Durable photobioreactor antibiofouling coatings for microalgae cultivation by photoreactive poly(2,2,2-trifluoroethyl methacrylate).

To improve the durability of the photobioreactor antibiofouling surface for microalgal cultivation, a series of photoreactive poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) were successfully synthesized and used to modify ethylene-vinyl acetate (EVA) films by a surface coating and UV light grafting method. Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy analysis (XPS) and fluorescence microscopy results indicated that PTFEMA were fixed successfully onto the EVA film surface through a covalent bond. During the microalgal adhesion assay, the number of EVA-PTFEMA film-adhered microalgae was 41.4% lower than that of the EVA film. Moreover, the number of microalgae attached to the EVA-PTFEMA film decreased by 61.7% after cleaning, while that of EVA film decreased by only 49.1%. It was found that the contact angle of EVA-PTFEMA film surface increased, and remained stable when immersed in acid and alkali solution for up to 90 days. HIGHLIGHTSDurable photobioreactor antibiofouling surfaces for microalgal cultivation were prepared successfully.The contact angle of antibiofouling coating surface remained stable in acid and base environment for 90 days.The attached microalgae on antibiofouling surface decreased 41.4% than those of unmodified surface.The attached microalgae on antibiofouling surface could be cleaned by 61.7% through changing the flow velocity of microalgal suspension.

Improved antifouling properties of photobioreactors by surface grafted sulfobetaine polymers.

To improve the antifouling (AF) properties of photobioreactors (PBR) for microalgal cultivation, using trihydroxymethyl aminomethane (tris) as the linking agent, a series of polyethylene (PE) films grafted with sulfobetaine (PE-SBMA) with grafting density ranging from 23.11 to 112 µg cm-2 were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). It was found that the contact angle of PE-SBMA films decreased with the increase in the grafting density. When the grafting density was 101.33 µg cm-2, it reached 67.27°. Compared with the PE film, the adsorption of protein on the PE-SBMA film decreased by 79.84% and the total weight of solid and absorbed microalgae decreased by 54.58 and 81.69%, respectively. Moreover, the transmittance of PE-SBMA film recovered to 86.03% of the initial value after cleaning, while that of the PE film recovered to only 47.27%. The results demonstrate that the AF properties of PE films were greatly improved on polySBMA-grafted surfaces.

Development of transferrin functionalized poly(ethylene glycol)/poly(lactic acid) amphiphilic block copolymeric micelles as a potential delivery system targeting brain glioma.

The aim of present study is to conceive a biodegradable poly(ethylene glycol)-polylactide (PEG-PLA) copolymer nanoparticle which can be surface biofunctionalized with ligands via biotin-avidin interactions and used as a potential drug delivery carrier targeting to brain glioma in vivo. For this aim, a new method was employed to synthesize biotinylated PEG-PLA copolymers, i.e., esterification of PEG with biotinyl chloride followed by copolymerization of hetero-biotinylated PEG with lactide. PEG-PLA nanoparticles bearing biotin groups on surface were prepared by nanoprecipitation technique and the functional protein transferrin (Tf) were coupled to the nanoparticles by taking advantage of the strong biotin-avidin complex formation. The flow cytometer measurement demonstrated the targeting ability of the nanoparticles to tumor cells in vitro, and the fluorescence microscopy observation of brain sections from C6 glioma tumor-bearing rat model gave the intuitive proof that Tf functionalized PEG-PLA nanoparticles could penetrate into tumor in vivo.

Outdoor cultivation of Chlorella sp. in an improved thin-film flat-plate photobioreactor in desertification areas.

In order to reduce the flow resistance of the thin-film flat plat photobioreactor (FPPBR) and make it more suitable for mass microalgae cultivation, the channel diameter was modified to 0.06 m and the thin-film FPPBR consisted of 10 parallel shunt-wound channels. A thin-film FPPBR system with 100 modified FPPBRs was constructed and used for Chlorella sp. cultivation in desertification areas (Ordos, China) from July to September of 2018. The pressure drop of the modified FPPBR system decreased significantly and the microalgae showed much higher productivity. The pressure drop was about 11.8 kPa when the liquid velocity was 0.238 m s-1. The final biomass concentration and area productivity reached 2.01 g L-1 and 49.79 g m-2 day-1 respectively, and the yearly productivity of Chlorella sp. was estimated to be about 15.24 t ha-2 year-1. The results demonstrated that high productivity of Chlorella sp. could be achieved in the improved FPPBR system in desertification areas and the improved FPPBR system was feasible for mass cultivation of microalgae in the commercial application.

