RESUMO
Oleaginous yeasts have received significant attention due to their substantial lipid storage capability. The accumulated lipids can be utilized directly or processed into various bioproducts and biofuels. Lipomyces starkeyi is an oleaginous yeast capable of using multiple plant-based sugars, such as glucose, xylose, and cellobiose. It is, however, a relatively unexplored yeast due to limited knowledge about its physiology. In this study, we have evaluated the growth of L. starkeyi on different sugars and performed transcriptomic and metabolomic analyses to understand the underlying mechanisms of sugar metabolism. Principal component analysis showed clear differences resulting from growth on different sugars. We have further reported various metabolic pathways activated during growth on these sugars. We also observed non-specific regulation in L. starkeyi and have updated the gene annotations for the NRRL Y-11557 strain. This analysis provides a foundation for understanding the metabolism of these plant-based sugars and potentially valuable information to guide the metabolic engineering of L. starkeyi to produce bioproducts and biofuels. KEY POINTS: ⢠L. starkeyi metabolism reprograms for consumption of different plant-based sugars. ⢠Non-specific regulation was observed during growth on cellobiose. ⢠L. starkeyi secretes ß-glucosidases for extracellular hydrolysis of cellobiose.
Assuntos
Biocombustíveis , Celobiose , Lipídeos , Lipomyces , Açúcares , LevedurasRESUMO
Ure2 regulates nitrogen catabolite repression in Saccharomyces cerevisiae. Deletion of URE2 induces a physiological state mimicking the nitrogen starvation and autophagic responses. Previous work has shown that deletion of URE2 increases the fermentation rate of some wine-producing strains of S. cerevisiae. In this work, we investigated the effect of URE2 deletion (ΔURE2) on the metabolism of S. cerevisiae. During growth on glucose, the ΔURE2 mutant grew at a 40% slower rate than the wild type; however, it produced ethanol at a 31% higher rate. To better under the behavior of this mutant, we performed transcriptomics and metabolomics. Analysis of the RNA sequencing results and metabolite levels indicates that the mutant strain exhibited characteristics of both nitrogen starvation and autophagy, including the upregulation of allantoin, urea, and amino acid uptake and utilization pathways and selective autophagic machinery. In addition, pyruvate decarboxylase and alcohol dehydrogenase isoforms were expressed at higher rates than the wild type. The mutant also accumulated less trehalose and glycogen, and produced more lipids. The induction of a nitrogen starvation-like state and increase in lipid production in nitrogen-rich conditions suggest that URE2 may be a promising target for metabolic engineering in S. cerevisiae and other yeasts for the production of lipids and lipid-derived compounds. KEY POINTS: ⢠Deletion of URE2 increases ethanol and lipid production in Saccharomyces cerevisiae. ⢠Deletion of URE2 reduces glycogen and trehalose production. ⢠Metabolic changes mimic nitrogen starvation and autophagic response.
Assuntos
Príons , Proteínas de Saccharomyces cerevisiae , Vinho , Fermentação , Glutationa Peroxidase , Piruvato Descarboxilase , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Rhodosporidium toruloides is an oleaginous yeast capable of producing a variety of biofuels and bioproducts from diverse carbon sources. Despite numerous studies showing its promise as a platform microorganism, little is known about its metabolism and physiology. In this work, we investigated the central carbon metabolism in R. toruloides IFO0880 using transcriptomics and metabolomics during growth on glucose, xylose, acetate, or soybean oil. These substrates were chosen because they can be derived from plants. Significant changes in gene expression and metabolite concentrations were observed during growth on these four substrates. We mapped these changes onto the governing metabolic pathways to better understand how R. toruloides reprograms its metabolism to enable growth on these substrates. One notable finding concerns xylose metabolism, where poor expression of xylulokinase induces a bypass leading to arabitol production. Collectively, these results further our understanding of central carbon metabolism in R. toruloides during growth on different substrates. They may also help guide the metabolic engineering and development of better models of metabolism for R. toruloides.Key points⢠Gene expression and metabolite concentrations were significantly changed.⢠Reduced expression of xylulokinase induces a bypass leading to arabitol production.⢠R. toruloides reprograms its metabolism to allow growth on different substrates.
