Combatting ageing in dermal papilla cells and promoting hair follicle regeneration using exosomes from human hair follicle dermal sheath cup cells.

Dermal papilla cells (DPCs) undergo premature ageing in androgenetic alopecia and senescent alopecia. As critical components of hair follicle reconstruction, DPCs are also prone to senescence in vitro, resulting in a diminished hair follicle inductivity capacity. Dermal sheath cup cells (DSCCs), a specific subset of hair follicle mesenchymal stem cells, intimately linked to the function of DPCs. The primary objective of this research is to investigate the anti-ageing effect of exosomes derived from DSCCs (ExoDSCCs ) on DPCs. Exosomes were utilized to treat H2 O2 -induced DPCs or long-generation DPCs(P10). Our findings demonstrate that ExoDSCCs(P3) promote the proliferation, viability and migration of senescent DPCs while inhibiting cell apoptosis. The expression of senescence marker SA-ß-Gal were significantly downregulated in senescent DPCs. When treated with ExoDSCCs(P3) , expression of inducibility related markers alkaline phosphatase and Versican were significantly upregulated. Additionally, ExoDSCCs(P3) activated the Wnt/ß-catenin signalling in vitro. In patch assay, ExoDSCCs(P3) significantly promoted hair follicle reconstruction in senescent DPCs. In summary, our work highlights that ExoDSCCs(P3) may restore the biological functions and improve the hair follicle induction ability of senescent DPCs. Therefore, ExoDSCCs(P3) may represent a new strategy for intervening in the ageing process of DPCs, contributing to the prevention of senile alopecia.

Endothelial dysfunction of syphilis: Pathogenesis.

Treponema pallidum is the causative factor of syphilis, a sexually transmitted disease (STD) characterized by perivascular infiltration of inflammatory cells, vascular leakage, swelling and proliferation of endothelial cells (ECs). The endothelium lining blood and lymphatic vessels is a key barrier separating body fluids from host tissues and is a major target of T. pallidum. In this review, we focus on how T. pallidum establish intimate interactions with ECs, triggering endothelial dysfunction such as endothelial inflammation, abnormal repairment and damage of ECs. In addition, we summarize that migration and invasion of T. pallidum across vascular ECs may occur through two pathways. These two mechanisms of transendothelial migration are paracellular and cholesterol-dependent, respectively. Herein, clarifying the relationship between T. pallidum and endothelial dysfunction is of great significance to provide novel strategies for diagnosis and prevention of syphilis, and has a great potential prospect of clinical application.

Resurgence of syphilis: focusing on emerging clinical strategies and preclinical models.

Syphilis, a sexually transmitted disease (STD) caused by Treponema pallidum (T. pallidum), has had a worldwide resurgence in recent years and remains a public health threat. As such, there has been a great deal of research into clinical strategies for the disease, including diagnostic biomarkers and possible strategies for treatment and prevention. Although serological testing remains the predominant laboratory diagnostic method for syphilis, it is worth noting that investigations pertaining to the DNA of T. pallidum, non-coding RNAs (ncRNAs), chemokines, and metabolites in peripheral blood, cerebrospinal fluid, and other bodily fluids have the potential to offer novel perspectives on the diagnosis of syphilis. In addition, the global spread of antibiotic resistance, such as macrolides and tetracyclines, has posed significant challenges for the treatment of syphilis. Fortunately, there is still no evidence of penicillin resistance. Hence, penicillin is the recommended course of treatment for syphilis, whereas doxycycline, tetracycline, ceftriaxone, and amoxicillin are viable alternative options. In recent years, efforts to discover a vaccine for syphilis have been reignited with better knowledge of the repertoire of T. pallidum outer membrane proteins (OMPs), which are the most probable syphilis vaccine candidates. However, research on therapeutic interventions and vaccine development for human subjects is limited due to practical and ethical considerations. Thus, the preclinical model is ideal for conducting research, and it plays an important role in clinical transformation. Different preclinical models have recently emerged, such as in vitro culture and mouse models, which will lay a solid foundation for clinical treatment and prevention of syphilis. This review aims to provide a comprehensive summary of the most recent syphilis tactics, including detection, drug resistance treatments, vaccine development, and preclinical models in clinical practice.

