A novel PVDF-TiO2@g-C3N4 composite electrospun fiber for efficient photocatalytic degradation of tetracycline under visible light irradiation.

A novel composite electrospun fiber with high photocatalytic efficiency, good stability, strong hydrophobicity, good pollution resistance, and easy separation and recovery was synthesized. The TiO2@g-C3N4 (TCN) with special core-shell structure (5-10 nm shell) facilitated the separation of photogenerated electron-holes and had high photocatalytic performance. The poly (vinylidene fluoride) (PVDF) electrospun fiber immobilized with TCN was successfully fabricated (PVDF-TCN) with uniform distribution and size of nanofibers by using electrospinning, which was used for degrading tetracycline under visible-light irradiation (> 400 nm). A special rougher surface of electrospun fiber obtained by washing of sacrificial PVP increased the specific surface area, which became more conducive to the adhesion of the catalyst. The water contact angle and FTIR results demonstrated that the electrospun fiber became extremely hydrophilic after adding TCN catalyst, which could effectively mitigate the fiber pollution. The PVDF-TCN-0.2g electrospun fiber exhibited excellent photocatalytic performance and the degradation efficiency of tetracycline was up to 97% in 300 min under visible-light irradiation. The mechanism of PVDF-TCN electrospun fiber degradation of tetracycline in the photocatalytic process was also proposed. In addition, the PVDF-TCN-0.2g exhibited a stable activity after 4 cycles experiments since the degradation efficiency remained about 90%. Therefore, we believed this study provided a new strategy in catalyst immobilization and wastewater treatment.

[Expression of ß-glucosidase An-bgl3 from Aspergillus niger for conversion of scopolin].

Scopoletin is a coumarin compound with various biological activities including detumescence and analgesic, insecticidal, antibacterial and acaricidal effects. However, interference with scopolin and other components often leads to difficulties in purification of scopoletin with low extraction rates from plant resource. In this paper, heterologous expression of the gene encoding ß-glucosidase An-bgl3 derived from Aspergillus niger were carried out. The expression product was purified and characterized with further structure-activity relationship between it and ß-glucosidase analyzed. Subsequently, its ability for transforming scopolin from plant extract was studied. The results showed that the specific activity of the purified ß-glucosidase An-bgl3 was 15.22 IU/mg, the apparent molecular weight was about 120 kDa. The optimum reaction temperature and pH were 55 ℃ and 4.0, respectively. Moreover, 10 mmol/L metal ions Fe2+ and Mn2+ increased the enzyme activity by 1.74-fold and 1.20-fold, respectively. A 10 mmol/L solution containing Tween-20, Tween-80 and Triton X-100 all inhibited the enzyme activity by 30%. The enzyme showed affinity towards scopolin and tolerated 10% methanol and 10% ethanol solution, respectively. The enzyme specifically hydrolyzed scopolin into scopoletin from the extract of Erycibe obtusifolia Benth with a 47.8% increase of scopoletin. This demonstrated that the ß-glucosidase An-bgl3 from A. niger shows specificity on scopolin with good activities, thus providing an alternative method for increasing the extraction efficiency of scopoletin from plant material.

Preparation and characterization of ethyl cellulose film modified with capsaicin.

Pure ethyl cellulose film cannot extend the shelf life of food, and adding capsaicin as an antibacterial agent can inhibit the activity of microorganisms on the surface of the film. The main purpose of this work is to study the properties and specific performance of the film formed by adding capsaicin to ethyl cellulose system. Importantly, the transparent, soft, and stretchable ethyl cellulose-capsaicin composite membrane (EC-Cap) is generally easy to produce and is environmentally friendly. It is the first successful preparation by a casting method. It is worth noting that the FTIR analysis of the film shows that there may be an interaction between the phenolic hydroxyl group in Cap and the hydroxyl group in EC, which means that Cap has successfully participated in the film formation system. Therefore, the cap-containing film not only exhibits a low water absorption, when the cap is appropriate, the elongation at break of the film reaches a maximum of 61.34 % ± 1.37 %. Compared with pure EC membrane, EC-Cap membrane has greater antibacterial activity than pure EC membrane. The practical application of EC-Cap films in the protection of bell peppers has shown positive results, which makes it possible to apply these films to food packaging.

Poly-γ-glutamic acid produced from Bacillus licheniformis CGMCC 2876 as a potential substitute for polyacrylamide in the sugarcane industry.

