Preparation and properties of modified chitosan as potential matrix materials for drug sustained-release beads

Modified chitosan such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS) were successfully prepared. The modified chitosan were employed in the formation of drug-loaded, iron(III)-crosslinked polymeric beads. The produced polymers were characterized by IR, NMR, WXRD and DSC measurements. The resulting beads were evaluated in vitro as drug prolonging and potentially orally administered delivery system. Theophylline was used as the loaded model drug. The generated beads proved to be successful in prolonging drug release. The release kinetics was evaluated by fitting the experimental data to standard release equations (zero-, first- and Higuchi equation). The best fit was found with Higuchi model for the polymeric beads.     

Optimization of an ethanol production medium in very high gravity fermentation

Concentrations of Mg²⁺, glycine, yeast extract, biotin, acetaldehyde and peptone were optimized by a uniform design process for ethanol production by Saccharomyces cerevisiae. Using non-linear step-wise regression analysis, a predictive mathematical model was established. Concentrations of Mg²⁺ and peptone were identified as the critical factors: 50 mM Mg²⁺ and 1.5% (w/v) peptone in the medium increased the final ethanol titre from 14.2% (v/v) to 17% (v/v) in 48 h.     

<Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> as a novel biocatalyst for pyruvate production from<Emphasis Type="SmallCaps"> DL</Emphasis>-lactate

Pseudomonas stutzeri SDM oxidized dl-lactic acid (25.5 g l^-1) into pyruvic acid (22.6 g l^-1) over 24 h. Both NAD⁺-independent d-lactate dehydrogenase and NAD⁺-independent l-lactate dehydrogenase were found for the first time in the bioconversion of lactate to pyruvate based on the enzyme activity assay and proteomic analysis. Jianrong Hao and Cuiqing Ma contributed equally to this work     

The Improvement of Spinach Growth by Nano-anatase TiO<Subscript>2</Subscript> Treatment Is Related to Nitrogen Photoreduction

The improvement of spinach growth is proved to relate to N₂ fixation by nano-anatase TiO₂ in this study. The results show that all spinach leaves kept green by nano-anatase TiO₂ treatment and all old leaves of control turned yellow white under culture with N-deficient solution. And the fresh weight, dry weight, and contents of total nitrogen, , chlorophyll, and protein of spinach by nano-anatase TiO₂ treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good as nano-anatase TiO₂ treatment under N-deficient condition, confirming that nano-anatase TiO₂ on exposure to sunlight could chemisorb N₂ directly or reduce N₂ to NH₃ in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO₂ effect, however, was not as significant as nano-anatase TiO₂. A possible metabolism of the function of nano-anatase TiO₂ reducing N₂ to NH₃ was discussed.     

Enzymatic synthesis of galactosyl lactic ethyl ester and its polymer for use as biomaterials

Lactate-based chemicals and polymers including poly(lactic acid) (PLA) are highly valuable materials for biomedical, food and general-purpose applications. Chemical synthesis, albeit the high reaction velocities achieved with it, often leaves chemical residues that are subject to health and safety concerns. Alternative biosynthesis is preferred in order to overcome these problems. Herein we report a novel enzymatic synthesis for the preparation of beta-d-galactosyl-l-lactic acid ethyl ester (GLAEE). Such a product, which may find applications in food and personal care products, is generally difficult to synthesize via traditional chemical routes because the reactions have to be highly selective due to the multiple hydroxyl groups of sugars. We further explore the enzymatic polymerization of GLAEE to form a unique biopolymer, poly(beta-d-galactoside-co-l-lactic acid) (PGLA). Novozyme 435 was found efficient in catalyzing the polymerization reaction in acetone with a conversion yield of 60% within 100 h. The molecular weight of the polymer product ranged from about 800-2000 as analyzed by using ESI-MS. It is expected that a variety of sugar-hydroxyl acids copolymers can be prepared through the same approach and a new class of biomaterials can thus be developed.     

Deproteinization of gellan gum produced by Sphingomonas paucimobilis ATCC 31461

Deproteinization is a technical bottleneck in the purification of viscous water-soluble polysaccharides. The aim of this work is to provide an appropriate approach to deproteinize crude gellan gum. Several methods of deproteinization were investigated, including Sevag method, alkaline protease, papain and neutral protease. The results revealed that Sevag method had high deproteinization efficiency (87.9%), but it showed dissatisfactory recovery efficiency of gellan gum (28.6%), which made it less advisable in industrial applications. The deproteinization by alkaline protease was demonstrated in this work for the first time, indicating alkaline protease was preferred in the deproteinization of crude gellan gum with high polysaccharide recovery (89.3%) and high deproteinization efficiency (86.4%).     

