In situ microscopy: A perspective for industrial bioethanol production monitoring

•In situ microscopy as a potential monitoring tool for bioethanol production.•Review of reagent-free methods that estimate cell viability from micrographs.•Comparison of the characteristics of different in situ microscopy systems.•Optical sampling in situ microscopy provides large statistics.

This work reviews the state-of-the-art in image-based in situ methods with regard to their potential use for fermentation of Saccharomyces cerevisiae in sugarcane wine. The integration of real time information from fermentation tanks in the control strategies has high potential to promote better fermentative performance. While several image-based techniques for the measurement of cell concentration have been established, a reliable and consistent viability measurement still remains a challenging task. Reagent-free methods that estimate viability from information contained in micrograph images are reviewed. Nevertheless, the inherent complexity of the sugarcane syrup medium imposes extra challenges regarding its representation in microscopic images and their evaluation by real time image analysis.