Evaluation of brewer's spent grain-derived lignocellulosic hydrolysate as a feedstock for amino acid production by submerged fermentation

Abstract

This study evaluated the potential of utilizing a lignocellulosic hydrolysate from brewer’s spent grain (BSG) as a substrate for amino acid (AA) production by submerged fermentation. The main objective was to explore AA production from BSG hydrolysate using selected microorganisms. Initially, different microorganisms were screened for their growth on BSG hydrolysate, and selected microorganisms were further investigated for AA production by cultivation in shake flasks and bioreactor. From this screening, Saccharomyces cerevisiae and Corynebacterium glutamicum were selected. C. glutamicum produced alanine, proline, valine, and glycine in shake flasks and bioreactor. Highest alanine production (193.6 0.09 mg/L) was found in shake flasks after 30 h while production of proline (22.5 1.03 mg/L), valine (34.8 0.11 mg/L), and glycine (18.7 1.30 mg/L) was highest in bioreactor after 4 h (proline and valine) and 8 h (glycine). To enhance AA production by C. glutamicum, a fed-batch fermentation experiment was performed. Except for glycine, no AAs were produced during the fed-batch phase. S. cerevisiae produced alanine, proline, valine, and glutamic acid in shake flask but not in bioreactor. Highest production of alanine (11.8 1.25 mg/L), proline (11.8 1.06 mg/L), and valine (4.94 1.01 mg/L) was obtained after 50 h while glutamic acid production (66.2 0.49 mg/L) peaked after 60 h. This study demonstrates the production of several AAs from BSG by submerged fermentation; however, further optimization is needed to improve the productivity.