Screening of Lactobacillus rhamnosus-producing gamma aminobutyric acid (GABA) isolated from Sumbawa mare milk and its potential application to increase GABA content in fermented milk

Abstract

The broad role of gamma aminobutyric acid (GABA) in human health has triggered various efforts to increase its concentration in foodstuffs. The use of microorganisms to increase the GABA content in food is a rational choice. The objective of this study was to identify the GABA-producing Lactobacillus rhamnosus strain isolated from Sumbawa mare milk and its potential application as a starter to increase GABA content in fermented milk. A total of 34 L. rhamnosus strains were screened for their ability to produce GABA in MRS medium containing 2% monosodium glutamate (MSG). GABA presence in the culture broth was analysed qualitatively by using TLC, whereas GABA concentration was determined using UPLC. The results showed that 17 out of 34 L. rhamnosus strains produced GABA at varying concentrations from 0.047 to 0.384 mg/mL. Six selected strains were determined for their capacity in GABA production in skim milk without MSG addition. The results showed that GABA was produced by L. rhamnosus strains on skim milk ranging from 0.07 to 2.01 mg/mL L. rhamnosus SMM37 possessed the highest GABA production capability, which produced 2.01 mg/mL in skim milk after fermentation for 72 hrs at 37oC. These results indicated that L. rhamnosus strains isolated from Sumbawa mare milk have the potential to be developed as a starter culture to increase GABA content in fermented milk. Nevertheless, further studies are needed in optimizing fermentation conditions to improve GABA production from the L. rhamnosus strains isolated from Sumbawa mare milk.