浓香型白酒窖泥放线菌的原位分离及代谢特性研究

以川南某浓香型白酒生产企业50年窖龄且发酵正常的窖泥为研究对象。通过高通量测序技术分析细菌群落结构以及放线菌群落结构,利用原位分离法从中分离得到2株放线菌,结合形态鉴定、生理生化和16S rRNA基因序列比对分析确定菌种属,并对其进行耐酸、耐乙醇特性研究,基于风味导向思路,分别对2株菌进行液态培养和固态培养,采用顶空固相微萃取法和气相色谱质谱联用对发酵挥发性产物进行分析,为放线菌的相关研究和应用提供理论参考。结果显示,放线菌在该窖泥样品含有较高操作分类单元(operational taxonomic unit,OTU),相对丰度达(10.7±3.4)%,且主要分布于链霉菌亚目(Streptomycineae)和科里氏杆菌亚目(Coriobacterineae)。采用原位分离法分离放线菌,将分离得到的2株菌编号为A1、A2,菌株A1鉴定为桑氏链霉菌(Streptomyces sampsonii),菌株A2鉴定为鲁地链霉菌(Streptomyces rutgersensis)。菌株A1、A2均可在pH>4.3或乙醇体积分数<6%的环境中生长。菌株A1在液态和固态发酵条件下都会产生大量土臭素以及萜烯类物质,菌株A2在液态条件下能产生多种酯类,其中己酸乙酯相对含量(5.384%)较高,而固态条件下能够检测出大量的3-羟基-2丁酮、2,3-丁二醇和吡嗪类物质。

In situ isolation and metabolic characteristics of actinomycetes from strong-flavor Baijiu pit mud

Taking a 50-year-old and well-fermented pit mud from a strong-flavor Baijiu production company in southern Sichuan as the research object,the bacterial and actinomycete community structure were analyzed by high-throughput sequencing technology.Two strains of actinomycetes were isolated from the pit mud by in situ cultivation.Combined morphological identification,physiological and biochemical results with 16S rRNA gene sequence analysis,the species of these two strains were determined.Then the characteristics of acid and ethanol resistance were studied.The two strains were cultured in both liquid and solid state.Headspace solid-phase micro-extractions and gas chromatography-mass spectrometry were used to analyze the volatile products of fermentation broth to provide theoretical reference for more research and application of actinomycetes.The results showed that the pit mud sample was rich in actinomycetes which accounted for(10.7±3.4)%and actinomycetes were mainly distributed in Streptomycineae and Coriobacterineae.The two isolated strains were numbered A1 and A2,strain A1 was identified as Streptomyces sampsonii,and strain A2 was identified as Streptomyces rutgersensis.Both strains could live in the environment with pH>4.3 or ethanol volume fraction<6%.Strain A1 produced lots of geosmin and terpene hydrocarbons under both liquid and solid fermentation conditions.Strain A2 produced a variety of esters under liquid culture conditions,of which ethyl caproate had a high relative content(5.384%),while a large amount of 3-hydroxy-2 butanone,2,3-butanediol and pyrazine could be detected under solid fermentation.