Thermoplastic cellulose-graft-poly(L-lactide) copolymers homogeneously synthesized in an ionic liquid with 4-dimethylaminopyridine catalyst.

An effective method for grafting L-lactide (LA) from unmodified cellulose by ring-opening polymerization (ROP) in homogeneous mild conditions is presented. By using 4-dimethylaminopyridine (DMAP) as an organic catalyst, cellulose-graft-poly(L-lactide) (cellulose-g-PLLA) copolymers with a molar substitution (MS(PLLA)) of PLLA in a range of 0.99-12.28 were successfully synthesized in ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) at 80 degrees C. The amount and length of grafted PLLA in cellulose-g-PLLA copolymers were controlled by adjusting the molar ratios of LA monomer to cellulose. The structure and thermal properties of cellulose-g-PLLA copolymers were characterized by (1)H NMR, (13)C NMR, wide-angle X-ray powder diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and optical microscopy. The DSC results revealed that the copolymers exhibited a single glass transition temperature, T(g), which sharply decreased with the increase of MS(PLLA) up to MS(PLLA) = 8.28 (DS(PLLA) = 2.19) and increased a little with a further increase of the lactyl content. When MS(PLLA) was above 4.40, the graft copolymers exhibited thermoplastic behavior, indicating the intermolecular and intramolecular hydrogen bonds in cellulose molecules had been effectively destroyed. By using a conventional thermal processing method, fibers and disks of cellulose-g-PLLA copolymers were prepared.

[A novel flat plate photobioreactor for microalgae cultivation].

Flashing light effect on microalgae could significantly improve the light efficiency and biomass productivity of microalgae. In this paper, the baffles were introduced into the traditional flat plate photobioreactor so as to enhance the flashing light effect of microalgae. Making Chlorella sp. as the model microalgae, the effect of light intensity and inlet velocity on the biomass concentration of Chlorella sp. and light efficiency were evaluated. The results showed that, when the inlet velocity was 0.16 m/s, with the increase of light intensity, the cell dry weight of Chlorella sp. increased and light efficiency decreased. With increasing the inlet velocity, the cell dry weight of Chlorella sp. and light efficiency both increased under the condition of 500 µmol/(m2 x s) light intensity. The cell dry weight of Chlorella sp. cultivated in the novel flat plate photobioreactor was 39.23% higher than that of the traditional one, which showed that the flashing light effect of microalgae could be improved in the flat plate photobioreactor with inclined baffles built-in.

Installation of flow deflectors and wing baffles to reduce dead zone and enhance flashing light effect in an open raceway pond.

To reduce the dead zone and enhance the flashing light effect, a novel open raceway pond with flow deflectors and wing baffles was developed. The hydrodynamics and light characteristics in the novel open raceway pond were investigated using computational fluid dynamics. Results showed that, compared with the control pond, pressure loss in the flow channel of the pond with optimized flow deflectors decreased by 14.58%, average fluid velocity increased by 26.89% and dead zone decreased by 60.42%. With wing baffles built into the raceway pond, significant swirling flow was produced. Moreover, the period of average L/D cycle was shortened. In outdoor cultivation of freshwater Chlorella sp., the biomass concentration of Chlorella sp. cultivated in the raceway pond with wing baffles was 30.11% higher than that of the control pond.

A novel photobioreactor structure using optical fibers as inner light source to fulfill flashing light effects of microalgae.

In this work, a novel photobioreactor structure using optical fibers being fixed vertically to culture flow direction as inner light source was proposed to fulfill flashing light effects (FLE) of microalgae, so as to obtain high light efficiency. Three types of optical-fiber photobioreactor fulfilling FLE of microalgae, i.e. air-driven panel, pump-driven panel and stirred tank type, were proposed and a 130 L airlift panel one was practically constructed on which both cold (light profile, liquid velocity) and hot model tests were carried out. Results demonstrated that it could produce uniformed light/dark frequencies being over 10 Hz and microalgae productivity increased by 43% and 38% for Spirulina platensis and Scenedesmus dimorphus respectively, compared with the control. This suggested the structure to be a viable and promising option for future photobioreactors.