Anti-Bacterial Adhesion Activity of Tropical Microalgae Extracts

Role of microalgae-bacterial consortium in wastewater treatment: A review

In the global effort to reduce CO2 emissions, the concurrent enhancement of pollutant degradation and reductions in fossil fuel consumption are pivotal aspects of microalgae-mediated wastewater treatment. Clarifying the degradation mechanisms of bacteria and microalgae during pollutant treatment, as well as regulatory biolipid production, could enhance process sustainability. The synergistic and inhibitory relationships between microalgae and bacteria are introduced in this paper. The different stimulators that can regulate microalgal biolipid accumulation are also reviewed. Wastewater treatment technologies that utilize microalgae and bacteria in laboratories and open ponds are described to outline their application in treating heavy metal-containing wastewater, animal husbandry wastewater, pharmaceutical wastewater, and textile dye wastewater. Finally, the major requirements to scale up the cascade utilization of biomass and energy recovery are summarized to improve the development of biological wastewater treatment.

Effect of culture conditions at lab-scale on metabolite composition and antibacterial and antibiofilm activities of Dunaliella tertiolecta

Dunaliella tertiolecta RCC6 was cultivated indoors in glass bubble column photobioreactors operated under batch and semi-continuous regimens and using two different conditions of light and temperature. Biomass was harvested by centrifugation, frozen, and then lyophilized. The soluble material was obtained by sequential extraction of the lyophilized biomass with solvents with a gradient of polarity (hexane, ethyl acetate, and methanol) and its metabolic composition was investigated through nuclear magnetic resonance (NMR) spectroscopy. The effect of light on chlorophyll biosynthesis was clearly shown through the relative intensities of the ¹ H NMR signals due to pheophytins. The highest signal intensity was observed for the biomasses obtained at lower light intensity, resulting in a lower light availability per cell. Under high temperature and light conditions, the ¹ H NMR spectra of the hexane extracts showed an incipient accumulation of triacylglycerols. In these conditions and under semi-continuous regimen, an enhancement of β-carotene and sterols production was observed. The antibacterial and antibiofilm activities of the extracts were also tested. Antibacterial activity was not detected, regardless of culture conditions. In contrast, the minimal biofilm inhibitory concentrations (MBICs) against Escherichia coli for the hexane extract obtained under semi-continuous regimen using high temperature and irradiance conditions was promising.

How Microalgae is Effective in Oxygen Deficiency Aggravated Diseases? A Comprehensive Review of Literature

Hypoxia can aggravate the conditions of many oxygen-deficiency-aggravated diseases (ODAD), such as cancer, ischemic heart disease, and chronic wounds. Photosynthetic microalgae can alleviate the hepatotoxicity of the local microenvironment by producing oxygen. In addition, microalgae extracts have antitumor, anti-inflammatory, antibacterial, and antioxidant effects. These properties make them attractive candidates for developing methods to treat ODAD. Although researchers have exploited the advantages of microalgae and developed a variety of microalgae-based biomaterials to treat ODAD, a comprehensive review of this topic has not been presented previously. Therefore, in this review, we summarize the development and progress made in the field of developing microalgae-based biomaterials toward the treatment of ODAD. The challenges and prospects of this field are also discussed.

Role of microalgal metabolites in controlling quorum-sensing-regulated biofilm

Bacterial infections are primarily caused due to the formation of biofilms on the surfaces. The formation of bacterial biofilms results in 60-70% of nosocomial infections in hospital-acquired infections for multidrug-resistant bacteria. Quorum-sensing (QS) is the process of cell-cell communications among bacterial cells. The formation and regulation of biofilm-producing signaling molecules, competence for DNA uptake and factors responsible for virulence occur. When the bacterial cell population density increases, auto-inducers bind with QS receptors and induce gene expression. To suppress the expression of the virulence genes, certain antibiotics and small molecules are used against the pathogenic bacteria. Since the microorganisms are becoming resistant to antibiotics, there is a need of new compounds or molecules which can suppress or inhibit the expression or regulation of virulence genes. Microalgae are an important and rich source of bioactive compounds which have the antimicrobial property. Microalgae have various antibacterial metabolites, such as Portoamides (peptides), flavonoids, eicosapentaenoic acid, alkaloids, peptides and many other secondary metabolites. This review focuses on the signaling molecule-regulated QS mechanism, biofilm formation, and microalgae compounds' effects against pathogenic bacteria. Consequently, most of the compounds have made it to the different levels of clinical trials, even some of the compounds are used therapeutically. Despite the promising applications of antibacterial peptides and the importance of searching for new natural sources of antibiotics, limitations persist for their pharmaceutical applications. However, given due research impetus, these marine metabolites might emerge as a new wave of promising drugs.

