Bacillus velezensis YXDHD1-7 Prevents Early Blight Disease by Promoting Growth and Enhancing Defense Enzyme Activities in Tomato Plants.

Bacillus velezensis is well known as a plant growth-promoting rhizobacteria (PGPR) and biocontrol agent. Nevertheless, there are very few reports on the study of B. velezensis on tomato early blight, especially the biocontrol effects among different inoculation concentrations. In this study, an IAA-producing strain, Bacillus velezensis YXDHD1-7 was isolated from the tomato rhizosphere soil, which had the strongest inhibitory effect against Alternaria solani. Inoculation with bacterial suspensions of this strain promoted the growth of tomato seedlings effectively. Furthermore, inoculations at 106, 107, and 108 cfu/mL resulted in control efficacies of 100%, 83.15%, and 69.90%, respectively. Genome sequencing showed that it possesses 22 gene clusters associated with the synthesis of antimicrobial metabolites and genes that are involved in the production of IAA. Furthermore, it may be able to produce spermidine and volatile compounds that also enhance plant growth and defense responses. Our results suggest that strain YXDHD1-7 prevents early blight disease by promoting growth and enhancing the defense enzyme activities in tomato plants. This strain is a promising candidate for an excellent microbial inoculant that can be used to enhance tomato production.

Inhibition of pathogenic microorganisms in solid organic waste via black soldier fly larvae-mediated management.

Inadequately managed solid organic waste generation poses a threat to the environment and human health globally. Biotransformation with the black soldier fly larvae (BSFL) is emerging as talent technology for solid waste management. However, there is a lack of understanding of whether BSFL can effectively suppress potential pathogenic microorganisms during management and the underlying mechanisms. In this study, we investigated the temporal variations of microorganisms in two common types of solid waste, i.e., kitchen waste (KW) and pig manure (PM). Natural composting and composting with BSFL under three different pH levels (pH 5, 7, and 9) were established to explore their impact on microbial communities in compost and the gut of BSFL. The results showed that the compost of kitchen waste and pig manure led to an increase in relative abundance of various potentially pathogenic bacteria. Temporal gradient analyses revealed that the most substantial reduction in the relative abundance and diversity of potentially pathogenic microorganisms occurred when the initial pH of both two wastes were adjusted to 7 upon the introduction of BSFL. Through network and pls-pm analysis, it was discovered that the gut microbiota of BSFL occupied an ecological niche in the compost, inhibiting the proliferation of potentially pathogenic microorganisms. This study has revealed the potential of BSFL in reducing public health risks during the solid waste management process, providing robust support for sustainable waste management.

Innate Root Exudates Contributed to Contrasting Coping Strategies in Response to Ralstonia solanacearum in Resistant and Susceptible Tomato Cultivars.

Tomato cultivars with contrasting resistance to pathogens regulate root exudates differentially in response to Ralstonia solanacearum attacks. However, strategies using innate root exudates against infection remain unknown. This study analyzed the innate root exudates of two tomato cultivars and their functions in regulating R. solanacearum infection. The innate root exudates differed between the two cultivars. Astaxanthin released from resistant plants inhibited colonization by R. solanacearum but promoted motility, while neferine released from susceptible plants suppressed motility and colonization. The secretion of astaxanthin in resistant tomatoes promoted the growth of biocontrol fungi in soil and reduced the abundance of pathogenic fungi. Neferine secreted by the susceptible cultivar inhibited the relative abundance of the bacterial-biocontrol-related Bacillus genus, indirectly reducing the soil's immune capacity. This study revealed contrasting strategies using root exudates in resistant and susceptible tomato cultivars to cope with R. solanacearum infection, providing a basis for breeding disease-resistant cultivars.

Genomic Insights and Functional Analysis Reveal Plant Growth Promotion Traits of Paenibacillus mucilaginosus G78.

