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Gewählte Doctoral Thesis:

Ida Bagus Agung Yogeswara (2021): Synthesis of γ-aminobutyric acid (GABA) by glutamate decarboxylase and lactic acid bacteria isolated from Indonesian fermented foods.
Doctoral Thesis - Institut für Lebensmitteltechnologie, BOKU-Universität für Bodenkultur, pp 121. UB BOKU obvsg FullText

Data Source: ZID Abstracts
γ-aminobutyric acid (GABA) is a non-protein amino acids that acts as a neural signal transmitter and has been well studied in medical and pharmaceutical fields. GABA synthesis is catalyzed by glutamate decarboxylase and the enzyme is widely distributed in microorganisms, various plants and the human brain. In the last decade, natural ways to synthesize GABA have been proposed as chemical synthesis has been rejected because of the corrosive reactants that are used. Currently, there is an increasing interest in GABA production using natural methods such as microbial fermentation and enzymatic synthesis. Most of these processes are based on the GABA-producing ability of lactic acid bacteria and relevant enzymes derived from LAB. Fermented foods are considered as an isolation sources of GABA-producing LAB. Hence, it is of great interest to isolate GABA-producing LAB as well as their GAD to cope with the limitation of GABA synthesis using chemical means. In this first part of this thesis, an overview of GAD from lactic acid bacteria is given. In this review paper, we outline the importance of gad genes in LAB along with phylogenetic analysis. Structural function and biochemical properties of GAD from LAB are also discussed and summarized. In the second part of the thesis, the isolation, screening and identification of GABA-producing LAB from Indonesian fermented foods is covered. Several fermented foods were used as an isolation source in this study. L. plantarum, identified by partial 16S rDNA sequencing and MALDI-TOF MS, is shown to be an efficient GABA-producing LAB. In addition, rep-PCR fingerprinting using the (GTG)5 primer was performed to classified GABA-producing LAB isolated from fermented foods. The third step of this thesis was to produce GABA using microbial fermentation and enzymatic synthesis. GAD from L. plantarum FNCC 260 showed optimum pH and temperature at 4.5 and 60oC respectively. GAD activity was enhanced by the addition of 0.6 mM PLP and the presence of 2 mM CaCl2. However, the enzyme showed poor thermostability at 20oC and 30oC respectively.

Betreuer: Haltrich Dietmar
1. Berater: Nguyen Thu Ha
2. Berater: Domig Konrad

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