Utilization of plant-derived sugars and lipids are coupled during colonization of rhizoplane and rhizosphere by the fungus Metarhizium robertsii.

Plant-derived sugars and lipids are key nutritional sources for plant associated fungi. However, the relationship between utilization of host-derived sugars and lipids during development of the symbiotic association remains unknown. Here we show that the fungus Metarhizium robertsii also needs plant-derived lipids to develop symbiotic relationship with plants. The fatty acid binding proteins FABP1 and FABP2 are important for utilization of plant-derived lipids as the deletion of Fabp1 and Fabp2 significantly reduced the ability of M. robertsii to colonize rhizoplane and rhizosphere of maize and Arabidopsis thaliana. Deleting Fabp1 and Fabp2 increased sugar utilization by upregulating six sugar transporters, and this explains why deleting the monosaccharide transporter gene Mst1, which plays an important role in utilization of plant-derived sugars, had no impact on the ability of the double-gene deletion mutant ΔFabp1::ΔFabp2 to colonize plant roots. FABP1 and FABP2 were also found in other plant-associated Metarhizium species, and they were highly expressed in the medium using the tomato root exudate as the sole carbon and nitrogen source, suggesting that they could be also important for these species to develop symbiotic relationship with plants. In conclusion, we discovered that utilization of plant-derived sugars and lipids are coupled during colonization of rhizoplane and rhizosphere by M. robertsii.

Metarhizium robertsii as a promising microbial agent for rice in situ cadmium reduction and plant growth promotion.

The toxic chemical element cadmium (Cd) in paddy fields triggered increasing problems of growth inhibition and food security in rice consistently. In this study, we found Metarhizium robertsii, which is widely used as a bioinsecticide and biofertilizer in agriculture and recently found to be resistant to Cd, developed intraradical and extraradical symbiotic hyphae in rice seedlings, and successfully colonized in the rice rhizosphere soil to more than 103 CFUs g-1 soil at harvesting. M. robertsii colonization significantly reduced Cd accumulations in both hydroponically cultured seedlings and the matured rice cultured in Cd contaminated potting soil (2 ppm). Notably, Cd accumulation reduction of the roots, stems, leaves, husks and grains of the matured rice induced by the fungus were 44.3%, 32.1%, 35.3%, 31.9% and 24.7%, respectively. It was caused by the M. robertsii-induced suppression of Cd intake transporter gene osNramp5 in the rice roots, and the chemical stabilizing of Cd to the residual fraction in the rhizosphere soil. In addition, the colonization of M. robertsii significantly promoted the growth characters and the photosynthesis of the rice plants. This is achieved by the increase of endogenous hormone levels of indole-3-acetic, gibberellin A3 and brassinolide induced by M. robertsii. Furthermore, the fungus enhanced the antioxidative capacities via increasing enzyme activities of catalase, peroxidase and the production of glutathione, ascorbic acid, proline in the rice plants. Our work provides theoretical basis for expanding the use of M. robertsii as in situ Cd accumulation reduction and detoxification agents for rice in contaminated paddy fields.

An inactivating mutation in the vacuolar arginine exporter gene Vae results in culture degeneration in the fungus Metarhizium robertsii.

Culture degeneration usually results in great commercial losses in the economically important filamentous fungi, but the genetic causes of the degeneration remain elusive. In the fungus Metarhizium robertsii, we found that deletion of the vacuolar arginine exporter gene Vae caused culture degeneration. Compared to the WT strain, the mutant showed increased apoptosis, reactive oxygen species (ROS) level and mitochondrial membrane potential collapse, reduced conidial yield and abnormal lipid droplet formation. The extent of the degeneration in the mutant gradually increased over the successive subculturing, which eventually became irreversible; compared to the third subculture of the mutant, the seventh subculture showed a lower conidial yield and pathogenicity to insects, stronger apoptosis, higher ROS level and a smaller number of conidial lipid droplets. Incorporation of the genomic clone of Vae could not restore the WT phenotypes in the seventh subculture, but could in the third one. Loss-of-function in Vae resulted in vacuolar arginine accumulation and reduction in the cytosolic arginine. This downregulated the expression of the regulator CAG9 of G protein signalling pathway, which accounted for most of the phenotypic changes associated with the degeneration of the mutant. We identified a deleterious mutation that causes culture degeneration in a filamentous fugus.

Chitosan nanoparticles embedded with curcumin and its application in pork antioxidant edible coating.

Curcumin (Cur) exhibits low water solubility and insufficient dispersibility in food systems, and cannot exert its excellent antioxidant properties. In this work, Chitosan (CS) nanoparticles were prepared by ionic crosslinking method using chitosan as carrier and sodium tripolyphosphate (TPP) as crosslinking agent, then Cur was loaded to obtain curcumin nanoparticles (CNPs). CNPs presented a spherical morphology with average size of 278.9 nm. Compared with the solubility of native Cur (0.017 µg/mL) at 25 °C, the water solubility of CNPs increased to 35.92 µg/mL of more than 2100 times. In addition, the antioxidant capacity of Cur was also studied based on DPPH free radical scavenging, the results showed that with the increase of the concentration, the antioxidant capacity of CNPs was significantly increased (p < 0.05), which was higher than that of Cur at the same concentration. The edible coating was prepared by adding CNPs into sodium carboxymethyl cellulose (CMC) to study the effects of CMC-CNPs coatings in improving the quality and shelf life of fresh pork stored at 4 ± 1 °C for 15 days. The results showed that CMC-CNPs edible coating could significantly inhibit lipid oxidation of fresh pork (p < 0.05) and could be further applied in lipid rich food packaging.

