Fig. 4
Optimization of fermentation medium. Effects of yeast extract on γ-PGA production (a). Effects of corn steep liquor on γ-PGA production (b). γ-PGA concentration produced using 2 g/L yeast extract as the sole nitrogen source was defined as 100%. The relative γ-PGA concentration was determined as (gC/gY) × 100%, where gC is γ-PGA concentration in the medium with corn steep liquor and gY is γ-PGA concentration in the medium with 2 g/L YE. Effects of cane molasses on γ-PGA production (c). Error bars represent SD calculated from three independent determinations