Halophilic archaea are one of the microorganism groups that have adapted to living in high saline environments and are important in terms of their potential use in biotechnology industry. One of the most important compounds they have, carotenoid, is used in food, cosmetics, and medical industries. The selected strain was identified as an extremely halophilic and thermophilic archaeon, Haloterrigena thermotolerans K15, based on morphological, biochemical, and physiological evidence as well as 16S rRNA analysis and screened by a scanning electron microscope and an atomic force microscope for the first time. The carotenoid contents of H. thermotolerans K15 isolated from Salt Lake (Tuz Gölü, Turkey) were determined by RP-HPLC–DAD and their isomers were characterized according to UV–Vis spectra by cis peak intensity and spectral fine structure. In addition to all-trans bacterioruberin as a major carotenoid, many isomers of the bacterioruberin such as monoanhydrobacterioruberin and bisanhydrobacterioruberin were also found. The antioxidant activity of carotenoid extract from H. thermotolerans was analyzed by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging method. The carotenoid extract showed antioxidant activity statistically significantly higher than ascorbic acid and butylated hydroxytoluene as reference compounds (p < 0.05). This is the first study about carotenoid characterization and antioxidant activity of H. thermotolerans K15. The obtained results suggest the potential use of H. thermotolerans K15 products as a substitute for synthesized chemical carotenoids and antioxidants.

嗜盐古生菌是适应生活在高盐环境中的微生物群落之一，就其在生物技术工业中的潜在用途而言非常重要。它们拥有的最重要的化合物之一是类胡萝卜素，用于食品、化妆品和医疗行业。根据形态学、生化和生理学证据以及16S rRNA分析，筛选出的菌株为极嗜盐嗜热古细菌Haloterrigena thermotolerans K15，并首次通过扫描电镜和原子力显微镜筛选。H. thermotolerans的类胡萝卜素含量通过 RP-HPLC-DAD 测定从盐湖（Tuz Gölü，土耳其）分离的 K15，并根据 UV-Vis 光谱通过顺式峰强度和光谱精细结构表征其异构体。除了作为主要类胡萝卜素的全反式细菌红素外，还发现了细菌红素的许多异构体，例如单脱水细菌红素和双脱水细菌红素。采用2,2-diphenyl-1-picrylhydrazyl 自由基清除法分析耐热嗜热菌类胡萝卜素提取物的抗氧化活性。类胡萝卜素提取物的抗氧化活性在统计学上显着高于作为参考化合物的抗坏血酸和丁基化羟基甲苯（p < 0.05)。这是第一项关于H. thermotolerans K15 的类胡萝卜素表征和抗氧化活性的研究。获得的结果表明H. thermotolerans K15 产品作为合成化学类胡萝卜素和抗氧化剂的替代品的潜在用途。