Sterilization of sweet sorghum stem juice for ethanol production (Thai)

Abstract

This research aimed to determine a suitable sterilization method for sweet sorghum stem juice giving high ethanol production efficiency and cost effectiveness. Six sterilization methods were tested as follows: (1) autoclave at 110 ํC 15 min (control), (2) no sterilization, (3) autoclave at 70 ํC 15 min, (4) autoclave at 90 ํC 5 min, (5) pH adjustment at 4 and (6) KMS addition (200 ppm) with pH adjustment at 4 for 24 h. The results show that the main composition of the juice sterilized by the various methods (except Method 6) were similar with the total soluble solids and total sugar in the juice ranging from 17.5-19.0 ํBrix and 171.13-180.70 g l-1, respectively. The sterilized juices were used for batch ethanol fermentation under static condition by Saccharomyces cerevisiae TISTR 5048. The juice sterilized by Method 3 gave the highest ethanol production efficiency with ethanol concentration, yield and productivity of 74.35 g l^-1 (9.41 % v/v), 0.44 g g^-1 and 3.10 g l^-1 h^-1, respectively. The sterilization cost of Method 3 (1.67 baht per 1 litre of the juice) was lower than that of the other methods except Methods 2 and 5.