Antifouling Potential Research Articles

Experimental and numerical study on underwater noise control of multigrooved metasurface coating with antifouling and drag reduction potential

Acoustic metasurfaces have garnered increasing attention due to their efficacy in low-frequency sound absorption, while achieving broadband sound absorption performance remains challenging. In this study, a novel approach employing a multigrooved metasurface integrated onto a nanocomposite material is undertaken. Before modification, the nanocomposite material exhibits commendable underwater sound absorption capabilities above 4000 Hz, but demonstrates lower performance below this threshold. Integrating the multigrooved metasurface yields a notable enhancement in sound absorption performance below 4000 Hz, with the average absorption coefficient increasing from 0.29 to 0.63. Remarkably, this enhancement almost does not impact the performance above 4000 Hz. Experimental findings additionally reveal improved performance under variable hydrostatic pressures. Notably, the multigrooved surfaces show enhanced antifouling properties, and also exhibit potential for drag reduction compared to smooth surfaces. The proposed multigrooved metasurface in this study introduces a novel strategy towards the development of multifunctional underwater sound absorption coatings.

The green resource recovery process of a new type of selective bipolar membrane electrodialysis system for saline wastewater treatment

The selective electrodialysis with bipolar membrane (BMSED) is an advanced electro-membrane process that combines monovalent perm-selective ion exchange membrane and a bipolar membrane, and presented significant potential in high salinity wastewater treatment and reclamation. Herein, we accomplished an in-depth assessment of the external-integration and internal-integration systems for the treatment of high-salinity mining wastewater and seawater desalination concentrate brine. The issues surrounding their cycling performance during batch operation, their anti-fouling potential in the presence of Mg2+/Ca2+ ions, and its specific operational cost were thoroughly investigated. The results suggest that the internal integration system demonstrates suitable stability during long-term operation under batch (cycling) mode. Nevertheless, the membrane exhibited inorganic scaling due to co-ion leakage at high current density. A highly pure NaOH was obtained through an internal integration process at a cost of 0.68 $/kg, outperforming the external integration system (98.96 %, 1.85 $/kg). The findings presented in this study offer valuable insights for the industrial application of BMSED technology in managing high salinity wastewaters.

Design Characteristics of a Neoteric, Superhydrophilic, Mechanically Robust Hydrogel Engineered To Limit Fouling in the Ocular Environment.

Current challenges with ocular drug delivery and the chronic nature of many ocular ailments render the use of traditional ocular devices for additional drug delivery purposes very attractive. To achieve this feat, there is the need to develop biomaterials that are biocompatible, mechanically robust for ocular applications, highly transparent (depending on the targeted ocular device), and with ultralow protein adhesion potential (the primary step in processes that lead to fouling and potential device failure). Herein is reported the facile synthesis of a novel, highly transparent, mechanically robust, nontoxic, bulk functionalized hydrogel with characteristics suited to scalable fabrication of ocular implantable and nonimplantable devices. Synergistic superhydrophilicity between methacrylated poly(vinyl alcohol) (PVAGMA) and zwitterionic sulfobetaine methacrylate was exploited to obtain a superhydrophilic polymer conjugate through facile photoinitiated cross-linking polymerization. Proton nuclear magnetic resonance (1H NMR), attenuated total reflectance-Fourier transform infrared spectroscopy (ATF-FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to confirm the synthesis and establish the physicochemical parameters for both the starting materials, the conjugated polymer, and the hydrogels. Cytotoxicity and cell adhesion potential evaluated in primary human retinal epithelial cells showed no toxicity or adhesion of the ocular cells. Biofilm adhesion studies in Escherichia coli and Staphylococcus aureus showed over 85% reduction in biofilm adhesion for the best-modified polymer compared to the unconjugated PVAGMA, highlighting its antifouling potential.

