Sen Suparna, Borah Siddhartha Narayan, Bora Arijit, Deka Suresh
Environmental Biotechnology Laboratory, Life Sciences Division, Institute of Advanced Study in Science and Technology(IASST), Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam, 781035, India.
Department of Bioengineering and Technology, Institute of Science and Technology, Gauhati University, Jalukbari, Guwahati, Assam, India.
Microb Cell Fact. 2017 May 30;16(1):95. doi: 10.1186/s12934-017-0711-z.
Sophorolipids are one of the most promising glycolipid biosurfactants and have been successfully employed in bioremediation and various other industrial sectors. They have also been described to exhibit antimicrobial activity against different bacterial species. Nevertheless, previous literature pertaining to the antifungal activity of sophorolipids are limited indicating the need for further research to explore novel strains with wide antimicrobial activity. A novel yeast strain, Rhodotorula babjevae YS3, was recently isolated from an agricultural field in Assam, Northeast India. This study was primarily emphasized at the characterization and subsequent evaluation of antifungal activity of the sophorolipid biosurfactant produced by R. babjevae YS3.
The growth kinetics and biosurfactant production by R. babjevae YS3 was evaluated by cultivation in Bushnell-Haas medium containing glucose (10% w/v) as the sole carbon source. A reduction in the surface tension of the culture medium from 70 to 32.6 mN/m was observed after 24 h. The yield of crude biosurfactant was recorded to be 19.0 g/l which might further increase after optimization of the growth parameters. The biosurfactant was characterized to be a heterogeneous sophorolipid (SL) with both lactonic and acidic forms after TLC, FTIR and LC-MS analyses. The SL exhibited excellent oil spreading and emulsifying activity against crude oil at 38.46 mm and 100% respectively. The CMC was observed to be 130 mg/l. The stability of the SL was evaluated over a wide range of pH (2-10), salinity (2-10% NaCl) and temperature (at 120 °C for time intervals of 30 up to 120 min). The SL was found to retain surface-active properties under the extreme conditions. Additionally, the SL exhibited promising antifungal activity against a considerably broad group of pathogenic fungi viz. Colletotrichum gloeosporioides, Fusarium verticilliodes, Fusarium oxysporum f. sp. pisi, Corynespora cassiicola, and Trichophyton rubrum.
The study reports, for the first time, the biosurfactant producing ability of R. babjevae, a relatively lesser studied yeast. The persistent surface active properties of the sophorolipid in extreme conditions advocates its applicability in diverse environmental and industrial sectors. Further, antifungal activities against plant and human pathogens opens up possibilities for development of efficient and eco-friendly antifungal agents with agricultural and biomedical applications.
槐糖脂是最具前景的糖脂类生物表面活性剂之一，已成功应用于生物修复及其他多个工业领域。文献还报道了其对不同细菌种类具有抗菌活性。然而，此前关于槐糖脂抗真菌活性的文献有限，表明需要进一步研究以探索具有广泛抗菌活性的新菌株。最近，从印度东北部阿萨姆邦的一块农田中分离出了一种新型酵母菌株——巴氏红酵母YS3。本研究主要着重于对巴氏红酵母YS3产生的槐糖脂生物表面活性剂进行表征及后续抗真菌活性评估。
通过在以葡萄糖（10% w/v）作为唯一碳源的布什内尔-哈斯培养基中培养，评估了巴氏红酵母YS3的生长动力学和生物表面活性剂产量。24小时后观察到培养基表面张力从70 mN/m降至32.6 mN/m。粗生物表面活性剂的产量记录为19.0 g/l，在优化生长参数后可能会进一步提高。经薄层色谱、傅里叶变换红外光谱和液相色谱-质谱分析，该生物表面活性剂被表征为同时含有内酯型和酸性型的异质槐糖脂（SL）。该槐糖脂对原油的油 spreading 活性和乳化活性分别为38.46 mm和100%。临界胶束浓度为130 mg/l。在较宽的pH范围（2 - 10）、盐度范围（2 - 10% NaCl）和温度范围（120°C下30至120分钟的时间间隔）内评估了槐糖脂的稳定性。发现该槐糖脂在极端条件下仍保留表面活性特性。此外，该槐糖脂对相当广泛的一组致病真菌，如胶孢炭疽菌、轮枝镰孢菌、尖孢镰刀菌豌豆专化型、瓜亡革菌和红色毛癣菌，表现出良好的抗真菌活性。
本研究首次报道了相对较少研究的巴氏红酵母产生生物表面活性剂的能力。槐糖脂在极端条件下持久的表面活性特性表明其适用于各种环境和工业领域。此外，对植物和人类病原体的抗真菌活性为开发具有农业和生物医学应用的高效且环保抗真菌剂开辟了可能性。
