云南野生食用牛肝菌对重金属镉、铅、汞的生物富集作用及其机理研究

Yunnan province is of the highest edible mushroom resources in China. Wild edible boletes is a kind of agricultural and forestry products with high yield for export in Yunnan, and amounted to 339 millions of US dollars was exported in 2010. Many wild edible mushroom species are known to accumulate high levels of cadmium, lead, and mercury. Some countries have established statutory limits for the detrimental metals in edible mushrooms. The levels of cadmium, lead, and mercury in some wild edible Boletus species from Yunnan were beyond the statuory limits, and the levels were related with substrate contamination. This project will collect the wild edible boletes samples from Yunnan, determine the levels of cadmium, lead, and mercury in the samples, and investigae the bioconcentration factors of each metal by the samples and the bioconcentration mechnisams. This project focus on three objectives: (1) to collect the fresh wild edible boletes samples from fields in Yunnan province, determine the levels of cadmium, lead, and mercury in the samples, and carry out the health risk assessments; (2) simultaneously with the mushrooms, to collect the soil samples at appropriate sampling place, determine the levels of cadmium, lead, and mercury in the soil samples, caculate the bioconcentration factor (BCF) of each metals, and analysis the relationships between the substrate contamination and BCF; (3) for each metal, to screen one or two Boletus species with both of the high metal level and the high BCF, carry out the fermentation of the selected Boletus species in labroray, and investigate the bioconcentration mechnisams of the selected Boletus species to the three detrimental metals. The present project will provide the scientific basis for the control of food safety and quanlity. Furthermore, the research will provide the theoretical basis for the development of macrofungi as biological agents for the restore of environmental contamination.

野生食用牛肝菌是云南大宗出口农产品，2010年出口产值339万美元，但是在贸易中存在重金属镉、铅、汞超标问题。云南矿藏丰富，环境中重金属基底浓度较高，影响了牛肝菌中重金属含量。本课题以云南野生食用牛肝菌为对象，研究其对重金属镉、铅、汞的生物富集作用及机理，包括：（1）测定各地采集的野生食用牛肝菌样品中镉、铅、汞的含量，评价其食品安全性；（2）对应采集牛肝菌样品的生长基质，测定基质中镉、铅、汞含量，以BCF值为指标分析牛肝菌样品对三种元素的生物富集作用，阐明该作用与环境污染的相关性；（3）筛选具有高富集能力的牛肝菌品种，进行实验室可控条件下的菌丝体培养，从生物吸附机制、在菌体内的赋存形态、菌体的解毒功能和抗性体系四个方面研究其对三种重金属元素的生物富集机理。该研究为云南野生食用牛肝菌食品安全与质量控制提供科学依据；同时，为探索高富集能力菌种作为生物治污剂提供一定的理论基础。

对云南省野生牛肝菌主要产区进行了大量样本的采样，2014～2015年采集野生食用牛肝菌11种356个样本。在野生食用牛肝菌重金属含量水平、食品安全评价及影响因素方面：测定了样本中镉、铅、汞的含量水平，进行食品安全性评价和食用风险评估，发现镉总量水平超国家标准限量的比例较高，可能是云南野生食用牛肝菌主要食品安全风险因素。对应收集了菌体样本的基质土壤，测定了土壤中镉、铅、汞的含量水平及pH等理化性质，对样本中镉元素含量与土壤元素含量及pH之间的线性关系进行考察，通过统计分析，评价了野生食用牛肝菌对镉、铅、汞的生物富集能力，分析了生长基质和环境污染对样本富集相关重金属的影响，发现野生食用牛肝菌对三种重金属的富集作用与种属和环境污染密切相关。采用全仿生消化模型评价镉元素高富集能力菌体中镉元素的生物利用率，进一步精确评价具体食用健康风险。在野生食用牛肝菌对重金属生物富集机制方面：采用Tessier五步连续提取和累进蛋白质组分分离，测定样本中镉元素在交换态、结合态的含量及生物吸附；对不同类型蛋白质组分中重金属含量进行分析，进一步对含重金属较高的蛋白质进行分离纯化，探索了野生食用牛肝菌体内对镉元素发挥富集能力的物质基础；对美味牛肝菌进行菌丝发酵，研究了实验室可控条件下美味牛肝菌对镉元素的生物富集作用及耐受机制。