Research progress on the mechanism of Treponema pallidum breaking through placental barrier.

Congenital syphilis, a significant cause of fetal mortality worldwide, is a congenital infectious disease instigated by the vertical transmission of Treponema pallidum during pregnancy. Clinical manifestations include preterm delivery, stillbirth, neonatal skin lesions, skeletal abnormalities, and central nervous system aberrations. The ongoing increase in the incidence of congenital syphilis, coupled with complexities in diagnosis, necessitates a detailed understanding of its pathogenesis for the development of improved diagnostic approaches, and to interrupt the route of vertical transmission. Drawing from the broader body of research associated with vertical transmission pathogens, we aim to clarify the potential mechanisms by which Treponema pallidum breaches the placental barrier to infect the fetus.

Kindlin-2 promoted the progression of keloids through the Smad pathway and Fas/FasL pathway.

Keloids are benign skin tumors characterized by aggressive growth. To date, there is no exact treatment because little is known about its pathological mechanism. Therefore, it is important to investigate the mechanism of its occurrence and development to identify therapeutic targets. In this study, the expression of Kindlin-2 was higher in keloid fibroblasts (KFs) than in normal skin fibroblasts (NFs). In vitro experiments showed that knocking down Kindlin-2 in KFs could promote cell apoptosis and inhibit cell proliferation, cell migration and invasion, and contractile capability. Western blot results showed that the phosphorylation of Smad3 in KFs was inhibited after knocking down Kindlin-2, inhibiting the activation of the Smad pathway. Moreover, knocking down Kindlin-2 increased the expression of Fas and FasL in KFs, which demonstrated that knocking down Kindlin-2 promoted the activation of the exogenous apoptotic pathway of KFs and then facilitated apoptosis. The above results revealed that knocking down Kindlin-2 in KFs can inhibit the activation of the Smad pathway and promote the activation of the Fas/FasL exogenous apoptosis pathway, thereby altering the cytological function of KFs. Therefore, Kindlin-2 might play an important role in the occurrence and development of keloids and could become a new target to treat keloids.

Kitchen-waste-derived biochar modified nanocomposites with improved photocatalytic performances for degrading organic contaminants.

Kitchen-waste-derived biochar (KBC) was produced by thermal treatment at 400 °C, and a series of KBC/BiOX (X = Br, Cl) photocatalysts were developed using ultrasonication and solvothermal treatment. The as-prepared photocatalysts were characterized by several tests and investigated by photocatalytic reactions towards methyl orange (MO) and tetracycline (TC). The best photocatalysts, 0.15KBC/BiOBr and 0.15KBC/BiOCl separately achieved complete MO photodegradation in 20 min and 35 min. Further study confirmed that 0.15KBC/BiOBr and 0.15KBC/BiOCl possessed excellent photocatalytic efficiency that was 17.9 and 14.8 times higher than BiOBr and BiOCl, respectively. In addition, 0.15KBC/BiOX showed higher activity removal of TC than pure BiOX in 60 min. Notably, 0.15KBC/BiOX maintained a reproducible high photocatalytic efficiency after five recycles. Estimated band gap energy for 0.15KBC/BiOBr (2.40 eV) and 0.15KBC/BiOCl (3.00 eV) was considerably lower than that of BiOBr (2.73 eV) and BiOCl (3.30 eV), indicating a delocalized state was created when forming electronic pathways on the interface. Besides, visible-light harvesting of photocatalysts got promoted by the modification of KBC. Active species trapping experiments and electron paramagnetic resonance (EPR) tests illustrated that photogenerated holes were the principal active species, while ∙OH was involved in the reaction. The successful synthesis of 0.15KBC/BiOX catalyst provided a new approach on simultaneously degrading organic contaminants in water and disposing of excessive kitchen waste.

