Lactose fermentation by engineered Saccharomyces cerevisiae capable of fermenting cellobiose

• Published in: Journal of biotechnology 2016-09, Vol.234, p.99-104
• Main Authors: Liu, Jing-Jing, Zhang, Guo-Chang, Oh, Eun Joong, Pathanibul, Panchalee, Turner, Timothy L., Jin, Yong-Su
• Format: Article
• Language: English
• Subjects: Adaptive evolution; beta-Galactosidase - metabolism; beta-Glucosidase - metabolism; Biotechnology; Byproducts; cdt-1; Cellobiose - chemistry; Cellobiose - metabolism; DNA Copy Number Variations; Enzyme Activation; Ethanol - chemistry; Ethanol - metabolism; Fermentation; Fuels; gh1-1; Lactose; Lactose - chemistry; Lactose - metabolism; Lactose fermentation; Metabolic Engineering; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - metabolism; Serials; Whey
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2016.07.018

Diagram of lactose-consuming strain carrying multi-copies of lactose transporter, CDT-1 and β-glucosidase/β-galactosidase, GH1-1. [Display omitted] •Engineered yeast capable of fermenting cellobiose can ferment lactose as well.•The GH1-1 from Neurospora crassa presents beta-galactosidase activity.•The evolved strain has higher copy numbers of cdt-1 and gh1-1.•The evolved strain fermented lactose with a consumption rate of 2.16g/Lh. Lactose is an inevitable byproduct of the dairy industry. In addition to cheese manufacturing, the growing Greek yogurt industry generates excess acid whey, which contains lactose. Therefore, rapid and efficient conversion of lactose to fuels and chemicals would be useful for recycling the otherwise harmful acid whey. Saccharomyces cerevisiae, a popular metabolic engineering host, cannot natively utilize lactose. However, we discovered that an engineered S. cerevisiae strain (EJ2) capable of fermenting cellobiose can also ferment lactose. This finding suggests that a cellobiose transporter (CDT-1) can transport lactose and a β-glucosidase (GH1-1) can hydrolyze lactose by acting as a β-galactosidase. While the lactose fermentation by the EJ2 strain was much slower than the cellobiose fermentation, a faster lactose-fermenting strain (EJ2e8) was obtained through serial subcultures on lactose. The EJ2e8 strain fermented lactose with a consumption rate of 2.16g/Lh. The improved lactose fermentation by the EJ2e8 strain was due to the increased copy number of cdt-1 and gh1-1 genes. Looking ahead, the EJ2e8 strain could be exploited for the production of other non-ethanol fuels and chemicals from lactose through further metabolic engineering.