Ash fouling characteristic analysis and prediction for pillow plate heat exchanger in waste heat recovery based on attentive-feature decision algorithm

Ash fouling on heat exchanger surfaces in waste heat recovery and utilization is an inevitable result of solid fuel combustion and particle deposition, affecting the efficiency, availability and operating cost of an energy utilization system. Fouling prediction plays a critical role in reasonable design and efficient operation of heat exchangers. However, credible monitoring and accurate prognostic towards fouling condition always remain a challenge, largely due to the complex flue gas component and abominable service environment of heat exchangers. In this paper, a novel ash fouling prediction method combined with Effective Particle Size Filtering and Multistep Attentive-Feature Decision algorithm (EF-MAFD) for Pillow Plate Heat Exchanger (PPHE) is proposed. First, a numerical fouling model with Discrete Phase Model (DPM) combined particle deposition and removal model is developed. Validation work is conducted on Nusselt number, pressure drop coefficient and normal restitution coefficient with existing experimental data. The effect of geometrical configuration of PPHE and condition on the fouling characteristic is then evaluated with this model. Next, the EF-MAFD ash fouling prediction model is established, in which the initial particle size distribution is transformed into an effective diameter innovatively and two indicators evaluating the fouling state, namely critical fouling resistance and critical fouling time are defined and predicted. The results indicate that fouling mainly occurs downstream of the welding spots and shows an asymptotic growing trend over time. PPHE with smaller diameter of welding spot, channel height and pitch ratio possess anti-fouling potential. In comparison to existing methods, the newly developed EF-MAFD method has the capacity to deal effectively with the complex particle distribution and provides the most satisfying prediction ability with coefficient of determination (R2) of 0.93 and mean absolute prediction error (MAPE) of 7.8 %. The proposed method could be utilized as a reliable tool to support fouling condition-based maintenance and design for various types of heat exchangers operating in fly ash conditions.

Reactive layered hydroxide membrane for advanced water treatment: Micropollutant degradation and antifouling potential

The effective removal of micropollutants by water treatment technologies remains a significant challenge. Herein, we develop a CoFe layered double hydroxide (CoFeLDH) catalytic membrane for peroxymonosulfate (PMS) activation to achieve efficient micropollutant removal with improved mass transfer rate and reaction kinetics. This study found that the CoFeLDH membrane/PMS system achieved an impressive above 98% degradation of the probe chemical ranitidine at 0.1 mM of PMS including five more micropollutants (Sulfamethoxazole, Ciprofloxacin, Carbamazepine, Acetaminophen and Bisphenol A) at satisfactory level (above 80%). Moreover, significant improvements in water flux and antifouling properties were observed, marking the membrane as a specific advancement in the removal of membrane fouling in water purification technology. The membrane demonstrated consistent degradation efficiency for several micropollutants and across a range of pH (4–9) as well as different anionic environments, thereby showing it suitability for scale-up application. The key role of reactive species such as SO4•–, and O2• − radicals in the degradation process was elucidated. This is followed by the confirmation of the occurrence of redox cycling between Co and Fe, and the presence of CoOH+ that promotes PMS activation. Over the ten cycles, the membrane could be operated with a flux recovery of up to 99.8% and maintained efficient performance over 24 h continuous operation. Finally, the efficiency in degrading micropollutants, coupled with reduced metal leaching, makes the CoFeLDH membrane as a promising technology for application in water treatment.

PVDF-Halloysite-Ceria multifunctional membrane for one-step treatment to industrial effluent

Industrial wastewater, containing diverse pollutants like dyes and oils, poses detrimental environmental challenges. Membrane technology addresses this complexity well but requires tailored nanofiller modifications that enhance hydrophilicity, oleophobicity, and antifouling potential for efficient separation. In this context, our work focuses on the development of mixed matrix membranes (PV-H-C) – PVDF, halloysite nanotubes (HNTs), and ceria nanoparticles – for effective dye and oil-water emulsion separation, enabling high flux recovery. The tubular structure of HNTs, with a lumen, enables the encapsulation and controlled distribution of ceria nanoparticles, preventing their agglomeration and leading to more uniform dispersion within the membrane matrix. HNTs porous structure, high surface area, and numerous adsorption sites within its nanotubes excel in rapid dye adsorption and ceria’s inherent hydrophobic properties along with low surface energy, forms a barrier against oil adhesion and spreading. Optimal results were achieved by loading 2% HNT and 1% ceria in the PVDF matrix, ensuring improved membrane performance. HNTs enhanced hydrophilicity and achieved pure water permeate flux of 1698 L/m2.h.bar. Developed membranes are super-oleophobic with an underwater contact angle of 132° + 3° and show a 100% increase in dyes and oils separation efficiency as compared to the pristine PVDF membranes. This unique integration of ceria with halloysite nanotubes in PV-H-C membranes is pivotal, bestowing exceptional anti-fouling characteristics and reusability, while providing a one-step, comprehensive solution for the effective treatment of complex industrial wastewater that encompasses both oil and complex dyes.