Paenibacillus mucilaginosus has widely been reported as a plant growth-promoting rhizobacteria (PGPR). However, the important genomic insights into plant growth promotion in this species remain undescribed. In this study, the genome of P. mucilaginosus G78 was sequenced using Illumina NovaSeq PE150. It contains 8,576,872 bp with a GC content of 58.5%, and was taxonomically characterized. Additionally, a total of 7337 genes with 143 tRNAs, 41 rRNAs, and 5 ncRNAs were identified. This strain can prohibit the growth of the plant pathogen, but also has the capability to form biofilm, solubilize phosphate, and produce IAA. Twenty-six gene clusters encoding secondary metabolites were identified, and the genotypic characterization indirectly proved its resistant ability to ampicillin, bacitracin, polymyxin and chloramphenicol. The putative exopolysaccharide biosynthesis and biofilm formation gene clusters were explored. According to the genetic features, the potential monosaccharides of its exopolysaccharides for P. mucilaginosus G78 may include glucose, mannose, galactose, fucose, that can probably be acetylated and pyruvated. Conservation of the pelADEFG compared with other 40 Paenibacillus species suggests that Pel may be specific biofilm matrix component in P. mucilaginosus. Several genes relevant to plant growth-promoting traits, i.e., IAA production and phosphate solubilization are well conserved compared with other 40 other Paenibacillus strains. The current study can benefit for understanding the plant growth-promoting traits of P. mucilaginosus as well as its potential application in agriculture as PGPR.

Pre-sowing seed treatment with kinetin and calcium mitigates salt induced inhibition of seed germination and seedling growth of choysum (Brassica rapa var. parachinensis).

In recent years, improving plants' resistance towards abiotic stresses with exogenous application of plant growth regulators and nutrients has emerged as a matter of great interest. The present study assessed the potential roles of kinetin (Kn, 0.2 mM) and calcium (Ca, 2 mM) in mitigating the salt (200 mM NaCl) induced inhibitory effects on seed germination and growth of choysum seedlings. The results indicated that NaCl stress significantly reduced the seed germination percentage (42.6%), germination potential (42.0%), germination index (52.1%), seedling vigor index (65.2%), and declined the fresh weight (43.8%), dry weight (52.2%), radicle length (37.2%), and plumule length (41.2%) of germinated seeds, compared to control treatment. The delayed germination and decrease in seedling growth were positively correlated with salinity-induced hormonal imbalance, ion toxicity, and oxidative stress. However, Kn and Ca pretreatment partially mitigated the adverse effects of NaCl stress, evident by early germination and enhanced seedling growth. Kn and Ca effectively increased the accumulation of proline, soluble protein, and soluble sugars, and upregulated the activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase that significantly reduced the production of malondialdehyde, hydrogen peroxide, and superoxide anions in germinating seeds, thereby minimizing the NaCl-induced oxidative damages. Moreover, Kn and Ca pretreatment counteracted the NaCl-induced ionic toxicity by decreasing Na+ and increasing K+ contents and maintained a balanced Na+/K+ ratio in radicles and plumules of choysum seeds. Additionally, Kn and Ca under NaCl stress enhanced hormonal regulation by decreasing the ABA levels with a concomitant increase of GAs (especially GA4) levels and promoted early germination. Remarkably, the co-application of Kn and Ca was most effective by completely counteracting the inhibitory effects of NaCl and maintaining seed germination kinetics, seedling growth, and biochemical parameters almost similar to that in the stress-free control treatment. These results demonstrate that supplementation of Kn and Ca on choysum seeds is an effective chemical strategy regulating the various physiological and biochemical responses that would result in better germination and growth of seeds under stress conditions.

Formosanin C attenuates lipopolysaccharide-induced inflammation through nuclear factor-κB inhibition in macrophages.

