Flocculation Efficiency and Mechanism of Carbamazepine by Microbial Flocculant Extracted from Klebsiella pneumoniae J1Read the full article
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Thermophilic Solid-State Anaerobic Digestion of Corn Straw, Cattle Manure, and Vegetable Waste: Effect of Temperature, Total Solid Content, and C/N Ratio
Thermophilic solid-state anaerobic digestion (SS-AD) of agricultural wastes, i.e., corn straw, cattle manure, and vegetable waste, was carried out in this study. The effects of temperature (40-60°C), initial solid content (ISC, 17.5-32.5%), and C/N ratio (15-32 : 1) on biogas production were evaluated using a Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). The results showed that optimization of process parameters is important to promote the SS-AD performance. All the factors, including interactive terms (except the ISC), were significant in the quadratic model for biogas production with SS-AD. Among the three operation parameters, the C/N ratio had the largest effect on biogas production, followed by temperature, and a maximum biogas yield of 241.4 mL gVS-1 could be achieved at 47.3°C, , and . After 20 d of SS-AD, the microbial community structure under different conditions was characterized by high-throughput sequencing, showing that Firmicutes, Bacteroidetes, Chloroflexi, Synergistetes, and Proteobacteria dominated the bacterial community, and that Firmicutes had a competitive advantage over Bacteroidetes at elevated temperatures. The biogas production values and relative abundance of OPB54 and Bacteroidia after 20 d of SS-AD can be fitted well using a quadratic model, implying that OPB54 and Bacteroidia play important roles in the methanogenic metabolism for agricultural waste thermophilic SS-AD.
Identification and Characterization of a Newly Isolated Chitinase-Producing Strain Bacillus licheniformis SSCL-10 for Chitin Degradation
Chitinases or chitinolytic enzymes have different applications in the field of medicine, agriculture, and industry. The present study is aimed at developing an effective hyperchitinase-producing mutant strain of novel Bacillus licheniformis. A simple and rapid methodology was used for screening potential chitinolytic microbiota by chemical mutagenesis with ethylmethane sulfonate and irradiation with UV. There were 16 mutant strains exhibiting chitinase activity. Out of the chitinase-producing strains, the strain with maximum chitinase activity was selected, the protein was partially purified by SDS-PAGE, and the strain was identified as Bacillus licheniformis (SSCL-10) with the highest specific activity of 3.4 U/mL. The induced mutation model has been successfully implemented in the mutant EMS-13 (20.2 U/mL) that produces 5-6-fold higher yield of chitinase, whereas the mutant UV-11 (13.3 U/mL) has 3-4-fold greater chitinase activity compared to the wild strain. The partially purified chitinase has a molecular weight of 66 kDa. The wild strain (SSCL-10) was identified as Bacillus licheniformis using 16S rRNA sequence analysis. This study explores the potential applications of hyperchitinase-producing bacteria in recycling and processing chitin wastes from crustaceans and shrimp, thereby adding value to the crustacean industry.
A Current Sensing Biosensor for BOD Rapid Measurement
In order to improve the practicality of the rapid biochemical oxygen demand (BOD) method, a highly sensitive rapid detection method for BOD that is based on establishing the correlation between current and dissolved oxygen (DO) was developed. In this experiment, Bacillus subtilis was used as the test microorganism, and the embedding method was used to achieve quantitative fixation of microorganisms, which could increase the content of microorganisms and prolong the service life of the biological element. The conductivity (COND) probe is used as a sensing element, so that the testing value can be read every second. In the program, the moving average method is used to process the collected data so that the value can be read every minute. National standard samples were detected to test the accuracy and stability of the method. The results showed that relative error and analytical standard deviations were less than 5%. Different polluted water was tested to evaluate its application range. The results showed that relative error was less than 5%. The results of the method are consistent with the results of the wastewater sample obtained by the BOD5 standard method. The proposed rapid BOD current sensing biosensor method should be promising in practical application of wastewater monitoring.
