Adaptation responses in C4 photosynthesis of sweet maize (Zea mays L.) exposed to nicosulfuron.

Nicosulfuron is an ingredient in photosynthesis-inhibiting herbicides and has been widely used in corn post-emergence weed control. In the current study, a pair of sister lines, HK301 (nicosulfuron-tolerence, NT) and HK320 (nicosulfuron-sensitive, NS), was used to study the effect of nicosulfuron in sweet maize seedlings on C4 photosynthetic enzymes and non-enzymatic substances, expression levels of key enzymes, and chloroplast structure. Nicosulfuron was sprayed at the four-leaf stage, and water was sprayed as a control. After nicosulfuron treatment, phosphoenolpyruvate carboxylase (PEPC), NADP-malic dehydrogenase (NADP-MDH), NADP-malic enzyme (NADP-ME), pyruvate orthophosphate dikinase (PPDK), and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities of NT were significantly higher than those of NS. Compared to NT, malate, oxaloacetic acid, and pyruvic acid significantly decreased as exposure time increased in NS. Compared to NS, nicosulfuron treatment significantly increased the expression levels of PEPC, NADP-MDH, NADP-ME, PPDK, and Rubisco genes in NT. Under nicosulfuron treatment, chloroplast ultrastructure of NS, compared to that of NT, nicosulfuron induced swelling of the chloroplast volume and reduced starch granules in NS. In general, our results indicate that in different resistant sweet maize, C4 photosynthetic enzymes activity and key genes expression play a critical role in enhancing the adaptability of plants to nicosulfuron stress at a photosynthetic physiological level.

Effect of chitooligosaccharides on human gut microbiota and antiglycation.

Chitooligosaccharides (COS) have garnered great attention in the field of human healthcare. The prebiotic activities and antiglycation of COS were investigated using a combination of in vitro and in vivo studies. COS supplementation dramatically increased the levels of acetic acid, while reducing the concentrations of propionic and butyric acids. It also decreased the total bacterial population; however, it did not affect diversity and richness of the gut microbiota. In addition, COS modulated the gut microbiota composition by increasing Bacteroidetes, decreasing Proteobacteria and Actinobacteria, and lowering the Firmicutes/Bacteroidetes ratio. COS promoted the generation of beneficial Bacteroides and Faecalibacterium genera, while suppressing the pathogenic Klebsiella genus. The antiglycation activity of COS and acetic acid was dose-dependent. Furthermore, COS prevented the decrease of serum Nε-(carboxymethyl) lysine (CML) level caused by CML ingestion in a mouse model of diet-induced obesity. To improve host health, COS could be potential prebiotics in food products.

Palladium-catalyzed decarbonylative annulation of phthalimides with arynes: direct construction of phenanthridinones.

A novel palladium-catalyzed decarbonylative annulation for the synthesis of phenanthridinones from phthalimides and arynes has been developed. This catalytic system tolerates a broad range of functional groups. Mechanistic experiments demonstrate that the Pd(ii) complex B is the key intermediate, which has been confirmed by X-ray crystallography for the first time.

Cellulosimicrobium cellulans strain E4-5 enzymatic hydrolysis of curdlan for production of (1 → 3)-linked ß-D-glucan oligosaccharides.

In order to find an efficient enzymatic tool for curdlan degradation to produce (1 → 3)-linked ß-D-glucan oligosaccharides, strain E4-5 (registration number JN089883, Genbank) was isolated from seaside soil. The 16S rRNA gene sequencing classified it as Cellulosimicrobium cellulans. It was the first reported microorganism that succeeded in degrading high-set heated curdlan blocks. The ferments of strain E4-5 also showed good degradation effects on laminaran and alkali-neutralized curdlan. Due to the products with less amount of glucose, it was assumed that endo-1,3-ß-glucanases of strain E4-5 had a greater hydrolyzing effect than exo-1,3-ß-glucanases. This indicated that strain E4-5 was a promising microorganism to hydrolyze (1 → 3)-linked ß-D-glucan. Moreover, alkali-neutralization pretreatment was effective for promoting a more diversified degree of polymerization (DP) of (1 → 3)-linked ß-D-glucan oligosaccharides under enzymatic hydrolysis and will pave the way for making full use of curdlan for production of glucan oligosaccharides.

Improvement of mannitol production by Lactobacillus brevis mutant 3-A5 based on dual-stage pH control and fed-batch fermentations.

Lactobacillus brevis 3-A5 was isolated and expected to produce mannitol efficiently by regulating pH in batch and fed-batch fermentations. In 48 h batch fermentations with free and constant pH, the optimal pH for cell growth and mannitol production in the first 24 h of incubation was 5.5, whereas that for mannitol production in the second 24 h of incubation was 4.5. To achieve high cell density and mannitol yield simultaneously, a dual-stage pH control strategy was proposed based on the kinetic analysis of mannitol production. The pH value was controlled at 5.5 for the first 12 h of fermentation and subsequently shifted to 4.5 until the fermentation was completed. Under dual-stage pH control fermentation, a 103 g/L yield of mannitol with a volumetric production rate of 3.7 g/L/h was achieved after 28 h. The dual-stage pH control fed-batch fermentation strategy was further developed to improve mannitol yield, wherein the yield increased by 109 % to 215 g/L after 98 h of fermentation. This value is the highest yield of mannitol ever reported using L. brevis.

Pedobacter hainanensis sp. nov., isolated from seaside soil.

A Gram-negative, aerobic, rod-shaped, motile, non-spore-forming bacterial strain, designated 13-Q(T), was isolated from seaside soil under the stacks of the red algae in Hainan province in China. Identification was carried out on the basis of polyphasic taxonomy. Phylogenetic analysis of 16S rRNA gene sequences showed that strain 13-Q(T) belonged to the genus Pedobacter, and the highest similarity was 94.4 % with Pedobacter terricola KCTC 12876(T). Strain 13-Q(T) was able to grow at 10-40 °C, in pH 5.0-10.0, in the presence of 0-2.0 % NaCl. The major fatty acids were iso-C(15:0) (40.4 %), summed feature 3 (comprising iso-C(15:0) 2-OH and/or C(16:1) ω7c) (18.9 %) and iso-C(17:0) 3-OH (18.4 %). The predominant menaquinone was MK-7. The G+C content of the genomic DNA was 42.7 mol%. Strain 13-Q(T) could be distinguished from the nearest phylogenetic neighbors by various chemotaxonomic and phenotypic properties. The results of the polyphasic analyses suggested that strain 13-Q(T) should be considered to represent a novel species of the genus Pedobacter, for which the name Pedobacter hainanensis sp. nov. is proposed. The type strain is 13-Q(T) (=CCTCC AB 2012076(T) = NRRL B-59850(T)).