Production of natural products through metabolic engineering of Saccharomyces cerevisiae

Transcriptional response of Saccharomyces cerevisiae to lactic acid enantiomers

The model yeast, Saccharomyces cerevisiae, is a popular object for both fundamental and applied research, including the development of biosensors and industrial production of pharmaceutical compounds. However, despite multiple studies exploring S. cerevisiae transcriptional response to various substances, this response is unknown for some substances produced in yeast, such as D-lactic acid (DLA). Here, we explore the transcriptional response of the BY4742 strain to a wide range of DLA concentrations (from 0.05 to 45 mM), and compare it to the response to 45 mM L-lactic acid (LLA). We recorded a response to 5 and 45 mM DLA (125 and 113 differentially expressed genes (DEGs), respectively; > 50% shared) and a less pronounced response to 45 mM LLA (63 DEGs; > 30% shared with at least one DLA treatment). Our data did not reveal natural yeast promoters quantitatively sensing DLA but provide the first description of the transcriptome-wide response to DLA and enrich our understanding of the LLA response. Some DLA-activated genes were indeed related to lactate metabolism, as well as iron uptake and cell wall structure. Additional analyses showed that at least some of these genes were activated only by acidic form of DLA but not its salt, revealing the role of pH. The list of LLA-responsive genes was similar to those published previously and also included iron uptake and cell wall genes, as well as genes responding to other weak acids. These data might be instrumental for optimization of lactate production in yeast and yeast co-cultivation with lactic acid bacteria. KEY POINTS: • We present the first dataset on yeast transcriptional response to DLA. • Differential gene expression was correlated with yeast growth inhibition. • The transcriptome response to DLA was richer in comparison to LLA.

Efficient Biosynthesis of Salidroside via Artificial in Vivo enhanced UDP-Glucose System Using Cheap Sucrose as Substrate

Salidroside, a valuable phenylethanoid glycoside, is obtained from plants belonging to the Rhodiola genus, known for its diverse biological properties. At present, salidroside is still far from large-scale industrial production due to its lower titer and higher process cost. In this study, we have for the first time increased salidroside production by enhancing UDP-glucose supply in situ. We constructed an in vivo UDP-glucose regeneration system that works in conjunction with UDP-glucose transferase from Rhodiola innovatively to improve UDP-glucose availability. And a coculture was formed in order to enable de novo salidroside synthesis. Confronted with the influence of tyrosol on strain growth, an adaptive laboratory evolution strategy was implemented to enhance the strain's tolerance. Similarly, salidroside production was optimized through refinement of the fermentation medium, the inoculation ratio of the two microbes, and the inoculation size. The final salidroside titer reached 3.8 g/L. This was the highest titer achieved at the shake flask level in the existing reports. And this marked the first successful synthesis of salidroside in an in situ enhanced UDP-glucose system using sucrose. The cost was reduced by 93% due to the use of inexpensive substrates. This accomplishment laid a robust foundation for further investigations into the synthesis of other notable glycosides and natural compounds.

Sustainable production of natural products using synthetic biology: Ginsenosides

Synthetic biology approaches offer potential for large-scale and sustainable production of natural products with bioactive potency, including ginsenosides, providing a means to produce novel compounds with enhanced therapeutic properties. Ginseng, known for its non-toxic and potent qualities in traditional medicine, has been used for various medical needs. Ginseng has shown promise for its antioxidant and neuroprotective properties, and it has been used as a potential agent to boost immunity against various infections when used together with other drugs and vaccines. Given the increasing demand for ginsenosides and the challenges associated with traditional extraction methods, synthetic biology holds promise in the development of therapeutics. In this review, we discuss recent developments in microorganism producer engineering and ginsenoside production in microorganisms using synthetic biology approaches.

High-level phenol bioproduction by engineered Pichia pastoris in glycerol fed-batch fermentation using an efficient pertraction system

This study aimed to establish a high-level phenol bioproduction system from glycerol through metabolic engineering of the yeast Pichia pastoris (Komagataella phaffii). Introducing tyrosine phenol-lyase to P. pastoris led to a production of 59 mg/L of phenol in flask culture. By employing a strain of P. pastoris that overproduces tyrosine-a precursor to phenol-we achieved a phenol production of 1052 mg/L in glycerol fed-batch fermentation. However, phenol concentrations exceeding 1000 mg/L inhibited P. pastoris growth. A phenol pertraction system utilizing a hollow fiber membrane contactor and tributyrin as the organic solvent was developed to reduce phenol concentration in the culture medium. Integrating this system with glycerol fed-batch fermentation resulted in a 214 % increase in phenol titer (3304 mg/L) compared to glycerol fed-batch fermentation alone. These approaches offer a significant framework for the microbial production of chemicals and materials that are highly toxic to microorganisms.

Therapeutic effects and mechanisms of Inonotus hispidus extract and active monomer compounds in a rat mammary gland hyperplasia model

ETHNOPHARMACOLOGICAL RELEVANCE

Inonotus hispidus is the traditional Chinese medicine Sanghuang. Since ancient times, Sanghuang has been documented to be used in the treatment of female breast diseases. However, the pharmacological mechanism of Sanghuang in the treatment of mammary gland hyperplasia (HMG) remains unclear.

AIM OF THE STUDY

The ethyl acetate extract of the aging fruiting body of I. hispidus (IEAE) was used to study the pharmacological mechanism of IEAE in the treatment of HMG using non-targeted metabolomics.

MATERIALS AND METHODS

The HMG rat model was established, and serum metabolomics was used to study the potential therapeutic mechanism of IEAE for HMG.

RESULTS

IEAE has obvious therapeutic effect on HMG model rats, and no obvious adverse reactions were observed. Non-targeted metabolomics showed that after IEAE intervention, the upstream metabolite D-erythrose 4-phosphate was significantly downregulated, aromatic amino acids such as tryptophan, tyrosine, and phenylalanine were downregulated, and the downstream metabolites N-acetyl-L-glutamate and L-proline were significantly upregulated. After an intervention with yakuchinone A, non-targeted metabolomics analyses demonstrated that yakuchinone A restored tetrahydrocorticosterone, cortisol, and etiocholanolone to normal levels, estriol was significantly upregulated, and steroid hormone biosynthesis was significantly activated.

CONCLUSION

IEAE was shown to have a good therapeutic effect on HMG in a rat model without adverse reactions. The mechanism of action was mainly based on the biosynthesis of amino acids. Small molecule metabolites such as D-erythrose 4-phosphate, N-acetyl-L-glutamate, and L-proline may be potential targets for IEAE in the treatment of HMG. Yakuchinone A is one of the main active components of IEAE, and plays a role by promoting the steroid hormone biosynthesis pathway. Estriol may be a potential target for the treatment of HMG with yakuchinone A, providing a new concept for clinical treatment of HMG.

Saccharomyces cerevisiae biofactory to produce naringenin using a systems biology approach and a bicistronic vector expression strategy in flavonoid production

IMPORTANCE

Flavonoids are a group of compounds generally produced by plants with proven biological activity, which have recently beeen recommended for the treatment and prevention of diseases and ailments with diverse causes. In this study, naringenin was produced in adequate amounts in yeast after in silico design. The four genes of the involved enzymes from several organisms (bacteria and plants) were multi-expressed in two vectors carrying each two genes linked by a short viral peptide sequence. The batch kinetic behavior of the product, substrate, and biomass was described at lab scale. The engineered strain might be used in a more affordable and viable bioprocess for industrial naringenin procurement.

Boosting production of cembratriene-ol in Saccharomyces cerevisiae via systematic optimization

Cembratriene-ol is a good biodegradable biopesticide ingredient with future potential applications in the field of sustainable agriculture. Cembratriene-ol is a monocyclic diterpenoid compound that is synthesized only in the trichome gland of Nicotiana plants. In this study, geranylgeranyl diphosphate synthase gene ggpps from Taxus canadensis and cbts*Δp were heterologously expressed in Saccharomyces cerevisiae W303-1A to successfully synthesize cembratriene-ol. The titer of cembratriene-ol was increased by 1.84-fold compared to the control by overexpressing the S. cerevisiae bifunctional (2E,6E)-farnesyl diphosphate synthase genes ERG20 and cbts*Δp under one promoter PGAP . The titer of cembratriene-ol in the engineered S. cerevisiae BY4741 was increased by 1.39-fold compared to the engineered S. cerevisiae W303-1A. The titer of cembratriene-ol in the engineered S. cerevisiae BY4741 was increased by 2.22-fold compared to the control by overexpressing ERG20 and cbts*Δp, respectively, using two promoters PGAP . Cembratriene-ol was found to be successfully synthesized via the integrated expression of cbts*Δp, ggpps and ERG20 on the genome of S. cerevisiae BY4741. The titer of cembratriene-ol in S. cerevisiae S25 was further increased by 1.80-fold compared to the control via dynamic control of the squalene synthase gene ERG9. Overexpression of the genes cbts*Δp and ggpps using pY26-GPD-TEF in S. cerevisiae S25 with their integration expression increased the titer of cembratriene-ol by 26.1-fold compared to S. cerevisiae S25. The titer of cembratriene-ol was significantly enhanced by mitochondrial compartmentalized expression of cbts*Δp and ggpps, which was 76.3-fold higher than that of the initial strain constructed. It was indicated that the systematic optimization has great potential in facilitating high-level production of cembratriene-ol production in S. cerevisiae.

Aromatic secondary metabolite production from glycerol was enhanced by amino acid addition in Pichia pastoris

Aromatic secondary metabolites are widely used in various industries, including the nutraceutical, dietary supplement, and pharmaceutical industries. Their production currently relies on plant extraction. Microbe-based processes have recently attracted attention as sustainable alternatives to plant-based processes. We previously showed that the yeast Pichia pastoris (Komagataella phaffii) is an optimal host for producing aromatic secondary metabolites. Additionally, titers of resveratrol, an aromatic secondary metabolite, increased by 156 % when glycerol was used as a carbon source instead of glucose. However, the mechanisms by which glycerol resulted in higher production has remained unclear. In this study, we aimed to elucidate how P. pastoris produces higher levels of aromatic secondary metabolites from glycerol than from glucose. Titers of p-coumarate, naringenin, and resveratrol increased by 103 %, 118 %, and 157 %, respectively, in natural complex media containing glycerol compared with that in media containing glucose. However, the titers decreased in minimal synthetic medium without amino acids, indicating that P. pastoris cells used the amino acids only when glycerol was the carbon source. Fermentation with the addition of single amino acids showed that resveratrol titers from glycerol varied depending on the amino acid supplemented. In particular, addition of aspartate or tryptophan into the medium improved resveratrol titers by 146 % and 156 %, respectively. These results suggest that P. pastoris could produce high levels of aromatic secondary metabolites from glycerol with enhanced utilization of specific amino acids. This study provides a basis for achieving high-level production of aromatic secondary metabolites by P. pastoris. KEY POINTS: • P. pastoris can produce high levels of aromatic metabolites from glycerol • P. pastoris cells use amino acids only when glycerol is the carbon source • Aromatic metabolite titers from glycerol increase with amino acids utilization.

An outlook to sophisticated technologies and novel developments for metabolic regulation in the Saccharomyces cerevisiae expression system

Saccharomyces cerevisiae is one of the most extensively used biosynthetic systems for the production of diverse bioproducts, especially biotherapeutics and recombinant proteins. Because the expression and insertion of foreign genes are always impaired by the endogenous factors of Saccharomyces cerevisiae and nonproductive procedures, various technologies have been developed to enhance the strength and efficiency of transcription and facilitate gene editing procedures. Thus, the limitations that block heterologous protein secretion have been overcome. Highly efficient promoters responsible for the initiation of transcription and the accurate regulation of expression have been developed that can be precisely regulated with synthetic promoters and double promoter expression systems. Appropriate codon optimization and harmonization for adaption to the genomic codon abundance of S. cerevisiae are expected to further improve the transcription and translation efficiency. Efficient and accurate translocation can be achieved by fusing a specifically designed signal peptide to an upstream foreign gene to facilitate the secretion of newly synthesized proteins. In addition to the widely applied promoter engineering technology and the clear mechanism of the endoplasmic reticulum secretory pathway, the innovative genome editing technique CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated system) and its derivative tools allow for more precise and efficient gene disruption, site-directed mutation, and foreign gene insertion. This review focuses on sophisticated engineering techniques and emerging genetic technologies developed for the accurate metabolic regulation of the S. cerevisiae expression system.

Sustainable metabolic engineering requires a perfect trifecta

The versatility of cellular metabolism in converting various substrates to products inspires sustainable alternatives to conventional chemical processes. Metabolism can be engineered to maximize the yield, rate, and titer of product generation. However, the numerous combinations of substrate, product, and organism make metabolic engineering projects difficult to navigate. A perfect trifecta of substrate, product, and organism is prerequisite for an environmentally and economically sustainable metabolic engineering endeavor. As a step toward this endeavor, we propose a reverse engineering strategy that starts with product selection, followed by substrate and organism pairing. While a large bioproduct space has been explored, the top-ten compounds have been synthesized mainly using glucose and model organisms. Unconventional feedstocks (e.g. hemicellulosic sugars and CO2) and non-model organisms are increasingly gaining traction for advanced bioproduct synthesis due to their specialized metabolic modes. Judicious selection of the substrate-organism-product combination will illuminate the untapped territory of sustainable metabolic engineering.

A newly identified β-amyrin synthase gene hypothetically involved in oleanane-saponin biosynthesis from Talinum paniculatum (Jacq.) Gaertn

Talinum paniculatum or Javanese ginseng in Indonesia is a plant widely used as a traditional medicine. The genus Talinum produces oleanane-type saponins, such as talinumoside I. The first aim of this study was to isolate the probable gene encoding β-amyrin synthase (bAS), a key enzyme involved in the cyclization of 2,3-oxidosqualene producing the backbone of the oleanane-type saponin β-amyrin and characterize the gene sequence and the predicted protein sequence using in silico approach. The second aim was to analyze the correlation between the TpbAS gene expression level and saponin production in various plant organs. Thus, TpbAS was isolated using degenerate primers and PCR 5'/3'-Rapid Amplification of cDNA Ends (RACE), then the gene sequence and the predicted protein were in silico analyzed using various programs. TpbAS expression level was analyzed using reverse transcriptase PCR (RT-PCR), and saponin content was measured using a spectrophotometer. The results showed that the full-length TpbAS gene consists of 2298 base pairs encoding for a 765-amino acid protein. From in silico study, the (GA)n sequence was identified in the 5'-untranslated regions and predicted to be a candidate of the gene expression modulator. In addition, functional RNA motifs and sites analysis predicted the presence of exon splicing enhancers and silencers within the coding sequence and miRNA target sites candidate. Amino acid sequence analysis showed DCTAE, QW, and WCYCR motifs that were conserved in all classes of oxidosqualene cyclase enzymes. Phylogenetic tree analysis showed that TpbAS is closely related to other plant oxidosqualene cyclase groups. Analysis of TpbAS expression and saponin content indicated that saponin is mainly synthesized and accumulated in the leaves. Taken together, these findings will assist in increasing the saponin content through a metabolic engineering approach.

Effects of Protein Components on the Chemical Composition and Sensory Properties of Millet Huangjiu (Chinese Millet Wine)

Millet Huangjiu is a national alcoholic beverage in China. The quality of Chinese millet Huangjiu is significantly influenced by the protein components in the raw materials of millet. Therefore, in this study, the impact of different protein components on the quality of millet Huangjiu was investigated by adding exogenous proteins glutelin and albumin either individually or in combination. The study commenced with the determination of the oenological parameters of different millet Huangjiu samples, followed by the assessment of free amino acids and organic acids. In addition, the volatile profiles of millet Huangjiu were characterized by employing HS-SPME-GC/MS. Finally, a sensory evaluation was conducted to evaluate the overall aroma profiles of millet Huangjiu. The results showed that adding glutelin significantly increased the contents of total soluble solids, amino acid nitrogen, and ethanol in millet Huangjiu by 32.2%, 41.5%, and 17.7%, respectively. Furthermore, the fortification of the fermentation substrate with glutelin protein was found to significantly enhance the umami (aspartic and glutamic acids) and sweet-tasting (alanine and proline) amino acids in the final product. Gas chromatography-quadrupole mass spectrometry coupled with multivariate statistical analysis revealed distinct impacts of protein composition on the volatile organic compound (VOC) profiles of millet Huangjiu. Excessive glutelin led to an over-accumulation of alcohol aroma, while the addition of albumin protein proved to be a viable approach for enhancing the ester and fruity fragrances. Sensory analysis suggested that the proper amount of protein fortification using a Glu + Alb combination could enhance the sensory attributes of millet Huangjiu while maintaining its unique flavor characteristics. These findings suggest that reasonable adjustment of the glutelin and albumin contents in millet could effectively regulate the chemical composition and improve the sensory quality of millet Huangjiu.

Modular Coculture to Reduce Substrate Competition and Off-Target Intermediates in Androstenedione Biosynthesis

Substrate competition within a metabolic network constitutes a common challenge in microbial biosynthesis system engineering, especially if indispensable enzymes can produce multiple intermediates from a single substrate. Androstenedione (4AD) is a central intermediate in the production of a series of steroidal pharmaceuticals; however, its yield via the coexpression of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17α-hydroxylase/17,20-lyase (CYP17A1) in a microbial chassis affords a nonlinear pathway in which these enzymes compete for substrates and produce structurally similar unwanted intermediates, thereby reducing 4AD yields. To avoid substrate competition, we split the competing 3β-HSD and CYP17A1 pathway components into two separate Yarrowia lipolytica strains to linearize the pathway. This spatial segregation increased substrate availability for 3β-HSD in the upstream strain, consequently decreasing the accumulation of the unwanted intermediate 17-hydroxypregnenolone (17OHP5) from 94.8 ± 4.4% in single-chassis monocultures to 24.8 ± 12.6% in cocultures of strains expressing 3β-HSD and CYP17A1 separately. Orthologue screening to increase CYP17A1 catalytic efficiency and the preferential production of desired intermediates increased the biotransformation capacity in the downstream pathway, further decreasing 17OHP5 accumulation to 3.9%. Furthermore, nitrogen limitation induced early 4AD accumulation (final titer, 7.71 mg/L). This study provides a framework for reducing intrapathway competition between essential enzymes during natural product biosynthesis as well as a proof-of-concept platform for linear steroid production.

Efficient biosynthesis of resveratrol via combining phenylalanine and tyrosine pathways in Saccharomyces cerevisiae

BACKGROUND

Resveratrol is a commercially available stilbenoid widely used as dietary supplements, functional food ingredients, and cosmetic ingredients due to its diverse physiological activities. The production of resveratrol in microorganisms provides an ideal source that reduces the cost of resveratrol, but the titer in Saccharomyces cerevisiae was still much lower than that in other hosts.

RESULTS

To achieve enhanced production of resveratrol in S. cerevisiae, we constructed a biosynthetic pathway via combining phenylalanine and tyrosine pathways by introducing a bi-functional phenylalanine/tyrosine ammonia lyase from Rhodotorula toruloides. The combination of phenylalanine pathway with tyrosine pathway led to a 462% improvement of resveratrol production in yeast extract peptone dextrose (YPD) medium with 4% glucose, suggesting an alternative strategy for producing p-coumaric acid-derived compounds. Then the strains were further modified by integrating multi-copy biosynthetic pathway genes, improving metabolic flux to aromatic amino acids and malonyl-CoA, and deleting by-pathway genes, which resulted in 1155.0 mg/L resveratrol in shake flasks when cultured in YPD medium. Finally, a non-auxotrophic strain was tailored for resveratrol production in minimal medium without exogenous amino acid addition, and the highest resveratrol titer (4.1 g/L) ever reported was achieved in S. cerevisiae to our knowledge.

CONCLUSIONS

This study demonstrates the advantage of employing a bi-functional phenylalanine/tyrosine ammonia lyase in the biosynthetic pathway of resveratrol, suggesting an effective alternative in the production of p-coumaric acid-derived compounds. Moreover, the enhanced production of resveratrol in S. cerevisiae lays a foundation for constructing cell factories for various stilbenoids.

Efficient production of cembratriene-ol in Escherichia coli via systematic optimization

BACKGROUND

The tobacco leaf-derived cembratriene-ol exhibits anti-insect effects, but its content in plants is scarce. Cembratriene-ol is difficult and inefficiently chemically synthesised due to its complex structure. Moreover, the titer of reported recombinant hosts producing cembratriene-ol was low and cannot be applied to industrial production.

RESULTS

In this study, Pantoea ananatis geranylgeranyl diphosphate synthase (CrtE) and Nicotiana tabacum cembratriene-ol synthase (CBTS) were heterologously expressed to synthsize the cembratriene-ol in Escherichia coli. Overexpression of cbts*, the 1-deoxy-D-xylulose 5-phosphate synthase gene dxs, and isopentenyl diphosphate isomerase gene idi promoted the production of cembratriene-ol. The cembratriene-ol titer was 1.53-folds higher than that of E. coli Z17 due to the systematic regulation of ggpps, cbts*, dxs, and idi expression. The production of cembratriene-ol was boosted via the overexpression of genes ispA, ispD, and ispF. The production level of cembratriene-ol in the optimal medium at 72 h was 8.55-folds higher than that before fermentation optimisation. The cembratriene-ol titer in the 15-L fermenter reached 371.2 mg L^- 1, which was the highest titer reported.

CONCLUSION

In this study, the production of cembratriene-ol in E. coli was significantly enhanced via systematic optimization. It was suggested that the recombinant E. coli producing cembratriene-ol constructed in this study has potential for industrial production and applications.

A well-characterized polycistronic-like gene expression system in yeast

Efficient expression of multiple genes is critical to yeast metabolic engineering for the bioproduction of bulk and fine chemicals. A yeast polycistronic expression system is of particular interest because one promoter can drive the expression of multiple genes. 2A viral peptides enable the cotranslation of multiple proteins from a single mRNA by ribosomal skipping. However, the wide adaptation of 2A viral peptides for polycistronic-like gene expression in yeast awaits in-depth characterizations. Additionally, a one-step assembly of such a polycistronic-like system is highly desirable. To this end, we have developed a modular cloning (MoClo) compatible 2A peptide-based polycistronic-like system capable of expressing multiple genes from a single promoter in yeast. Characterizing the bi-, tri-, and quad-cistronic expression of fluorescent proteins showed high cleavage efficiencies of three 2A peptides: E2A from equine rhinitis B virus, P2A from porcine teschovirus-1, and O2A from Operophtera brumata cypovirus-18. Applying the polycistronic-like system to produce geraniol, a valuable industrial compound, resulted in comparable or higher titers than using conventional monocistronic constructs. In summary, this highly-characterized polycistronic-like gene expression system is another tool to facilitate multigene expression for metabolic engineering in yeast.

Potential applications of pulsed electric field in the fermented wine industry

Fermented wine refers to alcoholic beverages with complex flavor substances directly produced by raw materials (fruit or rice) through microbial fermentation (yeast and bacteria). Its production steps usually include saccharification, fermentation, filtration, sterilization, aging, etc., which is a complicated and time-consuming process. Pulsed electric field (PEF) is a promising non-thermal food processing technology. Researchers have made tremendous progress in the potential application of PEF in the fermented wine industry over the past few years. The objective of this paper is to systematically review the achievements of PEF technology applied to the winemaking and aging process of fermented wine. Research on the application of PEF in fermented wine suggests that PEF treatment has the following advantages: (1) shortening the maceration time of brewing materials; (2) promoting the extraction of main functional components; (3) enhancing the color of fermented wine; (4) inactivating spoilage microorganisms; and (5) accelerating the formation of aroma substances. These are mainly related to PEF-induced electroporation of biomembranes, changes in molecular structure and the occurrence of chemical reactions. In addition, the key points of PEF treatments for fermented wine are discussed and some negative impacts and research directions are proposed.

A p-Coumaroyl-CoA Biosensor for Dynamic Regulation of Naringenin Biosynthesis in Saccharomyces cerevisiae

In vivo biosensors that can convert metabolite concentrations into measurable output signals are valuable tools for high-throughput screening and dynamic pathway control in the field of metabolic engineering. Here, we present a novel biosensor in Saccharomyces cerevisiae that is responsive to p-coumaroyl-CoA, a central precursor of many flavonoids. The sensor is based on the transcriptional repressor CouR from Rhodopseudomonas palustris and was applied in combination with a previously developed malonyl-CoA biosensor for dual regulation of p-coumaroyl-CoA synthesis within the naringenin production pathway. Using this approach, we obtained a naringenin titer of 47.3 mg/L upon external precursor feeding, representing a 15-fold increase over the nonregulated system.

Engineered biosynthesis of plant polyketides by type III polyketide synthases in microorganisms

Plant specialized metabolites occupy unique therapeutic niches in human medicine. A large family of plant specialized metabolites, namely plant polyketides, exhibit diverse and remarkable pharmaceutical properties and thereby great biomanufacturing potential. A growing body of studies has focused on plant polyketide synthesis using plant type III polyketide synthases (PKSs), such as flavonoids, stilbenes, benzalacetones, curcuminoids, chromones, acridones, xanthones, and pyrones. Microbial expression of plant type III PKSs and related biosynthetic pathways in workhorse microorganisms, such as Saccharomyces cerevisiae, Escherichia coli, and Yarrowia lipolytica, have led to the complete biosynthesis of multiple plant polyketides, such as flavonoids and stilbenes, from simple carbohydrates using different metabolic engineering approaches. Additionally, advanced biosynthesis techniques led to the biosynthesis of novel and complex plant polyketides synthesized by diversified type III PKSs. This review will summarize efforts in the past 10 years in type III PKS-catalyzed natural product biosynthesis in microorganisms, especially the complete biosynthesis strategies and achievements.

Construction of an l-Tyrosine Chassis in Pichia pastoris Enhances Aromatic Secondary Metabolite Production from Glycerol

Bioactive plant-based secondary metabolites such as stilbenoids, flavonoids, and benzylisoquinoline alkaloids (BIAs) are produced from l-tyrosine (l-Tyr) and have a wide variety of commercial applications. Therefore, building a microorganism with high l-Tyr productivity (l-Tyr chassis) is of immense value for large-scale production of various aromatic compounds. The aim of this study was to develop an l-Tyr chassis in the nonconventional yeast Pichia pastoris (Komagataella phaffii) to produce various aromatic secondary metabolites (resveratrol, naringenin, norcoclaurine, and reticuline). Overexpression of feedback-inhibition insensitive variants of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase (ARO4^K229L) and chorismate mutase (ARO7^G141S) enhanced l-Tyr titer from glycerol in P. pastoris. These engineered P. pastoris strains increased the titer of resveratrol, naringenin, and norcoclaurine by 258, 244, and 3400%, respectively, after expressing the corresponding heterologous pathways. The titer of resveratrol and naringenin further increased by 305 and 249%, resulting in yields of 1825 and 1067 mg/L, respectively, in fed-batch fermentation, which is the highest titer from glycerol reported to date. Furthermore, the resveratrol-producing strain accumulated intermediates in the shikimate pathway. l-Tyr-derived aromatic compounds were produced using crude glycerol byproducts from biodiesel fuel (BDF) production. Constructing an l-Tyr chassis is a promising strategy to increase the titer of various aromatic secondary metabolites and P. pastoris is an attractive host for high-yield production of l-Tyr-derived aromatic compounds from glycerol.

