Princeton University researchers have successfully used optogenetic technology to increase the production of Blue light allows growth of yeast in glucose, as well as ethanol formation, whereas dark conditions initiate the production phase. Source: Princeton Universityvaluable chemical feedstocks by yeast. Isobutanol production by a genetically modified strain of Saccharomyces cerevisiae increased fivefold with their approach.

The strain was initially engineered to yield large quantities of isobutanol, but the desired volumes of the compound are toxic to yeast. This limitation was eliminated with a combination of genetic engineering and light to fine tune isobutanol production. Using their light-switch technique, the researchers set out to keep the yeast alive while maximizing isobutanol production.

A modified gene from a marine bacterium that is controllable by blue light was inserted into yeast’s DNA. Light was then used to trigger a chemical process that activates enzymes that naturally allow yeast to grow and multiply by eating glucose and secreting ethanol. Since these enzymes impede the activity of enzymes responsible for isobutanol production, the team turned to darkness to switch off the ethanol-producing enzymes to make room for the expression of their competitors.

Exposure to bursts of blue light every few hours kept the cells viable, and the light was switched off at intervals to shift metabolism from powering growth to producing isobutanol. Before the cells completely arrested, the researchers dispersed more bursts of light.

Compared with techniques involving pure genetic engineering or chemical additives, the light-based method is much faster, cheaper and adjustable, meaning that turning it on and off can toggle the function of live cells on the spot at any point in the fermentation process.