Development of stable agar/carrageenan-Fe3O4-Klebsiella pneumoniae composite beads for efficient phenol degradation.

It's of practical importance but highly challenging for cell immobilization supports to maintain mechanical strength and reduce microbial leakage in environmental and industrial applications. Herein, we developed an agar/κ-carrageenan composite hydrogel to entrap Klebsiella pneumoniae with the combination of nano-Fe3O4 for processing phenol wastes. The agar/carrageenan-K. pneumoniae composite bead showed good pelletizing properties, superior material strength and high cell loading. Introduction of nano-Fe3O4 to the composite gel further enhanced phenol degradation rate by >10% owing to strengthened phenol oxidation by Fe3O4-induced hydroxyl radicals (·OH) and improved mass and electron transfers. 50 successive cycles of degradation and recycling using the agar/carrageenan-K. pneumoniae composite bead showed that 1500 mg/L phenol was fully degraded for all cycles with the highest rate of 55.12 mg L-1·h-1 obtained at the 15th cycles. The improved stability and recyclability render the as-prepared immobilized phenol-degrading bacteria with great potential for industrial applications.

Treatment of fracturing wastewater by anaerobic granular sludge: The short-term effect of salinity and its mechanism.

The effects of salinity shock on the anaerobic treatment of fracturing wastewater regarding chemical oxygen demand (COD) removal performance, sludge characteristics and microbial community were investigated. Results showed COD removal efficiency decreased from 76.0% to 69.1%, 65.6%, 33.7% and 21.9% with the increase of salinity from 2.5 g/L to 10, 15, 25 and 45 g/L, respectively. The cumulative biogas production decreased by 13.8%-81.1% when salinity increased to 15-85 g/L. The increase of salinity led to the decline in particle size of granular sludge, and the activity of granular sludge, including SMA, coenzyme F420 and dehydrogenase, was inhibited significantly. Flow cytometry indicated the percentage of damaged cells in granular sludge gradually increased with the increase of salinity. Sequence analysis illustrated that microbial community structure in anaerobic digestion reactor was influenced by the salinity, high salinity reduced the diversity of archaea and decreased the abundance of methanogens, especially Methanosaeta.

Use of extracellular polymeric substances as natural redox mediators to enhance denitrification performance by accelerating electron transfer and carbon source metabolism.

Extracellular polymeric substances (EPS) extracted from waste activated sludge were used as endogenous redox mediator to enhance denitrification performance. The nitrate reduction rate increased 1.42-fold when EPS were added at 75 mg C/L (C represents total organic carbon). EPS addition decreased the charge transfer resistance and improved the electron transport system activity. The nitrate reductase and nitrite reductase activities improved by 29.7% and 25.4%, respectively. The activation energy of the system with EPS addition (25.82 kJ/mol) was 31.1% lower than that of the control group (37.49 kJ/mol). Besides, EPS could be used as electron carriers to accelerate electron transport; its primary role was similar to that of the quinone loop in the electron transfer chain. More importantly, EPS addition enhanced carbon source metabolism, which increased the available nicotinamide adenine dinucleotide yield to 1.21 times that of the control group, and thus promoted the denitrification performance of activated sludge.

Effect of mechanical elutriation on carbon source recovery from primary sludge in a novel activated primary tank.

A novel activated primary tank (APT) with an elutriation unit was developed for recovering carbon by the fermentation and elutriation of primary sludge, and the mechanical elutriation mechanism was analysed by conducting a batch fermentation experiment to improve carbon source recovery. The results indicated that a high stirring velocity gradient could cause sludge disintegration, which could not only shorten the fermentation time, but also increase the production of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) by 8.3% and 9.5%, respectively. Moreover, mechanical elutriation could also promote the release of SCOD from sludge to water, resulting in an increase in the yield of SCOD by 9.2%, it was observed that elutriation intensity plays a more important role than the elutriation time. The microbial community structure of the fermentation system was influenced by the stirring intensity. The relative abundance of fermentative bacteria in the reactor with a stirring intensity (G) of 160 s-1 was 13.8%, which was significantly higher than that in the reactor with G = 31 s-1 (8.037%), so the accumulation of VFAs and SCOD in the reactor with G = 160 s-1 was improved.

Enhanced total nitrogen removal performance in a full scale Orbal oxidation ditch by a novel step aeration mode.

