The Formose Reaction: A Tool to Produce Synthetic Carbohydrates Within a Regenerative Life Support System

For long manned space missions, regenerative life support systems must provide carbohydrates. In addition to the necessity to develop such fully closed systems, the formose reaction (FR), the alkaline polymerisation of formaldehyde using Ca(OH)2, seems to be the only current single-step method for the production of synthetic carbohydrates. The FR received much attention with regard to edible carbohydrate production during the 1960s, 70s and 80s. In addition, its importance is also related to the prebiotic and interstellar synthesis of carbohydrates. This review gives an overview about the research attempts that have already been reported on the FR in the literature. The reaction system, mechanism, as well as basic physicochemical parameters are discussed. Many different research groups investigated the fundamentals of the FR as well as the side reaction (cannizzaro reaction (CR)) and downstream reaction (cross cannizzaro reaction (CCR)). In addition, a number of investigations focused on the selective synthesis of carbohydrates. Full conversion of formaldehyde leads to a very complex mixture of compounds, which represents an unfavourable downside of the FR-system. In order to minimize the product distribution, a partial formaldehyde conversion and variation of physicochemical parameters may be helpful. Finally, the FR-system is still not fully unravelled and represents an opportunity for exciting research.