A bioimpedance spectroscopy technique to monitor bioprocess involving complex growth micro-organisms

Although analytical methods (often offline) are considered as references (gold standards) for monitoring industrial bioprocesses, real-time monitoring (online) is always preferable for maximizing such processes. However, many of the real-time methods that measure total cell concentration cannot distinguish living micro-organisms from the dead ones or even other materials. Moreover, some real-time methods also lead to possible wrong results when the micro-organism involved in the bioprocess exhibits significant metabolic, physiological, and kinetic changes as it grows. This study presents a real-time technique intended to monitor this class of micro-organisms and that is based on an alternative method of bioimpedance spectroscopy. The feasibility of the proposed technique was evaluated during bacterial growth experiments using the bacteria Bacillus thuringiensis var. israelensis (Bti) with initial inocula of 5%, 10%, and 15% (v/v on 220 ml). Each growth experiment was monitored every hour over 18 h by the proposed technique and by a classical offline method (McFarland method). The results of monitoring the studied bioprocess by both methods exhibited an average Pearson correlation coefficient (r̄) of above 0.9 and good agreement when the Bland–Altman method was used to compare them.