Overexpression of a NAC-domain protein promotes shoot branching in rice

For a better understanding of shoot branching in rice (Oryza sativa), a rice activation-tagging library was screened for mutations in tiller development. Here, an activation-tagging mutant Ostil1 (Oryza sativa tillering1) was characterized, which showed increased tillers, enlarged tiller angle and semidwarf phenotype. Flanking sequence was obtained by plasmid rescue. RNA-interfering and overexpression transgenic rice plants were produced using Agrobacterium-mediated transformation. The mutant phenotype was cosegregated with the reallocation of Ds element, and the flanking region of the reallocated Ds element was identified as part of the OsNAC2 gene. Northern analysis showed that expression of OsNAC2 was greatly induced in the mutant plants. Transgenic rice overexpressing the OsNAC2 resulted in recapture of the mutant phenotype, while downregulation of OsNAC2 in the Ostil1 mutant through RNA interfering (RNAi) complemented the mutant phenotype, confirming that the Ostil1 was caused by overexpression of OsNAC2. Overexpression of OsNAC2 regulates shoot branching in rice. Overexpression of OsNAC2 contributes tiller bud outgrowth, but does not affect tiller bud initiation. This suggests that OsNAC2 has potential utility for improving plant structure for higher light-use efficiency and higher yield potential in rice.     

Salt tolerance requires cortical microtubule reorganization in Arabidopsis

Although the results of some studies indicate that salt stress affects the organization of microtubules, it remains an open question whether microtubules play an active role in the plant's ability to withstand salt stress. In the present study, we showed that salt stress-induced wild-type Arabidopsis seedling roots display right-handed skewed growth and depolymerization of the cortical microtubules. The results of a long-term observational study showed that cortical microtubules depolymerized then reorganized themselves under salt stress. Stabilization of microtubules with paclitaxel resulted in more seedling death under salt stress, while disruption of microtubules with oryzalin or propyzamide rescued seedlings from death. Seedlings in which the cortical microtubules were reorganized did not succumb to salt stress. These results suggest that both depolymerization and reorganization of the cortical microtubules are important for the plant's ability to withstand salt stress. Depolymerizing microtubules by drugs rescues seedlings from death under salt stress. This rescue effect was abolished by removing calcium from the medium or treatment with a calcium channel inhibitor. Depolymerization of the microtubules is followed by an increase in the free cytoplasmic calcium concentration. The addition of calcium to the growth medium increased the number of seedlings in which recovery of the cortical microtubules occurred, whereas the removal of calcium decreased the number of seedlings in which recovery occurred. Therefore, depolymerization of the cortical microtubules raises intracellular calcium concentrations, while reorganization of the cortical microtubules and seedling survival may be mediated by calcium influx in salt stress.     

Developmental steps in acquiring competence for shoot development in <Emphasis Type="Italic">Arabidopsis</Emphasis> tissue culture

Arabidopsis shoots regenerate from root explants in tissue culture through a two-step process requiring preincubation on an auxin-rich callus induction medium (CIM) followed by incubation on a cytokinin-rich shoot induction medium (SIM). During CIM preincubation, root explants acquire competence to respond to shoot induction signals. During CIM preincubation, pericycle cells in root explants undergo cell divisions and dedifferentiate, losing the expression of a pericycle cell-specific marker. These cells acquire competence to form green callus only after one day CIM preincubation and to form shoots after 2–3 days CIM preincubation. Reversible DNA synthesis inhibitors interfered with the acquisition of competence to form shoots. Genes requiring CIM preincubation for upregulation on SIM were identified by microarray analysis and included RESPONSE REGULATOR 15 (ARR15), POLYGALACTURONASE INHIBITING PROTEIN 2 (PGIP2) and WUSCHEL (WUS). These genes served as developmental markers for the acquisition of competence because the CIM preincubation requirements for ARR15 and PGIP2 upregulation correlated well with the acquisition of competence to form green callus, and the CIM preincubation requirements for WUS upregulation matched those for shoot formation. Unlike ARR15, another cytokinin inducible, A-type ARR gene, ARR5, was upregulated on SIM, but the induction did not require CIM preincubation. These findings indicate that competencies for various events associated with shoot regeneration are acquired progressively during CIM preincubation, and that a set of genes, normally upregulated on SIM, are repressed by a process that can be relieved by CIM preincubation.     

Effect of gap junctional intercellular communication on radiation responses in neoplastic human cells

Gap junctional intercellular communication (GJIC) is an important function of metazoan cells and is believed to have beneficial effects in anti-tumor therapy. In this study, we found that, when neoplastic human salivary gland (HSG) cells were irradiated with a 100 keV/microm carbon-ion beam, micronuclei, G(2)/M-phase arrest, and cell killing were induced and that their induction increased with dose. Treatment of confluent HSG cells with 8-Br-cAMP increased GJIC between cells. After release from this treatment, the cell cycle progress and the formation of binucleated cells were still similar to those of untreated cells. However, radiation-induced cellular damage, including micronucleus (MN) formation and G(2)/M-phase arrest of that cAMP-treated population, was less than that of the untreated population and that the surviving fraction was slightly enhanced by cAMP treatment, suggesting that increased GJIC protects HSG cells from lethal radiation damage. Moreover, when confluent HSG cells were treated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), a scavenger of nitric oxide (NO) free radical, MN induction and cell killing in the irradiated population were increased. Our results indicate that NO may be involved in GJIC-mediated radioprotection of HSG cells, which may have implications for radiotherapy.