土味素是链霉菌属的特征挥发性代谢产物,在痕量级别(阈值在ng/L水平)会引起泥土异味,严重破坏中国白酒的风味与品质。大曲制造过程中含水量随时间下降,制曲后期含水量约为10%时,可检测到约为6 μg/kg的土味素,严重影响大曲的质量。从大曲中筛选在低含水量条件下抑制土味素产生的功能微生物用于生物防治是提升大曲质量的必要手段。该研究对中温大曲中的微生物群落结构和土味素含量进行分析,并筛选能够抑制土味素的原位功能微生物。研究结果表明,制曲后期,含水量下降至10%~20%,土味素含量仍在上升,达到最高质量分数(9.75±0.50) μg/kg。大曲中主要的真菌为毕赤酵母属(Pichia)、嗜热子囊菌属(Thermoascus)等。基于Spearman等级相关性分析筛选出了6株对链霉菌有较好抑制作用的真菌Aspergillus sp.LBM32010、Aspergillus sp.LBM32013、Rhizopus sp.LBM32021、Trichosporon sp.LBM32022、Lichtheimia sp.LBM32026和Trichosporon sp.LBM32030,其中Aspergillus sp.LBM32010对土味素的抑制效果最好,在模拟实验中发现土味素含量从(34.79±2.34) μg/kg下降至(3.11±1.22) μg/kg,抑制率为91.06%(P<0.001)。该研究发现了大曲中原位微生物对痕量级别挥发性有机物具有防治的潜力,可通过靶向调控微生物群落解决大曲中土味素污染问题。
Geosmin is a volatile metabolite of Streptomyces spp., which causes earthy off-flavor at trace level content (the threshold is at ng/L level), seriously and extensively deteriorating the flavor and quality of Chinese Baijiu. The water content in Daqu (Chinese Baijiu fermentation starter)-making process decreased with time. When the water content was about 10% in the late stage, about 6 μg/kg of geosmin could be detected, which seriously affected the quality of Daqu. Screening of functional microorganisms from Daqu that inhibit the production of geosmin under low water content conditions for biocontrol is a necessary mean to improve the quality of Daqu. In this study, the microbial community structure and the geosmin content in Daqu were analyzed, and obtained the in situ functional microorganisms of Daqu according to the inhibition of Streptomyces. The results showed that in the late stage of Daqu-making, the water content decreased to 10%-20%, and the geosmin content was still increasing, reaching the highest content of (9.75±0.50) μg/kg. The main fungi in Daqu were Pichia, Thermoascus. Based on Spearman’s correlation analysis, it was found that Aspergillus sp. LBM32010, Aspergillus sp. LBM32013, Rhizopus sp. LBM32021, Trichosporon sp. LBM32022, Lichtheimia sp. LBM32026 and Trichosporon sp. LBM32030 have good inhibitory effects on Streptomyces and geosmin, among which Aspergillus sp. LBM32010 had the best inhibitory effect on geosmin, and geosmin content decreased from (34.79±2.34) μg/kg to (3.11±1.22) μg/kg, and the inhibition rate was 91.06% (P<0.001). This study highlights the biocontrol feasibility potential of the chemicals at trace level by precise regulation of microbial communities, and shows the possibility of achieving precise regulation of microbial communities.
[1] MCCRUMMEN S T, WANG Y F, HANSON T R, et al.Culture environment and the odorous volatile compounds present in pond-raised channel catfish (Ictalurus punctatus)[J].Aquaculture International, 2018, 26(2):685-694.
[2] MORALES-VALLE H, SILVA L C, PATERSON R R M, et al.Microextraction and gas chromatography/mass spectrometry for improved analysis of geosmin and other fungal “off” volatiles in grape juice[J].Journal of Microbiological Methods, 2010, 83(1):48-52.
[3] JOVÉ P, VIVES-MESTRES M, DE NADAL R, et al.Development, optimization and validation of a sustainable and quantifiable methodology for the determination of 2, 4, 6-trichloroanisole, 2, 3, 4, 6-tetrachloroanisole, 2, 4, 6-tribromoanisole, pentachloroanisole, 2-methylisoborneole and geosmin in air[J].Processes, 2021, 9(9):1 571.
[4] ZHI Y, WU Q, DU H, et al.Biocontrol of geosmin-producing Streptomyces spp.by two Bacillus strains from Chinese liquor[J].International Journal of Food Microbiology, 2016, 231:1-9.
[5] DU H, XU Y.Determination of the microbial origin of geosmin in Chinese liquor[J].Journal of Agricultural and Food Chemistry, 2012, 60(9):2 288-2 292.
[6] GERBER N N, LECHEVALIER H A.Geosmin, an earthly-smelling substance isolated from actinomycetes[J].Applied Microbiology, 1965, 13(6):935-938.