As an environmentally friendly and industrially useful biopolymer, poly-γ-glutamic acid (γ-PGA) from Bacillus licheniformis CGMCC 2876 was characterized by the high-resolution mass spectrometry and (1)H NMR. A flocculating activity of 11,474.47 U mL(-1) obtained with γ-PGA, and the effects of carbon sources, ions, and chemical properties (D-/L-composition and molecular weight) on the production and flocculating activity of γ-PGA were discussed. Being a bioflocculant in the sugar refinery process, the color and turbidity of the sugarcane juice was IU 1,877.36 and IU 341.41 with 0.8 ppm of γ-PGA, respectively, which was as good as the most widely used chemically synthesized flocculant in the sugarcane industry--polyacrylamide with 1 ppm. The γ-PGA produced from B. licheniformis CGMCC 2876 could be a promising alternate of chemically synthesized flocculants in the sugarcane industry.

Production of poly(hydroxybutyrate-hydroxyvalerate) from waste organics by the two-stage process: focus on the intermediate volatile fatty acids.

The two-stage process, coupling volatile fatty acids (VFAs) fermentation and poly(hydroxybutyrate-hydroxyvalerate) (P(HB/HV)) biosynthesis, was investigated for five waste organic materials. The overall conversion efficiencies were glycerol>starch>molasses>waste sludge>protein, meanwhile the maximum P(HB/HV) (1.674 g/L) was obtained from waste starch. Altering the waste type brought more effects on VFAs composition other than the yield in the first stage, which in turn greatly changed the yield in the second stage. Further study showed that even-number carbon VFAs (or odd-number ones) had a good positive linear relationship with P(HB/HV) content of HB (or HV). Additionally, VFA producing microbiota was analyzed by pyrosequencing methods for five wastes, which indicated that specific species (e.g., Lactobacillus for protein; Ethanoligenens for starch; Ruminococcus and Limnobacter for glycerol) were dominant in the community for VFAs production. Potential competition among acidogenic bacteria specially involved to produce some VFA was proposed as well.

Biosynthesis of poly(hydroxybutyrate-hydroxyvalerate) from the acclimated activated sludge and microbial characterization in this process.

This study investigated the effects of substrate composition (acetate and propionate) on synthesis of various mix of poly(hydroxybutyrate-hydroxyvalerate) (P(HB/HV)) from activated sludge, which was acclimated using a single carbon (acetate) and mixed carbons (acetate and propionate). Results of batch P(HB/HV) production tests indicated that the yield and synthesis rate of P(HB/HV) decreased as the proportion of propionate in the substrate increased. However, mixed-carbon-acclimated sludge with acetate and propionate exhibited better P(HB/HV) production performance than with acetate-acclimated sludge in terms of substrate utilization, yield of P(HB/HV) and HV fraction in P(HB/HV). The desired hydroxyvalerate (HV) fraction (0-74%) of the P(HB/HV) could be obtained based on the substrate composition and sludge acclimation. Furthermore, PCR-DGGE analysis indicated that specific species dominated the activated sludge used for P(HB/HV) production. Acidobacteria and Burkholderiales were the dominant bacterial populations and played an important role in HV synthesis.

Biosynthesis and thermal properties of PHBV produced from levulinic acid by Ralstonia eutropha.

Levulinic acid (LA) can be cost-effectively produced from a vast array of renewable carbohydrate-containing biomaterials. LA could facilitate the commercialization of the polymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and PHBV-based products as carbon substrates. Therefore, this paper focused on the production of PHBV by Ralstonia eutropha with LA for hydroxyvalerate (HV) production, which plays an important role in enhancing the thermal properties of PHBV. Accordingly, the HV content of PHBV varied from 0-40.9% at different concentrations of LA. Stimulation of cell growth and PHBV accumulation were observed when 2-6 g L(-1) LA was supplied to the culture. The optimal nitrogen sources were determined to be 0.5 g L(-1) ammonium chloride and 2 g L(-1) casein peptone. It was determined that the optimal pH for cell growth and PHBV accumulation was 7.0. When the cultivation was performed in large scale (2 L fermenter) with a low DO concentration of 30% and a pH of 7.0, a high maximum dry cell weight of 15.53 g L(-1) with a PHBV concentration of 12.61 g L(-1) (53.9% HV), up to 81.2% of the dry cell weight, was obtained. The melting point of PHBV found to be decreased as the fraction of HV present in the polymer increased, which resulted in an improvement in the ductility and flexibility of the polymer. The results of this study will improve the understanding of the PHBV accumulation and production by R. eutropha and will be valuable for the industrial production of biosynthesized polymers.

Xylitol production from D-xylose and horticultural waste hemicellulosic hydrolysate by a new isolate of Candida athensensis SB18.