Betaine Modulates Rumen Archaeal Community and Functioning during Heat and Osmotic Stress Conditions In Vitro
Rumen archaea play an important role in scavenging ruminal hydrogen (H2) and thus facilitate rumen fermentation. They require optimum temperature and osmolality for their growth and metabolism; however, a number of external factors may put archaea under heat and osmotic stress. Betaine is an osmolyte, molecular chaperone, and antioxidant; therefore, it bears potential to combat against these stressors. In this in vitro study, three betaine levels, namely, 0 (control), 51 (low), and 286 (high) ppm, were used. Each of these was subjected to two temperatures (39.5 and 42°C) and two osmolality conditions (295 and 420 mOsmol kg-1) with per treatment. Sequencing analyses of the solid phase (which use solid materials containing primarily fibrous materials of low-density feed particles) and the liquid phase (rumen fermenter liquid) using 16S rRNA revealed that more than 99.8% of the ruminal archaea in fermenters belong to the phylum Euryarchaeota. At the genus level, Methanobrevibacter was the most prevalent in both phases, and Methanosaeta was only detected in the liquid phase. The genera Methanobrevibacter and Methanobacterium both showed a positive correlation with methane (CH4) formation in the liquid and solid phases, respectively (). Heat stress increased the relative abundance of genus Methanimicrococcus at the expense of candidate archaeal genus Vadin CA11 (). In the solid phase, osmotic stress significantly reduced the Shannon and Simpson indices of diversity, and relative abundance was higher for Methanobrevibacter at the expense of Methanimicrococcus. In the liquid phase, osmotic stress increased not only the abundance-based coverage estimator (ACE) and singles parameters of diversity but also the relative abundances of Methanosphaera and Methanobacterium. The overall decrease in all gas parameters and estimated metabolic hydrogen ([2H]) utilization was observed during osmotic stress conditions (). Betaine enhanced the diversity of solid phase archaea as indicated by the increase in ACE and singles during heat stress, and only a high dose improved all diversity parameters in the liquid phase during osmotic stress (). Thus, betaine alleviates the effects of heat stress and osmotic stress on the archaea community.
Effects of Sludge Retention Time on the Performance of Anaerobic Ceramic Membrane Bioreactor Treating High-Strength Phenol Wastewater
Anaerobic ceramic membrane bioreactor (AnCMBR) is an attractive alternative for the treatment of high-strength phenol wastewater, but the effects of sludge retention time (SRT) on the performance and membrane fouling are still unclear. The results indicated that the AnCMBR was successfully employed to treat high-strength wastewater containing 5 g phenol L-1. The removal efficiencies of phenol and chemical oxygen demand (COD) reached over 99.5% and 99%, respectively, with long SRT and short SRT. SRT had no obvious effect on the performance of the AnCMBR treating high-strength phenol wastewater with long time operation. The strong performance robustness of AnCMBR benefited from the enrichment of hydrogenotrophic methanogens and syntrophic phenol-degrading bacteria. However, the decline of SRT led to a more severe membrane fouling in the AnCMBR, which was caused by the small size of sludge flocs and high concentration of protein in the biopolymers. Therefore, this work presented a comprehensive insight to the feasibility and robustness of the AnCMBR for treating high-strength phenol wastewater.
Simulation of a Novel Tubular Microalgae Photobioreactor with Aerated Tangent Inner Tubes: Improvements in Mixing Performance and Flashing-Light Effects
At present, large-scale and high-efficiency microalgal cultivation is the key to realizing the technology for carbon capture and storage (CCS) and bioresource recovery. Meanwhile, tubular photobioreactors (PBRs) have great potential for microalgal cultivation due to their high productivity. To improve the mixing performance and flashing-light effect, a novel tube PBR with the inner tube tangential to the outer tube was developed, whose radial aeration pores are situated along the length of the inner tube. The direction of aeration, aeration rate, light/dark cycle period (L/D), light-time ratio, average turbulent kinetic energy (TKE), and degree of synergy between the velocity and direction of the light field in the PBR were optimized by a computational fluid dynamics (CFD) simulation and field synergy theory. The results show that a downwards aeration direction of 30° and an aeration rate of 0.7 vvm are the most conducive to reducing the dead zone and improving the light/dark cycle frequency. Compared to the concentric double-tube PBR, the light/dark cycle frequency and light time of the tangent double-tube PBR increased by 78.2% and 36.2% to 1.8 Hz and 47.8%, respectively, and the TKE was enhanced by 48.1% from 54 to 80 cm2·s−2. Meanwhile, field synergy theory can be extended and applied to the design of tubular microalgae PBRs, and the average synergy of the light and velocity gradients across the cross-section increased by 38% to 0.69. The tangential inner tube aeration structure generated symmetrical vertical vortices between the light and dark areas in the PBR, which significantly improved the mixing performance and flashing-light effect. This novel design can provide a more suitable microenvironment for microalgal cultivation and is promising for bioresource recovery applications and improving the yield of microalgae.