Alginate production of Pseudomonas strains and its application in preparation of alginate-biomass hydrogel for heavy metal adsorption.

In this study, 7 Pseudomonas strains were isolated from a wastewater treatment plant, and the alginate production of Pseudomonas strains under different environmental conditions was evaluated. Subsequently, alginate-biomass hydrogel beads were prepared using alginate and biomass of Pseudomonas, and their adsorption performances and mechanism to Pb2+ and Cd2+ were analyzed. The results show that weakly acidic pH and 37 °C is favorable for alginate synthesis of Pseudomonas strains, and P. alcaligenes YLS18 have the highest alginate yield (29.4 mg/g). The adsorption processes of Pb2+ and Cd2+ by hydrogel beads are well described by Langmuir model, indicating that the adsorption process is monolayer. Among the biomass of these strains, P. nitroreducens YLB32 shows the highest biosorption capacities, reaching 110.7 mg/g for Pb2+ and 54.3 mg/g for Cd2+ at pH 5. Alginate-biomass hydrogel beads obtain higher adsorption capacity to Pb2+ (184.0 mg/g) and Cd2+ (92.4 mg/g), and exhibit good reusability. The adsorption mechanism of Pb2+ and Cd2+ by hydrogel beads involves physical tapping of ions, electrostatic interactions, complexation, cation exchange and precipitation. These results provide strong support for promoting alginate recovery from activated sludge and for treating heavy metal wastewater.

Cyanophycin Granule Polypeptide: a Neglected High Value-Added Biopolymer, Synthesized in Activated Sludge on a Large Scale.

Recovery of microbial synthetic polymers with high economic value and market demand in activated sludge has attracted extensive attention. This work analyzed the synthesis of cyanophycin granule peptide (CGP) in activated sludge and its adsorption capacity for heavy metals and dyes. The distribution and expression of synthetic genes for eight biopolymers in two wastewater treatment plants (WWTPs) were analyzed by metagenomics and metatranscriptomics. The results indicate that the abundance and expression level of CGP synthase (cphA) are similar to those of polyhydroxyalkanoate polymerase, implying high synthesis of CGP in activated sludges. CGP in activated sludge is mainly polymerized from aspartic acid and arginine, and its secondary structure is mainly ß-sheet. The crude yields of CGP are as high as 104 ± 26 and 76 ± 13 mg/g dry sludge in winter and in summer, respectively, comparable to those of polyhydroxyalkanoate and alginate. CGP has a stronger adsorption capacity for anionic pollutants (Cr (VI) and methyl orange) than for cationic pollutants because it is rich in guanidine groups. This study highlights prospects for recovery and application of CGP from WWTPs. IMPORTANCE The conversion of organic pollutants into bioresources by activated sludge can reduce the carbon dioxide emission of wastewater treatment plants. Identification of new high value-added biopolymers produced by activated sludge is beneficial to recover bioresources. Cyanophycin granule polypeptide (CGP), first discovered in cyanobacteria, has unique chemical and material properties suitable for industrial food, medicine, cosmetics, water treatment, and agriculture applications. Here, we revealed for the first time that activated sludge has a remarkable ability to produce CGP. These findings could further facilitate the conversion of wastewater treatment plants into resource recycling plants.

Metagenomics and metatranscriptomics analyses of antibiotic synthesis in activated sludge.

The generic of antibiotics is considered to be a main reason for the generation of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). However, little has been reported about the antibiotic biosynthesis by activated sludge. In this study, the distribution and expression of antibiotic biosynthetic genes (ABGs) in the floc sludge and biofilm from two WWTPs were deciphered using metagenomics and metatranscriptomics. The results showed that 2% of the community were in general well-linked to antibiotic production, indicating a non-negligible antibiotic synthetic ability of WWTPs. 93 ABGs belonging to 26 antibiotics were determined, among which aminoglycosides, ß-lactams, ansamycins, peptides, macrolides were majority. The relative abundances of detected ABGs had a large interval, ranging from 0.000006% to 0.042%. The predominant antibiotic types of synthetic genes with higher relative expression levels were monobactams, penicillin & cephalosporins and streptomycin, primarily belonging to ß-lactams and aminoglycosides. The hypothetical synthetic pathways of streptomycin synthesis and penicillin & cephalosporin synthesis were proposed. And the coexistence of ABGs and ARGs for these two antibiotics was also pronounced in activated sludge from meta-omics data. These findings for the first time demonstrated the antibiotic synthetic potential in activated sludges, revealing new sources of antibiotics and resistance genes in WWTPs, and thereby aggravating environmental pollution.

Nanoparticles-EPS corona increases the accumulation of heavy metals and biotoxicity of nanoparticles.

Microbial extracellular polymeric substances (EPS) coating nanoparticles (NPs) surface can form NPs-EPS corona, which significantly affect the adsorption of NPs to toxic substances and alter the ecotoxicological effect of NPs. In this work, the EPS coronas on TiO2 NPs (TNPs) and CeO2 NPs (CNPs) were characterized and the adsorption characteristics of NPs with and without EPS corona to five heavy metals were investigated in single-metal and multiple-metal systems. The results of spectral analysis showed that NPs-EPS corona exhibited new crystalline phases and abundant functional groups. Moreover, 42 and 13 proteins were identified in the TNPs-EPS and CNPs-EPS coronas, respectively. The rates of Cd2+, Pb2+, Cu2+, Ni2+ and Ag+ adsorption by NPs-EPS corona increased to values that were 6.7-7.6, 4.4-5.1, 4.2-5.5, 3.9-4.9 and 8.5-8.8 times those of NPs without EPS corona, respectively, in single-metal system. NPs-EPS coronas are effective in absorbing Ag+, Pb2+ and Cu2+ compared with Cd2+and Ni2+ in multiple metal adsorption. These results indicated that NPs-EPS corona effectively adsorb and remove heavy metals by forming NPs-EPS-metal complexes and inducing precipitation. However, NPs-EPS corona can enhance the toxicity of NPs by accumulating highly-toxic heavy metals in aquatic environments.

Stochastic DNA Walkers in Droplets for Super-Multiplexed Bacterial Phenotype Detection.

Pathogen detection is growing in importance in the global health arena because of the high morbidity and mortality associated with bacterial blood stream infections. In this work, we present stochastic DNA walkers in droplets (SDwalker-Drop), a one-step, rapid, and super-multiplex method for ultrahigh-throughput bacterial detection. The SDwalkers, by exploiting cascade signal amplification, endow our analytical platform with fast analysis times and single-cell analysis ability. The autonomous and multiple-step walking behavior of the SDwalkers provides a super-multiplex droplet-encoding strategy by embedding intensity coded barcodes into a sequence of color-multiplexed barcodes. We realized a theoretical coding capacity of 83 -1=511 and achieved 20 distinct patterns for bacterial phenotype detection and identification. Moreover, our SDwalker-Drop platform could be readily integrated with a flow cytometer to afford a general approach for super-multiplexed, high-throughput biological assays and screening.

Investigation of complete bandgaps in a piezoelectric slab covered with periodically structured coatings.

The propagation of elastic waves in a piezoelectric slab covered with periodically structured coatings or the so-called stubbed phononic crystal slab is investigated. Four different models are selected and the effects of distribution forms and geometrical parameters of the structured coatings on complete bandgaps are discussed. The phononic crystal slab with symmetric coatings can generate wider complete bandgaps while that with asymmetric coatings is favorable for the generation of multi-bandgaps. The complete bandgaps, which are induced by locally resonant effects, change significantly as the geometry of the coatings changes. Moreover, the piezoelectric effects benefit the opening of the complete bandgaps.

Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode.