Alleviation of the Byproducts Formation Enables Highly Efficient Biosynthesis of Rosmarinic Acid in Saccharomyces cerevisiae

p-Hydroxycinnamic Acids: Advancements in Synthetic Biology, Emerging Regulatory Targets in Gut Microbiota Interactions, and Implications for Animal Health

p-hydroxycinnamic acids (p-HCAs), a class of natural phenolic acid compounds extracted from plant resources and widely distributed, feature a C6-C3 phenylpropanoid structure. Their antioxidant, anti-inflammatory, and antibacterial activities have shown great potential for applications in food and animal feed. The interactions between p-HCAs and the gut microbiota, as well as their subsequent effects on animal health, have increasingly attracted the attention of researchers. In the context of a greener and safer future, the progress and innovation in biosynthetic technology have occupied a central position in ensuring the safety of food and feed. This review emphasizes the complex mechanisms underlying the interactions between p-HCAs and the gut microbiota, providing a solid explanation for the remarkable bioactivities of p-HCAs and their subsequent impact on animal health. Furthermore, it explores the advancements in the synthetic biology of p-HCAs. This review could aid in a basis for better understanding the underlying interactions between p-HCAs and gut microbiota and animal health.

Structure-guided engineering of 4-coumarate: CoA ligase for efficient production of rosmarinic acid in Saccharomyces cerevisiae

The utilization of genetically modified microbial cells for rosmarinic acid (RA) production is gaining increased attention as a cost-effective and sustainable approach. However, the substrate promiscuity of 4-coumarate: CoA ligase and RA synthase has been considered as a critical factor for low RA yields. In this study, we rationally engineered the substrate preference of 4-coumarate: CoA ligase (OPc4CL2) from Petroselinum crispum, resulting in a significant enhancement in RA production. Particularly, the introduction of the Y240C mutation led to a remarkable 176 % increase in RA yield. Subsequent enzymatic analysis of OPc4CL2 variants revealed diminished activity towards p-coumaric acid, resulting in insufficient time for the transformation of p-coumaric acid to 4-coumaroyl CoA to generate byproduct. Furthermore, to minimize the formation of undesired byproducts, the overexpression of 4-hydroxyphenylacetate 3-monooxygenase (OHpaB) and NADPH-flavin oxidoreductase (HpaC) was carried out to facilitate the conversion of p-coumaric acid to caffeic acid and 4-hydroxyphenyllactate to salvianic acid A, thus achieving a significant increase in RA yield of up to 329.9 mg/L (16.5 mg/g yield on glucose) in shake-flask cultivation. Finally, the engineered strain YRA113-24BHM achieved a notable RA production of 3.6 g/L (about 20.2 mg/g yield on glucose) by fed-batch fermentation. This study serves as a foundation for the sustainable biosynthesis of RA and other caffeic acid derivatives.

Proteome and metabolome of Caryocar brasiliense camb. fruit and their interaction during development

Considered the symbol fruit of the Brazilian Cerrado, pequi (Caryocar brasiliense Camb.) is an exotic and much-appreciated fruit with an internal mesocarp (edible part) with an eye-catching golden yellow color. In an unprecedented way, this study characterized the proteome throughout pequi development. The most influential and essential transcription factors operating in the regulation of pequi ripening identified were members of the MAD-box family. A group of proteins related to the methionine cycle indicates the high consumption and recycling of methionine. However this consumption does not occur mainly for the biosynthesis of ethylene, a process dependent on methionine consumption. In the bioactive compounds presented, different proteins could be correlated with the presence of these phytochemicals, such as monodehydroascorbate reductase and ascorbate peroxidase in ascorbic acid recycling; pyruvate kinase, fructose bisphosphate aldolase and phytoene synthase with carotenoid biosynthesis; S-adenosylmethionine synthase 1 as a donor of methyl groups in the formation of trigonelline and aspartate aminotransferase as a biomarker of initial regulation of the trigonelline biosynthetic pathway; phenylalanine ammonia lyase, chorismate synthesis and chalcone-flavononone isomerase in the biosynthesis of phenolic compounds. Among the volatile organic compounds identified, the majority compound in pequi was ethyl hexanoate ester, with an area of 50.68 % in the ripe fruit, and in this group of esters that was the most representative, alcohol dehydrogenase, a fundamental enzyme in the synthesis of esters, was identified with an increase of approximately 7.2 times between the first and last stages. Therefore, an extensive group of proteins and some metabolites can serve as biomarkers of ripening in pequi, as most were more expressed in the last stage, which is the ripe fruit suitable for consumption.

Strategy strengthens structural identification through hyphenating full collision energy ramp-MS2 and full exciting energy ramp-MS3 spectra: An application for metabolites identification of rosmarinic acid

"MS/MS spectrum to structure" analysis is the most challenging task for MS/MS-relied qualitative characterization. The conventional database- and computation-assisted strategies cannot reach confirmative identification, notably for isomers. Hence, an advanced strategy was proposed here through tackling the two determinant obstacles such as the transformation from elemental compositions to fragment ion structures and the linkage style amongst substructures. As typical conjugated structures, esters were measured for strategy illustration, and metabolite identification of a famous natural antioxidant namely rosmarinic acid (RosA) in rat was undertaken for applicability justification. Through programming online energy-resolved (ER)-MS for the first collision cell of Qtrap-MS device, full collision energy ramp (FCER)-MS2 spectrum was configured for [M-H]- ion of each ester to provide optimal collision energies (OCEs) for all concerned diagnostic fragment ions (DFIs), i.e. a-, b-, c-, y-, and z-type ions. The linear correlations between masses and OCEs were built for each ion type to facilitate DFIs recognition from chaotic MS2 spectrum. To identify 1st-generation fragment ions, full exciting energy ramp (FEER)-MS3 spectra were configured for key DFIs via programming the second ER-MS in the latter collision chamber. FEER-MS3 spectrum of 1st-generation fragment ion for ester was demonstrated to be identical with FEER-MS2 spectrum of certain hydrolysis product when sharing the same structure. After applying the advanced strategy to recognize DFIs and identify 1st-generation fragment ions, a total of forty metabolites (M1-M40), resulted from hydrolysis, methylation, sulfation, and glucuronidation, were unambiguously identified for RosA after oral administration. Together, the advanced bottom-up strategy hyphenating FCER-MS2 and FEER-MS3 spectra, is meaningful to strengthen "MS/MS spectrum to structure" analysis through recognizing and identifying fragment ions.

Mid-Long Chain Dicarboxylic Acid Production via Systems Metabolic Engineering: Progress and Prospects

Mid-to-long-chain dicarboxylic acids (DCAi, i ≥ 6) are organic compounds in which two carboxylic acid functional groups are present at the terminal position of the carbon chain. These acids find important applications as structural components and intermediates across various industrial sectors, including organic compound synthesis, food production, pharmaceutical development, and agricultural manufacturing. However, conventional petroleum-based DCA production methods cause environmental pollution, making sustainable development challenging. Hence, the demand for eco-friendly processes and renewable raw materials for DCA production is rising. Owing to advances in systems metabolic engineering, new tools from systems biology, synthetic biology, and evolutionary engineering can now be used for the sustainable production of energy-dense biofuels. Here, we explore systems metabolic engineering strategies for DCA synthesis in various chassis via the conversion of different raw materials into mid-to-long-chain DCAs. Subsequently, we discuss the future challenges in this field and propose synthetic biology approaches for the efficient production and successful commercialization of these acids.

Yeast: A platform for the production of L -tyrosine derivatives

L -Tyrosine derivatives are widely applied in the pharmaceutical, food, and chemical industries. Their production is mainly confined to chemical synthesis and plant extract. Microorganisms, as cell factories, exhibit promising advantages for valuable chemical production to fulfill the increase in the demand of global markets. Yeast has been used to produce natural products owing to its robustness and genetic maneuverability. Focusing on the progress of yeast cell factories for the production of L -tyrosine derivatives, we summarized the emerging metabolic engineering approaches in building L -tyrosoine-overproducing yeast and constructing cell factories of three typical chemicals and their derivatives: tyrosol, p-coumaric acid, and L -DOPA. Finally, the challenges and opportunities of L -tyrosine derivatives production in yeast cell factories were also discussed.

Coordinating caffeic acid and salvianic acid A pathways for efficient production of rosmarinic acid in Escherichia coli

Rosmarinic acid is a natural hydroxycinnamic acid ester used widely in the food and pharmaceutical industries. Although many attempts have been made to screen rate-limiting enzymes and optimize modules through co-culture fermentation, the titer of rosmarinic acid remains at the microgram level by microorganisms. A de novo biosynthetic pathway for rosmarinic acid was constructed based on caffeic acid synthesis modules in Escherichia coli. Knockout of competing pathways increased the titer of rosmarinic acid and reduced the synthesis of rosmarinic acid analogues. An L-amino acid deaminase was introduced to balance metabolic flux between the synthesis of caffeic acid and salvianic acid A. The ratio of FADH₂/FAD was maintained via the coordination of deaminase and HpaBC, which is responsible for caffeic acid synthesis. Knockout of menI, encoding an endogenous thioesterase, increased the stability of caffeoyl-CoA. The final strain produced 5780.6 mg/L rosmarinic acid in fed-batch fermentation, the highest yet reported for microbial production. The strategies applied in this study lay a foundation for the synthesis of other caffeic acid and rosmarinic acid derivatives.