Improvement of gamma-aminobutyric acid biosynthesis from Lactiplantibacillus plantarum B7 via optimisation, immobilisation and repeated-batch fermentation methods and its potential applications

This study focuses on enhancing the production of gamma-aminobutyric acid (GABA), a non-protein amino acid with various physiological benefits, using Lactiplantibacillus plantarum B7 isolated from Budu (fermented anchovy sauce). Through a combined optimisation method, including one factor at a time, twolevel factorial design, steepest ascent, and central composite design, the GABA production was improved from 11.68 g/L (unoptimised approach) to 32.18 g/L (equivalent to a 175.51% increment) along with increased cell growth. These improvements were achieved by developing an optimum fermentative medium (modified MRS medium containing 1% glucose, 2.5% yeast extract, 2 ppm each of tween 80, calcium carbonate, and potassium iodide together with 335.61 mM of initial MSG and 0.723 mM of PLP with an initial pH of 5.66) and conditions (at 35.6ºC with 125 rpm for 63.66 h). Further enhancements were achieved through repeated batch fermentation using watermelon rind and apple immobilised cells, resulting in GABA productions of 218.48 g/L (equivalent to a 570.18% increment) and 195.44 g/L (equivalent to a 499.51% increment), respectively, compared to free cells GABA production (32.6 g/L) in single batch fermentation mode. Additionally, compared to free cells, L. plantarum B7 was able to maintain 50% of its cell viability when immobilised on both natural supports even after the 12th cycle of RBF. In fermented milk product, optimisation led to an increase GABA concentration from 1.29 g/L to 4.85 g/L (equivalent to a 275.97% increment) using a food-grade medium (10% of skim milk containing 50 mM of food-grade MSG and 0.3 mM of food-grade PLP, incubated at 35.6ºC with 125 rpm for 48 h). The use of watermelon rind-immobilised L. plantarum B7 in a food-grade medium for fermented milk production exhibited superior GABA (5.98 g/L) and lactic acid (7.48 g/L) production, with a high viable cell count retained after 28 days of storage at 4ºC. Overall, the study showcases the potential of L. plantarum B7 in combination with optimisation, whole-cell immobilisation, and repeated batch fermentation for improved GABA production in functional food and pharmaceutical applications.

Text 122748.pdf Download (1MB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/18650

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