Bo Bai

Simultaneous optimization of the ultrasound-assisted extraction for phenolic compounds content and antioxidant activity of Lycium ruthenicum Murr. fruit using response surface methodology

Lycium ruthenicum Murr. (LR) is a functional food that plays an important role in anti-oxidation due to its high level of phenolic compounds. This study aims to optimize ultrasound-assisted extraction (UAE) of phenolic compounds and antioxidant activities of obtained extracts from LR using response surface methodology (RSM). A four-factor-three-level Box-Behnken design (BBD) was employed to discuss the following extracting parameters: extraction time (X1), ultrasonic power (X2), solvent to sample ratio (X3) and solvent concentration (X4). The analysis of variance (ANOVA) results revealed that the solvent to sample ratio had a significant influence on all responses, while the extraction time had no statistically significant effect on phenolic compounds. The optimum values of the combination of phenolic compounds and antioxidant activities were obtained for X1=30min, X2=100W, X3=40mL/g, and X4=33% (v/v). Five phenolic acids, including chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid, were analyzed by HPLC. Our results indicated that optimization extraction is vital for the quantification of phenolic compounds and antioxidant activity in LR, which may be contributed to large-scale industrial applications and future pharmacological activities research.

In vitro and in vivo biological activities of anthocyanins from Nitraria tangutorun Bobr. fruits

Anthocyanins are the main compounds in Nitraria tangutorun Bobr. The enrichment and purification of anthocyanins on macroporous resins were investigated. Regarding anthocyanin purification, static adsorption and desorption were studied. The optimal experimental conditions were the following: resin type: X-5; static adsorption time: 6h; desorption solution: ethanol-water-HCl (80:19:1, V/V/V; pH 1); desorption time: 40min. Furthermore, the in vitro and in vivo biological activities of the anthocyanins were evaluated. The anthocyanins showed ideal scavenging effects on free radicals in vitro, especially on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl free radical (OH). In the animal experiment, blood lipid metabolism of hyperlipidemia rats was regulated by anthocyanin contents. The superoxide dismutase (SOD) activity and the total antioxidant capacity (TAC) of hyperlipidemia rats were also improved by anthocyanins. These results showed that anthocyanins from N. tangutorun Bobr. fruits had potential biological activities in vivo as well as in vitro.

Biosorption of azo dyes by raspberry-like Fe3O4@yeast magnetic microspheres and their efficient regeneration using heterogeneous Fenton-like catalytic processes over an up-flow packed reactor

Abstract Raspberry-like Fe3O4@yeast composite microspheres, whose properties integrate the biosorption features of yeast cells with the excellent magnetic and catalytic properties of Fe3O4 nanoparticles, were synthesized by a simple electrostatic-interaction-driven self-assembly heterocoagulation. They were successfully applied in an up-flow packed column for the removal of the model water contaminant methylene blue dye (MB) by consecutive bioadsorption-heterogeneous Fenton oxidation cycles. The as-synthesized Fe3O4@yeast composites were characterized by field emission scanning electron microscopy, energy-dispersive spectroscopy (EDS), powder X-ray diffraction and Fourier transform infrared spectroscopy. The adsorption process was controlled by the electrostatic interactions between the adsorbent and contaminant. The adsorbent is suitable for the adsorption of positively charged compounds at mildly acidic pH, neutral and alkaline pH, with the highest performance observed at alkaline pH. The experimental breakthrough curves measured at different influent MB concentration, flow rate, bed height and pH were modeled by the Yoon-Nelson model. The in situ regeneration of the contaminant-loaded Fe3O4@yeast microspheres and their reuse in multiple cycles was demonstrated by triggering the heterogeneous Fenton-like reaction catalyzed by the supported magnetite. The raspberry-like Fe3O4@yeast magnetic microsphere should be a promising and practical adsorbent for removal and destruction of positively charged organic compounds in wastewater.