[7] OMÜR-OZBEK P, LITTLE J C, DIETRICH A M.Ability of humans to smell geosmin, 2-MIB and nonadienal in indoor air when using contaminated drinking water[J].Water Science and Technology:a Journal of the International Association on Water Pollution Research, 2007, 55(5):249-256.
[8] LIATO V, AÏDER M.Geosmin as a source of the earthy-musty smell in fruits, vegetables and water:Origins, impact on foods and water, and review of the removing techniques[J].Chemosphere, 2017, 181:9-18.
[9] XUE Q, SHIMIZU K, SAKHARKAR M K, et al.Geosmin degradation by seasonal biofilm from a biological treatment facility[J].Environmental Science and Pollution Research International, 2012, 19(3):700-707.
[10] SONG J K, TANG H L, LIANG H B, et al.Effect of bioaugmentation on biochemical characterisation and microbial communities in Daqu using Bacillus, Saccharomycopsis and Absidia[J].International Journal of Food Science & Technology, 2019, 54(8):2 639-2 651.
[11] DU H, WANG X S, ZHANG Y H, et al.Exploring the impacts of raw materials and environments on the microbiota in Chinese Daqu starter[J].International Journal of Food Microbiology, 2019, 297:32-40.
[12] DU H, LU H, XU Y, et al.Community of environmental Streptomyces related to geosmin development in Chinese liquors[J].Journal of Agricultural and Food Chemistry, 2013, 61(6):1 343-1 348.
[13] HE G Q, DONG Y, HUANG J, et al.Alteration of microbial community for improving flavor character of Daqu by inoculation with Bacillus velezensis and Bacillus subtilis[J].LWT, 2019, 111:1-8.
[14] DU H, LU H, XU Y.Influence of geosmin-producing Streptomyces on the growth and volatile metabolites of yeasts during Chinese liquor fermentation[J].Journal of Agricultural and Food Chemistry, 2015, 63(1):290-296.
[15] DU H, FAN W L, XU Y.Characterization of geosmin as source of earthy odor in different aroma type Chinese liquors[J].Journal of Agricultural and Food Chemistry, 2011, 59(15):8 331-8 337.
[16] SELLITTO V M, ZARA S, FRACCHETTI F, et al.Microbial biocontrol as an alternative to synthetic fungicides:Boundaries between pre- and postharvest applications on vegetables and fruits[J].Fermentation, 2021, 7(2):60.
[17] BRANCO P, SABIR F, DINIZ M, et al.Biocontrol of Brettanomyces/Dekkera bruxellensis in alcoholic fermentations using saccharomycin-overproducing Saccharomyces cerevisiae strains[J].Applied Microbiology and Biotechnology, 2019, 103(7):3 073-3 083.
[18] ZHANG H X, DU H, XU Y.Volatile organic compound-mediated antifungal activity of Pichia spp.and its effect on the metabolic profiles of fermentation communities[J].Applied and Environmental Microbiology, 2021, 87(9):e02992-e02920.
[19] FIORI S, URGEGHE P P, HAMMAMI W, et al.Biocontrol activity of four non- and low-fermenting yeast strains against Aspergillus carbonarius and their ability to remove ochratoxin A from grape juice[J].International Journal of Food Microbiology, 2014, 189:45-50.
[20] DU R B, LIU J, JIANG J, et al.Construction of a synthetic microbial community for the biosynthesis of volatile sulfur compound by multi-module division of labor[J].Food Chemistry, 2021, 347:129036.
[21] SONG Z W, DU H, ZHANG Y, et al.Unraveling core functional microbiota in traditional solid-state fermentation by high-throughput amplicons and metatranscriptomics sequencing[J].Frontiers in Microbiology, 2017, 8:1294.
[22] 周天慈. 基于高通量测序技术定量解析核心真菌群落的形成机制[D].无锡:江南大学, 2021.
ZHOU T C.Analyzing quantitatively the formation mechanism of Daqu core fungal community based on high-throughput sequencing technology[D].Wuxi:Jiangnan University, 2021.
[23] 杜海. 产土味素菌群对白酒酿造的影响机制及监测控制[D].无锡:江南大学, 2013.
DU H.The influence mechanism of geosmin-producing microflora on Chinese liquor brewing and its monitoring&controling[D].Wuxi:Jiangnan University, 2013.
[24] WANG X S, DU H, ZHANG Y, et al.Environmental microbiota drives microbial succession and metabolic profiles during Chinese liquor fermentation[J].Applied and Environmental Microbiology, 2018, 84(4):e02369-e02317.
[25] MCCLENDON S D, BATTH T, PETZOLD C J, et al.Thermoascus aurantiacus is a promising source of enzymes for biomass deconstruction under thermophilic conditions[J].Biotechnology for Biofuels, 2012, 5(1):54.
