Fig. (2) Average surface tension recorded for detoxification samples over 216 h fermentation period. Nutrient broth (NB), Nutrient broth + B. subtilis(NBBS), Nutrient broth + Chromium (NBCR), Nutrient + Leather dust (NBLD), Nutrient broth + B. subtilis+ Chromium (NBBSCR), Nutrient broth + B. subtilis+ Leather dust (NBBSLD), Nutrient broth + B. subtilis+ Chromium + Leather dust (NBBSCRLD).