Antifouling activity of aquatic macrophyte extracts on estuarine bacterial biofilms

ABSTRACT Ecologically safe antifouling solutions have received growing attention since the acknowledgment of the environmental risks of traditional biocides used currently. Given that bacteria constitute the initial stage of the biofouling process, this work aims to evaluate the antifouling potential of aquatic macrophyte extracts in inhibiting biofilm-forming bacteria and to evaluate their ecotoxicological effects on target and nontarget organisms (Thalassiosira pseudonana and Nitokra sp.). For this, the ability of 25 macrophyte extracts to inhibit and eradicate single and multispecies estuarine biofilms was evaluated. The extracts and respective serial dilutions that showed a biofilm inhibitory effect ≥ 60% were evaluated in ecotoxicological assays. Of the 25 extracts, only 6 extracts inhibited the biofilm ≥ 60%. The extracts of Cabomba caroliniana and Schoenoplectus californicus stood out as having a biofilm inhibitory effect ≥ 80% (p < 0.05) for bacterial isolates and ≥ 70% (p < 0.05) for multispecies biofilms. Furthermore, these extracts showed no toxic effects on nontarget organisms. These results demonstrate the biotechnological potential of macrophyte compounds.

Exploring fishery waste potential as antifouling component.

Marine biofouling is a global issue with economic and ecological implications. Existing solutions, such as biocide-based antifouling paints, are toxic for the environment. The search for better antifouling agents remains crucial. Recent research focuses on eco-friendly antifouling paints containing natural compounds like enzymes. This study evaluates enzymatic extracts from fishery residues for antifouling potential. Extracts from Pleoticus muelleri shrimp, Illex argentinus squid, and Lithodes santolla king crab were analyzed. Proteolytic activity and thermal stability were assessed, followed by bioassays on mussel byssus thread formation and barnacle cypris adhesive footprints. All three extracts demonstrated proteolytic activity and 24-h stability at temperate oceanic temperatures, except I. argentinus. P. muelleri extracts hindered cyprid footprint formation and mussel byssus thread generation. Further purification is required for L. santolla extract to assess its antifouling potential activity. This study introduces the use of fishery waste-derived enzyme extracts as a novel antifouling agent, providing a sustainable tool to fight against biofouling formation.

Hydrogel/mineral-integrated interface for synergistic antifouling membrane

Antifouling performance is significant for practical membrane separation, determining the membrane permselectivity, lifespan and maintenance cost. Integrating multi-component antifouling materials at the membrane interface is a promising solution for maximizing the membrane antifouling potential. Herein, a gel-mineral hybrid interface was constructed on polyvinylidene fluoride (PVDF) membrane via MnO2 mineralization induced by the tannic acid (TA)/polyvinylpyrrolidone (PVP) intermediate hydrogel layer. The resultant membrane exhibited superhydrophilicity and resulted in excellent enhancement in permeability and antifouling performance. The modified ultrafiltration membrane exhibited enhanced water flux, rejection of pollutants, and flux recovery rate (FRR) for organic solutions. The pure water flux of the optimal membrane is 40 % higher than that of PVDF. Most importantly, this hydrogel/mineral hybrid interface collectively resists the adhesion of pollutants and catalytic cleaning to remove pollutants. This integrated interface tailoring strategy paves a way for multi-scale antifouling separation membranes.

In vitro and in vivo assessment of antimicrobial, enzymatic, and antifouling properties of self-potent lichen symbiotic bacteria.