Prediction of Outcomes of Ultrasound-Guided Saline Enema in the Treatment of Pediatric Intussusception: A Retrospective Case-Control Study.

OBJECTIVES: Outcomes of ultrasound-guided saline enema include successful treatment, unsuccessful treatment, or recurrence. This study aimed to investigate the value of ultrasonic parameters of the ileocecal region during hydrostatic reduction to predict enema outcomes. METHODS: Ultrasound images of patients diagnosed with ileocolic intussusception and treated with ultrasound-guided saline enema at two different institutions between January 2019 and April 2021 were retrospectively analyzed to assess ileocecal-valve diameter (ICVD), intussusceptum thickness (IT), and the ratio of IT to ICVD (I/I). Logistic regression analysis was used to explore correlations between ICVD, IT, I/I, and patient characteristics (sex, age, symptom duration, and enema outcome). RESULTS: Of 291 patients with ileocolic intussusception (207 boys; mean ICVD, 8.6 [SD: 0.1] mm; mean IT, 26 [SD: 0.2] mm; mean I/I, 3.0 [SD: 0.01]), 268 had first successful reduction; 23, first failed reduction; 7, final failed reduction; and 41, early recurrence. Significant risk factors for failed reduction included symptom duration >24 hours (odds ratio [OR] = 10, P = .012), ICVD ≤ 8.5 mm (OR = 8, P = .01), and I/I > 3.25 (OR = 16, P < .001). Significant risk factors for early recurrence post-enema included age >1 year (OR = 10, P = .028), ICVD > 8.5 mm (OR = 4, P = .003), and I/I ≤ 2.95 (OR = 6, P < .001). CONCLUSIONS: ICVD and IT measured during ultrasound-guided hydrostatic reduction can predict enema outcomes. The mismatch between IT and ICVD is the primary cause of poor outcomes.

Effects of Vallisneria natans on H2S and S2- releases in black-odorous waterbody under additional nitrate: Comprehensive performance and microbial community structure.

Releases of hydrogen sulphide (H2S) and sulphur ions (S2-) through sulphate reduction in black-odorous waterbody is a great environmental health concern. Aquatic planting for blackening and odour controls has received great attention in research and practice. Nitrate concentration in black-odorous waterbody can vary significantly but little is known about the responses of aquatic plants on H2S and S2- releases under different nitrate levels. This controlled laboratory study explored the changes of H2S and S2- releases in simulated black-odorous waterbody planted with Vallisneria natans and artificial plants (control). V. natans growth was stimulated by additional nitrate (6.6 mg/L NO3--N), resulting in an increase of dissolved oxygen (DO) and pH in overlying water and an 11.0% decrease in removal efficiency of chemical oxygen demand (COD). At relatively low nitrate level (i.e., 2.0 mg/L NO3--N in the absence of additional nitrate), V. natans after the 48th day inhibited H2S and S2- releases by 81.5% and 66.8%, respectively, and their inhibition efficiencies were improved to 95.7% and 98.8% by the presence of additional nitrate. Additional nitrate reduced the relative abundance of sulphate-reducing bacteria (SRB) in the sediments while increased the relative abundance of sulphur-oxidizing bacteria (SOB) and nitrate-reducing sulphur-oxidizing bacteria (NR-SOB) in the leaf biofilms of V. natans and artificial plants. Genus compositions in leaf biofilms showed host specificity. Pearson correlation analysis showed that DO, pH, and nitrate concentration had a positive correlation with the relative abundance of SOB (Aeromonas) and NR-SOB (Hydrogenophaga), while were negatively correlated with the relative abundance of SRB (MSBL7). These results indicated that V. natans under additional nitrate altered microbial community to be unfavourable for H2S and S2- releases. This study clarified the inhibition of H2S and S2- releases by aquatic planting under additional nitrate and provided theoretical basis for improving black-odorous waterbody restoration technology.