Extended inflammation and cytokine production pathogenically contribute to a number of inflammatory disorders. Formosanin C (FC) is the major diosgenin saponin found in herb Paris formosana Hayata (Liliaceae), which has been shown to exert anti-cancer and immunomodulatory functions. In this study, we aimed to investigate anti-inflammatory activity of FC and the underlying molecular mechanism. RAW264.7 macrophages were stimulated with lipopolysaccharide (LPS) or pretreated with FC prior to being stimulated with LPS. Thereafter, the macrophages were subjected to analysis of the expression levels of pro-inflammatory mediators, including nitric oxide (NO), prostaglandin E2 (PGE), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and IL-6, as well as two relevant enzymes, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). The analysis revealed that FC administration blunted LPS-induced production of NO and PGE in a dose-dependent manner, while the expression of iNOS and COX-2 at both mRNA and protein levels was inhibited in LPS-stimulated macrophages pre-treated with FC. Moreover, LPS stimulation upregulated mRNA expression and medium release of TNF-α, IL-1ß, and IL- 6, whereas this effect was blocked upon FC pre-administration. Mechanistic studies showed that inhibitory effects of FC on LPS-induced inflammation were associated with a downregulation of IκB kinase, IκB, and p65/NF-κB pathway. Taken together, these data suggest that FC possesses an inflammation-suppressing activity, thus being a potential agent for the treatment of inflammation-associated disorders.

Jasmonic acid-mediated enhanced regulation of oxidative, glyoxalase defense system and reduced chromium uptake contributes to alleviation of chromium (VI) toxicity in choysum (Brassica parachinensis L.).

The cultivation of leafy vegetables on metal contaminated soil embodies a serious threat to yield and quality. In the present study, the potential role of exogenous jasmonic acid (JA; 0, 5, 10, and 20 µM) on mitigating chromium toxicity (Cr; 0, 150, and 300 µM) was investigated in choysum (Brassica parachinensis L.). With exposure to increasing Cr stress levels, a dose-dependent decline in growth, photosynthesis, and physio-biochemical attributes of choysum plants was observed. An increase in Cr levels also resulted in oxidative stress closely associated with higher lipoxygenase activity (LOX), hydrogen peroxide (H2O2) generation, lipid peroxidation (MDA), and methylglyoxal (MG) levels. Exogenous application of JA alleviated the Cr-induced phytotoxic effects on photosynthetic pigments, gas exchange parameters, and restored growth of choysum plants. While exposed to Cr stress, JA supplementation induced plant defense system via enhanced regulation of antioxidant enzymes, ascorbate and glutathione pool, and the glyoxalase system enzymes. The coordinated regulation of antioxidant and glyoxalase systems expressively suppressed the oxidative and carbonyl stress at both Cr stress levels. More importantly, JA restored the mineral nutrient contents, restricted Cr uptake, and accumulation in roots and shoots of choysum plants when compared to the only Cr-stressed plants. Overall, the application of JA2 treatment (10 µM JA) was more effective and counteracted the detrimental effects of 150 µM Cr stress by restoring the growth and physio-biochemical attributes to the level of control plants, while partially mitigated the detrimental effects of 300 µM Cr stress. Hence, JA application might be considered as an effective approach for minimizing Cr uptake and its detrimental effects in choysum plants grown on contaminated soils.

Nanoscale Technologies in Highly Sensitive Diagnosis of Cardiovascular Diseases.

Cardiovascular diseases (CVD) are the leading cause of death and morbidity in the world and are a major contributor to healthcare costs. Although enormous progress has been made in diagnosing CVD, there is an urgent need for more efficient early detection and the development of novel diagnostic tools. Currently, CVD diagnosis relies primarily on clinical symptoms based on molecular imaging (MOI) or biomarkers associated with CVDs. However, sensitivity, specificity, and accuracy of the assay are still challenging for early-stage CVDs. Nanomaterial platform has been identified as a promising candidate for improving the practical usage of diagnostic tools because of their unique physicochemical properties. In this review article, we introduced cardiac biomarkers and imaging techniques that are currently used for CVD diagnosis. We presented the applications of various nanotechnologies on diagnosis within cardiac immunoassays (CIAs) and molecular imaging. We also summarized and compared different cardiac immunoassays based on their sensitivities and working ranges of biomarkers.