This study aimed to comprehensively assess the antimicrobial, antifouling, and antibiofilm-forming potential of lichen symbiotic bacteria against marine fouling bacterial strains. A total of 50 lichen-associated bacteria (LAB) isolates were successfully characterized and evaluated for their effectiveness in mitigating biofouling caused by various marine biofoulers. Through a battery of biological assays encompassing enzymatic, antagonistic, antimicrobial, and antifouling assays, 15 LAB isolates were identified based on their antagonist activities. Notably, the strain LAB4 exhibited remarkable performance across all bioassays, demonstrating its proficiency as an antifouling agent. The production of crude LAB extracts was successfully scaled up using a large-scale fermentor and further optimized. Additionally, a phylogenetic analysis of the isolated strain Bacillus proteolyticus D65's 16S ribosomal RNA gene revealed a high query coverage and percentage identity of 92.62% (accession no. MK883171.1). In conclusion, the lichen bacterial symbiotic isolate B. proteolyticus exhibited significant in vitro and in vivo inhibition of foulants. This study highlights the potential of lichens as a valuable source of yet unexplored bacteria. The bacterial consortium associated with Parmotrema sp. holds promise in combatting biofouling, which poses a substantial threat to the maritime industries and their economic stability.

Graphitic carbon nitride enriched phytochemicals-based integrated membranes for perilous chromium (VI) ion removal

The current study signifies a competent method for the fabrication of banana leaf extract functionalised graphitic carbon nitride (BLE@g-C3N4) using banana leaves extract as a source of phytochemicals. BLE@g-C3N4 acts as an efficient additive to enhance the functional behaviour of graphitic carbon nitride (g-C3N4). The additive was further used as a novel composite to construct polysulfone composite membranes for the removal of chromium (Cr) (VI) ions as a function of pH. The aforementioned membrane was well characterised using spectroscopic and microscopic techniques to confirm the structural and functional integrity. The separation capacity of the membrane was assessed using Cr feed solution of different pH at varied operating pressure. The membrane containing 5 wt% BLE@g-C3N4 showed a Cr (VI) rejection up to > 99 % with a flux of 73.23 Lm-2h−1 at 5 bar pressure in acidic pH. The same membrane showed a rejection of 79.26 ± 0.76 % and 90 ± 0.55 % at basic and neutral pH respectively. On evaluating the antifouling potential of the membranes, M2 membrane (0.5 wt% of BLE@g-C3N4) showed the highest antifouling capability compared to M1 and M3, with a flux recovery aspect of 91.13 %. The as fabricated composite membranes were thereby confirmed to be well poised as far as trade-off between productivity and selectivity is concerned. Affirming BLE@g-C3N4 to be a promising material in removal of Cr (VI) ion at different pH.

Copper Nanoparticles Coupled with Fine-Powdered Active Carbon-Modified Ceramic Membranes for Improved Filtration Performance in a Membrane Bioreactor

Membrane fouling is a key factor limiting the application of a membrane bioreactor (MBR), and membrane-surface modification holds the potential to control membrane fouling and solves this problem. In the research, novel nanocomposite membranes were designed and fabricated using antimicrobial copper nanoparticles (CuNPs) coupled with powdered active carbon (PAC) to mitigate membrane fouling. The successful coating was confirmed by SEM, XRD, and FTIR analysis. Compared with a pristine membrane, the functionalization of CuNPs and PAC improved the hydrophilicity of the modified membrane but led to a lower permeate flux. The result of antimicrobial adhesion experiments showed that the modified M-CuOC displayed high antibacterial activity with the bacteria count decreased by 72%. In MBR operation, the modified M-CuOC leads to the removal efficiency of chemical oxygen demand (COD) increasing to 93%, with better filtration performance under a lower TMP rise. The fouling-resistance analysis demonstrated that, although the intrinsic membrane resistance of modified M-CuOC slightly increased, the reversible and irreversible fouling resistances obviously decreased by 45% and 90%. Moreover, the membrane flux recovery efficiency of the modified M-CuOC also increased by 35%. Overall, these results indicated that, in addition to an improvement in antifouling performance, the functionalization of CuNPs and PAC also enhanced the membrane flux recovery efficiency, revealing a good antifouling potential in a practical application.