Biomarker Prediction of Postoperative Healing of Diabetic Foot Ulcers: A Retrospective Observational Study of Serum Albumin.

PURPOSE: The purpose of this study was to investigate the relationship and to determine potential usefulness of serum albumin as a biomarker for predicting postoperative diabetic foot ulcer (DFU) healing. DESIGN: A retrospective study. SUBJECTS AND SETTING: The sample comprised 266 inpatients with type 2 diabetes receiving care in The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China. Among them, 174 had DFUs and underwent surgery for foot DFUs including amputation, skin grafting, and flap procedures. A comparison group consisted of 92 inpatients without a DFU or surgery. METHODS: The association between healing and preoperative albumin levels was analyzed via a logistic regression model and receiver operating characteristic (ROC) curve. RESULTS: The albumin value of patients with DFU grade 3 or more (3.23 ± 0.58 g/dL) was lower than that of patients with DFU grade 1-2 (3.58 ± 0.5 g/dL), and both were lower than that of the comparison group (3.89 ± 0.3 g/dL). Patients with a DFU with hypoalbuminemia (<3.5 g/dL) had a 2.5-fold higher risk of nonhealing at postoperative 28 days than patients with normal levels (odds ratio = 3.51; 95% confidence interval, 1.75-7.06; P < .001). For patients with a DFU overall, the ROC curve showed a preoperative albumin cutoff of 3.44 g/dL for DFU wound healing. CONCLUSIONS: For patients with a DFU undergoing surgery, preoperative serum albumin may be used as a biomarker for predicting postoperative healing.

In situ preparation of visible-light-driven carbon quantum dots/NaBiO3 hybrid materials for the photoreduction of Cr(VI).

In this study, different carbon quantum dots (CQDs)/NaBiO3 hybrid materials were synthesized as photocatalysts to effectively utilize visible light for the photocatalytic degradation of contaminants effectively. These hybrid materials exhibit an enhanced photocatalytic reduction of hexavalent chromium (Cr(VI)) in the aqueous medium. Zero-dimensional nanoparticles of CQDs were embedded within the two-dimensional NaBiO3 nanosheets by the hydrothermal process. Compared with that of the pure NaBiO3 nanosheets, the photocatalytic performance of the hybrid catalysts was significantly high and 6 wt.% CQDs/NaBiO3 catalyst exhibited better photocatalytic performance. We performed the first-principles density functional theory calculations to study the interfacial properties of pure NaBiO3 nanosheets and hybrid photocatalysts, and confirmed the CQDs played an important role in the CQDs/NaBiO3 composites. The experimental results indicated that the enhanced reduction of Cr(VI) was probably due to the high loading of CQDs (electron acceptor) on NaBiO3, which made NaBiO3 nanomaterials to respond in visible light and significantly improved their electron-hole separation efficiency.

Comparison of radical and non-radical activated persulfate systems for the degradation of imidacloprid in water.

The study focuses on degradation efficiency of non-radical activation and radical activation systems of persulfate (PS) to degrade imidacloprid (IMI) by using sodium persulfate (SPS) as PS source. Copper oxide (CuO)-SPS and CuO/biochar (BC)-SPS were selected as PS non-radical activation systems, and pyrite (PyR)-SPS was selected as PS radical activation system. The degradation by CuO-SPS, CuO/BC-SPS and PyR-SPS systems was investigated from acidic to basic conditions (pH 3.0-11.0). Highest degradation by CuO-SPS and CuO/BC-SPS systems was achieved over pH 11.0. In contrast, highest degradation by PyR-SPS system was achieved over pH 3.0, however, PyR-SPS system was also found effective up to pH 9.0. It was found that degradation was more efficient in PS radical activation system, indicating that IMI could be oxidized by radicals rather than by activated PS. Electron paramagnetic resonance (EPR) analysis was carried out to investigate the generation of sulfate (SO4-) and hydroxyl (OH) radicals, which indicated the presence of SO4- and OH in CuO-SPS, CuO/BC and PyR-SPS systems. However, free radical quenching analysis indicated that radicals were main reactive oxygen species for degradation. The lower degradation in PS non-radical activation systems was probably resulted from radicals existed as minor reactive oxygen species. The findings indicated that non-radical oxidation systems showed low reality for degradation and good degradation could be achieved by radical oxidation system. The degradation was also carried out in real waters to investigate the potential applicability of applied systems, which supported PyR-SPS system for effective degradation.

