초록
<P><B>Abstract</B></P> <P>In this work, waste-based raw materials; crude glycerol from biodiesel plant and tuna condensate from tuna canning factory, were used to substitute the expensive complex medium for ethanol production from <I>Enterobacter aeroegenes</I> TISTR 1468. The optimum crude glycerol concentration was 21.43 g/L (˜20 g/L), giving 6.72 g/L ethanol. Using tuna condensate as a nitrogen source for studying the effect of initial C/N ratio (115–365 g/g) revealed the insignificant difference on ethanol production in every C/N ratio tested with a noticeable increase of byproducts (2,3-butanediols) at the high C/N ratio. The addition of inorganic salts and trace element into crude glycerol-tuna condensate (GT) medium resulted in 2-fold increase of ethanol production (12.73 g/L), complete substrate consumption and reduced the formation of byproducts. Optimization studies based on Plackett-Burman design indicated that the most influential parameter amongst the inorganic salt components was phosphate buffer with 77.6% contribution. However, phosphate buffer could be replaced by keeping the pH constant at 7.0 using 3 N NaOH. Under the optimum condition; 20 g/L crude glycerol, initial C/N ratio of 115 g/g and the pH maintained at 7, the ethanol production was 12.33 g/L with 24% higher than the theoretical yield. The selectivity of ethanol production increased upto 3-fold larger than the expensive complex medium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Crude glycerol and tuna condensate (GT) could replace the complex medium for ethanol production. </LI> <LI> Addition of inorganic salts and trace elements exhibited similar results with the use of phosphate buffer. </LI> <LI> Maintaining pH at 7 using 3 N NaOH gave the same result as adding phosphate buffer. </LI> <LI> The optimum condition was 20 g/L glycerol at C/N ratio of 10:1 in GT medium and pH control at 7.0. </LI> <LI> The ethanol production increased 2 folds with higher yield than theory and ethanol was produced predominantly. </LI> </UL> </P>