Biofilm-based algal cultivation has received increased attention as a potential platform for algal production and other applications such as wastewater treatment. Algal biofilm cultivation systems ...represent an alternative to the suspension-based systems that have yet to become economically viable. One major advantage of algal biofilm systems is that algae can be simply harvested through scraping and thus avoid the expensive harvesting procedures used in suspension-based harvesting such as flocculation and centrifugation. In recent years, an assortment of algal biofilm systems have been developed with various design configurations and biomass production capacities. This review summarizes the state of the art of different algal biofilm systems in terms of their design and operation. Perspectives for future research needs are also discussed to provide guidance for further development of these unique cultivation systems.
The biofilm thickness in membrane biofilm reactors (MBfRs) is an important factor affecting system performance because excessive biofilm formation on the membrane surface inhibits gas diffusion to ...the interior of the biofilm, resulting in a significant reduction in the performance of contaminant removal. This study provides innovative insights into the control of biofilm thickness in O2‐based MBfRs by using the quorum quenching (QQ) method. The study was carried out in MBfRs operated at different gas pressures and hydraulic retention times (HRTs) using QQ beads containing Rhodococcus sp. BH4 at different amounts. The highest performance was observed in reactors operated with 0.21 ml QQ bead/cm2 membrane surface area, 12 HRTs and 1.40 atm. Over this period, the performance increase in chemical oxygen demand (COD) removal was 25%, while the biofilm thickness on the membrane surface was determined to be 250 μm. Moreover, acetate and equivalent oxygen flux results reached 6080 and 10 640 mg·m−2·d−1 maximum values, respectively. The extracellular polymeric substances of the biofilm decreased significantly with the increase of gas pressure and QQ beads amount. Polymerase chain reaction denaturing gradient gel electrophoresis results showed that the microbial community in the MBfR system changed depending on operating conditions and bead amount. The results showed that the QQ method was an effective method to control the biofilm thickness in MBfR and provide insights for future research.
1.Biofilm thickness on the surface of membrane is a critical problem for the MBfR systems.
2.QQ prevents the biofilm formation through the inhibition of QS among microorganisms.
3.QQ technology was newly applied to control biofilm thickness in MBfR.
In the current study, niosome‐encapsulated tobramycin based on Span 60 and Tween 60 was synthesized and its biological efficacies including anti‐bacterial, anti‐efflux, and anti‐biofilm activities ...were investigated against multidrug resistant (MDR) clinical strains of Pseudomonas aeruginosa. The niosomal formulations were characterized using scanning electron microscopy, transmission electron microscopy, and dynamic light scattering measurement. The encapsulation efficiency was found to be 69.54% ±; 0.67. The prepared niosomal formulations had a high storage stability to 60 days with small changes in size and drug entrapment, which indicates that it is a suitable candidate for pharmaceutical applications. The results of biological study showed the anti‐bacterial activity via reduction of antibiotic resistance, enhanced anti‐efflux and anti‐biofilm activities by more folds in comparison to free tobramycin. In addition, niosome encapsulated tobramycin down‐regulated the MexAB‐OprM efflux genes, pslA and pelA biofilm related genes in MDR P. aeruginosa strains. The anti‐proliferative activity of formulation was evaluated against HEK293 cell lines, which exhibited negligible cytotoxicity against HEK293 cells. The finding of our study shows that encapsulation of tobramycin in niosome enhanced the antibacterial activity and reduced antibiotic resistance in MDR strains of P. aeruginosa comparing to free tobramycin and it can be considered as a favorable drug delivery system.
The poor penetrability of many biofilms contributes to the recalcitrance of infectious biofilms to antimicrobial treatment. Here, a new application for the use of magnetic nanoparticles in ...nanomedicine to create artificial channels in infectious biofilms to enhance antimicrobial penetration and bacterial killing is proposed. Staphylococcus aureus biofilms are exposed to magnetic‐iron‐oxide nanoparticles (MIONPs), while magnetically forcing MIONP movement through the biofilm. Confocal laser scanning microscopy demonstrates artificial channel digging perpendicular to the substratum surface. Artificial channel digging significantly (4–6‐fold) enhances biofilm penetration and bacterial killing efficacy by gentamicin in two S. aureus strains with and without the ability to produce extracellular polymeric substances. Herewith, this work provides a simple, new, and easy way to enhance the eradication of infectious biofilms using MIONPs combined with clinically applied antibiotic therapies.
A novel application of magnetic nanoparticles is described in which magnetic nanoparticles are used to create artificial channels in infectious biofilms. Artificially dug channels relieve the barrier posed by the biofilm matrix toward antibiotic penetration to enhance eradication of the biofilm. Since magnetic nanoparticles are clinically used, this new application will be relatively easy to translate to clinical practice.
