• Journal of Ocean Engineering and Technology
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• v.37 no.4
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• pp.172-179
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• 2023

Biofouling initiated by biofilm (slime) formation is a key challenge for practical ocean engineering and construction. This study evaluated a new anti-biofilm technology using bioelectricity. The anti-microfouling electrical technology is based on the principles of the bioelectric effect, known as the application of an electrostatic force for biofilm removal. Previously, the electricity was optimized below 0.82V to avoid electrolysis, which can prevent the production of biocides. A test boat comprised of microelectronics for electrical signal generation with electrodes for an anti-biofouling effect was developed. The tests were conducted in the West Sea of Korea (Wangsan Marina, Incheon) for three weeks. The surface biofouling was quantified. A significant reduction of fouling was observed under the bioelectric effect conditions, with approximately 30% enhanced prevention of fouling progress (P<0.05). This technology can be an alternative eco-friendly technique for anti-microfouling that can be applied for canals, vessels, and coastal infrastructure because it does not induce electrolysis.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.151-157
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• 2020

Harmful aquatic organisms introduced by ship movement cause marine ecosystem disturbances and are in the form of ballastwater and biofouling. Harmful marine life from ballastwater has been considerably reduced because mandatory treatment on all vessels is required to install onboard vessels. However, there remains risk of migration because biofouling is recommended to countries for management through the IMO guidelines. In particular, biofouling management has recently attracted attention for achieving IMO GHG reduction targets because it contributes to energy efficiency, as well as there are reasons for marine ecosystem protection. In recent years, increasing international consensus on the need for biofouling management is likely to lead to enforcement regulations. Thus, this study suggests the management method of hull attachment organisms in Korea, focusing on the cases of foreign countries that have regulated hull attachment organisms.

• Membrane and Water Treatment
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• v.15 no.2
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• pp.51-57
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• 2024

The removal of phosphorus, especially phosphate-form phosphorus, is necessary in wastewater treatment. Biofouling induced by the quorum sensing mechanism is also a major problem in membrane bioreactor (MBR), which reduces membrane flux. This study introduces lanthanum-doped quorum quenching (QQ) beads into MBR, confirming their inhibitory effect on biofouling due to Rhodococcus sp. BH4 and their capacity for phosphorus removal through lanthanum adsorption. A batch test was conducted to access the phosphate adsorption of lanthanum-QQ (La-QQ) beads and lab-scale MBR to verify the effect of inhibition. The study aimed to identify distinctions among the MBR, QQ MBR, and La-QQ MBR. In the batch test, the phosphate removal rate increased as the volume of beads increased, while the unit volume removal rate of phosphate decreased. In the lab-scale MBR, the phosphate removal rates were below 20% in the control MBR and QQ MBR, whereas the La-QQ MBR achieved a phosphate removal rate of 74%. There was not much difference between the ammonia and total organic carbon (TOC) removal rates. Regarding the change in transmembrane pressure(TMP), 3.7 days were taken for the control MBR to reach critical pressure. In contrast, the QQ-MBR took 9.8 days, and the La-QQ MBR took 6.1 days, which confirms the delay in biofouling. It is expected that La-QQ can be used within MBR to design a more stable MBR process that regulates biofouling and enhances phosphate removal.

• Journal of Life Science
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• v.26 no.12
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• pp.1487-1497
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• 2016

Bacterial cell to cell communication strategies called quorum sensing (QS) using small diffusible signaling molecules (auto-inducers) govern the expression of various genes dependent on their population density manner. As a consequence of synthesis and response to the signaling molecules, individual planktonic cells synchronized group behaviors to control a diverse array of phenotypes such as maturation of biofilm, production of extra-polymeric substances (EPS), virulence, bioluminescence and antibiotic production. Many studies indicated that biofilm formations are associated with QS signaling molecules such as acyl-homoserine lactones (AHLs) mainly used by several Gram negative bacteria. The biofilm maturation causes undesirable biomass accumulation in various surface environments anywhere water is present called biofouling, which results in serious eco-technological problems. Numerous molecules that interfere the bacterial QS called quorum quenching (QQ), have been discovered from various microorganisms, and their functions and mechanisms associated with QS have also been elucidated. To resolve biofouling problems related to various industries, the novel approach based on QS interference has been emerged attenuating multi-drug resisting bacteria appearance and environmental toxicities, which may provide potential advantages over the conventional anti-biofouling approaches. Therefore this paper presents recent information related to bacterial quorum sensing system, quorum quenching enzymes that can control the QS signaling, and lastly discuss the anti-biofouling approaches using the quorum quenching.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.71-76
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• 2012

Biofouling by marine organisms such as algae and barnacles causes lots of significant problems in marine systems such as a rise of the maintenance-repair cost for the ship and the marine structures. In this work, a fluoropolymer, perfluoropolyether (PFPE), was applied as an anti-biofouling coating material that prevents the adhesion of marine organisms and facilitates the removal of them. Water contact angles of various surfaces were tested to examine the hydrophobicity of the PFPE-modified surface. The PFPE-modified surface showed the water contact angle of $64.5^{\circ}$ which is a remarkable rise from $46.7^{\circ}$ of amine-treated surface. When the substrate was treated with PFPE, the adhesion on the of the barnacle and other marine organisms were repressed around 15% by the enhanced hydrophobicity. In addition, the removal the of the adhered marine organisms were better comparing to that of the surface prepared by PDMS. Surfaces of the substrate treated by PFPE were characterized through physical and chemical methods to analyze the biofouling results. Degree of biomolecular adhesion to the substrate was quantified by the measurement the fluorescence intensity of marine organisms dyed with green fluorescence. PFPE is expected to be applicable not only to anti-biofouling systems but also to medical devices where the prevention of protein adhesion is required.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.10-18
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• 2022

