云南西双版纳热带雨林腐木中木糖发酵酵母菌多样性研究

Xylose-fermenting yeasts may have great potential in the cellulosic ethanol industry due to their ability to ferment xylose into ethanol. Rotten wood is an important source of novel yeasts. However, it is still very limited to understand the diversity of xylose-fermenting yeasts associated with rotten wood. Therefore, the rotten wood which is the most abundant in the Xishuangbanna Tropical Rainforest of Yunnan is chosen as the research project, we collect various rotten wood samples from different places in the Xishuangbanna Tropical Rainforest of Yunnan. A large number of xylose-fermenting yeasts are isolated from rotten wood samples and then preserved by using novel cultivation strategies. The isolates are preliminarily grouped according to their colony morphology and microsatellite-primed PCR fingerprints. Phylogenetic position of each group is determined based on sequence analyses of the D1/D2 domains of 26S rDNA, ITS and 18S rDNA. Among them, the new taxa are systematically investigated. The novel xylose-fermenting yeasts with excellent traits will obtain by screening their enzyme activity and determining their physiological characteristics. This research will reveal the distribution and diversity of yeasts associated with rotten wood, and obtain various kinds of yeasts with different physiological function, especially xylose-fermenting or inhibitor-tolerant yeasts. These results will provide science basis for studying molecular systematics of yeasts and for efficient utilization of xylose-fermenting yeasts to produce bioethanol.

木糖发酵酵母菌在纤维乙醇工业中具有潜在的应用价值。腐木是木糖发酵酵母菌新种多样性的重要来源。本项目选择云南西双版纳热带雨林拥有大量腐木样品为研究对象，从热带雨林不同地点大量采集不同种类的腐木样品。采用多样化培养策略，分离和保藏各种木糖发酵酵母菌株。依据形态学特征和MSP-PCR指纹图谱分析，对大样本多来源的分离菌株进行初步归类。在此基础上，使用26S rDNA D1/D2 区域、ITS和18S rDNA等序列对代表菌株进行分子系统学研究，确定木糖发酵酵母菌株的系统发育地位，发现并系统鉴定新的酵母菌类群。通过酶活性筛选和生理生化特性分析，获得具有潜在应用价的酵母菌新菌种。本项目将揭示腐木中木糖发酵酵母菌遗传多样性、物种多样性和生理功能多样性，获得具有不同生理功能尤其是可以发酵木糖和可以耐受抑制物的酵母菌菌株。研究成果将为酵母菌分子系统学研究及高效利用木糖发酵酵母菌生产生物乙醇提供科学依据。

木糖发酵酵母菌在纤维乙醇工业中具有潜在的应用价值。腐木是木糖发酵酵母菌新种多样性的重要来源。本项目选择云南西双版纳热带雨林拥有大量腐木样品为研究对象，研究腐木中木糖发酵酵母菌的多样性，研究成果体现在以下几个方面：（1）从西双版纳热带雨林腐木中分离酵母菌960株，分属51个属155个不同的分类单元。Apiotrichum、Candida、Barnettozyma、Cyberlindnera、Debaryomyces、Geotrichum、Pichia、Sugiyamaella、Wickerhamomyces和Vanrija为优势属，其中Candida属优势度最高，其次是Sugiyamaella属。腐木中酵母菌种类较多、丰度较高、多样性丰富。（2）从西双版纳热带雨林腐木中分离获得17属30个新种，其中木糖发酵酵母菌新种7个。腐木是木糖发酵酵母菌新种的重要来源。（3）对30个潜在新类群进行系统鉴定，规范描述并有效发表新种16个，包括Candida yunnanensis、Candida parablackwelliae、Cyberlindnera xishuangbannaensis、Deakozyma yunnanensis、Kazachstania jinghongensis、Kodamaea neixiangensis、Kazachstania menglunensis、Ogataea neixiangensis、Nematodospora anomalae、Pichia nanzhaoensis、Pichia paraexigua、Sugiyamaella xiaguanensis、Saturnispora galanensis和 Vanrija jinghongensis等。通过对Scheffersomyces、Spathaspora和Lodderomyces分支等进行分子系统学研究，修正部分种系统发育地位，另有Scheffersomyces、Spathaspora、Sugiyamaella 和 Saturnispora等属新种14个，正在描述与准备过程中，以后将陆续发表。（4）通过木糖发酵性能测定和抑制物耐受性分析，发现腐木中分离得到木糖发酵酵母菌对糠醛、乙酸等抑制物具有较好的耐受性，获得可以发酵木糖和可以耐受抑制物的优良酵母菌新菌种2个。