Glucosylglycerol (GG) has a range of potential applications in health, pharmacy and cosmetics due to its physiological, protein-stabilizing and antioxidative properties. In addition to chemical synthesis and enzymatic catalysis, GG can be produced as a protective osmolyte in salt-stressed bacteria, such as the cyanobacterium Synechocystis sp. PCC 6803. However, low efficiency and high cost makes scalable production of GG difficult.
Researchers from Microbial Metabolic Engineering Group at Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, reported an efficient GG production and secretion by genetically modified and encapsulated Synechocystis cells grown in a semi-continuous manner.
The researchers improved the production and secretion of GG in Synechocystis by first disrupting both the ggtC and ggtD genes, which encode the subunits of a GG uptake transporter, as well as the ggpR gene, which encodes a repressor for GG synthesis. Researchers confirmed that the rapid GG release from salt-stressed cells of Synechocystis depended on the ion gradient across the cell membrane. They further increased the GG titer of the above mutant to ~1 g/l by the semi-continuous culturing, and proved the feasibility of an agar gel encapsulation method in supporting cell growth and the GG production of Synechocystis under semi-continuous culturing conditions.
The research paper entitled "Photosynthetic and extracellular production of glucosylglycerol by genetically engineered and gel-encapsulated cyanobacteria" has been online published in Applied Microbiology and Biotechnology.
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Figure. Diagram of GG biosynthetic pathways of Synechocystis, genetic engineering strategy, and response mechanism of Synechocystis to salt shock. (Image by Microbial Metabolic Engineering Group) |
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