Effect of nisin and potassium sorbate additions on lipids and nutritional quality of Tan sheep meat.

Nisin and potassium sorbate as preservatives are used in a broad range of meat. A lipidomic evaluation was performed on Tan sheep meat treated by two types of preservatives. The addition of potassium sorbate resulted in higher lipid losses compared with nisin treatment. Furthermore, 106 significant lipids of 12 lipid classes (PC, PS, LPS, LPC, PE, PI, LPE, TG, Cer, DG, SM, Sph) with variable importance in projection scores greater than 1.0 were detected and qualified to distinguish different preservatives added meat using UHPLC-Q-Orbitrap MS/MS. LOD and LOQ were 0.12-0.32 µg kg-1 and 0.35-0.89 µg kg-1, indicating high sensitivity and excellent analytical characteristics in the study. Nisin was confirmed to be the better preservative for prolonging the shelf life of Tan sheep meat while reducing the loss of nutrients. These results could provide a strong cornerstone for future research on preservatives in meat products.

UHPLC-Q-Orbitrap HRMS-based quantitative lipidomics reveals the chemical changes of phospholipids during thermal processing methods of Tan sheep meat.

Thermal processing affects the lipid compositions of meat products. The study determined the effects of boiled, steamed and roasted processing methods on the lipidomics profiles of Tan sheep meat with a validated UPLC-Q-Orbitrap HRMS combined lipid screening strategy method. Combined with sphingolipid metabolism, the boiled approach was the suitable choice for atherosclerosis patients for more losses of sphingomyelin than ceramide in meat. The similarly less losses of phosphatidylcholine and lysophosphatidylcholine showed in glycerophospholipid metabolism implied that steamed Tan sheep meat was more suitable for the populations of elderly and infants. Furthermore, a total of 90 lipids with significant difference (VIP > 1) in 6 lipid subclasses (sphingomyelin, ceramide, lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamines, triacylglycerol,) were quantified among raw and three types of thermal processed Tan sheep meat, further providing useful information for identification of meat products with different thermal processing methods (LOD with 0.14-0.31 µg kg-1, LOQ with 0.39-0.90 µg kg-1).

Molecular mechanism of lipid transformation in cold chain storage of Tan sheep.

Cold chain (-20 °C) is one of the main transportation methods for storage of Tan sheep products. Lipids (66) in seven subclasses involved in sphingolipid, glycerophospholipid and fatty acid degradation metabolism were quantified in Tan sheep under cold chain storage, including fatty acyl carnitines, phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylethanolamine (PE), ceramides, sphingomyelin (SM) and lysophosphatidylethanolamine (LPE). Lipid transformation and molecular mechanism analyzed using fragmentation mechanisms and UHPLC-Q-Orbitrap MS/MS combined with lipidomics approaches determined transient increases of certain PC, PE and fatty acyl carnitine during the first 12 days of cold storage, subsequent declines of SM, PC, PE and fatty acyl carnitine, as well as increases of ceramide, LPC and LPE (24 days). These results offered insights into lipid transformation and quality of Tan sheep during cold chain storage.

Adsorption capacity and cold-water solubility of honeycomb-like potato starch granule.

Honeycomb-like granules, with 2-4 µm pores on the surface, were prepared by heating potato starch suspensions in water at the pasting temperature. These granules with a yield of 84% were most amorphous (relative crystallinity 1.9%). Their total pore area was 0.668 m2/g, porosity was 73.4%, and mean particle size (D50) was 154.3 µm. The molecular weights (MW) of honeycomb-like granules were: amylopectin, 8.7 × 107 g/mol; amylose, 3.1 × 105 g/mol, close to those of native starch. The chain length distribution profiles of honeycomb-like granules were similar to those of native starch, while the proportions of B2 and B3 chains were higher. The water and oil adsorption of honeycomb-like granules were about 1.5 and 2.4 times those of native starch, respectively; and the cold water solubility of honeycomb-like granules was 88.5%, while native starch showed no solubility in cold water. Thus honeycomb-like starch granules have the potential to be applied as adsorbents, thickeners and adhesives for their dispersibility, adsorption capacity and cold water solubility.

Effects of separation and purification on structural characteristics of polysaccharide from quinoa (Chenopodium quinoa willd).

