窖泥己酸菌是重要的窖泥产酸功能菌，所生成的己酸是生产浓香型白酒主体香气己酸乙酯的主要成分，将其应用于白酒的生产，可提高白酒的香气和质量。本研究从赊店老酒不同窖池的窖泥和黄水中筛选产己酸菌株并进行分离纯化，通过硫酸铜显色及气相色谱分析检测，初筛从118株菌株中获得了96株可产生己酸和丁酸的菌株，大部分为兼性厌氧型菌株。其中10株高产己酸菌经分子鉴定属于赖氨酸芽孢杆菌属（Lysinibacillus），芽孢杆菌属（Bacillus），拉梅尔芽胞杆菌属（Rummeliibacillus），寡养单胞菌属（Stenotrophomonas），棒杆菌属（Corynebacterium）。己酸菌拮抗对峙实验结果表明10个菌株之间均无拮抗作用，可以进行混合培养。培养基中乙酸钠浓度从0.5%增加到1.0%时，产物中丁酸和己酸的总酸量最高，超过1.5%时己酸和丁酸的总量反而下降。74%的菌株在厌氧条件下产总酸量要高于好氧条件下产总酸量，厌氧条件下63%的菌株在30 ℃时产总酸量高于37 ℃时的产酸量。5株高产己酸菌在18 d发酵过程中菌浓度随着培养时间而逐渐增加，丁酸在发酵中期达到高峰并逐渐下降，己酸在发酵后期逐渐累积，产量最高达到3 g/L。

Caproic acid-producing bacteria represent important acid-producing functional bacteria in pit mud. The generated hexanoic acid is the major component of ethyl caproate, which confers the characteristic aroma of Luzhou flavored liquor, and its application in liquor production may improve the aroma and quality. Here, caproic acid-producing bacterial strains were screened and purified from the pit mud and yellow water of different Shedian Laojiu cellars. Through copper sulfate color development and gas chromatographic detection, 96 caproic acid- and butyric acid-producing strains were screened from 118 strains, majority of which were facultative anaerobic bacteria. Moreover, using 16S rRNA sequencing, 10 microbial strains, including Lysinibacillus, Bacillus, Rummeliibacillus, Stenotrophomonas, and Corynebacterium, were identified. Antagonistic confrontation assay of these caproic acid-producing bacteria revealed no antagonistic effects among the 10 strains, indicating the feasibility of mixed culture. When sodium acetate concentration in the medium was increased from 0.5% to 1.0%, the total amount of butyric and caproic acid in the product was the highest. However, the total amount of caproic and butyric acid decreased when sodium acetate concentration exceeded 1.5%. Moreover, 74% of the strains produced more total acid under anaerobic conditions than under aerobic conditions, and 63% of the strains produced more total acid at 30℃ than at 37℃ under anaerobic conditions. During the 18-day fermentation process of five caproic acid-producing strains, bacterial cell concentration gradually increased with culture time. Butyric acid level peaked at the middle of fermentation, followed by a gradual decrease; however, caproic acid accumulated gradually at the later stages of fermentation, with the peak yield reaching 3 g/L.

河南省科技攻关项目（202102310022）