Homeopathy on cultures of Saccharomyces cerevisiaeand impact on fermentation

Studies have shownthat homeopathy modulates the activity of both single-and multi-celled organisms;therefore, we propose a study into the action of Arnica Montanaand S. cerevisiae fungus nosode on growth "in vitro", and on the fermentation of S. cerevisiaeon brewer's wort. Methods:250 µL of medication in 30% alcohol were placed in 5 mL of Sabouraud Broth (SB) or wort, with 20 µL of fungus ata McFarland standard of 0.5 and in a dilution of 1:100. Fungal growth was evaluated via spectrophotometry at 600 nm or a cell count in a Neubauer chamber in a kinetic of 1 to 5 days' incubation at 25ºC. The production of alcohol by the fungus was evaluated using the BRIX index in the samekinetic. 1x107fungi/mL were previously incubated with medication for 5 days and, afterwards, placed in 20 mL of fresh wort, incubated at 25ºC for 7 days and evaluated for growth and sugar consumption. Resultsand Discussion: The SB results revealed that after 2days incubation with Arnica30CH, an increase in fungal growth was observed (p<0.0001), whilewith nosode 6 and 30CH there was a reduction in growth after 2 and 5 days incubation (p<0.001). The fungi incubated with Arnica30CH exhibited increased sugar consumption after 2 and5 days incubation (p<0.05), while the nosode 30CH resulted in lower sugar consumption after 2 and 3 days incubation (p<0.05). The results for fungal growth and sugar consumption with the wort were similar to those using SB.The fungalcultures previously incubated with homeopathic medication and subsequent incubation with fresh wortindicated a loss of distinction, bothin terms of fungal growth and sugar consumption. This piece of data may suggest action by the homeopathic medication only when in contact with the cells. Conclusion: The treatment of the S. cerevisiae fungus using Arnica and the S. cerevisiae nosode produced a significant modulation in fungal growth and sugar consumption.

Metabolic engineering of yeasts for green and sustainable production of bioactive ginsenosides F2 and 3β,20S-Di-O-Glc-DM

Both natural ginsenoside F2 and unnatural ginsenoside 3β,20S-Di-O-Glc-DM were reported to exhibit anti-tumor activity. Traditional approaches for producing them rely on direct extraction from Panax ginseng, enzymatic catalysis or chemical synthesis, all of which result in low yield and high cost. Metabolic engineering of microbes has been recognized as a green and sustainable biotechnology to produce natural and unnatural products. Hence we engineered the complete biosynthetic pathways of F2 and 3β,20S-Di-O-Glc-DM in Saccharomyces cerevisiae via the CRISPR/Cas9 system. The titers of F2 and 3β,20S-Di-O-Glc-DM were increased from 1.2 to 21.0 mg/L and from 82.0 to 346.1 mg/L at shake flask level, respectively, by multistep metabolic engineering strategies. Additionally, pharmacological evaluation showed that both F2 and 3β,20S-Di-O-Glc-DM exhibited anti-pancreatic cancer activity and the activity of 3β,20S-Di-O-Glc-DM was even better. Furthermore, the titer of 3β,20S-Di-O-Glc-DM reached 2.6 g/L by fed-batch fermentation in a 3 L bioreactor. To our knowledge, this is the first report on demonstrating the anti-pancreatic cancer activity of F2 and 3β,20S-Di-O-Glc-DM, and achieving their de novo biosynthesis by the engineered yeasts. Our work presents an alternative approach to produce F2 and 3β,20S-Di-O-Glc-DM from renewable biomass, which lays a foundation for drug research and development.

Dynamic control of ERG20 expression to improve production of monoterpenes by engineering Saccharomyces cerevisiae / 中国中药杂志