Unveiling antimicrobial activity of microalgae Chlorella sorokiniana (UKM2), Chlorella sp. (UKM8) and Scenedesmus sp. (UKM9)

Microalgae represent promising sources of bioactive compounds for pharmaceutical and industrial applications. The emergence of antibiotic resistant bacteria leads to the need to explore new cost-effective, safe, and potent bioactive compounds from the microalgae. This study aimed to investigate the potential of local microalgae for their antimicrobial properties and bioactive compounds. Three local microalgae namely Chlorella sorokiniana (UKM2), Chlorella sp. UKM8, and Scenedesmus sp. UKM9 biomass methanol extracts (ME) were prepared and tested against Gram-positive and Gram-negative bacteria. Chlorella sp. UKM8-ME showed the highest antibacterial activity. UKM8-ME minimum inhibitory concentrations were in the range of 0.312 to 6.25 mg/mL. Cytotoxicity evaluation using MTT assay showed that the microalgae methanolic extracts did not exhibit cytotoxicity against Vero-cells. The UKM8-ME was mainly containing 28 compounds from the Gas Chromatography-Mass Spectrometry (GC–MS) analysis. Major compounds of UKM8-ME included phenol (18.5%), hexadecanoic acid (18.25%), phytol (14.43%), 9,12-octadecadienoic acid (13.69%), and bicyclo[3.1.1]heptane (7.23%), which have been previously described to possess antimicrobial activity. Hence, Chlorella sp. (UKM8) methanol extracts showed promising antibacterial activity. More comprehensive studies are required to purify these antimicrobial compounds and develop our understanding on their mechanism in UKM8-ME to unleash their specific potential.

In Vitro Antibacterial Activity of Marine Microalgae Extract against Vibrio harveyi

Marine microalgae may produce antibacterial substances. At the exponential phase of growth, four species of marine microalgae were examined for their potential to create secondary metabolites that limit the growth of Vibrio harveyi: Nannochloropsis oceanica, Chaetoceros gracilis, Isochrysis sp., and Thalassiosira weissflogii. V. harveyi is a pathogenic bacteria that can cause severe mortality and loss in aquaculture. Disc diffusion assay and co-culture assay were used to determine antibacterial activity. On TSA % NaCl media, the disc impregnated with microalgae and extracted with ethanol, methanol, saline water, and dimethyl sulfoxide (DMSO) was tested against V. harveyi at concentrations of 1.0 × 105, 106 and 107 CFU mL−1. The disc diffusion assay revealed that N. oceanica extracted with ethanol had the largest inhibitory zone against V. harveyi. Meanwhile, only N. oceanica, Isochrysis sp., and T. weissflogii reduced the growth of V. harveyi (105 CFU mL−1) in the co-culture assay (p < 0.05). The current findings reveal that the hydrophilic chemicals in microalgae extract have antibiotic activity against the highly virulent V. harveyi, which causes vibriosis, a serious disease in farmed fish and aquaculture cultivation around the world.

Bioactivity and Biotechnological Overview of Naturally Occurring Compounds from the Dinoflagellate Family Symbiodiniaceae: A Systematic Review

Marine invertebrates are a significant source of biologically active compounds. Recent studies have highlighted the role of microbiota associated with marine invertebrates in the production of bioactive compounds. Corals and sponges are the main marine invertebrates producing bioactive substances, and Symbiodiniaceae dinoflagellates are well-recognized endosymbionts with corals and sponges playing vital functions. The biological properties of Symbiodiniaceae-derived compounds have garnered attention in the past decades owing to their ecological implications and potentiality for bioprospecting initiatives. This study aims to systematically review studies on bioactivities and potential biotechnological applications of Symbiodiniaceae-derived compounds. The PRISMA guidelines were followed. Our study showed that anti-inflammatory and vasoconstrictive activities of Symbiodiniaceae-derived compounds have been the most investigated. However, very few studies have been published, with in vitro culturing of Symbiodiniaceae being the most significant challenge. Therefore, we surveyed for the metabolites reported so far, analyzed their chemodiversity, and discussed approaches to overcome culturing-related limitations.

Antifouling properties of amphiphilic poly(3-hydroxyalkanoate): an environmentally-friendly coating

The development of biofouling is a major problem for marine industries. The conception of antifouling and fouling release coatings, with controlled physical-chemical properties is a promising strategy. Among them, amphiphilic systems, such as those composed of a hydrophobic polydimethylsiloxane matrix and a hydrophilic polyethyleneglycol additive are the most efficient and up to date. Despite their effectiveness, these systems are questioned due to the petrochemical origin of PDMS. The aim of this project was to substitute the PDMS matrix with a biopolymer, poly(3-hydroxybuyrate-co-3-hydroxyvalerate) and to improve its anti-adhesion properties through the elaboration of an amphiphilic system, via the addition of PEG or PHBHHx-b-PEG copolymer. The results, including the physico-chemical properties of PHBHV based coatings and static adhesion tests on a marine bacterium, Bacillus 4J6 and a diatom, Phaeodactylum tricornutum are compared with those of PDMS and PEG-modified PDMS coatings. Real antiadhesion activity was obtained for the PHBHV/PHBHHx-b-PEG system for a promising eco-friendly strategy.

The Usefulness of Microalgae Compounds for Preventing Biofilm Infections

Biofilms play an important role in infectious diseases. It has been estimated that most medical infections are due to bacterial biofilms, and about 60-70% of nosocomial infections are also caused by the formation of a biofilm. Historically, microalgae are an important source of bioactive compounds, having novel structures and potential biological functions that make them attractive for different industries such as food, animal feed, aquaculture, cosmetics, and pharmaceutical. Several studies have described compounds produced by microalgae and cyanobacteria species with antimicrobial activity. However, studies on the antibiofilm activity of extracts and/or molecules produced by these microorganisms are scarce. Quorum-sensing inhibitor and anti-adherent agents have, among others, been isolated from microalgae and cyanobacteria species. The use of tools such as nanotechnology increase their power of action and can be used for preventing and treating biofilm-related infections.