Optimization of fermentation parameters for l-lysine production using tropical grass extracts by Corynebacterium glutamicum (ATCC 13032)

Abstract

This study evaluates the potential of tropical grasses—Elephant Grass (Pennisetum purpureum), Guinea Grass (Panicum maximum), and Water Hyacinth (Eichhornia crassipes)—as low-cost substrates for l-lysine production by Corynebacterium glutamicum (ATCC 13032). Aqueous extracts of all three grasses were fermented with C. glutamicum; however, only elephant grass, which yielded the highest l-lysine levels, was subjected to optimization of fermentation conditions (pH, temperature, nutrient concentration, and aeration) to enhance microbial growth and l-lysine biosynthesis. Batch-to-batch consistency was ensured by standardizing sample collection and processing. Maximum l-lysine production reached 195 mg/L at pH 7.0, with the highest production (168.7 mg/L) at 40 °C. Thermodynamic analysis revealed an endothermic and spontaneous biosynthesis process (ΔH = + 9.15 kJ/mol, negative ΔG). Biochemical analysis showed increases in soluble protein, glucose, antioxidant capacity, total phenols, and flavonoids, especially in Water Hyacinth extracts. Enzyme assays confirmed enhanced α-amylase and protease activities. These results demonstrate the feasibility of using tropical grasses, particularly Water Hyacinth, as sustainable substrates for l-lysine production.

Keywords

l-lysine production / Tropical grasses / Corynebacterium glutamicum / Fermentation optimization / Bioconversion

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