Enhanced synthesis of S-adenosyl-L-methionine through Combinatorial
metabolic engineering and Bayesian optimization in Saccharomyces
cerevisiae
Abstract
S-adenosyl-L-methionine (SAM) is a substrate for many enzyme-catalyzed
reactions and provides methyl groups in numerous biological
methylations, and thus has vast applications in the medical field.
Saccharomyces cerevisiae has been engineered as a platform with
significant potential for producing SAM, although the current production
has room for improvement. To surpass the restriction, a series of
metabolic engineering strategies were employed to enhance the synthesis
of SAM in this study. These strategies included enhancing SAM synthesis
by overexpression of SAM2, met6, and str2, increasing ATP
supply by integration of adkI and PYC, and down-regulating
SAM metabolism by disrupting erg4 and erg6 and replacing
the original promoter of CYS4 with a weaker promoter. After
combinatorial metabolic engineering, Bayesian optimization was conducted
on the obtained strain C262P6 to optimize the fermentation medium. A
final yield of 2972.8 mg/L at 36 h with 29.7% of the L-Met conversion
rate in the shake flask was achieved, which was 26.3 times higher than
that of its parent strain and the highest reported production in the
shake flask to date. This paper establishes a feasible foundation for
the construction of SAM-produced strains using metabolic engineering
strategies and demonstrates the effectiveness of Bayesian optimization
in optimizing fermentation medium to enhance the generation of SAM.