Synchronous removal of emulsions and organic dye over palladium nanoparticles anchored cellulose-based membrane.

Membrane is a considerable precursor for emulsions separation and organic dyes degradation used in water purification and oil reclamation. However, the tedious preparation method, the surface smears easily, and low degradation efficiency, these characteristics usually significantly hinder its applicability toward wastewater governance. Herein, a green, facile, and efficient fabrication strategy to prepare a bi-functional palladium nanoparticles (PdNPs)-loaded bacterial cellulose membrane (BCMPd) is proposed. A tri-functional bacterial cellulose membrane (BCM) was obtained by percolating bacterial cellulose (BC) on a basal membrane, and BCM served as a support, reducing agent, and stabilizer in the subsequent reduction of PdNPs. Bi-functional BCMPd was successfully obtained and used for continuously removing emulsions and reducing methylene blue (MB) from simulated wastewater via the integration of physical sieving and chemical reaction. Meanwhile, the enhancement factors for the water transfer ability and demulsification capacity correlated directly with the wettability and surface structure of BCMPd. Furthermore, the dosage of BC was adjusted to reveal the mechanism for the enhanced water transferability and demulsification capacity. Notably, PdNPs of BCMPd decreased Fermi potential difference between BH4- and MB, accelerating the electron transfer of the reduction reaction and thus exhibiting a remarkable MB degradation efficiency. Together, the information obtained in this work can be useful for comprehensively addressing the bottleneck of forming a cost-effective, eco-friendly, and bi-functional membrane reactor, providing an alternative approach for better treatment of complex wastewater.

Improvement of ethanol production from crystalline cellulose via optimizing cellulase ratios in cellulolytic Saccharomyces cerevisiae.

Crystalline cellulose is one of the major contributors to the recalcitrance of lignocellulose to degradation, necessitating high dosages of cellulase to digest, thereby impeding the economic feasibility of cellulosic biofuels. Several recombinant cellulolytic yeast strains have been developed to reduce the cost of enzyme addition, but few of these strains are able to efficiently degrade crystalline cellulose due to their low cellulolytic activities. Here, by combining the cellulase ratio optimization with a novel screening strategy, we successfully improved the cellulolytic activity of a Saccharomyces cerevisiae strain displaying four different synergistic cellulases on the cell surface. The optimized strain exhibited an ethanol yield from Avicel of 57% of the theoretical maximum, and a 60% increase of ethanol titer from rice straw. To our knowledge, this work is the first optimization of the degradation of crystalline cellulose by tuning the cellulase ratio in a cellulase cell-surface display system. This work provides key insights in engineering the cellulase cocktail in a consolidated bioprocessing yeast strain. Biotechnol. Bioeng. 2017;114: 1201-1207. © 2017 Wiley Periodicals, Inc.

Integrated multilevel investigation of photosynthesis revealed the algal response distinction to differentially charged nanoplastics.

Nanoplastics (NPs), especially those with different charges, as one of emerging contaminants pose a threat to aquatic ecosystems. Although differentially charged NPs could induce distinct biological effects, mechanistic understanding of the critical physiological processes of aquatic organisms from an integrated multilevel perspective on aquatic organisms is still uncertain. Herein, multi-effects of differentially charged nanosized polystyrene (nPS) including neutral nPS, nPS-COOH, and nPS-NH2 on the photosynthesis-related physiological processes of algae were explored at the population, individual, subcellular, protein, and transcriptional levels. Results demonstrated that both nPS and nPS-COOH exhibited hormesis to algal photosynthesis but nPS-NH2 triggered severe inhibition. As for nPS-NH2, the integrity of algal subcellular structure, chlorophyll biosynthesis, and expression of photosynthesis-related proteins and genes were interfered. Intracellular NPs' content in nPS treatment was 25.64 % higher than in nPS-COOH treatment, and the content of chloroplasts in PS and nPS-COOH treatment were 3.09 % and 4.56 % higher than control, respectively. Furthermore, at the molecular levels, more photosynthesis-related proteins and genes were regulated under nPS-COOH exposure than those exposed to nPS. Light-harvesting complex II could be recognized as an underlying explanation for different effects between nPS and nPS-COOH. This study first provides a novel approach to assess the ecological risks of NPs at an integrated multilevel.