Extracellular DNA (eDNA) is an essential structural component during biofilm formation, including initial bacterial adhesion, subsequent development, and final maturation. Herein, the construction of ...a DNase‐mimetic artificial enzyme (DMAE) for anti‐biofilm applications is described. By confining passivated gold nanoparticles with multiple cerium(IV) complexes on the surface of colloidal magnetic Fe3O4 /SiO2 core/shell particles, a robust and recoverable artificial enzyme with DNase‐like activity was obtained, which exhibited high cleavage ability towards both model substrates and eDNA. Compared to the high environmental sensitivity of natural DNase in anti‐biofilm applications, DMAE exhibited a much better operational stability and easier recoverability. When DMAE was coated on substratum surfaces, biofilm formation was inhibited for prolonged periods of time, and the DMAE excelled in the dispersion of established biofilms of various ages. Finally, the presence of DMAE remarkably potentiated the efficiency of traditional antibiotics to kill biofilm‐encased bacteria and eradiate biofilms.
An artificial enzyme for DNA cleavage was obtained by confining protected gold nanoparticles with multiple CeIV centers on colloidal magnetic Fe3O4/SiO2 core/shell particles. This system efficiently inhibited the formation of biofilms, dispersed preformed films, and enabled the eradication of biofilms when used in combination with common antibiotics.
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•Hexadecyl-methylimidazolium chloride was effective in inhibiting growth and biofilm formation by Navicula sp.•Activity of ionic liquid was dependent on the alkyl side chain ...length.•Ionic liquid disrupted cell membrane and caused leakage of intracellular components in diatom cells.•Natural phototrophic biofilms were prevented with ≤5μM of ionic liquid.
Biofilm formation is problematic and hence undesirable in medical and industrial settings. In addition to bacteria, phototrophic organisms are an integral component of biofilms that develop on surfaces immersed in natural waters. 1-Alkyl-3-methyl imidazolium ionic liquids (IL) with varying alkyl chain length were evaluated for their influence on the formation of monospecies (Navicula sp.) and multispecies biofilms under phototrophic conditions. An IL with a long alkyl side chain, 1-hexadecyl-3-methylimidaazolium chloride (C16(MIM)Cl) retarded growth, adhesion and biofilm formation of Navicula sp. at concentrations as low as 5μM. Interestingly, C16(MIM)Cl was very effective in preventing multispecies phototrophic biofilms on fibre reinforced plastic surfaces immersed in natural waters (fresh and seawater). SYTOX® Green staining and chlorophyll leakage assay confirmed that the biocidal activity of the IL was exerted through cell membrane disruption. The data show that C16(MIM)Cl is a potent inhibitor of phototrophic biofilms at micromolar concentrations and a promising agent for biofilm control in re-circulating cooling water systems. This is the first report that ionic liquids inhibit biofilm formation by phototrophic organisms which are important members of biofilms in streams and cooling towers.
Bioclogging is a main concern in infiltration systems as it may significantly shorten the service life of these low-technology water treatment methods. In porous media, biofilms grow to clog ...partially or totally the pore network. Dynamics of biofilm accumulation (e.g., by attachment, detachment, advective transport in depth) and their impact on both surface and deep bioclogging are still not yet fully understood. To address this concern, a 104 day-long outdoor infiltration experiment in sand tanks was performed, using secondary treated wastewater and two grain size distributions (GSDs): a monolayer system filled with fine sand, and a bilayer one composed by a layer of coarse sand placed on top of a layer of fine sand. Biofilm dynamics as a function of GSD and depth were studied through cross-correlations and multivariate statistical analyses using different parameters from biofilm biomass and activity indices, plus hydraulic parameters measured at different depths. Bioclogging (both surface and deep) was found more significant in the monolayer fine system than in the bilayer coarse-fine one, possibly due to an early low-cohesive biofilm formation in the former, driven by lower porosity and lower fluxes; under such conditions biomass is favorably detached from the top layer, transported and accumulated in depth, so that new biomass might colonize the surface. On the other hand, in the bilayer system, fluxes are highest, and the biofilm is still in a growing phase, with low biofilm detachment capability from the top sand layer and high microbial activity in depth, resulting in low bioclogging. Overall, the bilayer coarse-fine system allows infiltrating higher volume of water per unit of surface area than the monolayer fine one, minimizing surface and deep bioclogging, and thus increasing the longevity and efficiency of infiltration systems.
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•Early biofilm formation in fine sands results in an early surface bioclogging.•Homogeneous grain size favors biomass transport in depth promoting deep bioclogging.•Coarse-fine system develops an active biofilm minimizing deep bioclogging.
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