Neuroprotective Effect of Activated Protein C on Blood-Brain Barrier Injury During Focal Cerebral Ischemia/Reperfusion.

Although the effect of activated protein C (APC) on neuronal injury and neuroinflammatory responses has been extensively studied, the detailed mechanism underlying APC-protective effect in the blood-brain barrier (BBB) injury during ischemia is still not clear. In this study, the APC effect against neuroinflammatory responses was evaluated in the model of right middle cerebral artery occlusion in male Sprague-Dawley rats with 2 hours of ischemia and 22 hours of reperfusion. The results showed that APC can significantly improve the neurological function scoring and reduce the infarct volume and BBB permeability. Moreover, the expression of protein nuclear factor-kappa B (NF-κB), both in cytoplasm and nuclei, was reduced. The downstream of NF-κB activation, including tumor necrosis factor-α and interleukin-1ß secretion, was inhibited. In all, APC exerts a neuroprotective effect in focal cerebral ischemia-reperfusion in rats by inhibiting the activation and nuclear translocation of NF-κB. It may indicate a therapeutic approach for ischemic brain injury.

Intensification of sorption-reduction coupled gold biorecovery process through microbial surface modification: effect on gold sorption and reduction.

Biorecovery is emerging as a promising approach to retrieve gold from various sources, while its efficiency is usually restricted by the limited functional groups on natural microbial biomass surface. This study aims to intensify Pycnoporus sanguineus boosted sorption-reduction coupled gold biorecovery process via microbial surface modification. Results showed that grafting polyallylamine hydrochloride onto P. sanguineus biomass surface increased amino group content on microbial biomass surface from 1.29 to 2.81 mmol/g. When applying modified biomass to gold biorecovery with initial gold concentrations of 1.0, 2.0 and 3.0 mM, biosorption equilibrium time shortened to the 12.5%, 37.5% and 41.7% of those obtained with pristine biomass, and sorption rate constants correspondingly increased to 11.2, 3.1 and 3.7 folds as well. Maximum sorption capacity increased 30% and the affinity between biomass and gold enhanced heavily after microbial surface modification. Meanwhile, microbial surface modification favored gold reduction and gold nanoparticles (AuNPs) formation. The change of microbial biomass morphology from smooth surface with some branched structure to layered stacking structure with many pores and the increase of amino group content on microbial biomass surface were the main impetus for the gold bioreocovery process intensification.

Modulation of growth performance and coordinated induction of ascorbate-glutathione and methylglyoxal detoxification systems by salicylic acid mitigates salt toxicity in choysum (Brassica parachinensis L.).

Salinity represents a serious environmental threat to crop production and by extension, to world food supply, social and economic prosperity of the developing world. Salicylic acid (SA) is an endogenous plant signal molecule involved in regulating various plant responses to stress. In the present study, we characterized the regulatory role of exogenous SA for their ability to ameliorate deleterious effects of salt stress (0, 100, 150, 200 mM NaCl) in choysum plants through coordinated induction of antioxidants, ascorbate glutathione (AsA-GSH) cycle, and the glyoxalase enzymes. An increase in salt stress dramatically declined root and shoot growth, leaf chlorophyll and relative water content (RWC), subsequently increased electrolyte leakage (EL) and osmolytes accumulation in choysum plants. Salt stress disrupted the antioxidant and glyoxalase defense systems which persuaded oxidative damages and carbonyl toxicity, indicated by increased H2O2 generation, lipid peroxidation, and methylglyoxal (MG) content. However, application of SA had an additive effect on the growth of salt-affected choysum plants, which enhanced root length, plant biomass, chlorophyll contents, leaf area, and RWC. Moreover, SA application effectively eliminated the oxidative and carbonyl stress by improving AsA and GSH pool, upregulating the activities of antioxidant enzymes and the enzymes associated with AsA-GSH cycle and glyoxalase system. Overall, SA application completely counteracted the salinity-induced deleterious effects of 100 and 150 mM NaCl and partially mediated that of 200 mM NaCl stress. Therefore, we concluded that SA application induced tolerance to salinity stress in choysum plants due to the synchronized increase in activities of enzymatic and non-enzymatic antioxidants, enhanced efficiency of AsA-GSH cycle and the MG detoxification systems.