Monoterpenes are widely used in cosmetics, food, medicine, agriculture and other fields. With the development of synthetic biology, it is considered as a potential way to create microbial cell factories to produce monoterpenes. Engineering Saccharomyces cerevisiae to produce monoterpenes has been a research hotspot in synthetic biology. In S. cerevisiae, the production of geranyl pyrophosphate(GPP) and farnesyl pyrophosphate(FPP) is catalyzed by a bifunctional enzyme farnesyl pyrophosphate synthetase(encoded by ERG20 gene) which is inclined to synthesize FPP essential for yeast growth. Therefore, reasonable control of FPP synthesis is the basis for efficient monoterpene synthesis in yeast cell factories. In order to achieve dynamic control from GPP to FPP biosynthesis in S. cerevisiae, we obtained a novel chassis strain HP001-pERG1-ERG20 by replacing the ERG20 promoter of the chassis strain HP001 with the promoter of cyclosqualene cyclase(ERG1) gene. Further, we reconstructed the metabolic pathway by using GPP and neryl diphosphate(NPP), cis-GPP as substrates in HP001-pERG1-ERG20. The yield of GPP-derived linalool increased by 42.5% to 7.6 mg·L~(-1), and that of NPP-derived nerol increased by 1 436.4% to 8.3 mg·L~(-1). This study provides a basis for the production of monoterpenes by microbial fermentation.

Construction of cell factories for high production of ginsenoside Rh_2 in Saccharomyces cerevisiae / 中国中药杂志

Ginsenoside Rh_2 is a rare active ingredient in precious Chinese medicinal materials such as Ginseng Radix et Rhizoma, Notoginseng Radix et Rhizoma, and Panacis Quinquefolii Radix. It has important pharmacological activities such as anti-cancer and improving human immunity. However, due to the extremely low content of ginsenoside Rh_2 in the source plants, the traditional way of obtaining it has limitations. This study intended to apply synthetic biological technology to develop a cell factory of Saccharomyces cerevisiae to produce Rh_2 by low-cost fermentation. First, we used the high protopanaxadiol(PPD)-yielding strain LPTA as the chassis strain, and inserted the Panax notoginseng enzyme gene Pn1-31, together with yeast UDP-glucose supply module genes[phosphoglucose mutase 1(PGM1), α-phosphoglucose mutase(PGM2), and uridine diphosphate glucose pyrophosphorylase(UGP1)], into the EGH1 locus of yeast chromosome. The engineered strain LPTA-RH2 produced 17.10 mg·g~(-1) ginsenoside Rh_2. This strain had low yield of Rh_2 while accumulated much precursor PPD, which severely restricted the application of this strain. In order to further improve the production of ginsenoside Rh_2, we strengthened the UDP glucose supply module and ginsenoside Rh_2 synthesis module by engineered strain LPTA-RH2-T. The shaking flask yield of ginsenoside Rh_2 was increased to 36.26 mg·g~(-1), which accounted for 3.63% of the dry weight of yeast cells. Compared with those of the original strain LPTA-RH2, the final production and the conversion efficiency of Rh_2 increased by 112.11% and 65.14%, respectively. This study provides an important basis for further obtaining the industrial-grade cell factory for the production of ginsenoside Rh_2.

N-terminal truncation of prenyltransferase enhances the biosynthesis of prenylnaringenin / 生物工程学报

8-prenylnaringenin (8-PN) is a potent estrogen with high medicinal values. It also serves as an important precursor for many prenylated flavonoids. Microbial synthesis of 8-PN is mainly hindered by the low catalytic activity of prenyltransferases (PTS) and insufficient supply of precursors. In this work, a SfN8DT-1 from Sophora flavescens was used to improve the efficiency of (2S)-naringenin prenylation. The predicted structure of SfN8DT-1 showed that its main body is comprised of 9 α-helices and 8 loops, along with a long side chain formed by nearly 120 amino acids. SfN8DT-1 mutants with different side-chain truncated were tested in Saccharomyces cerevisiae. A mutant expressing the truncated enzyme at K62 site, designated as SfND8T-1-t62, produced the highest 8-PN titer. Molecular docking of SfN8DT-1-t62 with (2S)-naringenin and dimethylallyl diphosphate (DMAPP) showed that K185 was a potentially crucial residue. Alanine scanning within a range of 0.5 nm around these two substrates showed that the mutant K185A may decrease its affinity to substrates, which also indicated K185 was a potentially critical residue. Besides, the mutant K185W enhanced the affinity to ligands implied by the simulated saturation mutation, while the saturated mutation of K185 showed a great decrease in 8-PN production, indicating K185 is vital for the activity of SfN8DT-1. Subsequently, overexpressing the key genes of Mevalonate (MVA) pathway further improved the titer of 8-PN to 31.31 mg/L, which indicated that DMAPP supply is also a limiting factor for 8-PN synthesis. Finally, 44.92 mg/L of 8-PN was produced in a 5 L bioreactor after 120 h, which is the highest 8-PN titer reported to date.

