Galactose and glucose are two of the most abundant monomeric sugars in hydrolysates of marine biomasses. While Saccharomyces cerevisiae can ferment galactose, its uptake is tightly controlled in the presence of glucose by catabolite repression. It is desirable to construct engineered strains capable of simultaneous utilization of glucose and galactose for producing biofuels and chemicals from marine biomass. The MTH1 gene coding for transcription factor in glucose signaling was mutated in a pyruvate decarboxylase (Pdc)-deficient S. cerevisiae expressing heterologous 2,3-butanediol (2,3-BD) biosynthetic genes. The engineered S. cerevisiae strain consumed glucose and galactose simultaneously and produced 2,3-BD as a major product. Total sugar consumption rates increased with a low ratio of glucose/galactose, though, occurrence of the glucose depletion in a fed-batch fermentation decreased 2,3-BD production substantially. Through optimizing the profiles of sugar concentrations in a fed-batch cultivation with the engineered strain, 99.1 ± 1.7 g/L 2,3-BD was produced in 143 hours with a yield of 0.353 ± 0.022 g 2,3-BD/g sugars. This result suggests that simultaneous and efficient utilization of glucose and galactose by the engineered yeast might be applicable to the economical production of not only 2,3-BD, but also other biofuels and chemicals from marine biomass.
Bibliographical noteFunding Information:
This work was supported by the Advanced Biomass R&D Center (ABC) of Global Frontier Project (2011-0031359) and the National Research Foundation of Korea Grant (2014M1A2A2069904) funded by the Ministry of Science, ICT and Future Planning. The authors declare no financial or commercial conflict of interest.
- Catabolite repression
- Pyruvate decarboxylase
- Saccharomyces cerevisiae