Enhancing Trans-Nerolidol Productivity in Yarrowia lipolytica by Improving Precursor Supply and Optimizing Nerolidol Synthase Activity

Advances in metabolic engineering for enhanced acetyl-CoA availability in yeast

Acetyl-CoA is an intermediate metabolite in cellular central metabolism. It's a precursor for various valuable commercial products, including: terpenoids, fatty acids, and polyketides. With the advancement of metabolic and synthetic biology tools, microbial cell factories have been constructed for the efficient synthesis of acetyl-CoA and derivatives, with the Saccharomyces cerevisiae and Yarrowia lipolytica as two prominent chassis. This review summarized the recent developments in the biosynthetic pathways and metabolic engineering approaches for acetyl-CoA and its derivatives synthesis in these two yeasts. First, the metabolic routes involved in the biosynthesis of acetyl-CoA and derived products were outlined. Then, the advancements in metabolic engineering strategies for channeling acetyl-CoA toward the desired products were summarized, with particular emphasis on: enhancing metabolic flux in different organelles, refining precursor CoA synthesis, optimizing substrate utilization, and modifying protein acetylation level. Finally, future developments in advancing the metabolic engineering strategies for acetyl-CoA and related derivatives synthesis, including: reducing CO2 emissions, dynamically regulating metabolic pathways, and exploring the regulatory functions between acetyl-CoA levels and protein acetylation, are highlighted. This review provided new insights into regulating acetyl-CoA synthesis to create more effective microbial cell factories for bio-manufacturing.

Recent Advances and Multiple Strategies of Monoterpenoid Overproduction in Saccharomyces cerevisiae and Yarrowia lipolytica

Monoterpenoids are an important subclass of terpenoids that play important roles in the energy, cosmetics, pharmaceuticals, and fragrances fields. With the development of biotechnology, microbial synthesis of monoterpenoids has received great attention. Yeasts such Saccharomyces cerevisiae and Yarrowia lipolytica are emerging as potential hosts for monoterpenoids production because of unique advantages including rapid growth cycles, mature gene editing tools, and clear genetic background. Recently, advancements in metabolic engineering and fermentation engineering have significantly enhanced the accumulation of monoterpenoids in cell factories. First, this review introduces the biosynthetic pathway of monoterpenoids and comprehensively summarizes the latest production strategies, which encompass enhancing precursor flux, modulating the expression of rate-limited enzymes, suppressing competitive pathway flux, mitigating cytotoxicity, optimizing substrate utilization, and refining the fermentation process. Subsequently, this review introduces four representative monoterpenoids. Finally, we outline the future prospects for efficient construction cell factories tailored for the production of monoterpenoids and other terpenoids.

Engineering yeast for the production of plant terpenoids using synthetic biology approaches

Covering: 2011-2022The low amounts of terpenoids produced in plants and the difficulty in synthesizing these complex structures have stimulated the production of terpenoid compounds in microbial hosts by metabolic engineering and synthetic biology approaches. Advances in engineering yeast for terpenoid production will be covered in this review focusing on four directions: (1) manipulation of host metabolism, (2) rewiring and reconstructing metabolic pathways, (3) engineering the catalytic activity, substrate selectivity and product specificity of biosynthetic enzymes, and (4) localizing terpenoid production via enzymatic fusions and scaffolds, or subcellular compartmentalization.

Enhancing precursor supply and modulating metabolism to achieve high-level production of β-farnesene in Yarrowia lipolytica

β-Farnesene is a sesquiterpene commonly found in essential oils of plants, with applications spanning from agricultural pest control and biofuels to industrial chemicals. The use of renewable substrates in microbial cell factories offers a sustainable approach to β-farnesene biosynthesis. In this study, malic enzyme from Mucor circinelloides was examined for NADPH regeneration, concomitant with the augmentation of cytosolic acetyl-CoA supply by expressing ATP-citrate lyase from Mus musculus and manipulating the citrate pathway via AMP deaminase and isocitrate dehydrogenase. Carbon flux was modulated through the elimination of native 6-phosphofructokinase, while the incorporation of an exogenous non-oxidative glycolysis pathway served to bridge the pentose phosphate pathway with the mevalonate pathway. The resulting orthogonal precursor supply pathway facilitated β-farnesene production, reaching 810 mg/L in shake-flask fermentation. Employing optimal fermentation conditions and feeding strategy, a titer of 28.9 g/L of β-farnesene was attained in a 2 L bioreactor.

High-Yield Biosynthesis of trans-Nerolidol from Sugar and Glycerol

Isoprenoids, or terpenoids, have wide applications in food, feed, pharmaceutical, and cosmetic industries. Nerolidol, an acyclic C15 isoprenoid, is widely used in cosmetics, food, and personal care products. Current supply of nerolidol is mainly from plant extraction that is inefficient, costly, and of inconsistent quality. Here, we screened various nerolidol synthases from bacteria, fungi, and plants and found that the strawberry nerolidol synthase was most active in Escherichia coli. Through systematic optimization of the biosynthetic pathways, carbon sources, inducer, and genome editing, we constructed a series of deletion strains (single mutants ΔldhA, ΔpoxB, ΔpflB, and ΔtnaA; double mutants ΔadhE-ΔldhA; and triple mutants and beyond ΔadhE-ΔldhA-ΔpflB and ΔadhE-ΔldhA-ΔackA-pta) that produced high yields of 100% trans-nerolidol. In flasks, the highest nerolidol titers were 1.8 and 3.3 g/L in glucose-only and glucose-lactose-glycerol media, respectively. The highest yield reached 26.2% (g/g), >90% of the theoretic yield. In two-phase extractive fed-batch fermentation, our strain produced ∼16 g/L nerolidol within 4 days with about 9% carbon yield (g/g). In a single-phase fed-batch fermentation, the strain produced >6.8 g/L nerolidol in 3 days. To the best of our knowledge, our titers and productivity are the highest in the literature, paving the way for future commercialization and inspiring biosynthesis of other isoprenoids.