Polyethylene glycol-grafted graphene oxide nanosheets in tailoring the structure and reverse osmosis performance of thin film composite membrane

Introducing hydrophilic polymers such as polyethylene glycol (PEG) within the polyamide (PA) layer of thin film composite (TFC) membranes helps achieve high water desalination performance. Here, PEGs of different molecular weights (X: 1500, 6000, 16,000 g/mol) are effectively introduced into the PA layer of TFC membranes utilizing PEG-grafted graphene oxide (GOPX) nanosheets and their effects on the physicochemical properties and reverse osmosis (RO) performance of the thin film nanocomposite (TFN) membranes are investigated. Among the TFNs prepared the GOP16000/TFN exhibits the best performance with 68% improvement in water flux and almost constant salt rejection compared to those of the bare TFC. The influence of PEG molecular weight on the RO performance of the membranes is interpreted by different surface and bulk hydrophilicity as well as thickness and surface roughness of PA layers of GOPX/TFNs. Furthermore, TFNs with thinner and smoother PA layers and thus higher water flux are obtained by dispersing GOPXs in the aqueous phase of the PA interfacial polymerization reaction than by dispersing them in the organic phase of the reaction. Finally, the high antifouling potential of TFNs containing PEG-grafted GOs is demonstrated.

Reverse osmosis membranes applied in seawater desalination plants as a source of bacteria with antifouling activity: Isolation, biochemical and molecular characterization

BackgroundDuring lifespan of reverse osmosis systems applied in seawater desalination plants, a common phenomenon of undesirable growth and accumulation of biological material known as biofouling occurs. Microbial cells are first settlers, attaching and enclosing themselves in extracellular polymeric substances –biomass accumulation usually referred to as microfouling or biofilms, which becomes a serious issue when having a detrimental effect on materials or hampering industrial processes. Thus, control of microfouling on reverse osmosis membranes is crucial since chemical and physical treatments are usually costly and ineffective. In this context, even though microorganisms are the source of the problem, they can also provide possible solutions due to their capacity to produce secondary metabolites, being several of these competition mediators secreted compounds (i.e., bioactive molecules) produced during the stationary phase (e.g., lipases, proteases, DNases and other enzymes with alginate lyase and xanthine oxidases). Such bioactive substances can be utilized against the development of biofilms. Considering biofouled surfaces a niche for complex microbial interactions, here we have used reverse osmosis membranes and cartridge filters applied in a seawater desalination plant as a source for the isolation of bacteria with anti-fouling potential, among other biotechnological applications. ResultsWe obtained 27 bacterial isolates able to secrete exoenzymes displaying a wide array of bioactivity such as lipases, alginases, and glucosidases, among others. Additionally, we showed two main candidates able to inhibit the growth of common microbial colonizers of ROM and cartridge filter. ConclusionsThese results highlight the potential biotechnological application of bioactive molecules against biofouling formation.How to cite: Vera-Villalobos H, Cortes-Martinez A, Gonzalez-Gutierrez Á, et al. Reverse osmosis membranes applied in seawater desalination plants as a source of bacteria with antifouling activity: Isolation, biochemical and molecular characterization. Electron J Biotechnol 2023;66. https://doi.org/10.1016/j.ejbt.2023.09.003.

Evaluation of natural resveratrol multimers as marine antifoulants

In the current study we investigate the antifouling potential of three polyphenolic resveratrol multimers (–)-hopeaphenol, vaticanol B and vatalbinoside A, isolated from two species of Anisoptera found in the Papua New Guinean rainforest. The compounds were evaluated against the growth and settlement of eight marine microfoulers and against the settlement and metamorphosis of Amphibalanus improvisus barnacle cyprids. The two isomeric compounds (–)-hopeaphenol and vaticanol B displayed a high inhibitory potential against the cyprid larvae metamorphosis at 2.8 and 1.1 μM. (–)-Hopeaphenol was also shown to be a strong inhibitor of both microalgal and bacterial adhesion at submicromolar concentrations with low toxicity. Resveratrol displayed a lower antifouling activity compared to the multimers and had higher off target toxicity against MCR-5 fibroblasts. This study illustrates the potential of natural products as a valuable source for the discovery of novel antifouling leads with low toxicity.