URA3 affects artemisinic acid production by an engineered Saccharomyces cerevisiae in pilot-scale fermentation / 生物工程学报

CRISPR/Cas9 has been widely used in engineering Saccharomyces cerevisiae for gene insertion, replacement and deletion due to its simplicity and high efficiency. The selectable markers of CRISPR/Cas9 systems are particularly useful for genome editing and Cas9-plasmids removing in yeast. In our previous research, GAL80 gene has been deleted by the plasmid pML104-mediated CRISPR/Cas9 system in an engineered yeast, in order to eliminate the requirement of galactose supplementation for induction. The maximum artemisinic acid production by engineered S. cerevisiae 1211-2 (740 mg/L) was comparable to that of the parental strain 1211 without galactose induction. Unfortunately, S. cerevisiae 1211-2 was inefficient in the utilization of the carbon source ethanol in the subsequent 50 L pilot fermentation experiment. The artemisinic acid yield in the engineered S. cerevisiae 1211-2 was only 20%-25% compared with that of S. cerevisiae 1211. The mutation of the selection marker URA3 was supposed to affect the growth and artemisinic acid production. A ura3 mutant was successfully restored by a recombinant plasmid pML104-KanMx4-u along with a 90 bp donor DNA, resulting in S. cerevisiae 1211-3. This mutant could grow normally in a fed-batch fermentor with mixed glucose and ethanol feeding, and the final artemisinic acid yield (> 20 g/L) was comparable to that of the parental strain S. cerevisiae 1211. In this study, an engineered yeast strain producing artemisinic acid without galactose induction was obtained. More importantly, it was the first report showing that the auxotrophic marker URA3 significantly affected artemisinic acid production in a pilot-scale fermentation with ethanol feeding, which provides a reference for the production of other natural products in yeast chassis.

Engineering Saccharomyces cerevisiae for efficient production of glucaric acid / 生物工程学报

As an important dicarboxylic acids existing in nature, glucaric acid has been widely used in medical, health, and polymer materials industry, therefore it is considered as one of the "top value-added chemicals from biomass". In this study, using Saccharomyces cerevisiae as a chassis microorganism, the effects of overexpression of myo-inositol transporter Itr1, fusional expression of inositol oxygenase MIOX4 and uronate dehydrogenase Udh, and down-expression of glucose-6-phosphate dehydrogenase gene ZWF1 on the glucaric acid production were investigated. The results showed that the yield of glucaric acid was increased by 26% compared with the original strain Bga-3 under shake flask fermentation after overexpressing myo-inositol transporter Itr1. The yield of glucaric acid was increased by 40% compared with Bga-3 strain by expressing the MIOX4-Udh fusion protein. On these basis, the production of glucaric acid reached 5.5 g/L, which was 60% higher than that of Bga-3 strain. In a 5 L fermenter, the highest yield of glucaric acid was 10.85 g/L, which was increased 80% compared with that of Bga-3 strain. The application of the above metabolic engineering strategy improved the pathway efficiency and the yield of glucaric acid, which may serve as a reference for engineering S. cerevisiae to produce other chemicals.

Effect of key enzymes ubiquitination sites on the biosynthesis of naringenin / 生物工程学报