Exploring the potential of a newly constructed manganese peroxidase-producing yeast consortium for tolerating lignin degradation inhibitors while simultaneously decolorizing and detoxifying textile azo dye wastewater.

MnP-YC4, a newly constructed manganese peroxidase-producing yeast consortium, has been developed to withstand lignin degradation inhibitors while degrading and detoxifying azo dye. MnP-YC4 tolerance to major biomass-derived inhibitors was promising. MnP induced by lignin was found to be highly related to dye decolorization by MnP-YC4. Simulated azo dye-containing wastewater supplemented with a lignin co-substrate (3,5-Dimethoxy-4-hydroxybenzaldehyde) decolorized up to 100, 91, and 76% at final concentrations of 20, 40, and 60%, respectively. MnP-YC4 effectively decolorized the real textile wastewater sample, reaching up to 91.4%, and the COD value decreased significantly during the decolorization, reaching 7160 mg/l within 7 days. A possible dye biodegradation pathway was proposed based on the degradation products identified by UV-vis, FTIR, GC/MS, and HPLC techniques, beginning with azo bond cleavage and eventually mineralized to CO2 and H2O. When compared to the phytotoxic original dye, the phytotoxicity of MnP-YC4 treated dye-containing wastewater samples confirmed the nontoxic nature.

Application of biodegradable cellulose-based biomass materials in wastewater treatment.

Water bodies contain a large number of harmful environmental pollutants, including oil, heavy metal ions and dyes, which has become a major global problem. The current work focusses on the development and future prospect of sustainable application of biodegradable cellulose-biomass materials in water treatment, considering that they show an important prospect in wastewater treatment. This paper summarizes the advantages and disadvantages of cellulose-biomass materials in removing harmful substances and pollutants from water and the key problems the technology faces. Cellulose-biomass material has unique structure, is environment friendly, degradable, renewable and provides low energy cost benefits, among other advantages. In this paper, the research progress of wastewater treatment in recent years is reviewed from the following three aspects: oil-water separation, heavy metal ions in water, and dye adsorption. The future research direction is also discussed.

A sustainable solution to plastics pollution: An eco-friendly bioplastic film production from high-salt contained Spirulina sp. residues.

Plastic products have become a major contaminant in environmental ecology due to their recalcitrant biodegradation, poor management and risky disposal. Therefore, much research attention has been paid to developing the biodegradable bio-based plastics. However, many of the substitute bioplastics derived from agricultural materials may present a potential threat to food security and eco-systems. Herein, we propose a sustainable, eco-friendly and simple procedure to convert the hazardous high-salt contained microalgal residues into bioplastic film. With 35 % poly (vinyl alcohol) (PVA) assistance, the composite bioplastic films achieved 22 MPa tensile strength under alkali condition and 77 % elongation at break under acidic condition. The average maximum contact angle of 94.4° confirmed a desirable water resistance potential. The synthesis mechanism demonstrated that the inorganic salts existed in microalgal residues could act as the filler in shape of sheets under alkali condition or as the cross linker under acidic condition, significantly enhancing the practical feasibility. This work demonstrates a promising biodegradable bioplastics formed from sustainable eco-friendly waste reutilization process, providing a new insight for fundamentally reducing the plastics pollution.

Progress and perspective on algal plastics - A critical review.