First Report of Dieback Caused by Lasiodiplodia pseudotheobromae on Ormosia pinnata in China.

Ormosia pinnata (Lour.) Merr. is an important tree used for landscape and plant recovery of barren slopes in China. During an investigation of plant disease on landscape trees in 2018, a dieback was observed on O. pinnata trees in Guangzhou, Guangdong Province, China. Symptoms were characterized by initial dryness of the twigs and eventual death of the whole branch of the tree. Isolations from symptomatic branches yielded 13 isolates including two main morphotypes. Pathogenicity tests showed that isolate GDOP1 from Type I caused dieback of O. pinnata. Based on morphological characteristics and molecular analysis of the internal transcribed spacer rDNA (ITS1-5.8S-ITS2) and partial sequence of the translation elongation factor 1α (EF1-α), the fungus causing dieback on O. pinnata was identified as Lasiodiplodia pseudotheobromae. This is the first report of L. pseudotheobromae infecting O. pinnata in the world.

First report of Fusarium oxysporum Causing Fusarium Dieback on Archidendron clypearia in China.

Archidendron clypearia (Jack) Benth. (common name: Monkey-pod) is a perennial arbor tree belonging to the family Fabaceae. It is used to produce a traditional medicine to treat a variety of heat toxicity symptoms in China. The distribution of A. clypearia mainly include Guangdong, Fujian, and Zhejiang provinces in China as well as other countries in Southeast Asia. In 2018, about 30 Monkey-pod trees were observed showing typical dieback symptoms in a commercial plantation (114°36'09.401″E, 22°58'38.553″N) of Huizhou, Guangdong Province, China. In addition, white cylindrical sawdust exudates from exit holes of ambrosia beetles were observed on the trunks and main branches of the diseased trees. Discoloration was seen around the exit holes of the beetles by splitting the wood. Samples of symptomatic and asymptomatic wood tissues of branches, trunks, and roots were collected from 11 trees. To identify the pathogen, the samples were disinfected with a sodium hypochlorite solution containing 50 g/l chlorine for 60 s, rinsed three times with sterile distilled water, and placed on potato dextrose agar (PDA) for culture at 25℃ for 14 days. Beetles from exit holes of the pathogen-infected wood tissues were also collected and identified as Xyleborus affinis by their cytochrome c oxidase I (COI) sequences (GenBank accession numbers: MT921005 and MT921006) as well as morphological features. After two weeks incubation, 37 single-spore isolates were obtained (31 from galleries of branches and trunks, and 6 from mycangia and the body surface of beetles). Colonies on PDA were fusarium-like, pale orange, floccose with abundant aerial mycelia, and growing at the rate of 3.0 to 4.5 mm/d at 25℃. Conidiophores from the aerial mycelia often had single phialides. Microconidia were hyaline, 0-1 septate, (4-)6-12(-16) × 2-4 µm (n=100), Macroconidia were hyaline, ellipsoidal to falcate, 2-4 septate, (10-)25-45(-50) × 3-6 µm (n=100), with basal foot cells shaped to pointed and apical cells tapered and curved. Two representative isolates (CYML 367, 368) were used for molecular identification and pathogenicity tests. The internal transcriptional spacer region (ITS), ß-tubulin (TUB), and translation elongation factor-1α (TEF 1-α) regions were amplified with primers ITS1F/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass and Donaldson 1995), and EF1-728F (Carbone and Kohn 1999) /EF-2 (O'Donnell et al.1998), respectively. DNA extraction and PCR conditions were followed the methods described by Yin et al. (2019). The amplified fragments were sequenced. The results of BLAST demonstrated that the fragment sequences of ITS (468 bp), TEF 1-α (616 