Chemical diversity and antifouling activity of geniculate calcareous algae (Corallinales, Rhodophyta) from Brazil.

Marine biofouling is a natural process by which many organisms colonize and grow in submerged structures, causing serious economic consequences for the maritime industry. Geniculate calcareous algae (GCA; Corallinales, Rhodophyta) produce bioactive secondary metabolites and are a promise for new antifouling compounds. Here, we investigated the antifouling activity of four GCA species-Amphiroa beauvoisii, Jania sagittata (formerly Cheilosporum sagittatum), Jania crassa, and Jania prolifera (formerly Amphiroa flabellata)-from the Brazilian coast against macro- and microorganisms. Simultaneously, metabolomic tools were applied to assess the chemical profiles of these seaweeds using gas chromatography coupled to mass spectrometry (GC-MS). Data analysis by principal component and molecular networking analyses used the global natural products social molecular networking platform (GNPS). Our results showed that all extracts were active against different strains of marine bacteria and that the J. sagittata (JsSI) extract showed the highest percentage of bacterial inhibition. The J. sagittata (JsSI) extract was the most active against the mussel Perna perna, showing 100% byssus inhibition. Regarding toxicity, only the J. crassa (JcP) extract showed a 20% mortality rate. The chemical profiles of the evaluated GCA extracts differed qualitatively and quantitatively. Yet, the steroid (3β)-cholest-5-en-3-ol was the major compound commonly identified in all extracts, with the exception of J. sagittata (JsSI). Moreover, we observed intra- and interspecific chemical variabilities among GCA extracts for the different populations, which could explain their antifouling activity variability. This study contributed new information about the chemical compounds produced by this group of seaweeds and showed its antifouling potential. These GCA species may be the subject of future studies to obtain new bioactive compounds with biotechnological potential in maritime areas.

A Numerical Study to Compare the Antifouling Potential of two Bio-inspired Antifouling Topographies Derived from the Pilot whale skin and the Zebra mussels

Biofouling occurs naturally in aquatic environments when microorganisms attach to surfaces and form colonies. The destruction of equipment has occurred in a number of well-known economic sectors, including the power and water treatment industries. Large ships and boats face performance issues due to biofouling, such as increased fuel costs and drag. Inhibiting surfaces, toxic coatings, foul release coatings, and physical removal are just a few of the techniques that have been created and used to prevent biofouling. Some of these strategies are known to be expensive, not eco-friendly, and time-consuming. Inspired by the surface topography of zebra mussel shells and pilot whale’s skin, it stays biofoul free. This study’s objective is to assess the two bio-inspired topographies’ ability to prevent fouling. This study looks at how fouling organisms would respond to the hydrodynamic properties of the aforementioned topographies as well as whether geometric size and features have an effect on them. This study aims to clarify or advance our current understanding of biomimicry and antifouling technology because testing of biomimicry-based antifouling solutions is lacking. This research focuses on explaining the nature of microorganisms in water that settle on surfaces and how they react to disturbances caused by fluid flow. They don’t tend to build up on the surface due to the relationship between flow and the different sizes of the surface geometry. Test the hypothesis that the non-bounded high shear stress ripple features on the Zebra mussel’s shell have lower antifouling efficiency compared to the Pilot whale’s skin, which contributes to antifouling efficiency because of its high shear nanoridges, micropores, and gel-coated skin properties. Therefore, if the terrain size is smaller than the invasive organism, the effective range of antifouling is expected to be in the range of 100 µm - 300 µm. The performance of the two bio-inspired topographies was assessed using CFD ANSYS (Fluent) in an entirely numerical study. Two CAD-created representations of the bio-inspired topographies were positioned inside a fluid domain (5 mm, 5 mm, and 50 mm) under specific boundary conditions, including no slip walls assigned to the fluid domain walls, an inlet velocity of 0.05 ms-1, and the flowing fluid being water. Detailed surface meshing and mesh quality are necessary to prove a reliable solution. The velocity profile, vorticity, and wall shear stress of the surface were examined in order to determine the antifouling effectiveness. Utilizing contour and streamline plots, the flow over the topography models was examined. Based on the hypothesis, the results showed that not only does geometry affect microbial settlement but also size. Topographic patterns with larger sizes were associated with higher settlements of algae and barnacles in low velocity areas. Microbial settling may also be aided by the emergence of low shear stress and vorticity in the lower part of the topography. However, the high shear region that forms close to kink sites or sharp edges and the hydrodynamic disturbance near the surface both have an impact on reducing bacterial attachment. To add to this finding, it is still important for science to consider and conduct research on the novel strategy of using surfaces that mimic biological systems to reduce biofouling and other alternative methods to develop sustainable technology.

