胶红酵母控制苹果展青霉素产生与降解的生理机制研究

Patulin is a toxic fungal secondary metabolite, and is one of the mycotoxins that can cause the most serious health problems. Patulin has been identified in various fruits and fruit products throughout the world, especially in apples and apple products. Controlling patulin on fruits using antagonistic yeasts has represented a promising future, but the researches are just beginning, especially the mechanisms of controlling patulin synthesizing and biodegradation on apples by antagonistic yeast is unclear yet, which seriously affect the application of biological technology on controlling mycotoxins on postharvest fruits. In this study, a Rhodotorula mucilaginosa strain which was isolated by our research team is selected to be the model strain. The primary object of this study was to figure out the mechanisms of controlling synthesizing and biodegradation of patulin by antagonistic yeast, and determine (1) the control efficacy of the growth of Penicillium expansum and patulin synthesizing by R. mucilaginosa in vitro test; (2) the action mode of biodegradation of patulin by R.mucilaginosa; (3) the physiological mechanisms of controlling the growth of P. expansum and patulin synthesizing on apples by R. mucilaginosa. The research results will be expected to raise new idea on the physiological mechanisms of controlling and biodegradation of patulin on fruits by antagonistic yeast, which can promote the application of biological technology on controlling mycotoxins in postharvest fruits.

展青霉素是一种有毒的真菌次生代谢产物，是对人类危害最大的霉菌毒素之一。展青霉素对水果及水果制品的污染在全球范围内都比较严重，尤其是苹果及其制品。采用拮抗酵母控制水果上的展青霉素展现出良好的应用前景，但相关研究目前尚处于起步阶段，特别是拮抗酵母控制水果上的展青霉素的产生及降解已经存在的展青霉素的机制尚不明确，这严重影响了生物防治技术在水果采后霉菌毒素控制方面的应用。本项目拟以课题组前期筛选分离到的胶红酵母为模式菌株，从离体培养（In vitro）条件下胶红酵母对扩展青霉生长和产展青霉素的影响、胶红酵母降解展青霉素的机制、胶红酵母防治苹果扩展青霉生长及展青霉素产生的生理机制三个方面，阐明拮抗酵母控制苹果展青霉素产生与降解的生理机制。研究成果可望在阐明拮抗酵母控制苹果展青霉素产生与降解的生理机制方面产生新的理论依据，并为拮抗酵母控制水果及其制品中展青霉素的实际应用提供理论支撑。

展青霉素一种是由扩展青霉等水果致腐霉菌产生的真菌毒素,其在水果及其制品中的污染会严重危害食用者的健康,特别是对儿童的健康有严重影响。采用拮抗酵母控制水果上的展青霉素展现出良好的应用前景，但相关研究目前尚处于起步阶段，特别是拮抗酵母控制水果上的展青霉素的产生及降解已经存在的展青霉素的机制尚不明确，这严重影响了生物防治技术在水果采后霉菌毒素控制方面的应用。因此,本课题以胶红酵母和卡利比克毕赤酵母为模式菌株，研究了胶红酵母和卡利比克毕赤酵母对苹果由扩展青霉引起的青霉病和自然腐烂的防治效果，对展青霉素的控制效果，防治苹果采后病害的机制以及对展青霉素控制及降解的机制。课题的研究结果表明，胶红酵母和卡利比克毕赤酵母可有效地控制苹果青霉病及自然腐烂。拮抗酵母主要通过对致病菌营养与空间的竞争，诱导宿主抗病相关的酶活来抑制病原菌的生长从而达到控制水果采后病害的效果。两种拮抗酵母还可以有效地控制苹果伤口处展青霉素的含量，其机制与拮抗酵母抑制扩展青霉在水果伤口处的生长有关。体外试验结果表明，卡利比克毕赤酵母可以降解展青霉素，其机制为：在展青霉素存在的情况下，诱导拮抗酵母相关基因的表达，从而产生与降解功能相关的酶类（胞外酶和胞内酶），这些酶起到降解展青霉素的作用。上述研究结果为拮抗酵母控制水果展青霉素提供了理论支持。