Engineering Yeast To Perform Green Chemistry

By genetically modifying yeast, a team of scientists in Japan has managed to produce 1,2,4-butanetriol in a more environmentally-friendly manner.

AsianScientist (Sep. 19, 2019) – Scientists in Japan have discovered a more environmentally-friendly and sustainable method of producing the useful chemical 1,2,4-butanetriol. Their findings are published in the journal Metabolic Engineering.

The chemical 1,2,4-butanetriol has a wide variety of practical uses across different fields. For example, it is required to produce solvents and to synthesize various pharmaceutical products such as antiviral and cholesterol-lowering drugs, among others.

Current methods of producing 1,2,4-butanetriol rely on raw materials derived from oil and result in byproducts that are harmful to the environment. Typically, sodium borohydride (NaBH4) chemically reduces malic acid to 1,2,4-butanetriol, generating a large amount of borate salts in the process. Disposing of these salts causes pollution. Chromite and Rubidium can also be used as catalysts for 1,2,4-butanetriol production, but these methods require high temperature and high pressure, and also result in toxic byproducts.

In the present study, researchers led by Professor Akihiko Kondo at Kobe University, Japan, directly fermented xylose in rice straw using an engineered yeast strain to produce 1,2,4-butanetriol. To do so, the team had to genetically manipulate the yeast to express three enzymes not naturally found in the microbes.

In the first trial, the engineered yeast cells only produced 0.02g/L of 1,2,4-butanetriol. Analyzing the reactions, the researchers realized that iron sulfur clusters in yeast cells were essential for maintaining the catalysis of xylose. On the other hand, they were also aware that too much iron was toxic to yeast.

Hence, Kondo and his team performed further genetic tinkering to optimize the iron metabolism of their engineered yeast strain. They eventually succeeded in producing 1.7g/L of 1,2,4-butanetriol. Kondo noted that the findings from this study could be applied to produce other chemicals that require iron sulfur proteins, in turn reducing future dependence on finite oil resources and polluting methods of production.

The article can be found at: Bamba et al. (2019) Production of 1,2,4-butanetriol From Xylose by Saccharomyces cerevisiae Through Fe Metabolic Engineering.


Source: Kobe University; Photo: Shutterstock.
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