In Silico Design Strategies for the Production of Target Chemical Compounds Using Iterative Single-Level Linear Programming Problems

The optimization of metabolic reaction modifications for the production of target compounds is a complex computational problem whose execution time increases exponentially with the number of metabolic reactions. Therefore, practical technologies are needed to identify reaction deletion combinations to minimize computing times and promote the production of target compounds by modifying intracellular metabolism. In this paper, a practical metabolic design technology named AERITH is proposed for high-throughput target compound production. This method can optimize the production of compounds of interest while maximizing cell growth. With this approach, an appropriate combination of metabolic reaction deletions can be identified by solving a simple linear programming problem. Using a standard CPU, the computation time could be as low as 1 min per compound, and the system can even handle large metabolic models. AERITH was implemented in MATLAB and is freely available for non-profit use.

Developing Multi-Copy Chromosomal Integration Strategies for Heterologous Biosynthesis of Caffeic Acid in Saccharomyces cerevisiae

Caffeic acid, a plant-sourced phenolic compound, has a variety of biological activities, such as antioxidant and antimicrobial properties. The caffeic acid biosynthetic pathway was initially constructed in S. cerevisiae, using codon-optimized TAL (coTAL, encoding tyrosine ammonia lyase) from Rhodobacter capsulatus, coC3H (encoding p-coumaric acid 3-hydroxylase) and coCPR1 (encoding cytochrome P450 reductase 1) from Arabidopsis thaliana in 2 μ multi-copy plasmids to produce caffeic acid from glucose. Then, integrated expression of coTAL via delta integration with the POT1 gene (encoding triose phosphate isomerase) as selection marker and episomal expression of coC3H, coCPR1 using the episomal plasmid pLC-c3 were combined, and caffeic acid production was proved to be improved. Next, the delta and rDNA multi-copy integration methods were applied to integrate the genes coC3H and coCPR1 into the chromosome of high p-coumaric acid yielding strain QT3-20. The strain D9 constructed via delta integration outperformed the other strains, leading to 50-fold increased caffeic acid production in optimized rich media compared with the initial construct. The intercomparison between three alternative multi-copy strategies for de novo synthesis of caffeic acid in S. cerevisiae suggested that delta-integration was effective in improving caffeic acid productivity, providing a promising strategy for the production of valuable bio-based chemicals in recombinant S. cerevisiae.

Engineering eukaryote-like regulatory circuits to expand artificial control mechanisms for metabolic engineering in Saccharomyces cerevisiae

Temporal control of heterologous pathway expression is critical to achieve optimal efficiency in microbial metabolic engineering. The broadly-used GAL promoter system for engineered yeast (Saccharomyces cerevisiae) suffers from several drawbacks; specifically, unintended induction during laboratory development, and unintended repression in industrial production applications, which decreases overall production capacity. Eukaryotic synthetic circuits have not been well examined to address these problems. Here, we explore a modularised engineering method to deploy new genetic circuits applicable for expanding the control of GAL promoter-driven heterologous pathways in S. cerevisiae. Trans- and cis- modules, including eukaryotic trans-activating-and-repressing mechanisms, were characterised to provide new and better tools for circuit design. A eukaryote-like tetracycline-mediated circuit that delivers stringent repression was engineered to minimise metabolic burden during strain development and maintenance. This was combined with a novel 37 °C induction circuit to relief glucose-mediated repression on the GAL promoter during the bioprocess. This delivered a 44% increase in production of the terpenoid nerolidol, to 2.54 g L^-1 in flask cultivation. These negative/positive transcriptional regulatory circuits expand global strategies of metabolic control to facilitate laboratory maintenance and for industry applications.

Saccharomyces cerevisiae as a Heterologous Host for Natural Products

Cell factories can provide a sustainable supply of natural products with applications as pharmaceuticals, food-additives or biofuels. Besides being an important model organism for eukaryotic systems, Saccharomyces cerevisiae is used as a chassis for the heterologous production of natural products. Its success as a cell factory can be attributed to the vast knowledge accumulated over decades of research, its overall ease of engineering and its robustness. Many methods and toolkits have been developed by the yeast metabolic engineering community with the aim of simplifying and accelerating the engineering process.In this chapter, a range of methodologies are highlighted, which can be used to develop novel natural product cell factories or to improve titer, rate and yields of an existing cell factory with the goal of developing an industrially relevant strain. The addressed topics are applicable for different stages of a cell factory engineering project and include the choice of a natural product platform strain, expression cassette design for heterologous or native genes, basic and advanced genetic engineering strategies, and library screening methods using biosensors. The many engineering methods available and the examples of yeast cell factories underline the importance and future potential of this host for industrial production of natural products.

Metabolism and strategies for enhanced supply of acetyl-CoA in Saccharomyces cerevisiae

Acetyl-CoA is a kind of important cofactor that is involved in many metabolic pathways. It serves as the precursor for many interesting commercial products, such as terpenes, flavonoids and anthraquinones. However, the insufficient supply of acetyl-CoA limits biosynthesis of its derived compounds in the intracellular. In this review, we outlined metabolic pathways involved in the catabolism and anabolism of acetyl-CoA, as well as some important derived products. We examined several strategies for the enhanced supply of acetyl-CoA, and provided insight into pathways that generate acetyl-CoA to balance metabolism, which can be harnessed to improve the titer, yield and productivities of interesting products in Saccharomyces cerevisiae and other eukaryotic microorganisms. We believe that peroxisomal fatty acid β-oxidation could be an attractive strategy for enhancing the supply of acetyl-CoA.

The sensory and flavor characteristics of Shaoxing Huangjiu (Chinese rice wine) were significantly influenced by micro-oxygen and electric field

In order to improve the high cost of equipment and difficult management caused by the natural aging of Chinese rice wine (Huangjiu), micro-oxygen (MO) and electric field (PEF) technology are used to accelerate the aging of Huangjiu. The results showed that micro-oxygen and electric field have a significant effect on the sensory characteristics and flavor characteristics of Huangjiu. Compared with the naturally aged Huangjiu, the flavor compounds of Huangjiu treated with micro-oxygen and electric field increase significantly. Based on principal component analysis, Huangjiu processed at 0.35 mg L/day or 0.5 mg L/day combined electric field exhibited similar flavor to the natural aged Huangjiu, which was highly associated with long-chain fatty acid ethyl esters (C13-C18). Moreover, partial least squares regression demonstrated that sensory attributes of cereal aroma and astringency were highlighted after aging time, while fruit aroma, continuation, and full body were dominant after micro-oxygen and electric field treatment. Micro-oxygen and electric field effectively enhanced the quality of Huangjiu, which could be applied in other alcoholic beverages.