This paper describes the production of xylitol from d-xylose and horticultural waste hemicellulosic hydrolysate by a new strain of Candida athensensis SB18. Strain SB18 completely consumed 250 and 300 g L(-1) D-xylose and successful converted it to xylitol in the respective yield of 0.83 and 0.87 g g(-1), resulting in 207.8 and 256.5 g L(-1) of xylitol, respectively. The respective volumetric productivity were 1.15 and 0.97 g L(-1) h(-1). Approximately 100.1 g L(-1) of xylitol was obtained from the bioconversion of detoxified horticultural waste hemicellulosic hydrolysate using strain SB18. The yield and productivity were 0.81 g g(-1) xylose and 0.98 g L(-1) h(-1), respectively. Strain C. athensensis SB18 was able to completely utilize glucose, mannose, xylose and partially arabinose. This work demonstrates that stain C. athensensis SB18 is a promising strain for high-titer and high-yield xylitol production and it has great potential in bioconversion of hemicellulosic hydrolysate.

Effects of lignin-derived phenolic compounds on xylitol production and key enzyme activities by a xylose utilizing yeast Candida athensensis SB18.

Candida athensensis SB18 is potential xylitol producing yeast isolated in Singapore. It has excellent xylose tolerance and is able to produce xylitol in high titer and yield. However, by-products, such as phenolic compounds, derived in lignocellulosic biomass hydrolysate might negatively influence the performance of this strain for xylitol production. In this work, four potential phenolic inhibitors, such as vanillin, syringaldehyde, 4-hydroxybenzaldehyde and phenol, were evaluated for their inhibitory effects on xylitol production by C. athensensis SB18. Phenol was shown to be the most toxic molecule on this microorganism followed by syringaldehyde. Vanillin and 4-hydroxylbenzaldehyde was less toxic than phenol and syringaldehyde, with vanillin being the least toxic. Inhibition was insignificant when the total content of inhibitors was below 1.0 g/L. The presence of phenolic compounds affected the activity of xylose reductase, however not on that of xylitol dehydrogenase. C. athensensis SB18 is therefore a potential xylitol producer from hemicellulosic hydrolysate due to its assimilation of such phenolic inhibitors.

New isolate of Trichoderma viride strain for enhanced cellulolytic enzyme complex production.

A new Trichoderma viride stain was isolated from Singapore soil samples. Its mutants were developed by using ethyl methyl sulfonate (EMS) treatment and UV-irradiation followed by a semi-quantitative plate clearing assay on phosphoric-acid-swollen cellulose plates. Mutant EU2-77 proved to be the most promising extracellular cellulase producer among 20 mutants in a screening program performed in shake flask fermentation after plate screening. Soluble protein content, filter paper cellulase (FPase) activity, ß-glucosidase activity and endoglucanase (CMCase) activity of the fermentation broths of the mutant strain were increased to 1.67, 2.49, 2.16, and 2.61 folds, respectively, compared with the wild strain. This enzyme complex produced by mutant EU2-77 contained FPase (2.19 IU/ml), CMCase (16.46 IU/ml), ß-glucosidase (4.04 IU/ml), xylanase (42.37 IU/ml), and ß-xylosidase (0.12 IU/ml). The soluble protein concentration in the enzyme complex was 1.69 mg/ml. The hydrolytic capacities of fermentation supernatants of T. reesei Rut-C30, the wild strain T. viride NP13a and mutant T. viride EU2-77 were compared with the commercial enzymes on the hydrolysis of waste newspaper. The crude enzymes prepared by T. viride EU2-77 showed much higher hydrolysis performance than that from the commercial strain Rut-C30 and demonstrated much comparable hydrolytic performances with the commercial enzyme mixtures. T. viride mutant EU2-77 produced high levels of extracellular cellulases as well as ß-glucosidase, rendering the supplementation of ß-glucosidase unnecessary in waste newspaper hydrolysis.

Optimization of polyhydroxybutyrate (PHB) production by excess activated sludge and microbial community analysis.

In this study, a high value-added and biodegradable thermoplastic, polyhydroxybutyrate (PHB), was produced by excess activated sludge. The effects of the nutritional condition, aeration mode, sodium acetate concentration and initial pH value on PHB accumulation in the activated sludge were investigated. The maximum PHB content and PHB yield of 67.0% (dry cell weight) and 0.740gCODgCOD(-1) (COD: chemical oxygen demand), respectively, were attained by the sludge in the presence of 6.0gL(-1) sodium acetate, with an initial pH value of 7.0 and intermittent aeration. The analysis of the polymerase chain reaction (PCR)-denaturing gradient-gel-electrophoresis (DGGE) sequencing indicated that the microbial community of the sludge was significantly different during the process of PHB accumulation. Three PHB-accumulating microorganisms, which were affiliated with the Thauera, Dechloromonas and Competibacter lineages, were found in the excess activated sludge under different operating conditions for PHB accumulation.