Metabolic Engineering of Oleaginous Yeast Rhodotorula toruloides for
Overproduction of Triacetic Acid Lactone
Abstract
The plant-sourced polyketide triacetic acid lactone (TAL) has been
recognized as a promising platform chemical for the biorefinery
industry. However, its practical application was rather limited due to
low natural abundance and inefficient cell factories for biosynthesis.
Here we report the metabolic engineering of oleaginous yeast
Rhodotorula toruloides for TAL overproduction. We first
introduced a 2-pyrone synthase gene from Gerbera hybrida (
GhPS) into R. toruloides and investigated the effects of
different carbon sources on TAL production. We then systematically
employed a variety of metabolic engineering strategies to increase the
flux of acetyl-CoA by enhancing its biosynthetic pathways and disrupting
its competing pathways. We found that overexpression of citrate lyase
(ACL1) improved TAL production by 45% compared to the GhPS
overexpressing strain, and additional overexpression of acetyl-CoA
carboxylase (ACC1) further increased TAL production by 29%. Finally, we
characterized the resulting strain I12- ACL1-ACC1 using fed-batch
bioreactor fermentation in glucose or oilcane juice medium with acetate
supplementation and achieved a titer of 28 g/L or 23 g/L TAL,
respectively. This study demonstrates that R. toruloides is a
promising host for production of TAL and other acetyl-CoA-derived
polyketides from low-cost carbon sources.