Optimization of fermentation culture medium containing food waste for l-glutamate production using native lactic acid bacteria and comparison with industrial strain

Abstract

l-glutamate as non-essential amino acid is one of the most abundant amino acids in the body, which plays an important role in various cellular processes and commercially produced as an important industrial amino acid. In this study, the production of l-glutamate by three native Lactic Acid Bacteria (LAB) (Levilactobacillus brevis PML1, Lactiplantibacillus plantarum 1058 and Limosilactobacillus fermentum 4–17) was optimized in culture medium containing dairy sludge and soybean meal using Central Composite Design (CCD) of Response Surface Methodology (RSM). Then, l-glutamate production was analyzed by chromatography and the characteristics of the fermented extract containing this amino acid were evaluated. The results of CCD showed that 500 mg/ml l-glutamate was produced under optimal conditions of 20% dairy sludge, 5% soybean meal, and 48 h of fermentation time (37 °C) at P < 0.05. The IC50 of the sample was 25 mg/ml that indicated proper antioxidant activity. The results of the fermented extract also showed acceptable antimicrobial, and toxicity properties (against cancer cells). Based on the obtained results, dairy sludge as a carbon source and soybean meal as a nitrogen source can be a suitable culture medium for the inexpensive production of l-glutamate.