Zhansheng Wu

Microwave-assisted one-step synthesis and characterization of a slow release nitrogen fertilizer with inorganic and organic composites

A slow-release fertilizer (SRF) was synthesized in one step based on urea incorporated in a polymer matrix composed of sodium alginate (NaAlg), acrylic acid (AA), acrylamide (AM) and bentonite (Bent) via microwave irradiation. The proposed microwave-assisted method yielded high reaction rates with less reaction time of 5 minutes at 300 W. The raw materials and final products were characterized in terms of the structure and properties through Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and uniaxial compression measurements. The application potential was verified on the basis of swelling in different environments, largest water-holding ratio and water-retention capacity of soil, release study in soil, and the effect of the proposed SRF product on the germination rate of cotton seed. Results indicated that the addition of Bent not only contributed to the increase in water absorbency, largest water-holding ratio and water-retention capacity of soil, but also caused the system to liberate the nutrient in a more prolonged manner based on a Case II release mechanism with skeleton erosion. Thus, microwave irradiation would be a possible method to produce SRFs for potential agricultural and horticultural applications.

Preparation and characterization of monodisperse microcapsules with alginate and bentonite via external gelation technique encapsulating Pseudomonas putida Rs-198

Abstract This paper evaluated the external gelation technique for preparing microcapsules. The microcapsules were consisted of Pseudomonas putida Rs-198 (Rs-198) core and sodium alginate (NaAlg)-bentonite (Bent) shell. Different emulsification rotation speeds and core/shell ratios were used to prepare the microcapsules of each formulation. The near-spherical microcapsules were monodisperse with a mean diameter of 25–100 μm and wrinkled surfaces. Fourier transform infrared spectrophotometry (FTIR) and thermogravimetric analysis (TGA) revealed the physical mixture of the wall material and the superior thermal stability of the microcapsules. Percentage yield, water content, and encapsulation efficiency were evaluated and correlated with the changes in emulsification rotation speed and core/shell ratio. In vitro release experiments demonstrated that 60% of the bacteria were released from the NaAlg-Bent microcapsules within three days. Considerably better survival was observed for encapsulated cells compared to free cells, especially in pH 4.0 and 10.0. In summary, the desired properties of microcapsules can be obtained by external gelation technique and the microcapsules on the bacteria had a good protective effect.

Preparation of Microencapsulated Bacillus subtilis SL-13 Seed Coating Agents and Their Effects on the Growth of Cotton Seedlings.

Inoculation of the bacterial cells of microbial seed coating agents (SCAs) into the environment may result in limited survival and colonization. Therefore, the application efficacy of an encapsulated microbial seed coating agent (ESCA) was investigated on potted cotton plants; the agent was prepared with polyvinyl alcohol, sodium dodecyl sulfate, bentonite, and microencapsulated Bacillus subtilis SL-13. Scanning electron micrography revealed that the microcapsules were attached to ESCA membranes. The ESCA film was uniform, bubble-free, and easy to peel. The bacterial contents of seeds coated with each ESCA treatment reached 106 cfu/seed. Results indicated that the germination rate of cotton seeds treated with ESCA4 (1.0% (w/v) sodium alginate, 4.0% polyvinyl alcohol, 1.0% sodium dodecyl sulfate, 0.6% acacia, 0.5% bentonite, and 10% (v/v) microcapsules) increased by 28.74%. Other growth factors of the cotton seedlings, such as plant height, root length, whole plant fresh weight, and whole plant dry weight, increased by 52.70%, 25.13%, 46.47%, and 33.21%, respectively. Further analysis demonstrated that the peroxidase and superoxide dismutase activities of cotton seedlings improved, whereas their malondialdehyde contents decreased. Therefore, the ESCA can efficiently improve seed germination, root length, and growth. The proposed ESCA exhibits great potential as an alternative to traditional SCA in future agricultural applications.

Screening and optimization of low-cost medium for Pseudomonas putida Rs-198 culture using RSM

The plant growth-promoting rhizobacterial strain Pseudomonas putida Rs-198 was isolated from salinized soils from Xinjiang Province. We optimized the composition of the low-cost medium of P. putida Rs-198 based on its bacterial concentration, as well as its phosphate-dissolving and indole acetic acid (IAA)-producing capabilities using the response surface methodology (RSM), and a mathematical model was developed to show the effect of each medium component and its interactions on phosphate dissolution and IAA production. The model predicted a maximum phosphate concentration in medium containing 63.23 mg/L inorganic phosphate with 49.22 g/L corn flour, 14.63 g/L soybean meal, 2.03 g/L K2HPO4, 0.19 g/L MnSO4 and 5.00 g/L NaCl. The maximum IAA concentration (18.73 mg/L) was predicted in medium containing 52.41 g/L corn flour, 15.82 g/L soybean meal, 2.40 g/L K2HPO4, 0.17 g/L MnSO4 and 5.00 g/L NaCl. These predicted values were also verified through experiments, with a cell density of 1013 cfu/mL, phosphate dissolution of 64.33 mg/L, and IAA concentration of 18.08 mg/L. The excellent correlation between predicted and measured values of each model justifies the validity of both the response models. The study aims to provide a basis for industrialized fermentation using P. putida Rs-198.