bp), and TUB (295 bp) of isolates CYML367 and CYML368 had 100% similarity to correspondence sequences from the Fusarium oxysporum Schlecht. emend. Snyder & Hansen species complex (GenBank accession numbers MT032694, JF740777, and MN451171, respectively). Sequences generated from this study were deposited into GenBank under accession numbers MN826824 and MN826825 (ITS), MN839680 and MN839681 (TUB), and MN839682 and MN839683 (TEF 1-α). Pathogenicity tests were conducted on 2-year-old seedlings (60-70 cm height, 1.0-1.2 cm in diameter) of A. clypearia with the representative isolates. Ten seedlings were inoculated with each isolate. The stem surface was disinfected with 75% ethanol for 30 s, and rinsed with sterilized water, wounded by removing part of the phloem and xylem, and placed with a mycelial plug (5 mm diameter) from the margin of a 7-day-old PDA plate with mycelia facing the cambium. The inoculated wounds were wrapped with a medical sterile gauze to prevent desiccation and contamination. Control plants were inoculated with non-colonized PDA plugs. These inoculated and control plants were incubated in a chamber at 25℃, 50% humidity, 12 h light/12 h dark cycle. After 3 weeks, all inoculated plants displayed Fusarium dieback symptoms similar to those observed on the original diseased trees in the plantation. The average lesion lengths (1.2/1.7 cm) caused by two isolates were all significantly longer than the wounds in the negative controls (P<0.05). The same fungus was re-isolated from the symptomatic plants, thus fulfilling the Koch's postulates. Further studies should be conducted on the potential vector association, transmission route, and management strategies of this pathogen on A. clypearia in growing regions of China. To our best knowledge, this is the first report of F. oxysporum causing dieback on A. clypearia in China.

Enhancement of using combined packing materials on the removal of mixed sulfur compounds in a biotrickling filter and analysis of microbial communities.

BACKGROUND: Packing materials is a critical design consideration when employing biological reactor to treat malodorous gases. The acidification of packing bed usually results in a significant drop in the removal efficiency. In the present study, a biotrickling filter (BTF2) packed with plastic balls in the upper layer and with lava rocks in the bottom layer, was proposed to mitigate the acidification. RESULTS: Results showed that using combined packing materials efficiently enhanced the removal performance of BTF2 when compared with BTF1, which was packed with sole lava rocks. Removal efficiencies of more than 92.5% on four sulfur compounds were achieved in BTF2. Average pH value in its bottom packing bed was about 4.86, significantly higher than that in BTF1 (2.85). Sulfate and elemental sulfur were observed to accumulate more in BTF1 than in BTF2. Analysis of principal coordinate analysis proved that structure of microbial communities in BTF2 changed less after the shutdown but more when the initial pH value was set at 5.5. Network analysis of significant co-occurrence patterns based on the correlations between microbial taxa revealed that BTF2 harbored more diverse microorganisms involving in the bio-oxidation of sulfur compounds and had more complex interactions between microbial species. CONCLUSIONS: Results confirmed that using combined packing materials effectively improved conditions for the growth of microorganisms. The robustness of reactor against acidification, adverse temperature and gas supply shutdown was greatly enhanced. These provided a theoretical basis for using mixed packing materials to improve removal performance.

Hybrid microbial electrolytic/UV system for highly efficient organic pollutants removal.