Monoterpenoid biosynthesis by engineered microbes

Monoterpenoids are C10 isoprenoids and constitute a large family of natural products. They have been used as ingredients in food, cosmetics and therapeutic products. Many monoterpenoids such as linalool, geraniol, limonene and pinene are volatile and can be found in plant essential oils. Conventionally, these bioactive compounds are obtained from plant extracts by using organic solvents or by distillation method, which are costly and laborious if high purity product is desired. In recent years, microbial biosynthesis has emerged as alternative source of monoterpenoids with great promise for meeting the increasing global demand for these compounds. However, current methods of production are not yet at levels required for commercialization. Production efficiency of monoterpenoids in microbial hosts is often restricted by high volatility of the monoterpenoids, a lack of enzymatic activity and selectivity, and/or product cytotoxicity to the microbial hosts. In this review, we summarize advances in microbial production of monoterpenoids over the past three years with particular focus on the key metabolic engineering strategies for different monoterpenoid products. We also provide our perspective on the promise of future endeavors to improve monoterpenoid productivity.

¡Viva la mitochondria!: harnessing yeast mitochondria for chemical production

The mitochondria, often referred to as the powerhouse of the cell, offer a unique physicochemical environment enriched with a distinct set of enzymes, metabolites and cofactors ready to be exploited for metabolic engineering. In this review, we discuss how the mitochondrion has been engineered in the traditional sense of metabolic engineering or completely bypassed for chemical production. We then describe the more recent approach of harnessing the mitochondria to compartmentalize engineered metabolic pathways, including for the production of alcohols, terpenoids, sterols, organic acids and other valuable products. We explain the different mechanisms by which mitochondrial compartmentalization benefits engineered metabolic pathways to boost chemical production. Finally, we discuss the key challenges that need to be overcome to expand the applicability of mitochondrial engineering and reach the full potential of this emerging field.

A Review on the Obtaining of Functional Beers by Addition of Non-Cereal Adjuncts Rich in Antioxidant Compounds

Beer is one of the oldest and most consumed beverages worldwide, and recent trends point to increased consumption of functional beers. However, there is a lack in the scientific literature on the effects of adding functional adjuncts in distinct steps of the manufacturing process and its implications on the final physicochemical and sensorial profile. Therefore, the present review analyzes the ingredients used and their insertion stage to achieve a functional beer with bioactive compounds, higher antioxidant activity, and improved sensory characteristics. The addition of fruits, herbal extracts, plants, and mushrooms in beers was documented. Furthermore, adjuncts were successfully added in wort boiling, fermentation, maturation, and packaging. The wort boiling step stands out among these four due to the superior extraction of phenolic compounds from the added adjuncts. On the other hand, adjunct addition in the maturation step induced low increases in antioxidant and phenolic content of the respective enriched beers. Fruits represented the majority of adopted adjuncts among the studies evaluated. Furthermore, the addition of fruits represented a positive increment in the beer’s volatile profile and an increase in sensory acceptability. A gap in the literature was found regarding the analysis of phenolic compounds with appropriate techniques such as HPLC-MS. Furthermore, there is a need to study the bioavailability of the incorporated bioactive compounds to prove the health claims inferred about these beers. In conclusion, functional beers are a little-explored relevant field, with potential for new studies.

De Novo Biosynthesis of the Oleanane-Type Triterpenoids of Tunicosaponins in Yeast

Tunicosaponins are natural products extracted from Psammosilene tunicoides, which is an important ingredient of Yunnan Baiyao Powder, an ancient and famous Asian herbal medicine. The representative aglycones of tunicosaponins are the oleanane-type triterpenoids of gypsogenin and quillaic acid, which were found to manipulate a broad range of virus-host fusion via wrapping the heptad repeat-2 (HR2) domain prevalent in viral envelopes. However, the unknown biosynthetic pathway and difficulty in chemical synthesis hinder the therapeutic use of tunicosaponins. Here, two novel cytochrome P450-dependent monooxygenases that take part in the biosynthesis of tunicosaponins, CYP716A262 (CYP091) and CYP72A567 (CYP099), were identified from P. tunicoides. In addition, the whole biosynthesis pathway of the tunicosaponin aglycones was reconstituted in yeast by transforming the platform strain BY-bAS with the CYP716A262 and CYP716A567 genes, the resulting strain could produce 146.84 and 314.01 mg/L of gypsogenin and quillaic acid, respectively. This synthetic biology platform for complicated metabolic pathways elucidation and microbial cell factories construction can provide alternative sources of important natural products, helping conserve natural plant resources.

A genome-scale metabolic model of Saccharomyces cerevisiae that integrates expression constraints and reaction thermodynamics

Eukaryotic organisms play an important role in industrial biotechnology, from the production of fuels and commodity chemicals to therapeutic proteins. To optimize these industrial systems, a mathematical approach can be used to integrate the description of multiple biological networks into a single model for cell analysis and engineering. One of the most accurate models of biological systems include Expression and Thermodynamics FLux (ETFL), which efficiently integrates RNA and protein synthesis with traditional genome-scale metabolic models. However, ETFL is so far only applicable for E. coli. To adapt this model for Saccharomyces cerevisiae, we developed yETFL, in which we augmented the original formulation with additional considerations for biomass composition, the compartmentalized cellular expression system, and the energetic costs of biological processes. We demonstrated the ability of yETFL to predict maximum growth rate, essential genes, and the phenotype of overflow metabolism. We envision that the presented formulation can be extended to a wide range of eukaryotic organisms to the benefit of academic and industrial research.

Improving squalene production by blocking the competitive branched pathways and expressing rate-limiting enzymes in Rhodopseudomonas palustris

Squalene is a medically valuable bioactive compound that can be used as a raw material for fuels. Microbial fermentation is the preferred method for the squalene production. In this study, we employed several metabolic engineering strategies to increase squalene yield in Rhodopseudomonas palustris. A 57% increase in squalene titer was achieved by blocking the carotenoid pathway, thus directing more FPP into the squalene biosynthetic pathway. In order to cut down the conversion of squalene to haponoids, a recombinant strain R. palustris [Δshc, ΔcrtB] in which both carotenoid and haponoid pathways were blocked was then constructed, resulting in a 50-fold increase in squalene titer. Based on the expression of rate-limiting enzymes involved in the squalene pathway, the final squalene content reached 23.3 mg/g DCW, which was 178-times higher than that of the wild-type strain. In this study, several methods effective in improving squalene yield have been described and the potential of R. palustris for producing squalene has been demonstrated.