There is a growing interest in developing bio-based biodegradable plastics to reduce the dependence on depleting fossil fuels and provide a sustainable alternative. Bio-based plastics can usually be produced from lipids, proteins or carbohydrates, which are major components of microalgae. Despite its potential for algal plastics, little information is available on strain selection, culture optimization and bioplastics fabrication mechanism. In this review, we summarized the recent developments in understanding the utilization of seaweed polysaccharides, such as alginate and carrageenan for bio-based plastics. In addition, a conceptual biorefinery framework for algal plastics through promising components (e.g., lipids, carbohydrates and proteins) from microalgae is comprehensively presented. Moreover, the reasons for variations in bioplastics performance and underlying mechanism of various algal biocomposites have been critically discussed. We believe this review can provide valuable information to accelerate the development of innovative green technologies for improving the commercial viability of algal plastics.

A novel clean production approach to utilize crop waste residues as co-diet for mealworm (Tenebrio molitor) biomass production with biochar as byproduct for heavy metal removal.

Proper management of waste crop residues has been an environmental concern for years. Yellow mealworms (larvae of Tenebrio molitor Linnaeus, 1758) are major insect protein source. In comparison with normal feed wheat bran (WB), we tested five common lignocellulose-rich crop residues as feedstock to rear mealworms, including wheat straw (WS), rice straw (RS), rice bran (RB), rice husk (RH), and corn straw (CS). We then used egested frass for the production of biochar in order to achieve clean production. Except for WS and RH, the crop residues supported mealworms' life activity and growth with consumption of the residues by 90% or higher and degraded lignin, hemicellulose and cellulose over 32 day period. The sequence of degradability of the feedstocks is RS > RB > CS > WS > RH. Egested frass was converted to biochar which was tested for metal removal including Pb(II), Cd(II), Cu(II), Zn(II), and Cr(VI). Biochar via pyrolysis at 600 °C from RS fed frass (FRSBC) showed the best adsorption performance. The adsorption isotherm fits the Langmuir model, and kinetic analysis fits the Pseudo-Second Order Reaction. The heavy metal adsorption process was well-described using the Intra-Particle Diffusion model. Complexation, cation exchange, precipitation, reduction, deposition, and chelation dominated the adsorption of the metals onto FRSBC. The results indicated that crop residues (WS, RS, RB, and CS) can be utilized as supplementary feedstock along with biochar generated from egested frass to rear mealworms and achieve clean production while generating high-quality bioadsorbent for environment remediation and soil conditioning.

Engineering of a novel cellulose-adherent cellulolytic Saccharomyces cerevisiae for cellulosic biofuel production.

Cellulosic biofuel is the subject of increasing attention. The main obstacle toward its economic feasibility is the recalcitrance of lignocellulose requiring large amount of enzyme to break. Several engineered yeast strains have been developed with cellulolytic activities to reduce the need for enzyme addition, but exhibiting limited effect. Here, we report the successful engineering of a cellulose-adherent Saccharomyces cerevisiae displaying four different synergistic cellulases on the cell surface. The cellulase-displaying yeast strain exhibited clear cell-to-cellulose adhesion and a "tearing" cellulose degradation pattern; the adhesion ability correlated with enhanced surface area and roughness of the target cellulose fibers, resulting in higher hydrolysis efficiency. The engineered yeast directly produced ethanol from rice straw despite a more than 40% decrease in the required enzyme dosage for high-density fermentation. Thus, improved cell-to-cellulose interactions provided a novel strategy for increasing cellulose hydrolysis, suggesting a mechanism for promoting the feasibility of cellulosic biofuel production.

Characterization of flocculating agent from the self-flocculating microalga Scenedesmus obliquus AS-6-1 for efficient biomass harvest.

In the present work, the extracellular biopolymers from the self-flocculating microalga Scenedesmus obliquus AS-6-1 were studied. It was revealed that the self-flocculation of the microalgal cells was mediated by cell wall-associated polysaccharides with a molecular weight of 127.9 kDa. Sugar compositions analysis indicated that the monomers consist of glucose, mannose, galatose, rhamnose and fructose with the molar ratio of 8:5:3:2:1. Addition of 0.6 mg/L purified flocculating agent resulted in the fast flocculation of freely suspended cells of S. obliquus and Chlorella vulgaris. The flocculating activity is stable between pH 6 and 8 and at 20-60°C.