Development of low-cost medium for ethanol production by using glutamic acid mother liquor

In this study, glutamic acid mother liquor (GML) was used as a nitrogen source for a low-cost medium development by substituting yeast extract and peptone (YP) to produce ethanol from oil palm trunk (OPT) fibers using simultaneous saccharification and fermentation (SSF). The optimum medium components predicted by the model were 3.95 g.nitrogen/L of GML, 0.05 g/L MgSO4‧7H2O and 0.27 g/L KH2PO4 to produce ethanol 90.03 g/L by Saccharomyces cerevisiae TISTR 5606. The maximum ethanol concentration of 89.59 ± 2.36 g/L with a theoretical yield of 95.61 ± 2.06 % was observed at initial glucose concentration of 180 g/L. The GML media containing 10 % OPT fibers gave 26.55 ± 1.52 g/L ethanol concentration and 68.33 ± 3.92 % ethanol theoretical yield. Additionally, ethanol concentration increased to 54.75 ± 0.67 g/L with a theoretical yield of 70.48 ± 0.85 % at 20 % substrate (w/v) loading. The results exhibited that low-cost medium saved 2.34 USD/L (173.5 %) as compared to YP media.