Effects of sulphur and Thiobacillus thioparus 1904 on nitrogen cycle genes during chicken manure aerobic composting.

Severe nitrogen (N) loss is a barrier for composting treatment. Since N transformation during composting is closely related to nitrogen loss, the impacts of adding sulphur and Thiobacillus thioparus 1904 to N transformation during composting were investigated in this work. Physicochemical properties and the expression of genes encoding N-related proteins were analysed to evaluate microbiological processes associated with N dynamics. The results indicated that (1) sulphur addition reduced the pH and cumulative NH3 emission, and decreased N losses by 44.23%, while no significant differences were observed in the expression of N cycle-associated genes compared with the control treatment; (2) the application of T. thioparus 1904 increased NO3--N content, reduced N loss by 28.20%, and significantly enhanced the expression of ammonia monooxygenase A (archaeal amoA; AOA) and nitrite oxidoreductase A (nxrA) during the mature phase; (3) the combined application of sulphur and T. thioparus 1904 significantly affected the expression of functional genes related to nitrification and denitrification, which contributed to a reduction in accumulated NH3 emission, an increase in NO4+-N content, and a decrease in N losses by 70.94%. Expression of ammonia monooxygenase A (bacterial amoA; AOB), nxrA and nitrous oxide reductase Z (nosZ) genes in the combined treatment was positively correlated with NO3--N, whereas expression of AOA and accumulation of NH3 were negatively correlated with NO3--N. These results indicate that the combined application of sulphur and T. thioparus 1904 had a significant regulatory effect on N cycle genes and effectively reduced the N loss during composting.

Sorption-reduction coupled gold recovery process boosted by Pycnoporus sanguineus biomass: Uptake pattern and performance enhancement via biomass surface modification.

Biorecovery is emerging as a promising process to retrieve gold from secondary resources. The present study aimed to explore the uptake pattern of Pycnoporus sanguineus biomass for gold, identify the effective functional groups in gold recovery process, and thus further intensify the process via microbial surface modification. Results showed that P. sanguineus biomass could effectively recover gold with the formation of highly crystal AuNPs without any exogeneous electron donor. Under the conditions of various initial gold concentrations (1.0, 2.0, and 3.0 mM), biomass dosage of 2.0 g/L, solution pH value of 4.0, and incubation temperature of 30°C, the uptake equilibrium established after 4, 8, and 12 h, respectively. The uptake process could be well described by pseudo-second order kinetics model (R2  = 0.9988) and Langmuir isotherm model (R2  = 0.9958). The maximum uptake capacity of P. sanguineus reached as high as 358.69 mg/g. Further analysis indicated that amino, carboxyl and hydroxyl groups positively contributed to the uptake process. Among them, amino group significantly favored the uptake of gold during recovery process. When P. sanguineus biomass was modified by introduction of amino group, the gold uptake process was successfully intensified by shortening the uptake period and enhancing the uptake capacity. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1314-1322, 2017.

Layer-by-layer assembly surface modified microbial biomass for enhancing biorecovery of secondary gold.

Enhancement of the biosorption capacity for gold is highly desirable for the biorecovery of secondary gold resources. In this study, polyethylenimine (PEI) was grafted on Shewanella haliotis surface through layer-by-layer assembly approach so as to improve the biosorption capacity of Au(III). Results showed that the relative contribution of amino group to the biosorption of Au(III) was the largest one (about 44%). After successful grafting 1, 2 and 3-layer PEI on the surface of biomass, the biosorption capacity significantly enhanced from 143.8mg/g to 597.1, 559.1, and 536.8mg/g, respectively. Interestingly, the biomass modified with 1-layer PEI exhibited 4.2 times higher biosorption capacity than the untreated control. When 1-layer modified biomass was subjected to optimizing the various conditions by response surface methodology, the theoretical maximum adsorption capacity could reach up to 727.3mg/g. All findings demonstrated that PEI modified S. haliotis was effective for enhancing gold biorecovery.