Enhanced mechanical stability and sensitive swelling performance of chitosan/yeast hybrid hydrogel beads

Up to the present time, improving the mechanical stability of hydrogel beads is still a challenging task for future applications of chitosan hydrogels. In this work, novel and eco-friendly chitosan/yeast hybrid hydrogel beads were fabricated by facile introduction of yeast cells into the chitosan matrix through alkali gelation. A detailed mechanism of formation of the beads is proposed and the structures and morphologies of the manufactured products were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The mechanical stability test showed that impregnation of yeast cells into the chitosan matrix could effectively enhance the mechanical stability of chitosan/yeast hybrid hydrogel beads under the effects of various intensities of ultrasonic waves and centrifugal forces in comparison with pure chitosan hydrogel beads. The resultant product with 40 wt% yeast content achieved a maximum swelling ratio of 31.7 g g−1 in distilled water. The swelling kinetics and diffusion kinetics of chitosan/yeast hybrid hydrogel beads in distilled water were also investigated. Benefiting from the coupling effect of its crosslinked three-dimensional network structure and ample chemical functional groups derived from its own components, chitosan/yeast hybrid hydrogel beads have manifested a rapid and adjustable response to external environmental stimuli including the pH of the external solution, salt concentration, ionic valence and temperature. In particular, the distinct loading and slow-release efficiency of chitosan/yeast hybrid hydrogel beads for humic acid as a fertilizer model is pH-dependent. This makes the chitosan/yeast hybrid hydrogel beads good candidates for controlled-release carrier biomaterials, which is very likely to develop into a patented utilization of chitosan/yeast hybrid hydrogel beads in future applications.

Synthesis and properties of the rapeseed meal-grafted-poly(methyl methacrylate-co-butyl acrylate) oil-absorbents

Owing to the unique properties such as oil body (OB) membranes and cellulose components within the structures of rapeseed meals (RSMs), the novel rapeseed meal-grafted-poly(methyl methacrylate-co-butyl acrylate) (RSMs-g-P(MMA-co-BA)) oil-absorbents were prepared and used for oil/water separation in the present study. Specifically, the RSMs-g-P(MMA-co-BA) were successfully synthesized through free radical graft copolymerization from RSMs, methyl methacrylate (MMA) and butyl acrylate (BA) with benzoyl peroxide (BPO) as initiator and N,N′-methylene-bisacrylamide (MBA) as crosslinker. The synthetic mechanism and 3D network structures were confirmed by FTIR and SEM, and the effects of reaction conditions, swelling kinetics, thermodynamics as well as reusability were investigated in detail. The RSMs-g-P(MMA-co-BA) demonstrated good absorption capacity for both organic solvents and oils, and the change of oil absorbency after eight repeated cycles of swelling/deswelling was marginal. Furthermore, the RSMs-g-P(MMA-co-BA) could selectively remove oils from water rapidly, which is promising for their potential applications in oil spill cleanup.

Degradation of tetracycline hydrochloride by heterogeneous Fenton-like reaction using Fe@Bacillus subtilis

A novel heterogeneous catalyst Fe@Bacillus subtilis has been synthesized though the impregnation method with iron(III)chloride hexahydrate. Field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), energy dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the materials. The as-prepared materials were employed as a heterogeneous Fentons reagent with the addition of H2O2 for degradation of tetracycline hydrochloride (TC). This new heterogeneous Fenton-like system resulted in nearly complete elimination of TC and negligible release of iron leaching from the catalyst was achieved. The catalytic performance could be maintained in three consecutive runs without a significant drop. This behavior was attributed to the synergistic structural and functional effect of the combined B. subtilis and iron ions. The FTIR and XPS characterizations of the catalyst before and after the Fenton-like reaction showed that no structural deformation of the particles occurred.

Thermo-chemical modification to produce citric acid–yeast superabsorbent composites for ketoprofen delivery

Owing to their unique physicochemical/biological properties and natural abundance, native yeast microbes were used to prepare a novel eco-friendly superabsorbent composite through thermo-chemical modification of yeast with citric acid in semi-dry conditions. The structure and morphology of the as-produced citric acid–yeast superabsorbent composites were characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The surface characteristics were studied systematically, including carboxyl content, degree of esterification, degree of substitution and zeta potential. The detailed formation mechanism was proposed. The evaluation of equilibrium welling showed that the species were able to absorb up to 38 times their weight in distilled water, and the water absorption capacity was affected by reaction temperature and external solution (the charge number, salt concentration and pH value). The results implied that citric acid–yeast superabsorbent composites exhibited enhanced water absorption, salt tolerance and pH sensitivity. The excellent swelling performance and special functional groups allowed the citric acid–yeast composites to target drug delivery. Ketoprofen, as a model drug, was utilized to monitor the loading and cumulative release efficiency to evaluate the suitability of citric acid–yeast composites as drug carriers. Its pH-sensitivity, biocompatibility and degradability make it a potential candidate for drug delivery.

