Characterization of microbial communities in industrial malting to enhance malt processing quality

Description of topic - Optimization of malt quality in terms of fast filtration is a critical factor in the malting and brewing industry. Since malt quality is inversely related to the concentration of endosperm cell wall components, management of cell wall degrading microorganisms may result in enhanced processing. An essential step in microflora management during malting, however, requires the understanding of the microbial community structure as well as the population dynamics in the processing. Although most studies undertaken so far focus on specific microbial populations using culture-dependent techniques, in this study an integrated approach of different technologies for microbial community profiling is presented as a basis for process optimization. Materials and methods - Both culture dependent and culture independent molecular techniques will be used to characterize the microbial (bacterial) communities in different industrial malting settings, generating malt of different quality. 16S ribosomal DNA-targeted Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis, supported by sequencing of clone libraries, will be used to screen and compare the microbial communities in the different maltings at different stages of the malting process, i.e. from barley up to kilned malt. In addition, the microflora present in used irrigation water and the air will be monitored. Specific patterns associated with high-quality malt will be further investigated, aiming at obtaining cultures responsible for the malt quality. Subsequently, promising bacterial strains will be screened for their cell wall degrading capacity using agar plate assays. Finally, one or more bacterial strains will be selected to evaluate their performance in practice using inoculation trials on a representative pilot scale malting facility. In addition, based on an off line closed-circuit perfusion approach, efforts will be made to manage the microbial community in such a way that desired populations will be stimulated and can be re-inoculated in the process. Novelty - With the increased demand for ‘clean-label’ technology, the malting and brewing industry is seeking for novel approaches to optimize the use of in-house microflora in the malting process. This study may result in the discovery of promising, process-borne microorganisms which may enhance malt processability, or the malting and brewing process in general. Most presumably, this research will reveal previously unidentified species as novel detection technologies will be used to unravel the microbial communities. Altogether, this project might be the basis for further process optimization such as the improvement of the filtration step.status: publishe