Shuijiao Liao

Solid-phase photocatalytic degradation of polyethylene-goethite composite film under UV-light irradiation

A novel photodegradable polyethylene-goethite (PE-goethite) composite film was prepared by embedding the goethite into the commercial polyethylene. The degradation of PE-goethite composite films was investigated under ultraviolet light irradiation. The photodegradation activity of the PE plastic was determined by monitoring its weight loss, scanning electron microscopic (SEM) analysis and FT-IR spectroscopy. The weight of PE-goethite (1 wt%) sample steadily decreased and led to the total 16% reduction in 300 h under UV-light intensity for 1 mW/cm(2). Through SEM observation there were some cavities around the goethite powder in the composite films, but there were few changes except some surface chalking phenomenon in pure PE film. The degradation rate could be controlled by changing the concentration of goethite particles in PE plastic. The degradation of composite plastic initiated on PE-goethite interface and then extended into polymer matrix induced by the diffusion of the reactive oxygen species generated on goethite particle surface. The photocatalytic degradation mechanism of the composite films was briefly discussed.

Arsenite Oxidation Using Biogenic Manganese Oxides Produced by a Deep-Sea Manganese-Oxidizing Bacterium, Marinobacter sp. MnI7-9

Marinobacter sp. MnI7-9, a deep-sea manganese [Mn(II)]-oxidizing bacterium isolated from the Indian Ocean, showed a high resistance to Mn(II) and other metals or metalloids and high Mn(II) oxidation/removal abilities. This strain was able to grow well when the Mn(II) concentration reached up to 10 mM, and at that concentration, 76.4% of the added Mn(II) was oxidized and 23.4% of the Mn(II) was adsorbed by the generated biogenic Mn oxides (total 99.9% Mn removal). Scanning electron microscope observation and X-ray diffraction analysis showed that the biogenic Mn oxides were in stick shapes, adhered to the cell surface, and contained two typical crystal structures of γ-MnOOH and δ-MnO2. In addition, the biogenic Mn oxides generated by strain MnI7-9 showed abilities to oxidize the highly toxic As(III) to the less toxic As(V), in both co-culture and after-collection systems. In the co-culture system containing 10 mM Mn(II) and 55 μM As(III), the maximum percentage of As(III) oxidation was 83.5%. In the after-collection system using the generated biogenic Mn oxides, 90% of the As(III) was oxidized into As(V), and the concentration of As(III) decreased from 55.02 to 5.55 μM. This study demonstrates the effective bioremediation by a deep-sea Mn(II)-oxidizing bacterium for the treatment of As-containing water and increases the knowledge of deep-sea bacterial Mn(II) oxidation mechanisms. Supplemental materials are available for this article. Go to the publishers online edition of Geomicrobiology Journal to view the supplemental file.

Genome Sequence of Deep-Sea Manganese-Oxidizing Bacterium Marinobacter manganoxydans MnI7-9

Here we report the draft genome of Marinobacter manganoxydans MnI7-9, isolated from a deep-sea hydrothermal vent in the Indian Ocean and capable of oxidizing manganese even when there is a very high concentration of Mn(2+). The strain also displayed high resistance and adsorption ability toward many metal(loid)s.

Pseudaminobacter manganicus sp. nov., isolated from sludge of a manganese mine

A Gram-staining-negative, aerobic, non-motile, capsule-forming and rod-shaped bacterium, designated JH-7T, was isolated from sludge of a manganese mine. The 16S rRNA gene sequence of JH-7T showed highest similarities to those of Pseudaminobacter salicylatoxidans BN12T (97.4 %), Mesorhizobiumthiogangeticum SJTT (97.0 %) and Pseudaminobacter defluvii THI 051T (96.5 %). Phylogenetic trees clustered JH-7T together with P. salicylatoxidans BN12Tand P. defluvii THI 051T. The DNA-DNA hybridization values between JH-7T and P. salicylatoxidans DSM 6986T and between JH-7T and M. thiogangeticum DSM 17097T were 34.8 and 20.1 %, respectively. The major fatty acids of JH-7T (>10 %) were C18 : 1ω7c, C19 : 0cyclo ω8c and C16 : 0. The genomic DNA G+C content was 61.6 mol%. The polyamines of JH-7T were sym-homospermidine (83 %) and putrescine (17 %), and the respiratory quinone was ubiquinone-10. The major polar lipids were phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, two unidentified aminolipids and two unidentified lipids. Compared with the members of the genera Pseudaminobacter and Mesorhizobium, JH-7T showed some unique physiological and biochemical characters, such as being negative for H2S production, hydrolysis of Tween 40 and Tween 60, esterase lipase (C8) activity and assimilation of d-ribose and positive for acid production from d-galactose and assimilation of d-fructose. On the basis of the results of the polyphasic taxonomic analysis, JH-7T was considered to represent a novel species of the genus Pseudaminobacter, for which the name Pseudaminobacter manganicus sp. nov. is proposed. The type strain is JH-7T (=KCTC 52258T=CCTCC AB 2016107T).

Immobilization of cadmium by immobilized Alishewanella sp. WH16-1 with alginate-lotus seed pods in pot experiments of Cd-contaminated paddy soil

This study prepared immobilized Alishewanella sp. WH16-1 using alginate and lotus seed pods as a matrix and investigated the effects of its immobilization on Cd2+ in a culture solution and in soil. Compared with the free WH16-1 strain, the immobilized WH16-1 strain possessed greater stability for long-term use and storage and higher removal ability for Cd2+ in the culture solution. A model of Cd2+ removal by the immobilized WH16-1 strain was proposed. The immobilized WH16-1 strain was incubated in the pot experiments of Cd-contaminated paddy soil for 120 days, and the pot experiments of Cd-contaminated paddy soil without the immobilized WH16-1 strain were used as a control. Compared with the control, the exchangeable and carbonate-bound Cd in the paddy soil incubated with the immobilized WH16-1 strain significantly decreased by 33.6% (P < 0.05) and 17.36%, respectively, and the Cd concentrations in the rice significantly decreased by 78.31% (P < 0.05). The results indicate that alginate-lotus seed pods can be used as excellent cost-effective cell carriers for the immobilization of Alishewanella sp. WH16-1 and that the immobilized WH16-1 strain may be applicable for the biological stabilization of Cd in Cd-contaminated paddy soil.

Carbofuran Degradation by Biogenic Manganese Oxides.

This work studied the effect of biogenic manganese oxides (Bio-MnOx) on carbofuran degradation.The results showed that 21.05 % and 90.63 % carbofuran, respectively, were degraded in 4 days by Bio-MnOx with and without NaN3 at initial pH 4.80, whereas carbofuran was hardly degraded by chemical manganese oxides in the same condition. Bio-MnOx promoted carbofuran hydrolysis by changing the pH of the environment and encouraged carbofuran phenol cleavage by its oxidization. Both the oxidation of carbofuran phenol by Bio-MnOx and the reoxidation of the released Mn(II) by Mn(II)-oxidizing microorganisms ensured the continuous reactivity of Bio-MnOx and prevented the secondary pollution of Mn(II). Carbofuran phenol was the major transformation product in the degradation and was further oxidized into small organic molecules as monitored by a GC/MS analyzer. This report offers an efficient, feasible, and no-secondary-pollution approach to controlling carbofuran pollution.