Evaluation of Ethanol Production from Tannin-Reduced Carob Pod Extracts by Zymamonas Mobilis

Regarding some reported antimicrobial properties of tannins; zymomonas mobilis was used to obtain ethanol from tannin-reduced carob pod extract (tr-cpe). culture of 50 ml volume containing 7.5 g sugar at ph 5.5 and 0.03 g bacterial inoculums with shaking at 80 rpm was used. using response surface methodology (rsm), the maximum ethanol concentration of 5.34 % w/v (higher than that reported earlier, 4.01% w/v) was obtained at the optimized addition levels of yeast extract, peptone, and fermentation time; 0.13 g, 0.62 g, and 43.78 h, respectively. carob pods extract (cpe) containing 62.23gl^-1 sugar was treated with 3 gl^-1 gelatin to decrease its tannin content by 57.87 %. sugar loss was not observed during gelatin treatment. the results revealed that there was no significant difference in ethanol production, yield, and productivity between tr-cpe and non-tr-cpe. in conclusion, tannin showed no inhibiting effect to maximum ethanol production by zymomonas mobilis.