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Item Biosynthesis of gamma-aminobutyric acid by Lactiplantibacillus plantarum K16 as an alternative to revalue agri-food by-products(2022-11) Diez-Gutiérrez, Lucía; Vicente, Leire San; Sáenz, Jessica; Esquivel, Argitxu; Barron, Luis Javier R.; Chávarri, María; Tecnalia Research & Innovation; Alimentación SostenibleProbiotic metabolites, known as postbiotics, have received attention due to their wide variety of promoting health effects. One of the most exciting postbiotic is gamma-aminobutyric acid (GABA), widely produced by lactic acid bacteria, due to its benefits in health. In addition, the performance of the biosynthesis of GABA by Lactiplantibacillus plantarum could be modulated through the modification of fermentation parameters. Due to their high nutritional value, agri-food by-products could be considered a useful fermentation source for microorganisms. Therefore, these by-products were proposed as fermentation substrates to produce GABA in this study. Previously, several experiments in Man Rogosa Sharpe (MRS) broth were performed to identify the most critical parameters to produce GABA using the strain Lactiplantibacillus plantarum K16. The percentage of inoculum, the initial pH, and the concentration of nutrients, such as monosodium glutamate or glucose, significantly affected the biosynthetic pathway of GABA. The highest GABA yield was obtained with 500 mM of monosodium glutamate and 25 g/L of glucose, and an initial pH of 5.5 and 1.2% inoculum. Furthermore, these investigated parameters were used to evaluate the possibility of using tomato, green pepper, apple, or orange by-products to get GABA-enriched fermented media, which is an excellent way to revalorise them.Item Efficient production of acetoin by fermentation using the newly isolated mutant strain Lactococcus lactis subsp. lactis CML B4(2017-07) Roncal, Tomás; Caballero, Susana; Díaz de Guereñu, María del Mar; Rincón, Inés; Prieto-Fernández, Soraya; Ochoa-Gómez, Jose R.; Tecnalia Research & Innovation; BIOECONOMÍA Y CO2; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; TECNOLOGÍAS DE HIDRÓGENO; GENERALWith the aim of applying biotechnology to produce acetoin, a chemical that can be used as an aroma and as a building block for other compounds, several putative mutants with reduced lactic acid synthesis were obtained from a wild-type homolactic strain of L. lactis subjected to chemical mutagenesis. Among these mutants, a strain was isolated, CML B4, that showed reduced lactate dehydrogenase (LDH) and increased NADH oxidase (NOX) activities. Shaken flask cultures of this mutant strain mainly produced acetoin, increasing the levels produced compared to the wild-type strain by 15-fold. A point mutation detected in the ldh gene encoding LDH was probably the genetic defect responsible for this phenotype. In pH-controlled aerobic batch fermentation, the CML B4 strain produced more than 40 gL−1 acetoin, which was increased by up to 59 gL−1 in fed-batch fermentations, with yields close to 88 and 74%, respectively, and productivities exceeding 2 gL−1 h−1. These results indicate that this strain could be used industrially as a cell factory for the production of acetoin from bioresources.