With the increase in world trade through ships, the destruction of the marine ecosystem and socioeconomic damage due to invasive alien species (IAS) are continuously increasing. In particular, marine organisms attached on the hull surface and niche area increase the friction resistance of ships as well as the invasion of non-indigenous species, and causes a decrease in operational efficiency and an increase in GHG (Green House Gas) emissions. The International Maritime Organization (IMO) has recently begun revising guidelines for the control and management of ship's biofouling, and New Zealand and California in the United States are already regulating biofouling management under their own laws. This study investigated the management status of the submerged surface of ships and marine organisms attachments on five international ships entering South Korea, and analyzed species group and coverage (%) of biofouling communities to evaluate the LoF (Level of Fouling) rank. Macroflouling was observed on all ships surveyed, and specially, the adhesion of macro organisms in niche areas such as bow thruster, bilge keels and sea-chest gratings appeared to be at a serious level. This study proposed the management direction our country should take with regard to ship's biofouling and the improvement measures for evaluation of LoF rank and inspection methods of hull and niche ares.

• Environmental Engineering Research
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• v.24 no.4
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• pp.543-558
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• 2019

In comparison to alternative advanced wastewater treatment technologies, the main problem associated with membrane bioreactor (MBR) technology, which has become prominent in recent years, is biofouling. Within these systems, biofouling is typically the result of a biofilm layer resulting from bacterial gathering. One biological system that can be employed to interrupt the process of bacterial gathering is called 'Quorum Quenching (QQ)'. Existing QQ applications can be classified using three main types: 1) bacterial/whole-cell applications, 2) direct enzyme applications, and 3) natural sourced compounds. The most common and widely recognized applications for membrane fouling control during MBR operation are bacterial and direct enzyme applications. The purpose of this review was to identify and assess biofilm formation mechanism and results, the suggestion of the QQ concept and its potential to control biofilm formation, and the means by which these QQ applications can be applied within the MBR and present QQ MBR studies.

• Environmental Engineering Research
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• v.14 no.1
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• pp.19-25
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• 2009

In this study, total bacteria, enteric members of the $\gamma$-proteobacteria, and microbial communities in seawater were analyzed as indirect indicators for quantifying biofouling. Biomass in seawater can significantly affect feed water pretreatment and membrane biofouling of reverse osmosis desalination processes. The purpose of this paper is to investigate microbiological quantity and quality of seawater at the potential intake of a desalination plant. For this analysis, the total direct cell count (TDC) using 4'-6-diamidino-2-phenylindole (DAPI)-staining and DNA-based real-time PCR were used to quantify the total bacteria and relative content of enteric members of $\gamma$-proteobacteria in seawater, respectively. In addition, microbial communities were examined using 16S rRNA gene cloning and bacterial isolation to identify the most abundant bacteria for a further biofouling study. The experimental results of this study identified about $10^6$ cells/mL of (total) bacteria, $10^5$ 16S rRNA gene copies/mL of enteric $\gamma$-proteobacteria, and the presence of more than 20 groups of bacteria.

• Journal of Microbiology and Biotechnology
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• v.24 no.1
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• pp.97-105
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• 2014

Quorum quenching (QQ) with a microbial vessel has recently been reported as an economically feasible biofouling control platform in a membrane bioreactor (MBR) for wastewater treatment. In this study, a quorum quenching MBR with a ceramic microbial vessel (CMV) was designed to overcome the extremely low F/M ratio inside a microbial vessel. The CMV was prepared with a monolithic ceramic microporous membrane and AHL-degrading QQ bacteria, Pseudomonas sp. 1A1. The "inner flow feeding mode" was introduced, under which fresh feed was supplied to the MBR only through the center lumen in the CMV. The inner flow feeding mode facilitated nutrient transport to QQ bacteria in the CMV and thus enabled relatively long-term maintenance of cell viability. The quorum quenching effect of the CMV on controlling membrane biofouling in the MBR was more pronounced with the inner flow feeding mode, which was identified by the slower increase in the transmembrane pressure as well as by the visual observation of a biocake that formed on the used membrane surface. In the QQ MBR with the CMV, the concentrations of extracellular polymeric substances were substantially decreased in the biocake on the membrane surface compared with those in the conventional MBR. The CMV also showed its potential with effective biofouling control over long-term operation of the QQ MBR.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.279-284
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• 2018

Membrane biofouling is a critical operational problem that hinders the rapid commercialization of MBRs. Quorum quenching (QQ) has been investigated widely to control membrane biofouling and is accepted as a promising anti-fouling strategy. Various QQ strategies based on bacterial and enzymatic agents have been identified and applied successfully. Whereas, this study aimed to compare indigenously isolated QQ strain i.e., Enterobacter cloaca with well reported Rhodococcus sp. BH4. Both bacterial species were immobilized in polymeric beads and introduced to two different MBRs keeping the overall beads to volume ratio as 1%. Efficiencies of these strains were monitored in terms of prolonging the membrane filtration cycle of MBR, release of extra-cellular polymeric substances, membrane resistivity measurements and mineralization of signal molecules and permeate quality. Indigenous strain (Enterobacter cloaca) was added to $QQ-MBR_E$ while Rhodococcus sp. BH4 was introduced to $QQ-MBR_R$. QQ bacterial embedded beads showed enhanced filtration cycles up to 1.4 and 2.3 times for $QQ-MBR_E$ and $QQ-MBR_R$ respectively as compared to control MBR (C-MBR). Soluble EPS concentration of 52 mg/L was observed in C-MBR while significantly lower EPS concentration of 20 and 10 mg/L was witnessed in $QQ-MBR_E$ and $QQ-MBR_R$, respectively. Therefore, substantial reduction in biofouling showed the effectiveness of indigenous strain.