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.

近几十年来，海洋微生物因其产生多种次生生物活性代谢物的能力而闻名。几种化合物已从海洋微生物中分离出来，用于开发用于食品和制药行业的新型生物活性物质。在这项研究中，使用各种提取技术和抗菌试验评估了许多微藻对革兰氏阳性和革兰氏阴性细菌（包括食物和植物病原体）的抗菌活性。进行圆盘扩散和草坪点测定以确认抗菌活性。为了测量提取物的效力，测量了最小抑制浓度 (MIultCs)。三种微藻，即Isochrysis galbana、Scenedesmus sp。NT8c，和小球藻sp。FN1，对革兰氏阳性菌具有较强的抑制活性。然后选择这些微藻物种进行进一步纯化和分析，从而进行化合物鉴定。通过混合使用不同的色谱技术，气相色谱-质谱 (GC-MS) 和高效液相色谱 (HPLC) 以及超高效液相色谱-四极杆飞行时间质谱 (UHPLC-Q-TOF- MS），我们能够分离和鉴定导致抑制活性的主要化合物。此外，核磁共振 (NMR) 用于确认这些化合物的存在。在提取物中鉴定和纯化的主要化合物是亚油酸、油酸、二十二碳六烯酸 (DHA) 和二十碳五烯酸 (EPA)。这些化合物是抑制革兰氏阳性菌生长的潜在候选物。这表明微藻及其抗菌化合物作为生物防治剂对抗食物和植物病原体的潜在用途。