Mannitol: physiological functionalities, determination methods, biotechnological production, and applications.

Mannitol is a naturally occurring six-carbon sugar alcohol that has wide applications in the food and pharmaceutical industry because of its many properties, namely being a natural sweetener with a low metabolism and no glycemic index. The increasing demand for mannitol has spurred many studies of its production. Compared with its chemical synthesis and extraction from plants, both of which are difficult to satisfy for industrial requirements, biotechnological production of mannitol has received considerably more attention and interest from scientists because of its known advantages over those two methods. Accordingly, in this review, we summarize recent advances made in the production of mannitol through various biotechnological methods. The physicochemical properties, sources, and physiological functionalities and applications of mannitol are systematically covered and presented. Then, different determination methods for mannitol are also described and compared. Furthermore, different biotechnological strategies for the production of mannitol via fermentation engineering, protein engineering, and metabolic engineering receive a detailed overview in terms of mannitol-producing strains, enzymes, and their key reaction parameters and conditions. KEY POINTS: • Physiological functionalities and applications of mannitol are presented in detail. • Different determination methods for mannitol are also described and compared. • Various biotechnological strategies for the production of mannitol are reviewed.