Novel Fabrication of Biodegradable Superabsorbent Microspheres with Diffusion Barrier through Thermo-Chemical Modification and Their Potential Agriculture Applications for Water Holding and Sustained Release of Fertilizer

Synergistic utilization of water and fertilizer has vital contribution to the modern production of agriculture. This work reports on a simple and facile strategy to prepare biodegradable yeast/sodium alginate/poly(vinyl alcohol) superabsorbent microspheres with a diffusion barrier merit by thermo-chemical modification route. The integrated performances, including water absorbency, water retention, water evaporation ratio, leaching loss control, sustained-release behaviors, and degradation in soil, were systematically investigated. The results revealed that the modified microspheres were a triumphant water and fertilizer manager to effectively hold water and control the unexpected leakage of fertilizer for sustained release. Therefore, this work provides a promising approach to ameliorate the utilization efficiency of water and fertilizer in potential agriculture applications.

Controlled pesticide release of a novel superabsorbent by grafting citric acid onto water hyacinth powders with the assistance of dopamine

With the purpose of treating the presence of abundant water hyacinth, increasing biodegradability and reducing costs of water-absorbing material, ecofriendly composite CA–PD@WH was fabricated by chemical modification of dopamine-coated water hyacinth with citric acid. FTIR and SEM revealed that dopamine was first deposited on the surface of water hyacinth and then reacted with citric acid. The product exhibited good water absorption (12.0 g g−1 in distilled water) that is much stronger than that of raw WH (1.3 g g−1) and can be thoroughly degraded. Moreover, the resultant composite shows a pH-responsive controlled avermectin-release property and has a high loading capacity for avermectin (about 98.1 mg g−1). This simple and intriguing approach not only extends any future utilization of water hyacinth but also supplies a potential method to control pesticide release and mitigate negative effects on the environment.

Facile fabrication of sea buckthorn biocarbon (SB)@α-Fe2O3 composite catalysts and their applications for adsorptive removal of doxycycline wastewater through a cohesive heterogeneous Fenton-like regeneration

A facile, low-cost and novel route for successful synthesis of SB@α-Fe2O3 composite catalysts was described through a simple thermal conversion process from SB@β-FeOOH precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Fourier transformed infrared spectroscopy (FTIR) analysis, respectively. The experimental results indicated that α-Fe2O3 phase nanoparticles in the SB@α-Fe2O3 composites appeared in spindly nanorods and were highly dispersed on the surface of sea buckthorn biocarbon (SB) platform. The mechanism of thermal conversion from SB@β-FeOOH precursor to SB@α-Fe2O3 products was discussed. Subsequently, the naked SB and resultant SB@α-Fe2O3 composites were applied in fixed-bed columns for the effective pre-adsorption of doxycycline (DO) from an aqueous solution. Breakthrough curves for DO adsorption were carried out at different empty bed contact times (EBCTs). The results showed that the adsorption capacity of SB@α-Fe2O3 was much better than that of SB at all tested EBCTs. The DO-saturated SB@α-Fe2O3 bed was almost completely regenerated in situ through triggering a succedent heterogeneous Fenton-like regeneration process with an H2O2 dose of 1% w/v for 3 h, while the naked SB was hardly regenerated by a parallel processes. In view of the facile synthetic method of composites, the superior adsorption performance and the effective way of regeneration for consecutive pre-adsorption/regeneration cycles, the heterogeneous Fenton-like oxidation of DO-exhausted SB@α-Fe2O3 presents to be a promising and viable strategy for the regeneration of adsorbent. Regeneration mechanism of SB@α-Fe2O3 was in-depth investigated.