Immobilization of Acidithiobacillus ferrooxidans on cotton gauze for biological oxidation of ferrous ions in a batch bioreactor.

The ability of Acidithiobacillus ferrooxidans to oxidize ferrous iron has been extensively studied in bioleaching to recover metal resources. Although immobilization of A. ferrooxidans is of great importance to achieve high bioleaching performance in practical application, the reported approaches of immobilization of A. ferrooxidans are still limited. This paper is attempting to develop a novel method to immobilize A. ferrooxidans by a less-costly effective carrier from zeolite, activated carbon, and cotton gauze. The results showed that cotton gauze was the most suitable carrier to immobilize A. ferrooxidans cells in comparison with zeolite and activated carbon. Acidithiobacillus ferrooxidans immobilized on the cotton gauze by gravity dehydration could achieve an average ferrous iron oxidation rate of 0.73 g/(L·h). Furthermore, the ferrous iron oxidation ratio attained in the bioreactor under batch operation was maintained above 97.83%. All results indicated that cotton gauze could be an efficient carrier for immobilizing A. ferrooxidans cells for the biooxidation of ferrous ions.

Bioreduction of Precious Metals by Microorganism: Efficient Gold@N-Doped Carbon Electrocatalysts for the Hydrogen Evolution Reaction.

The uptake of precious metals from electronic waste is of environmental significance and potential commercial value. A facile bioreductive synthesis is described for Au nanoparticles (ca. 20 nm) supported on N-doped carbon (Au@NC), which was derived from Au/Pycnoporus sanguineus cells. The interface and charge transport between Au and N-doped carbon were confirmed by HRTEM and XPS. Au@NC was employed as an electrocatalyst for the hydrogen evolution reaction (HER), exhibiting a small onset potential of -54.1 mV (vs. RHE), a Tafel slope of 76.8 mV dec(-1) , as well as robust stability in acidic medium. Au@NC is a multifunctional electrocatalyst, which demonstrates high catalytic activity in the oxygen reduction reaction (ORR), as evidenced by an onset potential of +0.97 V, excellent tolerance toward methanol, and long-term stability. This work exemplifies dual recovery of precious Au and fabrication of multifunctional electrocatalysts in an environmentally benign and application-oriented manner.

Biorecovery of gold as nanoparticles and its catalytic activities for p-nitrophenol degradation.

Recovery of gold from aqueous solution using simple and economical methodologies is highly desirable. In this work, recovery of gold as gold nanoparticles (AuNPs) by Shewanella haliotis with sodium lactate as electron donor was explored. The results showed that the process was affected by the concentration of biomass, sodium lactate, and initial gold ions as well as pH value. Specifically, the presence of sodium lactate determines the formation of nanoparticles, biomass, and AuCl4 (-) concentration mainly affected the size and dispersity of the products, reaction pH greatly affected the recovery efficiency, and morphology of the products in the recovery process. Under appropriate conditions (5.25 g/L biomass, 40 mM sodium lactate, 0.5 mM AuCl4 (-), and pH of 5), the recovery efficiency was almost 99 %, and the recovered AuNPs were mainly spherical with size range of 10-30 nm (~85 %). Meanwhile, Fourier transforms infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that carboxyl and amine groups might play an important role in the process. In addition, the catalytic activity of the AuNPs recovered under various conditions was testified by analyzing the reduction rate of p-nitrophenol by borohydride. The biorecovered AuNPs exhibited interesting size and shape-dependent catalytic activity, of which the spherical particle with smaller size showed the highest catalytic reduction activity with rate constant of 0.665 min(-1).

Ecotoxicity monitoring and bioindicator screening of oil-contaminated soil during bioremediation.