Preliminary Results on the Antifouling Potential of Copper Wire and Dyneema® Fiber Combined Twines for Aquaculture Net Cages

Antifouling management for aquaculture cage nets has developed over the years to reduce the costs of cleaning the nets and minimize the damages caused to the nets by the encrustation of benthic organisms. There have been various approaches to this end such as using toxic paints (TBT-SPC, etc.) and nanomaterial coatings, mechanical cleaning using brushes, and constructing the net using copper alloys instead of nylon (or other) material, etc. We designed and constructed experimental fish farm nets substituting Dyneema® fibers with uncoated copper wire 0.15-0.2 mm in diameter by 5%, 10%, 20%, and 40% and deployed them in a commercial operating fish farm for almost 7 months. We examined their antifouling performance based on the percentage of mesh openness remaining by the end of the experimental period. The results showed that the antifouling performance increased with copper substitution level and peaked at a level of 29.79% and maximum mesh openness at 46.5%.

ANTIFOULING STUDY OF ZINC TANNATE (TZn) FOR MILD STEEL IN TROPICAL SEAWATER

This study was coordinated to investigate the potential of tannin extracted from mangrove bark (Rhizophora apiculata sp.) as an antifouling agent. Using natural resources as antifouling agents is an environmentally friendly alternative in industrial applications. Extracted tannin was formulated in a readily available epoxy coating and then coated on the mild steel samples. The samples were immersed in seawater for 60 days in Chendering Port and Marang Jetty. A screening test was performed via the anti-biofilm assay method to characterise the antimicrobial abilities. The IC50 of zinc tannate extract against Bacillus Cereus and Salmonella sp was 2.6 mg/ml and 28.75 mg/ml, respectively. It was discovered that fouling attachment is more noticeable in Chendering Port due to the physical parameters of the surrounding waters. Furthermore, the percentage of the weight acquired at Chendering port is higher than at Marang jetty. Surface inspection using digital photographs and scanning electron microscopy (SEM) reveals a denser tubeworm and mollusc attachment on the substrate without TZn. Higher tannin concentration has resulted in greater antifouling potential. Overall, the findings implicate that TZn has great potential as an antifouling additive in commercial marine coating.

Antifouling activity and biodegradable potential of the bioactive metabolites isolated from mangrove Avicennia officinalis L

The present study explores the antifouling potentials of ethanol extract of mangrove Avicennia officinalis. Results of antibacterial activity inferred that extract had strongly inhibited the growth of fouling bacterial strains with significant differences in halos (9-16 mm) and showed minimal bacteriostatic (12.5–100 µg ml−1) and bactericidal (25-200µg ml−1) values. It had also strenuously suppressed fouling microalgae with appreciable MIC (12.5 and 50 µg ml−1). The extract had also effectively deterred settlement of larvae of Balanus amphitrite and byssal thread of mussel Perna indica with lower EC50 (11.67 and 37.43 µg ml−1) and higher LC50 (257.33 and 817 µg ml−1) values. Further 100% recuperation of mussels from toxicity assay and therapeutic ratio of >20 substantiated its non-toxicity. GC-MS profile of bioassay guided fraction showed four (M1-M4) major bioactive metabolites. In silico biodegradability study revealed that metabolites M1 (Pentanoic acid, 5-methoxy-, phenyl ester) and M3 (Benzaldehyde, methyl-) have rapid biodegradation rates and eco-friendly in nature.