RESEARCH GROUP BEVERAGE BIOTECHNOLOGY
Group Leader: Dipl.-Ing. Roland Kerpes
The research topics of the workgroup are the functionality of biomolecules, biotechnology and microbiology in the area of beverages an cereals focusing on the fermentation technology. New research areas are the use of recombinant microorganism for the expression of beverage-relevant proteins, the kinetic analysis of malt peptidases, the age-dependent fractionation of singular yeast cells, the influence of exogenous stressors on yeast and the application of microorganism in the juice segment. Our comprehensive equipment concerning the performance of cereal- and beverage-related analysis in the area of microbiology, molecular biotechnology and genetics can be found under the link S1-laboratory and microbiology.
Komagataella phaffii for Enhanced Protein Production
The methylotrophic yeast Komagataella phaffii (commonly known as Pichia pastoris) is renowned for its ability to support high cell-density growth and exhibit a high secretory capacity, making it a favored organism for heterologous protein production. Unlike other yeasts, K. phaffii boasts tightly regulated, methanol-inducible promoters and glycosylation pathway to mimic the mammalian system. The optimisation of K. phaffii cultivation is still necessary due to strain- and product-specifc problems such as promoter strength, methanol utilisation type and culturing conditions to realize the high yields of heterologous protein of interest (POI).In this project, we are focusing on the production yeast expression system platform. Our approach includes diverse genetic engineering, co-expression of chaperones, and comprehensive transcriptional analyses, shedding light on the molecular mechanisms underlying optimized protein production.
As POIs, we intend to utilize eGFP as a model protein, proteinase A for subsequent application in brewing technology, specifically for evaluating beer foam stability, and PETase for the eco-friendly decomposition of PET waste.
Detection of mold spores harmful to fruit juice (01IF23311N)
Heat-resistant germs occur naturally ubiquitously in the soil and especially in vineyards and orchards. These include microorganisms from the genera Byssochlamys, Neosartorya, Talaromyces, Eupenicillium and Eurotium, which classically attack the (over-)ripe fruit in the field. The germs themselves are killed during further processing by pasteurization or hot filling. The problem with these primary contaminants does not lie in their vegetative form, but rather begins with sporulation. Classic preservation is ineffective here; On the contrary, the heat activates the spores, which germinate in the finished, apparently preserved drink and can spoil it.
The research project is developing a method that uses fluorescence-labeled protein linkers to enable the selective enrichment and detection of heat-resistant spores that damage fruit juice in minutes. In addition, a multiplex PCR is to be developed that assigns the sporulating organism from the suspension to heat-resistant mold genera or species.
The method enables the beverage industry - with a focus on SMEs - to quickly expand its quality assurance and ensure product quality using mostly already established laboratory equipment.
Microfluidic fractionation of a heterogeneous yeast cell culture for analysis of age-dependent population dynamics
The yeast metabolism reacts sensitively to abiotic and biotic stressors, whereby the fermentation process depends essentially on how the sum of the physiological states of the individual cells affects the overall behavior of the yeast culture (viability and vitality). This physiological state is inhomogeneous in yeast cell cultures and depends on the age of the singular cell. The aim of the study is therefore the targeted fractionation of yeast cell populations of different ages, which allows a deeper analysis of the effect of age-dependent metabolism on fermentation performance.
The de-novo synthesis of malt peptidases represents the basic biochemical step of the germination process. The hereby mainly involved peptidases have not been sufficiently investigated from a brewing science perspective and the impact on the final product (beer) is not known. The scope of this research is the kinetic investigation on the endo- and exopeptidases involved in the malting and brewing process and their impact on proteolytic substrates such as gluten.
The detection of gluten in food is carried out via an antibody mediated standard analysis, the ELISA. Due to the currently used reference materials, the detection method is susceptible to over- and under-estimation of gluten contents of food. These reference materials consist of a mixture of wheat, barley and rye proteins and are used globally to determine gluten content of each food independent of its composition. The use of recombinant reference materials produced in yeast can improve the reproducibility and thus the reliability of gluten analyses.
The technique CRISPR / Cas9 was developed from the naturally occurring bacterial immune system. It enables the targeted cutting of genes in living cells. This makes it possible to selectively knock out individual target genes of interest. Thus, this technique makes it possible to elucidate the molecular-biological basics of aroma formation in yeast under industrial fermentation conditions or the flocculation behaviour of yeast.
