title: Biocontrol of geosmin-producing Streptomyces spp. by two Bacillus strains from Chinese liquor.
abstract: Streptomyces spp. producing geosmin have been regarded as the most frequent and serious microbial contamination causing earthy off-flavor in Chinese liquor. It is therefore necessary to control the Streptomyces community during liquor fermentation. Biological control, using the native microbiota present in liquor making, appears to be a better solution than chemical methods. The objective of this study was to isolate native microbiota antagonistic toward Streptomyces spp. and then to evaluate the possible action mode of the antagonists. Fourteen Bacillus strains isolated from different Daqu (the fermentation starter) showed antagonistic activity against Streptomyces sampsonii, which is one of the dominant geosmin producers. Bacillus subtilis 2-16 and Bacillus amyloliquefaciens 1-45 from Maotai Daqu significantly inhibited the growth of S. sampsonii by 57.8% and 84.3% respectively, and effectively prevented the geosmin production in the simulated fermentation experiments (inoculation ratio 1:1). To probe the biocontrol mode, the ability of strain 2-16 and 1-45 to produce antimicrobial metabolites and to reduce geosmin in the fermentation system was investigated. Antimicrobial substances were identified as lipopeptides by ultra-performance liquid chromatography tandem electrospray ionization/quadrupole-time-of-flight mass spectrometry (UPLC-ESI/Q-TOF MS) and in vitro antibiotic assay. In addition, strains 2-16 and 1-45 were able to remove 45% and 15% of the geosmin respectively in the simulated solid-state fermentation. This study highlighted the potential of biocontrol, and how the use of native Bacillus species in Daqu could provide an eco-friendly method to prevent growth of Streptomyces spp. and geosmin contamination in Chinese liquor fermentation.
authors.affiliation: State Key Laboratory of Food Science and Technology, The Key Laboratory of Industrial Biotechnology, Ministry of Education, Synergetic Innovation Center of Food Safety and Nutrition, School of Biotechnology, Jiangnan University, 1800 Lihu Ave., Wuxi, Jiangsu 214122, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhi
authors.affiliation: State Key Laboratory of Food Science and Technology, The Key Laboratory of Industrial Biotechnology, Ministry of Education, Synergetic Innovation Center of Food Safety and Nutrition, School of Biotechnology, Jiangnan University, 1800 Lihu Ave., Wuxi, Jiangsu 214122, China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Food Science and Technology, The Key Laboratory of Industrial Biotechnology, Ministry of Education, Synergetic Innovation Center of Food Safety and Nutrition, School of Biotechnology, Jiangnan University, 1800 Lihu Ave., Wuxi, Jiangsu 214122, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Du
authors.affiliation: State Key Laboratory of Food Science and Technology, The Key Laboratory of Industrial Biotechnology, Ministry of Education, Synergetic Innovation Center of Food Safety and Nutrition, School of Biotechnology, Jiangnan University, 1800 Lihu Ave., Wuxi, Jiangsu 214122, China. Electronic address: yxu@jiangnan.edu.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000434:Alcoholic Beverages / Q000382:microbiology; D005285:Fermentation; D005421:Flavoring Agents / Q000378:metabolism; D005516:Food Microbiology; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D009284:Naphthols / Q000737:chemistry / Q000378:metabolism*; D013302:Streptomyces / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism; D013649:Taste
chemical_list: D005421:Flavoring Agents; D009284:Naphthols; C001278:geosmin
keywords: Bacillus; Biocontrol; Chinese liquor; Geosmin; Lipopeptides; Streptomyces