Flavonoids have a variety of biological activities and have important applications in food, medicine, cosmetics, and many other fields. Naringenin is a platform chemical for the biosynthesis of many important flavonoids. Ubiquitination plays a pivotal role in the post-translational modification of proteins and participates in the regulation of cellular activities. Ubiquitinated proteins can be degraded by the ubiquitin-protease system, which is important for maintaining the physiological activities of cells, and may also exert a significant impact on the expression of exogenous proteins. In this study, a real-time in-situ detection system for ubiquitination modification has been established in Saccharomyces cerevisiae by using a fluorescence bimolecular complementation approach. The ubiquitination level of protein was characterized by fluorescence intensity. By using the approach, the potential ubiquitination sites of proteins involved in the naringenin biosynthesis pathway have been obtained. The lysine residues of the relevant ubiquitination sites were mutated to arginine to reduce the ubiquitination level. The mutants of tyrosine ammonia-lyase (FjTAL) and chalcone synthase (SjCHS, SmCHS) showed decreased fluorescence, suggested that a decreased ubiquitination level. After fermentation verification, the S. cerevisiae expressing tyrosine ammonia-lyase FjTAL mutant FjTAL-K487R accumulated 74.2 mg/L p-coumaric acid at 72 h, which was 32.3% higher than that of the original FjTAL. The strains expressing chalcone synthase mutants showed no significant change in the titer of naringenin. The results showed that mutation of the potential ubiquitination sites of proteins involved in the naringenin biosynthesis pathway could increase the titer of p-coumaric acid and have positive effect on naringenin biosynthesis.

Probiotic Saccharomyces boulardii Alleviates Lung Injury by Reduction of Oxidative Stress and Cytokine Response Induced by Supraceliac Aortic Ischemia-Reperfusion Injury in Rats

Abstract Objectives: Ischemia-reperfusion injury is an important cause of multiple organ failure in cardiovascular surgery. Our aim is to investigate the effect of the probiotic Saccharomyces boulardii on oxidative stress, inflammatory response, and lung injury in an experimental model of aortic clamping. Methods: Twenty-one Wistar rats were randomized into three groups (n=7). Control group animals received saline gavage for a week before undergoing median laparotomy. In other groups, supraceliac aorta was clamped for 45 minutes to induce ischemia followed by reperfusion for 60 minutes. In the ischemia-reperfusion group, saline gavage was given preoperatively for one week. Ischemia-reperfusion+probiotic group rats received probiotic gavage for seven days before aortic clamping. The levels of oxidative stress markers and pro-inflammatory cytokines were determined in both serum and lung tissue samples. Ileum and lung tissues were harvested for histological examination. Results: Ischemia-reperfusion caused severe oxidative damage and inflammation evident by significant increases in malondialdehyde and cytokine levels (tumor necrosis factor alpha and interleukin-1 beta) and decreased glutathione levels in both serum and lung tissues. There was severe histological tissue damage to the lung and ileum in the ischemia-reperfusion group. Probiotic pretreatment before aortic clamping caused significant suppression of increases in serum and lung tissue malondialdehyde and tumor necrosis factor alpha levels. Histological damage scores in tissue samples decreased in the ischemia-reperfusion+probiotic group (P<0,005). Conclusions: Oral supplementation of probiotic S. boulardii before supraceliac aortic ischemia-reperfusion in rats alleviates lung injury by reducing oxidative stress, intestinal cellular damage, and modulation of inflammatory processes.

Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro

BACKGROUND: Cecropin P1, acting as an antimicrobial, has a broad-spectrum antibacterial activity with some antiviral and antifungal properties. It is a promising natural alternative to antibiotics which is originally isolated from the pig intestinal parasitic nematode Ascaris suum. Many studies have shown that Cecropin P1 is helpful for the prevention or treatment of clinical diseases. Therefore, it is very necessary to establish a safe, nontoxic, and efficient expression method of Cecropin P1. RESULTS: The results indicated that the recombinant protein was about 5.5 kDa showed by Tricine­SDS­ PAGE and Western blot. And Cecropin P1 was efficiently secreted and expressed after 12 h of induction, with an increasing yield over the course of the induction. Its maximum concentration was 7.83 mg/L after concentration and purification. In addition, in vitro experiments demonstrated that Cecropin P1 not only exerted a strong inhibitory effect on Escherichia coli, Salmonella sp., Shigella sp., and Pasteurella sp., but also displayed an antiviral activity against PRRSV NADC30-Like strain. CONCLUSIONS: Collectively, the strategy of expressing Cecropin P1 in Saccharomyces cerevisiae is harmless, efficient, and safe for cells. In addition, the expressed Cecropin P1 has antiviral and antibacterial properties concurrently.

