Abstract
l-glutamaic acid is the principal excitatory neurotransmitter in the brain and an important intermediate in metabolism. In the present study, lactic acid bacteria (218) were isolated from six different fermented foods as potent sources of glutamic acid producers. The presumptive bacteria were tested for their ability to synthesize glutamic acid. Out of the 35 strains showing this capability, strain MNZ was determined as the highest glutamic-acid producer. Identification tests including 16S rRNA gene sequencing and sugar assimilation ability identified the strain MNZ as Lactobacillus plantarum. The characteristics of this microorganism related to its glutamic acid-producing ability, growth rate, glucose consumption and pH profile were studied. Results revealed that glutamic acid was formed inside the cell and excreted into the extracellular medium. Glutamic acid production was found to be growth-associated and glucose significantly enhanced glutamic acid production (1.032 mmol/L) compared to other carbon sources. A concentration of 0.7% ammonium nitrate as a nitrogen source effectively enhanced glutamic acid production. To the best of our knowledge this is the first report of glutamic acid production by lactic acid bacteria. The results of this study can be further applied for developing functional foods enriched in glutamic acid and subsequently γ-amino butyric acid (GABA) as a bioactive compound.
Highlights
Glutamic acid is a multifunctional amino acid involved in taste perception, excitatory neurotransmission and intermediary metabolism [1]
Higher concentrations of glutamic acid produced by Lactic acid bacteria (LAB) strains isolated from fermented soybean showed that these strains were more efficient in biosynthesizing glutamic acid as compared to LAB strains isolated from other food samples
A new glutamic acid-producing strain of Lactobacilli isolated from a traditional fermented food locally available in Malaysia was identified as Lactobacillus plantarum MNZ according to the phenotypic and genotypic tests
Summary
Glutamic acid is a multifunctional amino acid involved in taste perception, excitatory neurotransmission and intermediary metabolism [1]. The key advantage of the glutamic acid production by LAB is that the amino acid produced in this way is biologically active (L-glutamic acid) and the production process is considered to be safe and eco-friendly This can be achieved through selection of appropriate LAB strains from indigenous micro-organisms which are well-adapted to a particular product, more competitive and with elevated metabolic capacities. Selection of the most efficient glutamic acid-producing LAB strains may contribute to new fermented products with improved general standards with respect to the naturally-biosynthesized glutamic acid. This could lead to the development of fermented foods rich in glutamic acid and GABA.
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