In recent decades, marine microorganisms have become known for their ability to produce a wide variety of secondary bioactive metabolites. Several compounds have been isolated from marine microorganisms for the development of novel bioactives for the food and pharmaceutical industries. In this study, a number of microalgae were evaluated for their antimicrobial activity against gram-positive and gram-negative bacteria, including food and plant pathogens, using various extraction techniques and antimicrobial assays. Disc diffusion and spot-on-lawn assays were conducted to confirm the antimicrobial activity. To measure the potency of the extracts, minimum inhibition concentrations (MIultCs) were measured. Three microalgae, namely Isochrysis galbana, Scenedesmus sp. NT8c, and Chlorella sp. FN1, showed strong inhibitory activity preferentially against gram-positive bacteria. These microalgal species were then selected for further purification and analysis, leading to compound identification. By using a mixture of different chromatography techniques gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS), we were able to separate and identify the dominant compounds that are responsible for the inhibitory activity. Additionally, nuclear magnetic resonance (NMR) was used to confirm the presence of these compounds. The dominant compounds that were identified and purified in the extracts are linoleic acid, oleic acid, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These compounds are the potential candidates that inhibit the growth of gram-positive bacteria. This indicates the potential use of microalgae and their antimicrobial compounds as biocontrol agents against food and plant pathogens.

Evaluation of microalgae and cyanobacteria as potential sources of antimicrobial compounds

Bioprospecting for bioactive compounds in microalgae: Antimicrobial compounds.

In the current work, zinc oxide nanoparticles (ZnONPs) synthesized by the cell-free supernatant of Phaeodactylum tricornutum cultures were first examined for their physicochemical and antimicrobial proprieties. They were then applied as spray coating on the surface of fresh sweet cherries to evaluate their efficacy on quality maintenance of the fruit over 10 days of storage at 25 °C. Synthesized nanoparticles showed a large-scale inhibitory effect against Escherichia coli (ATCC 25922), Staphylococcus aureus MRSA (ATCC 43300) and Candida albicans (ATCC 14053) with minimum inhibitory concentrations (MIC) ranged between 0.078 and 0.156 mg/mL. Furthermore, ZnONPs at 100–1000 mg/L effectively inhibited mycelia growth of Mucor heimalis, a causative agent of Mucor rot in sweet cherries. The results also indicated that ZnONPs significantly delayed the changes of visual and biochemical attributes of the fruit. Compared to untreated control, coated cherries with ZnONP at a concentration of 500 mg/L showed very small change in moisture and total sugar content. Therefore, all coated fruits exhibited less decay rates. In addition, spray coating with ZnONPs had a positive effect on maintaining suitable amounts of ascorbic acid (29.74 mg/100 g FW), polyphenols (579.2 μg/g FW) and flavonoids in the fruits (1991.87 μg/g FW). Data from this study showed 5.11% and 11.63%, increase in flavonoid content and antioxidant activity in the fruits coated with 500 mg/L ZnONPs, respectively, at the end of storage. These data together suggest that green ZnONPs-based coating is one of the safest and effective ways to preserve commercial fruits for prolonged storage. 

Antibacterial and antifungal activity of zinc oxide nanoparticles produced by Phaeodactylum tricornutum culture supernatants and their potential application to extend the shelf life of sweet cherry (Prunus avium L.)

Hydroponics is a promising method for growing agricultural plants and is especially relevant in the context of global climate change. Microscopic algae, including Chlorella vulgaris, has great potential for use in hydroponic systems as natural growth stimulators. The effect of the suspension of an authentic strain of Chlorella vulgaris Beijerinck on the length of cucumber shoots and roots, as well as its dry biomass, was studied. During cultivation in a Knop medium with the addition of Chlorella suspension, the length of the shoots was shortened from 11.30 to 8.15 cm, while the length of the roots also decreased from 16.41 to 10.59 cm. At the same time, the biomass of the roots increased from 0.04 to 0.05 g. The data obtained indicate the positive effect of the suspension of the Chlorella vulgaris authentic strain on the dry biomass of cucumber plants in hydroponic conditions and make it possible to recommend this strain for use when growing plants in hydroponic systems.

/pdf/application-of-chlorella-vulgaris-beijerinck-as-a-1tihcxcu.pdf

Application of Chlorella vulgaris Beijerinck as a Biostimulant for Growing Cucumber Seedlings in Hydroponics

Работа посвящена исследованию объектов полезных для создания технологий, удовлетворяющих требованиям строящейся экономики замкнутого цикла, основанной на широком использовании возобновляемых ресурсов, максимальной переработке вторичного сырья, имеющей в качестве одной из задач переход от ископаемого топлива к использованию возобновляемых источников энергии. Проведено исследование возможности производства эфиров жирных кислот (ЭЖК) из возобновляемого сырья растительного происхождения микроводоросли Chlorella vulgaris с использованием муниципальных сточных вод. Рассмотрены подходы к созданию технологий производства ЭЖК и перспективные пути совершенствования ключевых стадий таких производств. Показано, что муниципальные сточные воды при определенных условиях (температуре 10-32 °С, освещенности 7-14 клк) могут подвергаться очистке и одновременно служить питательной средой в процессе культивирования биомассы микроводорослей с содержанием липидов 10-18 % от сухого вещества. В зависимости от условий культивирования клетки штамма микроводорослей Chlorella vulgaris IPPAS C-2 снижают концентрацию катионов аммония, фосфат-анионов и общего микробного числа в муниципальных сточных водах на 93 – 95% (масс.), 90 – 97% (масс.) и 86 – 95%, соответственно. Проанализировано влияние технологических условий проведения процесса на скорость роста биомассы и жирнокислотный состав накапливаемых липидов. Экспериментально установлено, что триглицериды, Одиалкилмоноглицериды и жирные кислоты оказывают наибольшее ингибирующее влияние на микрофлору сточных вод. С использованием теории растворимости Ч. Хансена выбрана система полярного и неполярного растворителей, состоящая из этанола и петролейного эфира в соотношении (1:2) об., обеспечивающая эффективное проведение процесса экстракции. Получен выход эфиров жирных кислот КЭЖК =45% при проведении реакции переэтерификации с использованием этанола в соотношении с липидами 6:1 (мол.) при температуре реакции 60 °С в присутствии щелочного катализатора – гидроксида натрия (3% от массы липидов).

/pdf/on-integration-of-wastewater-treatment-technologies-and-2eluz7uku4.pdf

On integration of wastewater treatment technologies and production of renewable energy sources

An experimental research into the antibiotic properties of Chlorella vulgaris Beijer IPPAS C-2 microalgae exometabolites under different cultivation conditions was carried out. It has been established that the inhibitory effect of triglycerides, O-dialkyl monoglycerides, fatty acids, O-dialkyl glycerol esters and long-chain alcohols on the microflora of wastewater is highly dependent on the intensity and time of illumination. The antibiotic effect of non-polar substances - exometabolites of microalgae of lipid nature varies depending on the intensity and time of illumination.

Experimental Research Into the Antibiotic Properties of Chlorella Vulgaris Algal Exometabolites

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Experimental Research Into the Antibiotic Properties of Chlorella Vulgaris Algal Exometabolites