A series of toxicity bioassays was conducted to monitor the ecotoxicity of soils in the different phases of bioremediation. Artificially oil-contaminated soil was inoculated with a petroleum hydrocarbon-degrading bacterial consortium containing Burkholderia cepacia GS3C, Sphingomonas GY2B and Pandoraea pnomenusa GP3B strains adapted to crude oil. Soil ecotoxicity in different phases of bioremediation was examined by monitoring total petroleum hydrocarbons, soil enzyme activities, phytotoxicity (inhibition of seed germination and plant growth), malonaldehyde content, superoxide dismutase activity and bacterial luminescence. Although the total petroleum hydrocarbon (TPH) concentration in soil was reduced by 64.4%, forty days after bioremediation, the phytotoxicity and Photobacterium phosphoreum ecotoxicity test results indicated an initial increase in ecotoxicity, suggesting the formation of intermediate metabolites characterized by high toxicity and low bioavailability during bioremediation. The ecotoxicity values are a more valid indicator for evaluating the effectiveness of bioremediation techniques compared with only using the total petroleum hydrocarbon concentrations. Among all of the potential indicators that could be used to evaluate the effectiveness of bioremediation techniques, soil enzyme activities, phytotoxicity (inhibition of plant height, shoot weight and root fresh weight), malonaldehyde content, superoxide dismutase activity and luminescence of P. phosphoreum were the most sensitive.

[Bio-inspired Recovery of Platinum Nanoparticle and Its Mechanism].

This paper illustrated an approach of using a self-isolated bacterium Enterococcus faecalis Z5(CCTCC M2012445) to recover platinum nanoparticles from aqueous solution, and exploring its possibility under the condition of providing an exogenous electron donor. At the same time, the impacts of initial Pt concentration, biomass, temperature and pH on recovery process were researched to explore the possible mechanism of recovery process. The results showed that Enterococcus faecalis Z5 could recover platinum nanoparticles and there were two steps:bio-sorption and bio-reduction. And the initial Pt concentration 286.46 mg·L-1, biomass 3.2 g·L-1, temperature 50℃ and pH 6 for biorecovering were optimized. The TEM and XRD results indicated that the reduction products were platinum nanoparticles, of which most were distributed on the periplasm and the diameters were about 5 nm. Moreover, as shown by XPS figures, Pt (Ⅳ) was firstly reduced to Pt (Ⅱ), then further reduced to Pt (0) and nanoparticles were formed. The reduction of Pt (Ⅱ) to Pt (0) was a rate-limiting step. And the FTIR result showed the corresponding peaks of hydroxyl and amide group changes on the bacterium before and after reduction, probably playing an important role in the reduction process.

Simultaneous heavy metals removal and municipal sewage sludge dewaterability improvement in bioleaching processes by various inoculums.

The heavy metals content and dewaterability of municipal sewage sludge (MSS) are important parameters affecting its subsequent disposal and land application. Six kinds of inoculums were prepared to examine the characteristics of heavy metals removal and MSS dewaterability improvement in bioleaching processes. The results showed that Cu, Zn and Cd bioleaching efficiencies (12 days) were 81-91, 87-93 and 81-89%, respectively, which were significantly higher than those of Fe-S control (P < 0.05) and blank control (P < 0.01). The bioleaching boosted by the prepared inoculums could also significantly enhance MSS dewaterability (P < 0.01). The centrifugal dehydration efficiency of MSS rose from 73.00 to 90.00% at day 12. Microscopic observations and energy dispersive spectrum analysis demonstrated that the dewaterability improvement might be attributed to the changes of sludge structure from flocculent to obvious granular and the formation of secondary minerals mainly consisting of iron, oxygen and sulfur elements. The results above demonstrated that bacterial consortium enriched from acid mine drainage (AMD) was suitable to boost sludge bioleaching for heavy metals removal and dewaterability improvement. It also suggested that the synergy of sulfur/ferrous-oxidizing bacteria (SFOB) enriched from AMD and the cooperation of exogenous and indigenous SFOB significantly promoted bioleaching efficiencies.