RESEARCH & DEVELOPMENT
KOMBUCHA & CO.
Production of acetic acid bacteria as starter cultures: influence of yeast extract on biomass Maximilian Schmacht, Dr.-Ing. Martin Senz, VLB Berlin, Research Institute for Biotechnology and Water, Department Bioprocess Engineering and Applied Microbiology
Fermented low or non-alcoholic beverages such as Kombucha or water kefir enjoy increasing popularity against the background of an increasing awareness of a healthy and conscious lifestyle. The traditional production methods applying undefined microbial consortia, however, are contrasting the need for reproducible and scalable industrial production processes. The VLB Research Institute for Biotechnology and Water (FIBW) serves its customers with appropriate starter cultures. Traditionally fermented beverages, such as Kombucha, water kefir or kvass are getting increasing attention by costumers interested in natural beverages that potentially aid in fostering a healthy lifestyle. The traditional production methods, however, rely on the usage of non-defined microbial communities. Thus, a reproducible production of products showing always the same characteristics is hard to achieve. A solution to this issue is the usage of defined starter cultures resulting in a more controllable fermentation process. The Research Institute for Biotechnology and Water has served its customers with starter cultures for a wide variety of beverages for decades and is also currently active in
expanding the range of offerings. In the case of Kombucha, the socalled SCOBY (symbiotic culture of bacteria and yeast) is deployed for the fermentation of sugared tea to an acetic refreshing drink. It mainly consists of acetic acid bacteria (e.g. Acetobacter, Komagataeibacter) and yeast (e.g. Brettanomyces, Zygosaccharomyces). In order to achieve high biomasses, the fermentation media need to be adapted to the requirements of the respective strains. In general, the usage of complex media is usually the most efficient way for high biomass production as they provide a broad range of nutrients. However, the selection of specific components, such as yeast extract, can have a high impact on the final
Tab. 1: Different yeast derivatives used for fermentation studies with K. hansenii Ko-0201
Product
Product Feature
Reference yeast extract
Commonly used in microbiology laboratories
X‐SEED® KAT(Ohly GmbH, Germany)
Yeast extract rich in free amino acids
X‐SEED® Nucleo Advanced (Ohly GmbH, Germany)
Yeast extract rich in free ribonucleotides
X‐SEED® Nucleo Max (Ohly GmbH, Germany) Yeast extract with highest content of free ribonucleotides X‐SEED® Peptone (Ohly GmbH, Germany)
Yeast peptone rich in small peptides (< 2 kDa)
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Brauerei Forum International – October 2021
result. Herein, a study on the influence of different yeast derivatives on the growth of Komagataeibacter hansenii was conducted using the miniaturized fermentation platform BioLector ® Pro (m2plabs GmbH). This state-of-the-art fermentation unit was funded by the Federal Ministry for Economic Affairs and Energy (INNO-KOM module IZ: IZ150029) and allows high-throughput screening of different experimental conditions in batch as well as fed-batch mode in microliter scale. Batch screening experiments without pH control A s a first step, fermentation media containing 50 g/L glucose and 10 g/L of different yeast derivatives (see Table 1) were used for biomass growth of Komagataeibacter hansenii Ko-0201 (VLB strain collection). The fermentations in the different media proceeded equally in the first stage. Within the phase of exponential growth, however, XSEED® KAT allowed a significantly improved growth compared to all other used yeast derivatives by achieving 25.37 AU, which corresponded to 5.52∙109 cells/mL (Figure 1). The usage of X-SEED Peptone resulted approximately in the same final biomass, yet taking additional 10 h. Concluding, it can be assumed that K. hansenii