Two aeration modes, namely point aeration and step aeration, were proposed and implemented in a full scale Orbal oxidation ditch, and nitrogen removal performance was studied. The results showed that nitrogen removal performance under point aeration mode depended on oxygen supply control. Highest total nitrogen (TN) removal efficiency of 73.2% was achieved when oxygen input in the outer, middle and inner channel accounted for 50, 25 and 25% of total oxygen supply, respectively. With the same oxygen supply, both aeration modes demonstrated complete nitrification with over 97% ammonia nitrogen removal efficiencies. However, TN removal efficiency was 78.8% under step aeration mode, which was higher than that under point aeration. The pyrosequencing results indicated that microbial community composition was affected by aeration modes and step aeration mode was beneficial to the enrichment of denitrifiers. The greater diversity and relative abundance of denitrifiers enhanced TN removal under step aeration mode.

Feasibility study on repair for cranial defect of immaturity.

AIM: To evaluate use of a titanium mesh to fill cranial defects in growing animals, as a model for juvenile humans. MATERIAL AND METHODS: Thirty two-month-old Seghers pigs were evenly assigned to one of three groups: controls, a defect group (unrepaired 5 x 5 cm lesion), and a repair group (repaired 5 x 5 cm lesions). Histological evaluations and morphological measurements were conducted to compare the groups. RESULTS: Two pigs in the defect group died. New bone formation was evident in the cranial lesions of pigs in the defect and repair groups. There were no differences in histological observations (p = 0.081), brain weight (p = 0.063), or indexed brain circumference measurements (p = 0.066) between the groups. CONCLUSION: Closure of cranial defects with a titanium mesh did not limit growth of the cranium or cause abnormal central nervous system development. While there was new bone growth in the cranial defects, the bone was not sufficiently strong to withstand external trauma.

Genetic screening for mutations in the chip gene in intracranial aneurysm patients of Chinese Han nationality.

We performed a case-control study to investigate whether SNPs of CHIP might affect the development of IA in Chinese Han nationality. We believe we are the first to have screened IA patients for mutations in the CHIP gene to determine the association with these variants. The study group comprised 224 Chinese Han nationality patients with at least one intracranial aneurysm and 238 unrelated healthy Han nationality controls. Genomic DNA was isolated from blood leukocytes. The entire coding regions of CHIP were genotyped by PCR amplification and DNA sequencing. Differences in genotype and allele frequencies between patients and controls were tested by the chi-square method. Genotype and allele frequencies of the SNP rs116166850 was demonstrated to be in Hardy-Weinberg equilibrium. No significant difference in genotype or allele frequencies between case and control groups was detected at the SNP. Our data do not support the hypothesis of a major role for the CHIP gene in IA development in the Chinese Han population.

Association between XRCC1 gene polymorphisms and risk of glioma development: a meta-analysis.

OBJECTIVE: Previous studies of the association between X-ray cross-complementing group 1 (XRCC1) gene polymorphisms and the gliomas risk have yielded conflicting results, and thus a meta-analysis was performed to provide a more accurate estimation. METHODS: A computerized literature search of 5 electronic databases was conducted to identify the relevant studies. Fixed or random effect models were selected based on the heterogeneity test. Publication bias was estimated using Begg's funnel plots and Egger's regression test. RESULTS: A total of 11 studies (3,810 cases and 6,079 controls), 7 studies (2,928 cases and 5,048 controls), and 4 studies (1,461 cases and 2,593 controls) were finally included in the analyses of the association between XRCC1 Arg399Gln, Arg194Trp, and Arg280His polymorphisms and glioma risk, respectively. The pooled results showed that GlnGln carriage was associated with moderately increased risk of gliomas in Asians (GlnGln vs. ArgArg, OR=1.490, 95%CI 1.031-2.153; GlnGln/ArgGln vs. ArgArg, OR=1.321, 95%CI 1.037- 1.684), whereas a marginal association was revealed in Caucasians. For the Arg194Trp polymorphism, although a significant association was shown in the homozygous genotype comparisons (TrpTrp vs. ArgArg, OR = 2.209, 95%CI 1.398- 2.945), no significant link was found on subgroup analysis stratified by ethnicity. With regard to the Arg280His polymorphism, no significant association was found in each comparison. No particular study was found to significantly influence the pooled results, and no potential publication bias was detected. CONCLUSIONS: This meta-analysis suggested that the XRCC1 Arg399Gln polymorphism is moderately associated with increased risk of gliomas in Asians, while Arg194Trp and Arg280His polymorphisms demonstrated no significant influence. Due to the limited studies and the potential confounders, further studies are needed to confirm these results.