The effects of separation and purification on structural characteristics of polysaccharide from quinoa (Chenopodium quinoa Willd) was investigated. Using quinoa as raw material, the quinoa polysaccharide (QP) was extracted by ultrasonic-assisted method and isolated and purified to obtain three sub-fractions (QPI, QPI-I, QPI-I-I) by resin adsorption, anion-exchange and gel filtration chromatography, respectively. After separation and purification, the polysaccharide content of quinoa polysaccharide increased from 83.29% to 90.12%. XRD and Congo red experiments showed that this process contributed to the formation of crystal structure and triple helix structure. Moreover, the intensity of fourier transform infrared spectroscopy (FT-IR), 1H and 13C Nuclear magnetic resonance spectroscopy (NMR), particle size, dispersion index gradually decreased according to separation and purification, which indicated that a more uniform and stable polysaccharide structure was formed. In addition, FT-IR, 1H NMR and 13C NMR analysis showed that QP, QPI, QPI-I, QPI-I-I were all neutral polysaccharides. The above results suggested that the separation and purification process significantly enhanced the stability of polysaccharide structure. In this process, the aggregation state changed with the polarity change, and the final structure changed, which led to the change of its solubility, viscosity and other physical and chemical properties.

Morphological changes of blocklets during the gelatinization process of tapioca starch.

After combined hydrolysis by α-amylase and ß-amylase at room temperature, spherical blocklets in diameters of 27-60nm were observed on the surface of tapioca starch granules by scanning electron micrography (SEM). Tapioca starch (1%, w/w, db, distilled water) was heated by using a rapid visco analyzer (RVA) in four different programs, then the samples were settled and freeze dried, respectively. The SEM images showed that the blocklets swelled at 52°C; the swollen blocklets deformed to olive shape, and linked by molecular chains, formed bead-like structure at 62°C; they started to merge at 72°C (pasting temperature); then the blocklets fused together and their shapes disappeared completely, and the gel network formed at 95°C. Furthermore, the morphological changes of the blocklets were not simultaneously.

Recognizing the importance of exposure-dose-response dynamics for ecotoxicity assessment: nitrofurazone-induced antioxidase activity and mRNA expression in model protozoan Euplotes vannus.

The equivocality of dose-response relationships has, in practice, hampered the application of biomarkers as a means to evaluate environmental risk, yet this important issue has not yet been fully recognized or explored. This paper evaluates the potential of antioxidant enzymes in the ciliated protozoan Euplotes vannus for use as biomarkers. Dose-response dynamics, together with both the enzyme activity and the gene expression of the antioxidant enzymes, superoxide dismutase, and glutathione peroxidase, were investigated when E. vannus were exposed to graded doses of nitrofurazone for several discrete durations. Mathematical models were explored to characterize the dose-response profiles and, specifically, to identify any equivocality in terms of endpoint. Significant differences were found in both enzyme activity and messenger RNA (mRNA) expression in the E. vannus treated with nitrofurazone, and the interactions between exposure dosage and duration were significant. Correlations between enzyme activity, mRNA expression, and nitrofurazone dose varied with exposure duration. Particularly, the dose-responses showed different dynamics depending on either endpoint or exposure duration. Our findings suggest that both the enzyme activity and the gene expression of the tested antioxidant enzymes can be used as biomarkers for ecotoxicological assessment on the premise of ascertaining appropriate dosage scope, exposure duration, endpoint, etc., which can be achieved by using dose-response dynamics.

Comparison of waxy and normal potato starch remaining granules after chemical surface gelatinization: pasting behavior and surface morphology.

To understand the contribution of granule inner portion to the pasting property of starch, waxy potato starch and two normal potato starches and their acetylated starch samples were subjected to chemical surface gelatinization by 3.8 mol/L CaCl2 to obtain remaining granules. Native and acetylated, original and remaining granules of waxy potato starch had similar rapid visco analyzer (RVA) pasting profiles, while those of two normal potato starches behaved obviously different from each other. All remaining granules had lower peak viscosity than the corresponding original granules. Contribution of waxy potato starch granule's inner portion to the peak viscosity was significant more than those of normal potato starches. The shell structure appearing on the remaining granule surface for waxy potato starch was smoother and thinner than that for normal potato starches as observed by scanning electron microscopy, indicating a more regular structure of shell and a more ordered packing of shell for waxy potato starch granules. The blocklet size of waxy potato starch was smaller and more uniform than those of normal potato starches as shown by atomic force microscopy images of original and remaining granules. In general, our results provided the evidence for the spatial structure diversity between waxy and normal potato starch granules: outer layer and inner portion of waxy potato starch granule had similar structure, while outer layer had notably different structure from inner portion for normal potato starch granule.

Outer shell, inner blocklets, and granule architecture of potato starch.

Potato starch was heated in distilled water and acetic acid solution (pH = 1.5), respectively, then washed with anhydrous ethanol and dried. After cooked in water with certain program, high-resolution scanning electron micrographs (SEM) of broken granules showed isolated outer shells. After treatment with acetic acid, SEM images of dissilient granules exhibited outer shells with randomly assembled spherical inner blocklets. A refined blocklet model was proposed for potato starch granule, the smaller blocklets were compacted densely to form the stiffer outer shell, and the larger blocklets were packed loosely to form the inner shells.