Probióticos y prebióticos: rol en la terapéutica de la enfermedad diarreica aguda infantil / Probiotics and prebiotics: its role in childhood acute diarrheal disease therapy

RESUMEN: La enfermedad diarreica aguda infantil (EDAI), constituye un problema de salud pública, representando la 2ª causa de morbimortalidad infantil en menores de 5 años, en el Ecuador. La hidratación oral y parenteral en los niños hospitalizados bajo normas de administración de conformidad con el grado de deshidratación y pérdida de peso, así como medidas preventivas como la vacunación obligatoria contra el rotavirus, han contribuido a disminuir, pero no a solucionar este problema de salud infantil. Múltiples factores contribuyen para que no se resuelva: socioeconómicos, educacionales, el destete temprano y malas prácticas alimenticias, entre otros. Últimos estudios han propuesto la utilización de probióticos que contribuyan a disminuir el problema sugieriendo el usode Saccharomyces boulardii (SB), asociado a un prebiótico; lo que permitiría acortar el tiempo de tratamiento de una EDAI; por lo que la simbiosis entre SB y un prebiótico denominado fructooligosacárido (FOS), podría ser una alternativa para reducir costos y complicaciones. Una alternativa para medir el curso clínico de una EDAI en infantes es la escala BITTS, de reciente creación y fácil aplicación por clínicos. El objetivo de este manuscrito fue resumir la evidencia existente respecto del rol de losprobióticos y prebióticos en la terapéutica de de la EDAI.

SUMMARY: In Ecuador childhood acute diarrheal disease (CADD) constitutes a serious public health problem, representing the 2nd cause of infant morbidity and mortality in children under 5 years of age. Oral and parenteral hydration in hospitalized children, with standard treatments according to their degree of dehydration and weight loss, as well as preventive measures such as mandatory vaccination against rotavirus, have contributed to a decrease. Nevertheless, this childhood disease has still not been resolved. There are multiple contributing factors involved that prevent complete eradication of the disease Among these are socio-economic problems, education, early weaning and poor feeding practices, all of which continue to affect infants. Recent studies have proposed the use of probiotics that help reduce the problem and it has been suggested that Saccharomyces boulardii (SB), associated with a prebiotic, would reduce the treatment time of an CADD. Therefore, the symbiosis between the SB probiotic and a prebiotic called fructo- oligosaccharide (FOS) could be an alternative to reduce complications and reduce costs. An alternative to measure the clinical course of an CADD in infants is the BITTS scale, which was recently created and can easily be applied by clinicians. The aim of this manuscript was to summarize the existing evidence regarding the role of PROBIOTICS and prebiotics in the treatment of CADD.

Selenium-Enriched Probiotic Saccharomyces boulardii CCT 4308 Biomass Production Using Low-Cost Sugarcane Molasses Medium

Abstract Food supplements have been increasingly investigated. Probiotics have several benefits for human and animal health and selenium (Se) is widely recommended against oxidative stress. In this context, the aim of this study was to develop a low-cost bioprocess to produce a functional food product comprising both probiotic and Se accumulation. Yeast cells of Saccharomyces boulardii CCT 4308 were cultivated using sugarcane molasses as substrate. Optimization studies were performed to evaluate the best medium composition for biomass production and Se-accumulation in batch and fed-batch systems. Optimized conditions were defined with a medium composed of 150 g L-1 sugarcane molasses and 12 g L-1 yeast extract, with feeding of 100 g L-1 sugarcane molasses and 100 μg mL-1 of Se incorporation after 4 h and 10 h of fermentation, respectively, during 48 h in STR (stirred tank reactor). Best biomass production reached 14.52 g L-1 with 3.20 mg Se g-1 biomass at 12 h. Process optimization led to 4.82-fold increase in biomass production compared to initial condition. A final Se-enriched S. boulardii CCT 4308 biomass was obtained, which is comparable to commercial products. An alternative probiotic yeast biomass was efficiently produced as a new food-form of Se supplement in a sustainable process using an inexpensive agro-industrial residue.

