Screening of Lactic Acid Bacteria from “TapaiPulut” for Biosynthesis of Glutamic Acid

Abstract

Glutamic acid (glutamate) is an amino acid used in human body to build proteins. Glutamate can be converted to glutamine via glutamine synthetase, and to γ — aminobutyric acid (GABA) via glutamate decarboxylase. The objective of this study is to screen potential of lactic acid bacteria from “tapaiubi” for biosynthesis of glutamic acid. The traditional fermented food, “tapaipulut” was used as a source of lactic acid bacteria (LAB). The sample was cultivated on DeMan-Rogosa-Sharpe MRS agar containing 0.16% bromocresol purple and placed under anaerobic condition at 37°C for 48 hours. A total of 25 strains were isolated with 8 strains were determined to be LAB based on their morphology. The 8 strains were inoculated into 8 bottles of fermentation medium (4% v/v) in duplicate determinations and fermented in rotary shaker (180 rpm, 37°C, 4 days). After 18 hours, the fermented media were centrifuged at 10000 rpm (4°C) for 10 minutes and the supernatants were derivatised at 100°C for 10 minutes. Glutamic acid concentrations were determined by using HPLC with fluorescence detector (C18S) on a 250 × 4.6 mm column at a flow rate of 1.2 ml/min. Cut of 25 strains, 8 strains were shown to have the capability of producing glutamic acid. Five strains, including (TUS 25 (18.409 μg/ml), TUS 17 (18.437 μg/ml), TUS 7 (17.228 μg/ml), TUS 8 (14.033 μg/ml), TUS 3 (7.810 μg/ml) showed the capability of producing glutamic acid after 72 hours fermentation. While the other three strains TUS 11 (4.894 μg/ml), TUS 2 (0.0245 μg/ml), TUS 20 (0.405 μg/ml) were become 48 hours and 72 hours fermentation. The highest glutamate was registered after 48 hours and 96 hours. This study shows that LAB from “tapaipulut” has the capability of producing glutamic acid.