This study for the first time proposed an efficient microbial electrolyte/UV system for Methyl Orange decomposition. With an external applied voltage of 0.2 V and cathode aeration of 20 mL/min, H2O2 could be in-situ generated from two-electron reduction of oxygen in cathode, reaching to 8.1 mg/L in 2 hr and continued to increase. The pollutant removal efficiency of approximate 94.7% was achieved at initial neutral pH, with the activation of •OH in the presence of UV illumination. Although the nature of its guiding principles remain on the vista of practical exploration, this proof-of-concept study provides an alternative operation pattern of solar-microbial hybrid technology for future wastewater treatment from a basic but multidisciplinary view.

Heterotrophic nitrogen removal in Bacillus sp. K5: involvement of a novel hydroxylamine oxidase.

An aerobic denitrifying bacterium isolated from a bio-trickling filter treating NOx, Bacillus sp. K5, is able to convert ammonium to nitrite, in which hydroxylamine oxidase (HAO) plays a critical role. In the present study, the performance for simultaneous nitrification and denitrification was investigated with batch experiments and an HAO was purified by an anion-exchange and gel-filtration chromatography from strain K5. The purified HAO's molecular mass was determined by SDS-PAGE and its activity by measuring the change in the concentration of ferricyanide, the electron acceptor. Results showed that as much as 87.8 mg L-1 ammonium-N was removed without nitrite accumulation within 24 hours in the sodium citrate medium at C/N of 15. The HAO isolated from the strain K5 was approximately 71 KDa. With hydroxylamine (NH2OH) as a substrate and potassium ferricyanide as an electron acceptor, the enzyme was capable of oxidizing NH2OH to nitrite in vitro when the pH varied from 7 to 9 and temperature ranged from 25 °C to 40 °C. This is the first time that an HAO has been purified from the Bacillus genus, and the findings revealed that it is distinctive in its molecular mass and enzyme properties.

Study of extracellular polymeric substances in the biofilms of a suspended biofilter for nitric oxide removal.

The extraction and quantitative analysis of extracellular polymeric substances (EPS) have been frequently reported in studies of activated sludge. However, little is currently known about the EPS in the biofilms of biofilter systems. This study investigates the EPS in biofilms of Chelatococcus daeguensis TAD1 established in a suspended biofilter for nitric oxide (NO) removal under thermophilic conditions. Polysaccharide was the main EPS component under all experimental operation conditions of the aerobic biofilter, although the EPS contents and components varied under different operating conditions. As the concentration of the inlet NO varied from 200 to 2000 mg/m3, the EPS and protein contents generally increased. At the highest inlet concentration (2000 mg/m3), the EPS and protein contents reached 0.118 and 0.055 mg/g, respectively (representing increases of 7.3 and 35 %, respectively, over the inlet concentration of 200 mg/m3). In contrast, the polysaccharide content was quite stable against inlet NO concentration. Decreasing the empty bed residence time increased the EPS and polysaccharide contents, but exerted little effect on the protein content. Varying the pH of the circulating fluid from 4 to 8 changed the EPS and its components in complex ways. We also found a strong correlation between the total EPS content and the NO removal efficiency. Therefore, it is possible to take EPS into consideration for biofilter control.

Improved productivity of poly (3-hydroxybutyrate) (PHB) in thermophilic Chelatococcus daeguensis TAD1 using glycerol as the growth substrate in a fed-batch culture.