Besides the improvement of the fermentation performance of classical fermentation using Saccharomyces cerevisiae sp. the focus is put on modern biotechnological fermentations using recombinant strains of Escherichia coli and Pichia pastoris. These strains serve as host organisms for the production of recombinant proteins, whose application lies in the area of beverage and cereal biotechnology. Further information regarding the existing equipment can be obtained from the link S1-Laboratory.
The purification of proteins can be realized in different ways. The most used technique is fast protein liquid chromatography, which does among other things include metal ion affinity chromatography (IMAC) for purification of recombinant proteins. Wild type organism proteins are stepwise purified using ion exchange (IEX) and hydrophobic interaction (HIC) chromatography to reach highest degree of purity. Following purification and concentration of recombinant or native proteins using FPLC, a Tricine SDS-PAGE and Western-Blotting (example) for qualitative evaluation is applied. Further information regarding the existing equipment can be obtained from the link S1-Laboratory.
Reducing the level of sugars and added flavourings in soft drinks is sought-after equally by consumers and manufacturers. This can be achieved through fermentation using acetic acid bacteria found in beehives, which are adapted to high sugar environments. When used to ferment fruit juices, they not only break fruit sugars but also create a unique aroma spectrum. As sugar-reduced, non-alcoholic beverage ingredients, these fermentation products can expand the flavour range of non-alcoholic beverages.
Gewinnung von funktionalen Hefezellwandfragmenten als Grundstoff für die Mikroverkapselung
The encapsulation technology is used in the food industry to protect the capsule contents from external influences, e.g. oxidation and / or to increase handling. First the upcycling of brewer’s waste yeast to a high-quality encapsulation material for food and non-food industry needs to be done by suitable processes. The aim of the study is the use of yeast cell wall fragments for the encapsulation of high-quality food ingredients with the aim to produce stable and sensory appealing drinks.
Untersuchung und Erhöhung von DPP-IV Inhibitoren in fermentierten malzbasierten Getränken
Diabetes constitutes the biggest global health risk of the 21st century. The international diabetes federation (idf) estimates the increase of patients suffering from diabetes to be 642 million until 2014. The aim of this study is the analysis and technological modeling, to which extend cereal based peptides have an inhibitory effect towards human dipeptidyl-peptidase IV and which strategies can be derived to enrich these peptides in food by technological improvement during malting and enzymatic hydrolysis during mashing.
The nervus trigeminus is a facial nerve that supports the perception of olfactory and gustatory stimuli. Amongst the trigeminal stimuli are the heat of chilis or the cooling effect of menthol. The goal of this project is the deeper understanding of the trigeminal stimulus processing in the human brain and the influence of food matrix on the stimulation. These findings will be used for example for the improvement of the recipes for non-alcoholic drinks.
With the use of green biotechnology it is possible to construct brewer's yeast modified with new genetic characteristics, to optimize the brewing process and flavor profiles of the beer. As genetically modified yeasts are not approved in the European Union, these processes should be improved by using Self-cloning via overexpression or knockout of specific genes.
During germination a peptidase mixture is anabolized in a natural way, which is capable of reducing harmful gluten for celiac patients. The hereby mainly involved peptidases have not been sufficiently investigated from a brewing science perspective and the impact on the final product (beer) is not known. The scope of this research is the investigation on the gluten degradation during the malting and brewing process, resulting in traditional beers (barley, wheat beer), which do not significantly differ regarding quality attributes but are gluten-free.
The project deals with the possibility to degrade dhurrin (HCN) from sorghum via modification of malting and mashing. Especially the mash acidification via different lactic acid bacteria and their enzymatic capacity to degrade dhurrin will be investigated. Thus, a sorghum based beverage with a minimum of toxic HCN shall be produced.
Treatment of spent grains by hydrothermal cleavage for the development of food-grade beverage ingredients
Seventy-five percent of all organic residues originating from brewing are spent grains, which constitute the most important and energy-rich by-product from the brewing process. Refining spent grains rich in beneficial ingredients is of great interest for a valuable preservation of human nutrition. Though being a remnant, they still contain high-quality dietary fibers, which are difficult to utilize. It is the aim of the project to break down the complex insoluble polysaccharides, to educe and transfer the cleavage products into a soluble state, in order to add them to new beverages as an ingredient with health beneficial attributes.
Effect of nitrogen assimilation and gene expression on sensory active amino acid metabolites of Saccharomyces yeasts
The aim of this project is to identify the influence of individual amino acids on yeast gene expression of Saccharomyces yeasts. The responding synthesis of fermentative by-products by varying the process and substrate parameters will help to generate defined amounts of aroma-active metabolites in fermented beverages biosynthetically to regulate targeted sensory impressions.