酱香型酒醅中一株曲霉的鉴定及生物学特性分析

Identification and biological characteristics of a Aspergillus strain in Maotai flavored fermented grains

本研究以乳酸为唯一碳源,从酱香型酒醅中筛选能够利用乳酸的霉菌,根据菌株的菌落特征、菌丝形态及18S rDNA的分子生物学特性对菌株进行鉴定,以透明圈法检测糖化酶等7种胞外酶产生能力,检测菌株对温度、乳酸及乙醇的耐受性,用GC-MS测定菌株的发酵产物。从酱香型酒醅中筛选得到一株霉菌JP7,该霉菌菌落上呈现1种以上颜色,中部为黄色,边缘为灰白色,在显微镜下能观察到曲霉特征的菊花状分生孢子头。基于18S rDNA的系统发育分析,该菌属于杂色曲霉(Aspergillus versicolor,A. versicolor)。A. versicolor JP7具有产纤维素酶的能力,在改良YP培养基上形成的透明圈与菌落直径比为5。A. versicolor JP7对乳酸的耐受性较高,可达到50 g/L。在以乳酸为唯一碳源的发酵培养基中,A. versicolor JP7利用乳酸主要产生7种代谢产物,其中1,2-丙二醇和n-己烷的产量最高。分离自酱香型酒醅中的A. versicolor JP7具有较强的纤维素酶产生能力和较强的乳酸耐受性,利用乳酸能够产生工业原料1,2-丙二醇和n-己烷。

In this study,using lactic acid as the sole carbon source,the moulds capable of utilizing lactic acid were screened from Maotai-flavor fermented grains.These strains were identified according to their colony characteristics,mycelial morphology and molecular biology characteristics of 18 S rDNA.The production ability of glucoamylase and 7 extracellular enzymes was detected by transparent ring method.The tolerance of strains to temperature,lactic acid and ethanol were tested,and the fermentation products of strains were determined by GC-MS.A mould numbered JP7 was screened from Maotai-flavor fermented grains.The mould colony showed more than one color,with yellow in the middle and gray on the edge.The chrysanthemum-like conidium head with Aspergillus characteristics could be observed under the microscope.Based on phylogenetic analysis of 18 S rDNA,the strain belonged to Aspergillus versicolo.A.versicolor JP7 had the ability to produce cellulase,and the ratio of transparent circle to colony diameter on modified YP medium was 5.A.versicolor JP7 had a high tolerance to lactic acid,up to 50 g/L.In the fermentation medium with lactic acid as the sole carbon source,A.versicolor JP7 mainly produced seven kinds of metabolites from lactic acid,among which the yield of1,2-propylene glycol and hexane was the highest.A.versicolor JP7 isolated from Maotai-flavor fermented grains had strong cellulase production capacity and high lactic acid tolerance.Lactic acid could be used to produce industrial raw materials1,2-propylene glycol and n-hexane.