银耳菌糠黑色素的理化性质及抗氧化和抑菌活性

银耳菌糠中存在一种银耳的伴生菌——炭团菌(俗称香灰菌)，其菌丝生长到一定阶段后会产生大量的黑色素，具有广泛的应用价值。本研究从银耳菌糠中提取黑色素，研究其理化性质、抗氧化活性及抑菌作用。通过紫外-可见光谱、傅里叶红外光谱对提取的黑色素进行鉴定，表明银耳菌糠黑色素具有黑色素的典型特征。通过对银耳菌糠黑色素理化性质的研究，表明银耳菌糠黑色素是一种趋于黑色并略带红色和黄色的粉末；该黑色素易溶于碱性溶液；具有较好的热稳定性和光稳定性，其稳定性受氧化剂和还原剂的影响较小，受Ca²⁺、Cu²⁺的影响较明显。通过总抗氧化能力(FRAP法)、自由基清除能力检测银耳菌糠黑色素的抗氧化活性，研究表明黑色素具有较高的抗氧化活性，羟自由基、ABTS自由基清除的EC₅₀值分别为0.429 mg/mL和0.016 mg/mL。本研究还检测了黑色素对革兰氏阳性、革兰氏阴性细菌的抑菌能力，结果表明该黑色素在浓度为3.2 mg/mL时对供试菌株的抑菌率超过90%，且对革兰氏阳性菌会较敏感。本研究为银耳菌糠的有效利用及其黑色素产品的开发提供了理论基础，具有较高的经济价值。

Physicochemical properties and antioxidant and antibacterial activities of melanin from Tremella fuciformis bran

Hypoxylon sp. intermixed with Tremella fuciformis bran can produce a lot of melanin when its hyphae grow at a certain stage, having wide application value. In this study, melanin was extracted from T. fuciformis bran to study its physicochemical properties, antioxidant activity and antibacterial activity. The extracted melanin was identified by UV-vis and FTIR spectra. T. fuciformis bran melanin was black-powdery with slightly reddish and yellow color, and easily soluble in alkaline solution. It has good thermal stability and photostability, and its stability is less affected by oxidant and reducing agent, but more significantly affected by Ca²⁺ and Cu²⁺. The total antioxidant capacity (FRAP) and free radical scavenging capacity were used to evaluate antioxidant activity of the melanin. The results showed that the melanin had high antioxidant activity, and the EC₅₀ value of hydroxyl radical and ABTS free radical scavenging was 0.429 mg/mL and 0.016 mg/mL, respectively. Bacteriostatic ability of the melanin to Gram-positive and Gram-negative bacteria was also detected. The results showed that the bacteriostatic rate of the melanin to the tested strains was more than 90% under melanin concentration of 3.2 mg/mL, and Gram-positive bacteria were more sensitive to the melanin. This study suggests that the effective utilization of T. fuciformis bran and the development of melanin products could bring in high economic value.