A particularly successful polyhydroxyalkanoate (PHA) in industrial applications is poly (3-hydroxybutyrate) (PHB). However, one of the major obstacles for wider application of PHB is the cost of its production and purification. Therefore, it is desirable to discover a method for producing PHB in large quantities at a competitive price. Glycerol is a cheap and widely used carbon source that can be applied in PHB production process. There are numerous advantages to operating fermentation at elevated temperatures; only several thermophilic bacteria are able to accumulate PHB when glycerol is the growth substrate. Here, we report on the possibility of increasing PHB production at low cost using thermophilic Chelatococcus daeguensis TAD1 when glycerol is the growth substrate in a fed-batch culture. We found that (1) excess glycerol inhibited PHB accumulation and (2) organic nitrogen sources, such as tryptone and yeast extract, promoted the growth of C. daeguensis TAD1. In the batch fermentation experiments, we found that using glycerol at low concentrations as the sole carbon source, along with the addition of mixed nitrate (NH4Cl, tryptone, and yeast extract), stimulated PHB accumulation in C. daeguensis TAD1. The results showed that the PHB productivity decreased in the following order: two-stage fed-batch fermentation > fed-batch fermentation > batch fermentation. In optimized culture conditions, a PHB amount of 17.4 g l(-1) was obtained using a two-stage feeding regimen, leading to a productivity rate of 0.434 g l(-1) h(-1), which is the highest productivity rate reported for PHB to date. This high PHB biosynthetic productivity could decrease the total production cost, allowing for further development of industrial applications of PHB.

Degradation of forchlorfenuron by nitrification and denitrification reactions in the gut and shell biofilm of Limnoperna fortunei.

The capacity and mechanism of Limnoperna fortunei to reduce the concentration of forchlorfenuron [or 1-(2-chloropyridin-4-yl)-3-phenylurea (CPPU)] in water has been studied under laboratory conditions. Firstly, the evasive response of mussels to CPPU (10, 20, 40 and 60 mg L(-1)) was evaluated, and a toxicity test was carried out at these concentrations. Secondly, the effect of two different sizes of mussels on CPPU concentrations was investigated in a 24-day experiment. Thirdly, the role of intact mussels and valvae only were respectively evaluated in another 24-day experiment. The CPPU concentration decreased by about 40 % in the presence of large mussels and about 20 % in the presence of valvae only. Finally, nucleic acid extracts from the gut and biofilm microbial communities of L. fortunei were analyzed, and the number of copies of the bacterial genes amoA, nirK and nirS were determined. Based on these results, we propose possible mechanisms for CPPU degradation involving bacteria-associated nitrification and denitrification reactions. In summary, we found that the CPPU half-life depended on the presence of mussels, their size and their associated microorganisms.

Comparative study on the production of poly(3-hydroxybutyrate) by thermophilic Chelatococcus daeguensis TAD1: a good candidate for large-scale production.

In spite of numerous advantages on operating fermentation at elevated temperatures, very few thermophilic bacteria with polyhydroxyalkanoates (PHAs)-accumulating ability have yet been found in contrast to the tremendous mesophiles with the same ability. In this study, a thermophilic poly(3-hydroxybutyrate) (PHB)-accumulating bacteria (Chelatococcus daeguensis TAD1), isolated from the biofilm of a biotrickling filter used for NOx removal, was extensively investigated and compared to other PHB-accumulating bacteria. The results demonstrate that C. daeguensis TAD1 is a growth-associated PHB-accumulating bacterium without obvious nutrient limitation, which was capable of accumulating PHB up to 83.6 % of cell dry weight (CDW, w/w) within just 24 h at 45 °C from glucose. Surprisingly, the PHB production of C. daeguensis TAD1 exhibited strong tolerance to high heat stress as well as nitrogen loads compared to that of other PHB-accumulating bacterium, while the optimal PHB amount (3.44 ± 0.3 g l(-1)) occurred at 50 °C and C/N = 30 (molar) with glucose as the sole carbon source. In addition, C. daeguensis TAD1 could effectively utilize various cheap substrates (starch or glycerol) for PHB production without pre-hydrolyzed, particularly the glycerol, exhibiting the highest product yield (Y P/S, 0.26 g PHB per gram substrate used) as well as PHB content (80.4 % of CDW, w/w) compared to other carbon sources. Consequently, C. daeguensis TAD1 is a viable candidate for large-scale production of PHB via utilizing starch or glycerol as the raw materials.