Effect of encapsulated pseudomonas putida Rs-198 strain on alleviating salt stress of cotton

ABSTRACT The present investigation was carried out to determine the inter-relationship between some physiological attributes of cotton and encapsulated Rs-198 strain. The pot experiment had seven treatments (with or without encapsulated bacteria under different salt stress conditions, 10 replicates) and was carried out in the greenhouse during April–June 2014. Pot results showed that the inoculated encapsulated Rs-198 significantly increased the plant biomass under 0.5% salt stress. Besides, an approximately 19.47% increase in the soluble protein content of cotton with encapsulated Rs-198 inoculated in salt condition and relatively higher chlorophylls a, b and carotenoid concentrations of 0.626, 0.304, and 0.564 mg/g, respectively, were maintained. The proline content and peroxidase activity in cotton plants inoculated Rs-198 under 0.5% salt stress of were reduced by 42.30% and by 24.98%, respectively. In conclusion, application of encapsulated Rs-198 strain was effective in relieving salt stress under saline conditions. microcapsule bioinoculants are potential alternatives for sustainable agriculture due to their low cost of production.

Plant growth promotion and alleviation of salinity stress in Capsicum annuum L. by Bacillus isolated from saline soil in Xinjiang

To maintain the growth and development of pepper in saline condition, candidates of plant growth promoting rhizobacteria (PGPR) were isolated, and detected to plant growth promoting (PGP) potential under salt stress was investigated. Thirteen bacterial strains with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, WU-1-13, were isolated from saline soil in Xinjiang, China. The isolates were shown to belong to the genera Bacillus by partial sequencing analysis of their respective 16 S rRNA genes. Seven isolates had the ability to solubilize phosphate. Moreover, the amount of solubilized phosphate was significantly high (P < 0.05), which ranged from 157.33 μg/mL to 922.41 μg/mL. All tested bacterial strains were shown to produce a large amount of ACC deaminase and NH3. Furthermore, nine strains were detected for siderophore production. On the aspect of extracellular enzyme, all bacterial isolates produced lipase, amylase and cellulose, whereas only a minority produced chitinase (15.4%) and 10 isolates produced β-glucanase or protease. In growth room experiments, the results showed that the strain WU-5 exhibited better growth promotion of pepper seedlings in terms of fresh weight (75.60%), dry weight (86.68%), shoot length (12.12%) and root length (146.52%) over the control under saline stress followed by WU-13. Furthermore, seedlings accumulated high amounts of proline induced by the different PGPR inoculation treatments to alleviate the negative effects of salt stress. Further growth-promoting assays under different salt stress were set up to confirm that the fresh and dry weight, shoot and root length of pepper plants inoculated by three strains all were significantly higher than non-inoculated control under different saline stress. In summary, the results demonstrated that WU-9, which induced high levels of proline production and antioxidant enzyme activities, and three strains (WU-5, WU-9 and WU-13) can be of great value in maintaining the growth and development of seedlings on saline lands.

Rhizospheric Bacillus subtilis Exhibits Biocontrol Effect against Rhizoctonia solani in Pepper (Capsicum annuum)

This study aimed at evaluating the ability of SL-44 to control Rhizoctonia solani and promote pepper (Capsicum annuum) growth. Strain SL-44 was isolated from plant rhizosphere and the pot experiment results indicated that the dry and fresh weights of pepper in SL-44 and Rhizoctonia solani (S-R) treatment were 45.5% and 54.2% higher than those in Rhizoctonia solani (R) treatment and 18.2% and 31.8% higher than those in CK (control, noninoculation) treatment. The plant height in S-R treatment increased by 14.2% and 9.0% compared with those in the R and CK treatments, respectively. In vitro antagonism assay showed that SL-44 exhibited strong antifungal activity against the mycelial growth of Rhizoctonia solani, with an inhibition rate of 42.3%. The amount of phosphorus dissolved by SL-44 reached 60.58 mg·L−1 in broth and 7.5 μg·mL−1 IAA were secreted by SL-44. Strain SL-44 inhibited the growth of R. solani and improved biomass of pepper plants. Mass exchange and information transmission between the pepper plants and SL-44 mutually promoted their development. Bacillus subtilis SL-44 has a great potential as biocontrol agent against Rhizoctonia solani on pepper plants.