reduced the working volume in order to achieve a better ratio between surface area and solution
volume. Evidently, this way would make rotating drum bioreactor commercially unacceptable in bioleaching processes. Even so, the gas–liquid mass transfer performance of rotating drum bioreactor was still less than the typical kLa (0.01 s−1 bkLab0.06 s−1) of pilot-scale stirred tank bioreactor in bioleaching processes