Advance in glycosyltransferases, the important bioparts for production of diversified ginsenosides

Ginsenosides are a series of glycosylated triterpenoids predominantly originated from Panax species with multiple pharmacological activities such as anti-aging, mediatory effect on the immune system and the nervous system. During the biosynthesis of ginsenosides, glycosyltransferases play essential roles by transferring various sugar moieties to the sapogenins in contributing to form structure and bioactivity diversified ginsenosides, which makes them important bioparts for synthetic biology-based production of these valuable ginsenosides. In this review, we summarized the functional elucidated glycosyltransferases responsible for ginsenoside biosynthesis, the advance in the protein engineering of UDP-glycosyltransferases (UGTs) and their application with the aim to provide in-depth understanding on ginsenoside-related UGTs for the production of rare ginsenosides applying synthetic biology-based microbial cell factories in the future.

Bioproduction process of natural products and biopharmaceuticals: Biotechnological aspects

Decades of research have been put in place for developing sustainable routes of bioproduction of high commercial value natural products (NPs) on the global market. In the last few years alone, we have witnessed significant advances in the biotechnological production of NPs. The development of new methodologies has resulted in a better understanding of the metabolic flux within the organisms, which have driven manipulations to improve production of the target product. This was further realised due to the recent advances in the omics technologies such as genomics, transcriptomics, proteomics, metabolomics and secretomics, as well as systems and synthetic biology. Additionally, the combined application of novel engineering strategies has made possible avenues for enhancing the yield of these products in an efficient and economical way. Invention of high-throughput technologies such as next generation sequencing (NGS) and toolkits for genome editing Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated 9 (CRISPR/Cas9) have been the game changers and provided unprecedented opportunities to generate rationally designed synthetic circuits which can produce complex molecules. This review covers recent advances in the engineering of various hosts for the production of bioactive NPs and biopharmaceuticals. It also highlights general approaches and strategies to improve their biosynthesis with higher yields in a perspective of plants and microbes (bacteria, yeast and filamentous fungi). Although there are numerous reviews covering this topic on a selected species at a time, our approach herein is to give a comprehensive understanding about state-of-art technologies in different platforms of organisms.

Native and non-native host assessment towards metabolic pathway reconstructions of plant natural products

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Plant metabolic networks are highly complex.

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Engineering the phytochemical pathways fully in heterologous hosts is challenging.

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Single plant cells with amplified multiple fission enable homogeneity.

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Homogeneity and high cell division rate can facilitate stable product scale-up.

Plant-based biopreparations are reasonably priced and are devoid of viral, prion and endotoxin contaminants. However, synthesizing these natural plant products by chemical methods is quite expensive. The structural complexity of plant-derived natural products poses a challenge for chemical synthesis at a commercial scale. Failure of commercial-scale synthesis is the chief reason why metabolic reconstructions in heterologous hosts are inevitable. This review discusses plant metabolite pathway reconstructions experimented in various heterologous hosts, and the inherent challenges involved. Plants as native hosts possess enhanced post-translational modification ability, along with rigorous gene edits, unlike microbes. To achieve a high yield of metabolites in plants, increased cell division rate is one of the requisites. This improved cell division rate will promote cellular homogeneity. Incorporation and maintenance of plant cell synchrony, in turn, can program stable product scale-up.

Effect of magnesium ions on glucaric acid production in the engineered Saccharomyces cerevisiae

Glucaric acid has been successfully produced in Escherichia coli and fungus. Here, we first analyzed the effects of different metal ions on glucaric acid production in the engineered Saccharomyces cerevisiae Bga-3 strain harboring the glucaric acid synthesis pathway. We found that magnesium ions could promote the growth rate of yeast cells, and thus, increase the glucaric acid production by elevating the glucose and myo-inositol utilization of Bga-3 strain. RNA-Seq transcriptome analysis results showed that the upregulation of genes involved in the gluconeogenesis pathway, as well as the downregulation of genes associated with the glycolysis pathway and pentose phosphate pathway in response to MgCl₂ were all benefit for the enhancement of the glucose-6-phosphate flux, which was the precursor for myo-inositol and glucaric acid. In addition, we found that MgCl₂ could also increase the activity of MIOX4, which was also crucial for glucaric acid synthesis. At last, a final glucaric acid titer of 10.6 g/L, the highest reported titer, was achieved in the fed-batch fermentation using a 5-L bioreactor by adding 100 mM MgCl₂. Our findings will provide a new way of promoting the production of other chemicals in the engineered yeast cells.

Fermentation Strategies for Production of Pharmaceutical Terpenoids in Engineered Yeast

Terpenoids, also known as isoprenoids, are a broad and diverse class of plant natural products with significant industrial and pharmaceutical importance. Many of these natural products have antitumor, anti-inflammatory, antibacterial, antiviral, and antimalarial effects, support transdermal absorption, prevent and treat cardiovascular diseases, and have hypoglycemic activities. Production of these compounds are generally carried out through extraction from their natural sources or chemical synthesis. However, these processes are generally unsustainable, produce low yield, and result in wasting of substantial resources, most of them limited. Microbial production of terpenoids provides a sustainable and environment-friendly alternative. In recent years, the yeast Saccharomyces cerevisiae has become a suitable cell factory for industrial terpenoid biosynthesis due to developments in omics studies (genomics, transcriptomics, metabolomics, proteomics), and mathematical modeling. Besides that, fermentation development has a significant importance on achieving high titer, yield, and productivity (TYP) of these compounds. Up to now, there have been many studies and reviews reporting metabolic strategies for terpene biosynthesis. However, fermentation strategies have not been yet comprehensively discussed in the literature. This review summarizes recent studies of recombinant production of pharmaceutically important terpenoids by engineered yeast, S. cerevisiae, with special focus on fermentation strategies to increase TYP in order to meet industrial demands to feed the pharmaceutical market. Factors affecting recombinant terpenoids production are reviewed (strain design and fermentation parameters) and types of fermentation process (batch, fed-batch, and continuous) are discussed.

In-depth understanding of molecular mechanisms of aldehyde toxicity to engineer robust Saccharomyces cerevisiae

Aldehydes are ubiquitous electrophilic compounds that ferment microorganisms including Saccharomyces cerevisiae encounter during the fermentation processes to produce food, fuels, chemicals, and pharmaceuticals. Aldehydes pose severe toxicity to the growth and metabolism of the S. cerevisiae through a variety of toxic molecular mechanisms, predominantly via damaging macromolecules and hampering the production of targeted compounds. Compounds with aldehyde functional groups are far more toxic to S. cerevisiae than all other functional classes, and toxic potency depends on physicochemical characteristics of aldehydes. The yeast synthetic biology community established a design-build-test-learn framework to develop S. cerevisiae cell factories to valorize the sustainable and renewable biomass, including the lignin-derived substrates. However, thermochemically pretreated biomass-derived substrate streams contain diverse aldehydes (e.g., glycolaldehyde and furfural), and biological conversions routes of lignocellulosic compounds consist of toxic aldehyde intermediates (e.g., formaldehyde and methylglyoxal), and some of the high-value targeted products have aldehyde functional group (e.g., vanillin and benzaldehyde). Numerous studies comprehensively characterized both single and additive effects of aldehyde toxicity via systems biology investigations, and novel molecular approaches have been discovered to overcome the aldehyde toxicity. Based on those novel approaches, researchers successfully developed synthetic yeast cell factories to convert lignocellulosic substrates to valuable products, including aldehyde compounds. In this mini-review, we highlight the salient relationship of physicochemical characteristics and molecular toxicity of aldehydes, the molecular detoxification and macromolecules protection mechanisms of aldehydes, and the advances of engineering robust S. cerevisiae against complex mixtures of aldehyde inhibitors. KEY POINTS: • We reviewed structure-activity relationships of aldehyde toxicity on S. cerevisiae. • Two-tier protection mechanisms to alleviate aldehyde toxicity are presented. • We highlighted the strategies to overcome the synergistic toxicity of aldehydes.