Biological and Oxidative Effect of Ellagic Acid on Saccharomyces cerevisiae: A New Way for Culture Developing

Abstract In this study, the effects of Ellagic acid (EA) on protein expression in yeasts and cellular development were investigated. Four groups were formed. Groups: 1) Control group; yeast only cultivated group; 2) Ellagic Acid (EA) group: EA (10%) given group; 3) Hydrogen peroxide (H2O2) Group: The group given H2O2 (15 mM); 4) EA + H2O2 group: EA (10%) + H2O2 (15 mM) group. After sterilization, EA (10%) and H2O2 (15 mM) were added to the Saccharomyces cerevisiae (S. cerevisiae) cultures and the cultures were grown at 30 °C for 1 hour, 3 hours, 5 hours and 24 hours (overnight). S. cerevisiae cell growth, lipid peroxidation MDA (malondialdehyde) analysis and GSH (glutathione) level were analyzed by spectrophotometer. Total protein changes were determined by SDS-PAGE electrophoresis and measured by the Bradford method. According to the obtained results, compared with the H2O2 group, cell development (1, 3, 5 and 24 hours), GSH level and total protein synthesis (24 hours) were increased with EA, while MDA level (24 hours) decreased. These results show that EA reduces oxidative damage, increases cell growth and it has a protective effect to promote protein synthesis in S. cerevisiae culture.

Construction of yeast cell factories for production of azadirachtin precursor tirucalla-7,24-dien-3β-ol / 中国中药杂志

Azadirachtin, as a botanical insecticide, is a highly oxidized limonoid triterpenoid existing in the seeds of Azadirachta indica. However, due to the low content in the seeds, the production of azadirachtin by seed extraction has low yield. Chemical synthesis of azadirachtin is characterized by complex process and low yield. Synthetic biology provides an alternative for the supply of azadirach-tin. In this study, two oxidosqualene cyclases AiOSC1 and MaOSC1 respectively derived from A. indica and Melia azedarach were identified in yeast. A yeast strain producing tirucalla-7,24-dien-3β-ol was constructed by integration of AiOSC1, Arabidopsis thaliana-derived squalene synthase gene(AtAQS2), and Saccharomyces cerevisiae-derived truncated 3-hydroxy-3-methyl-glutaryl coenzyme A reductase gene(PgtHMGR) into the delta site of yeast. Then, the function of MaCYP71BQ5 was successfully verified in yeast after this gene was introduced into the constructed yeast strain. This study not only laid a foundation for the biosynthesis of tirucalla-7,24-dien-3β-ol, but also provided a chassis cell for the functional identification of cytochrome oxidases(CYP450 s) in azadirachtin biosynthesis pathway.

Research progress of mechanism of action of Saccharomyces boulardii and its application in ulcerative colitis / 国际生物医学工程杂志

Saccharomyces boulardii is a subspecies of Saccharomyces cerevisiae and is a fungal probiotic. It can regulate the intestinal flora and enhance the barrier function of the intestinal tract. Compared with bacterial probiotics, Saccharomyces boulardii is more resistant to acid and oxidation, does not transmit genetic material with bacteria, and can be used in combination with antibiotics. Saccharomyces boulardii can function through a variety of mechanisms, and many proteases secreted by it have antitoxin effects; its own bacteria contain more polyamines, which can nourish the intestinal mucosal cells and regulate the body's metabolic balance. Besides, it can regulate multiple signal pathways to enhance intestinal immunity. Saccharomyces boulardii has been used in the treatment of ulcerative colitis (UC). The results of animal experiments and clinical studies have shown that the application of Saccharomyces boulardii can improve intestinal inflammation and enhance the therapeutic effect of mesalazine. Saccharomyces boulardii can be used as an auxiliary drug for the treatment of UC.

Overexpression of a leucine transfer RNA gene tL(CAA)K improves the acetic acid tolerance of Saccharomyces cerevisiae / 生物工程学报

Acetic acid is a common inhibitor present in lignocellulosic hydrolysate. Development of acetic acid tolerant strains may improve the production of biofuels and bio-based chemicals using lignocellulosic biomass as raw materials. Current studies on stress tolerance of yeast Saccharomyces cerevisiae have mainly focused on transcription control, but the role of transfer RNA (tRNA) was rarely investigated. We found that some tRNA genes showed elevated transcription levels in a stress tolerant yeast strain. In this study, we further investigated the effects of overexpressing an arginine transfer RNA gene tR(ACG)D and a leucine transfer RNA gene tL(CAA)K on cell growth and ethanol production of S. cerevisiae BY4741 under acetic acid stress. The tL(CAA)K overexpression strain showed a better growth and a 29.41% higher ethanol productivity than that of the control strain. However, overexpression of tR(ACG)D showed negative influence on cell growth and ethanol production. Further studies revealed that the transcriptional levels of HAA1, MSN2, and MSN4, which encode transcription regulators related to stress tolerance, were up-regulated in tL(CAA)K overexpressed strain. This study provides an alternative strategy to develop robust yeast strains for cellulosic biorefinery, and also provides a basis for investigating how yeast stress tolerance is regulated by tRNA genes.

