Microbes in the tailoring of barley malt properties

Malted barley (malt) is traditionally used in the production of beer and distilled spirits. In addition, it can be processed into ingredients for different areas of the food industry. Malting, the controlled germination of cereal grains, is a complex biological process involving a wide range of biochemical and physiological reactions. The diverse microbial communities naturally colonizing barley grains play a crucial role in this process. Therefore, the malting process can be considered as an ecosystem involving two metabolically active groups: the germinating grains and the diverse microbiota. It is evident that the multitude of microbes greatly influences the malting process as well as the quality of the final product. The main goal of this thesis was to study the relationships between microbes and the germinating grain during the malting process. Furthemore, this study provides a basis for tailoring of malt properties with natural, malt-derived microbes. The results of this study showed that the malting ecosystem is indeed a dynamic process and exhibits continuous change. Microbes embedded in biofilms within the husk tissues were well protected. Reduction of one population within the complex ecosystem led to an increase in competing microbes. This should be taken into account when changes are made in the malting process. Using different molecular approaches we also found that the diversity of microbes in malting was much greater than previously anticipated. Some potentially novel bacterial and fungal species were found in the malting ecosystem. The microbial communities greatly influenced grain germination and malt properties. By suppressing Gram-negative bacteria during steeping, barley vitality and malt brewhouse performance were improved even in the case of good-quality malting barley. The fungal community consisting of both yeasts