism spectra test suggested that the residue (Glu41) was essential for its activity, might be a potential active site. Based on our data, we proposed that Cel124 might represent a new type of endoglucanase.

Transmission of nanoplastics from Culex quinquefasciatus to Pardosa pseudoannulata and its impact on predators.

Many studies have explored the effects of plastic particles on aquatic organisms. To date, however, few studies have reported on the effects of plastic particles on terrestrial invertebrates. Here, Culex quinquefasciatus (southern house mosquito, prey) and Pardosa pseudoannulata (wolf spider, predator) were used to explore the transmission of nanoplastics (NPs) from aquatic to terrestrial invertebrates and to verify the effects of NPs in prey on predators. Mosquito larvae were exposed to 0, 200, and 1000 NPs mL-1 polystyrene, respectively, and then fed to spiders when they matured. Results showed that ingestion of NP-exposed mosquitoes affected the growth, development, and behavior of P. pseudoannulata, and the intestinal tissue structure, intestinal flora composition, and related enzymatic activities were also impacted. These results indicate that after spiders ingested NP-exposed mosquitoes, their growth, development, and predation ability were affected. This may prolong time to maturation and decrease the ability of spiders to survive and reproduce in the environment. Thus, plastic particles likely have a wide range of effects on organisms as well as the whole ecosystem.

Study on Integrated Pharmacokinetics of the Component-Based Chinese Medicine of Ginkgo biloba Leaves Based on Nanocrystalline Solid Dispersion Technology.

Background: To improve the dissolution and bioavailability of the component-based Chinese medicine of Ginkgo biloba leaves (GBCCM), a novel nanocrystalline solid dispersion of GBCCM (GBCCM NC-SD) was first prepared. Methods: GBCCM mainly containing high pure flavonoid aglycones (FAs) and terpenoid lactones (TLs) was used as the model drug. PVP K30 and SDS were used as solubilizers, combined stabilizers and carriers, and GBCCM NC-SD was prepared by high-pressure homogenization combined with freeze-dryer. Morphology and crystal characteristic of GBCCM NC-SD were analyzed. The dissolution and bioavailability evaluation were performed to investigate the feasibility of GBCCM NC-SD by in vitro dissolution and in vivo integrated pharmacokinetic models. Results: After homogenizing for 30 cycles under the pressure of 650 bar and freeze-drying, GBCCM NC-SD with uniform quality would be obtained. The particle size, PDI and zeta potential were found to be 335.9 ± 32.8 nm, 0.29 ± 0.02 and -28.4 ± 0.7 mV respectively. Based on charged aerosol detector (CAD) technology, a new chromatographic method for simultaneous detection of eight components in GBCCM was developed. In vitro drug release study showed that the cumulative dissolution of FAs and TLs in GBCCM NC-SD increased from 12.77% to 52.92% (P < 0.01) and 90.91% to 99.21% (P < 0.05) respectively. In comparison with physical mixture of GBCCM and stabilizer (PM), the integrated pharmacokinetics AUC0-t of FAs and TLs in GBCCM NC-SD were significantly increased (P < 0.05), and the T1/2 of TLs was also significantly prolonged (P < 0.05). Conclusion: This study demonstrated that novel GBCCM NC-SD was prepared using Polyvinylpyrrolidone K30 (PVP K30) and Sodium dodecyl sulfate (SDS) as a synergetic stabilizer and also provided a feasible way to improve the dissolution and oral bioavailability of poorly soluble candidate antihypertensive drugs.

Preparation of Icaritin-Loaded mPEG-PLA Micelles and Evaluation on Ischemic Brain Injury.

Icaritin is an active ingredient derived from the plant Herba Epimedium, which exhibits various pharmacological and biological activities. However, icaritin has solubility in water of less than 1.0 µg/ml and the low aqueous solubility hampered its use as a therapeutic agent. In this work, as shown in Scheme 1, we synthesized a series of mPEG-PLA (Methyl poly (ethylene glycol)-Polylactic acid) with different hydrophilic and hydrophobic segment ratios via ring-opening polymerization and prepared mPEG-PLA/icaritin micelles by solid dispersion method to improve the solubility of icaritin. After studying the particle size, zeta potential, encapsulation efficiency and drug loading efficiency, mPEG2000-PLA50(hydrophilic/hydrophobic segment ratio = 5:6) was selected for subsequent experiment, including single factor experiments and orthogonal experiments for optimizing mPEG-PLA (5:6)/icaritin micelles preparation. The particle size and zeta potential of the mPEG-PLA (5:6)/icaritin micelles were about (64.25 ± 0.21) nm and (-1.37 ± 0.31) mV, the encapsulation efficiency (EE) and drug loading efficiency (DL) were 83.96% and 9.33%, the critical micelle concentration was about 2.24 µg/ml and the solubility about 2.0 mg/ml in water. In vivo studies have shown that mPEG-PLA (5:6)/icaritin micelles have a longer circulation time in plasma and have a distribution in the brain of mice. The pharmacodynamic results indicated that pretreatment with mPEG-PLA (5:6)/icaritin micelles can decrease neurological deficit score, diminish the infarct volume and brain edema. These results suggested that mPEG-PLA (5:6)/icaritin micelles have a good advantage to improve the bioavailability of icaritin, potentially to be a neuroprotectant for ischemic brain injury.

Metabolic engineering of Escherichia coli for the production of butyric acid at high titer and productivity.

BACKGROUND: Several anaerobic bacteria produce butyric acid, a commodity chemical with use in chemical, pharmaceutical, food and feed industries, using complex media with acetate as a co-product. Butyrate titer of various recombinant Escherichia coli did not exceed 10 g l-1 in batch fermentations in any of the media tested. RESULTS: A recombinant E. coli (strain LW393) that produced butyrate as the major fermentation product was constructed with genes from E. coli, Clostridium acetobutylicum and Treponema denticola. Strain LW393 produced 323 ± 6 mM (28.4 ± 0.4 g l-1) butyric acid in batch fermentations in mineral salt medium with glucose as C source at a yield of 0.37 ± 0.01 g (g glucose consumed)-1. Butyrate accounted for 90% of the total products produced by the culture. Supplementing this medium with yeast extract further increased butyric acid titer to 375 ± 4 mM. Average volumetric productivity of butyrate with xylose as C source was 0.89 ± 0.07 g l-1 h-1. CONCLUSIONS: The butyrate titer reported in this study is about 2.5-3-times higher than the values reported for other recombinant E. coli and this is achieved in mineral salt medium with an expectation of lower purification and production cost of butyrate.

Efficient production of polymer-grade L-lactate by an alkaliphilic Exiguobacterium sp. strain under nonsterile open fermentation conditions.

In this study, a newly isolated alkaliphile Exiguobacterium sp. strain 8-11-1 was used to produce optically pure L-lactate. With an initial glucose concentration of 80 g/L, a high overall L-lactic acid productivity of 8.15 g/L/h was achieved using NaOH as a neutralizing agent. The fed-batch fermentations were carried out under both sterile and nonsterile conditions. Under the nonsterile condition, 125 g/L L-lactic acid was obtained with a high percent yield and average productivity of 98.33% and 3.79 g/L/h, respectively. These values were consistent with the results from sterile condition. No d-isomers of lactic acid were detected, resulting in an optical purity of 100% in both conditions. The high levels of optically pure L-lactic acid produced by Exiguobacterium sp. 8-11-1, combined with the ease of handling and low costs associated with the open fermentation strategy, provide a novel and potentially important approach for L-lactic acid production in the future.