Sugar and Sugar Alcohol Production in Genetically Modified Cyanobacteria

Abstract Cyanobacteria, previously known as blue-green algae, are photosynthetic microorganisms that are abundant in nature. Some cyanobacteria have been consumed by humans for centuries while others are known for their toxicity. The initial metabolic products of photosynthesis are sugar phosphates. Excess photosynthates in cyanobacteria are stored as polysaccharides (primarily glycogen) and may constitute up to 60% of the biomass. Thus cyanobacteria have a natural potential to produce sugars from photosynthesis using CO 2 as the sole carbon source. Although cyanobacteria produce a limited number of sugar compounds naturally, genetic engineering can increase the diversity of produced sugars, as well as increase the production yield. Sucrose, fructose, glucose, glycerol, erythritol, and mannitol have been produced in genetically engineered cyanobacteria, although the yields need to be improved before these are of practical significance. It is possible that these and other more valuable simple sugar compounds, such as mannose, fucose, tagatose, and l -sugars can be produced in cyanobacteria on a commercially relevant scale.