Reinforcement of sterols production through directed storage and transportation in yeast: a review / 生物工程学报

Sterols, a class of cyclopentane poly-hydrophenanthrene derivatives, are the predominant membrane constituent of eukaryotes. These substances have a variety of biological activities and have been widely used in food and pharmaceutical industries. The presence of endogenous ergosterol biosynthetic pathway in Saccharomyces cerevisiae cells make it an ideal chassis for the de novo synthesis of sterol and its derivatives. Most recently, the rational modification of organelles provides a novel strategy for the directed transportation and storage of target products and the ultimate enhanced product synthesis. This review summarizes the phenotypic responses of S. cerevisiae cells upon different physiological stimulations and the underlying molecular mechanisms. Reinforcement of sterol production through directed storage, transportation, and excretion of sterols offers a novel strategy for breaking the limitation of de novo biosynthesis of sterols in yeast.

Construction and optimization of cordycepin-producing Saccharomyces cerevisiae / 生物工程学报

Cordycepin is the key active component of medicinal fungus Cordyceps militaris, and it shows multiple functional activities such as anti-tumor and anti-virus. Cordycepin was conventionally produced by liquid fermentation of C. militaris, but the long production cycle and the low productivity constrained its development and application. In this study, two key genes for cordycepin biosynthesis (ScCNS1 and ScCNS2) were introduced into Saccharomyces cerevisiae S288C, producing 67.32 mg/L cordycepin at 240 h. Analysis of gene expression profiles indicated that ZWF1, PRS4, ADE4, ScCNS1 and ScCNS2 which encode enzymes involved in pentose phosphate pathway, purine metabolism and cordycepin biosynthesis pathway, were significantly up-regulated in the late phage of fermentation. Optimization of fermentation medium determined that 50 g/L initial glucose followed by feeding, supplemented with 5 mmol/L Cu²⁺ and 1.0 g/L adenine were the best condition. Fed-batch fermentation using the engineered yeast in a 5 L stirred fermenter produced 137.27 mg/L cordycepin at 144 h, with a productivity up to 0.95 mg/(L·h) reached, which was 240% higher than that of the control.

Advances in metabolic engineering of Saccharomyces cerevisiae for terpenoids biosynthesis / 生物工程学报

Terpenoids are a group of structurally diverse compounds with good biological activities and versatile functions such as anti-cancer and immunity-enhancing effects, and are widely used in food, healthcare and medical industries. Facilitated by the increasing understandings on the natural biosynthetic pathways of terpenoids in recent years, Saccharomyces cerevisiae has been engineered into high-yield strains for production of a variety of terpenoids, some of which have reached or become close to the level required by industrial production. In this connection, synthetic biology driven biotechnological production of terpenoids has become a promising alternative to chemical synthesis and traditional extraction approaches. This article summarizes the recent process in engineering S. cerevisiae for terpenoids biosynthesis, highlighting the effect of synthetic biology strategies by taking a couple of typical terpenoids as examples.

Metabolic engineering tools for Saccharomyces cerevisiae / 生物工程学报

Since its birth in the early 1990s, metabolic engineering technology has gone 30 years rapid development. As one of the preferred chassis for metabolic engineering, S. cerevisiae cells have been engineered into microbial cell factories for the production of a variety of bulk chemicals and novel high value-added bioactive compounds. In recent years, synthetic biology, bioinformatics, machine learning and other technologies have also greatly contributed to the technological development and applications of metabolic engineering. This review summarizes the important technological development for metabolic engineering of S. cerevisiae in the past 30 years. Firstly, classical metabolic engineering tools and strategies were reviewed, followed by reviewing systems metabolic engineering and synthetic biology driven metabolic engineering approaches. The review is concluded with discussing future perspectives for metabolic engineering of S. cerevisiae in the light of state-of-the-art technological development.