Overproduction of α-Farnesene in Saccharomyces cerevisiae by Farnesene Synthase Screening and Metabolic Engineering

Maximizing the flux of farnesyl diphosphate (FPP) to farnesene biosynthesis is the main challenge of farnesene overproduction in Saccharomyces cerevisiae. In this study, we screened α-farnesene synthase from soybean (Fsso) with a higher catalytic ability. Combining the overexpression of the mevalonate (MVA) pathway with the expression of Fsso, an engineered yeast strain producing 190.5 mg/L α-farnesene was screened with poor growth. By decreasing the copies of 3-hydroxy-3-methylglutaryl-coenzyme (HMGR) overexpressed, the titer was increased to 417.8 mg/L. Then, the coexpression of Fsso and HMGR under the control of the GAL promoter and inactivation of lipid phosphate phosphatase encoded by DPP1 promoted the titer to 1163.7 mg/L. The titer was further increased to 1477.2 mg/L at the shake flask level with better growth by the construction of a prototrophic strain. Finally, the highest α-farnesene production of 10.4 g/L in S. cerevisiae was obtained by fed-batch fermentation in a 5 L bioreactor.

Yarrowia lipolytica: a multitalented yeast species of ecological significance

Yarrowia lipolytica is characterized by GRAS (Generally regarded as safe) status, the versatile substrate utilization profile, rapid utilization rates, metabolic diversity and flexibility, the unique abilities to tolerate to extreme environments (acidic, alkaline, hypersaline, heavy metal-pollutions and others) and elevated biosynthesis and secreting capacities. These advantages of Y. lipolytica allow us to consider it as having great ecological significance. Unfortunately, there is still a paucity of relevant review data. This mini-review highlights ecological ubiquity of Y. lipolytica species, their ability to diversify and colonize specialized niches. Different Y. lipolytica strains, native and engineered, are beneficial in degrading many environmental pollutants causing serious ecological problems worldwide. In agriculture has a potential to be a bio-control agent by stimulating plant defense response, and an eco-friendly bio-fertilizer. Engineered strains of Y. lipolytica have become a very promising platform for eco-friendly production of biofuel, commodities, chemicals and secondary metabolites of plant origin, obtaining which by other method were limited or economically infeasible, or were accompanied by stringent environmental problems. Perspectives to use potential of Y. lipolytica's capacities for industrial scale production of valuable compounds in an eco-friendly manner are proposed.

Plant terpenes on treating cardiovascular and metabolic disease: a review

The use of medicinal plants as a therapy alternative is old as human existence itself. Nowadays, the search for effective molecules for chronic diseases treatments has increased. The cardiometabolic disorders still the main cause of death worldwide and plants may offer potential pharmacological innovative approaches to treat and prevent diseases. In the range of plant molecules are inserted the terpenes, which constituent essential elements with several pharmacological characteristics and applications, including cardiovascular and metabolic properties. Thus, the aim of the present review is to update the terpenes use on chronic disorders such as obesity, diabetes, hypertension and vascular conditions. The review includes a brief terpenes description based on the scientific literature in addition to data collected from secondary sources such as books and conference proceedings. We concluded that terpenes could act as adjuvant or main alternative treatment (when started earlier) to improve cardiometabolic diseases, contributing to reduce side effects of conventional drugs, in addition to preserving ethnopharmacological knowledge.

Metabolic engineering and synthetic biology for isoprenoid production in Escherichia coli and Saccharomyces cerevisiae

Isoprenoids, often called terpenoids, are the most abundant and highly diverse family of natural organic compounds. In plants, they play a distinct role in the form of photosynthetic pigments, hormones, electron carrier, structural components of membrane, and defence. Many isoprenoids have useful applications in the pharmaceutical, nutraceutical, and chemical industries. They are synthesized by various isoprenoid synthase enzymes by several consecutive steps. Recent advancement in metabolic engineering and synthetic biology has enabled the production of these isoprenoids in the heterologous host systems like Escherichia coli and Saccharomyces cerevisiae. Both heterologous systems have been engineered for large-scale production of value-added isoprenoids. This review article will provide the detailed description of various approaches used for engineering of methyl-D-erythritol-4-phosphate (MEP) and mevalonate (MVA) pathway for synthesizing isoprene units (C₅) and ultimate production of diverse isoprenoids. The review particularly highlighted the efforts taken for the production of C₅-C₂₀ isoprenoids by metabolic engineering techniques in E. coli and S. cerevisiae over a decade. The challenges and strategies are also discussed in detail for scale-up and engineering of isoprenoids in the heterologous host systems.Key points• Isoprenoids are beneficial and valuable natural products.• E. coli and S. cerevisiae are the promising host for isoprenoid biosynthesis.• Emerging techniques in synthetic biology enabled the improved production.• Need to expand the catalogue and scale-up of un-engineered isoprenoids. Metabolic engineering and synthetic biology for isoprenoid production in Escherichia coli and Saccharomyces cerevisiae.

Recent progress in metabolic engineering of Saccharomyces cerevisiae for the production of malonyl-CoA derivatives

To reduce dependence on petroleum, the biosynthesis of important chemicals from simple substrates using industrial microorganisms has attracted increased attention. Metabolic engineering of Saccharomyces cerevisiae offers a sustainable and flexible alternative for the production of various chemicals. As a key metabolic intermediate, malonyl-CoA is a precursor for many useful compounds. However, the productivity of malonyl-CoA derivatives is restricted by the low cellular level of malonyl-CoA and enzymatic performance. In this review, we focused on how to increase the intracellular malonyl-CoA level and summarize the recent advances in different metabolic engineering strategies for directing intracellular malonyl-CoA to the desired malonyl-CoA derivatives, including strengthening the malonyl-CoA supply, reducing malonyl-CoA consumption, and precisely controlling the intracellular malonyl-CoA level. These strategies provided new insights for further improving the synthesis of malonyl-CoA derivatives in microorganisms.