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Microbial community dynamics of Dan'er barley grain during the industrial malting process
Xiaomin Li1, Guolin Cai1, Dianhui Wu1
1The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.
Abstract:
The microbes associated with barley grains are known to have either deleterious or beneficial effects on the malting process, thereby affecting the quality of malt and even beer. Dan'er barley is the major cultivar grown in Jiangsu Province in China, malt derived from this cultivar, however, invariably causes filtration problems. To understand the microbial community of Dan'er barley and its probable effects on malt quality and subsequent brewing process, the present study combined culture-dependent methods and culture-independent PCR denaturing gradient gel electrophoresis (PCR-DGGE) strategies. The results showed that as the dominant microbes, bacterial community structure varied considerably during the malting process, while the fungi load increased at the end of malting process, even in the kilning stage. The great abundance of gram-negative bacteria, which can produce exopolysaccharides and form biofilms, may be the main reason for the filtration defects of Dan'er malt. Pathogenic fungi may also have a negative impact on grain germination and malt nutritional value. Several beneficial lactic acid bacteria and fungi strains were also found. These results may contribute to our knowledge of barley grain-associated microbes, and help optimizing the malting process using the Dan'er barley cultivar to get malt product with better quality.
Insights
Microbial communities in Dan'er barley impact malting quality. High levels of gram-negative bacteria likely cause filtration issues in Dan'er malt, while beneficial microbes were also identified.
Area of Science:
- Agricultural Microbiology
- Food Science
- Brewing Science
Background:
- Barley grain microbes influence malting and beer quality.
- Dan'er barley, a major Chinese cultivar, exhibits filtration problems during malting.
- Understanding the microbial community is crucial for improving malt quality.
Purpose of the Study:
- To investigate the microbial community of Dan'er barley during malting.
- To identify microbes responsible for filtration defects in Dan'er malt.
- To assess the impact of microbes on malt quality and brewing.
Main Methods:
- Combined culture-dependent methods and PCR denaturing gradient gel electrophoresis (PCR-DGGE).
- Analyzed bacterial and fungal communities throughout the malting process.
- Identified dominant microbial groups and their characteristics.
Main Results:
- Bacterial community structure varied significantly during malting.
- Fungal load increased towards the end of malting and kilning.
- Abundant gram-negative bacteria, producing exopolysaccharides and biofilms, are linked to filtration defects.
- Pathogenic fungi may negatively affect germination and nutritional value.
- Beneficial lactic acid bacteria and fungi were also detected.
Conclusions:
- Gram-negative bacteria are implicated in the filtration problems of Dan'er malt.
- Microbial analysis provides insights into barley malting quality.
- Findings can guide process optimization for improved Dan'er malt production.