Assuntos
Carbono , Transcriptoma , Metabolômica , RhodotorulaRESUMO
Polysaccharide degradation by marine microbes represents one of the largest and most rapid heterotrophic transformations of organic matter in the environment. Microbes employ systems of complementary carbohydrate-specific enzymes to deconstruct algal or plant polysaccharides (glycans) into monosaccharides. Because of the high diversity of glycan substrates, the functions of these enzymes are often difficult to establish. One solution to this problem may lie within naturally occurring microdiversity; varying numbers of enzymes, due to gene loss, duplication, or transfer, among closely related environmental microbes create metabolic differences akin to those generated by knock-out strains engineered in the laboratory used to establish the functions of unknown genes. Inspired by this natural fine-scale microbial diversity, we show here that it can be used to develop hypotheses guiding biochemical experiments for establishing the role of these enzymes in nature. In this work, we investigated alginate degradation among closely related strains of the marine bacterium Vibrio splendidus One strain, V. splendidus 13B01, exhibited high extracellular alginate lyase activity compared with other V. splendidus strains. To identify the enzymes responsible for this high extracellular activity, we compared V. splendidus 13B01 with the previously characterized V. splendidus 12B01, which has low extracellular activity and lacks two alginate lyase genes present in V. splendidus 13B01. Using a combination of genomics, proteomics, biochemical, and functional screening, we identified a polysaccharide lyase family 7 enzyme that is unique to V. splendidus 13B01, secreted, and responsible for the rapid digestion of extracellular alginate. These results demonstrate the value of querying the enzymatic repertoires of closely related microbes to rapidly pinpoint key proteins with beneficial functions.
Assuntos
Alginatos/metabolismo , Organismos Aquáticos/fisiologia , Proteínas de Bactérias/metabolismo , Polissacarídeo-Liases/metabolismo , Vibrio/fisiologia , Alginatos/química , Organismos Aquáticos/enzimologia , Organismos Aquáticos/crescimento & desenvolvimento , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biomarcadores/metabolismo , Cristalografia por Raios X , Regulação Bacteriana da Expressão Gênica , Técnicas de Inativação de Genes , Genômica/métodos , Ácido Glucurônico/química , Ácido Glucurônico/metabolismo , Ácidos Hexurônicos/química , Ácidos Hexurônicos/metabolismo , Concentração de Íons de Hidrogênio , Hidrólise , Isoenzimas/genética , Isoenzimas/isolamento & purificação , Isoenzimas/metabolismo , Estrutura Molecular , Peso Molecular , Filogenia , Polissacarídeo-Liases/química , Polissacarídeo-Liases/genética , Proteômica/métodos , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Especificidade da Espécie , Especificidade por Substrato , Vibrio/enzimologia , Vibrio/crescimento & desenvolvimentoRESUMO
Microorganisms can produce a number of different bioproducts from the sugars in plant biomass. One challenge is devising processes that utilize all of the sugars in lignocellulosic hydrolysates. D-xylose is the second most abundant sugar in these hydrolysates. The microbial conversion of D-xylose to ethanol has been studied extensively; only recently, however, has conversion to bioproducts other than ethanol been explored. Moreover, in the case of yeast, D-xylose may provide a better feedstock for the production of bioproducts other than ethanol, because the relevant pathways are not subject to glucose-dependent repression. In this review, we discuss how different microorganisms are being used to produce novel bioproducts from D-xylose. We also discuss how D-xylose could be potentially used instead of glucose for the production of value-added bioproducts.
Assuntos
Bactérias/metabolismo , Produtos Biológicos/metabolismo , Xilose/metabolismo , Leveduras/metabolismo , Biomassa , Etanol/metabolismo , Glucose/metabolismo , Humanos , Plantas/metabolismo , Plantas/microbiologiaRESUMO
The sugar alcohol D-arabitol is one of the Department of Energy's top twelve bio-based building block chemicals. In this study, we found that the oleaginous yeast Rhodosporidium toruloides IFO0880 produces D-arabitol during growth on xylose in nitrogen-rich medium. Efficient xylose utilization was a prerequisite for extracellular D-arabitol production. During growth in complex media, R. toruloides produced 22 ± 2, 32 ± 2, and 49 ± 2 g/L D-arabitol from 70, 105, and 150 g/L xylose, respectively. In addition, we found that R. toruloides could potentially be used for the co-production of lipids and D-arabitol from xylose. These results demonstrate that R. toruloides can be used to produce multiple value-added chemicals from xylose.
Assuntos
Rhodotorula/metabolismo , Álcoois Açúcares/metabolismo , Xilose/metabolismo , Biomassa , Fermentação , Metabolismo dos Lipídeos , Lipídeos/biossíntese , Álcoois Açúcares/análise , Xilose/análiseRESUMO
Alginate lyases are enzymes that degrade alginate through ß-elimination of the glycosidic bond into smaller oligomers. We investigated the alginate lyases from Vibrio splendidus 12B01, a marine bacterioplankton species that can grow on alginate as its sole carbon source. We identified, purified, and characterized four polysaccharide lyase family 7 alginates lyases, AlyA, AlyB, AlyD, and AlyE, from V. splendidus 12B01. The four lyases were found to have optimal activity between pH 7.5 and 8.5 and at 20 to 25°C, consistent with their use in a marine environment. AlyA, AlyB, AlyD, and AlyE were found to exhibit a turnover number (kcat) for alginate of 0.60 ± 0.02 s(-1), 3.7 ± 0.3 s(-1), 4.5 ± 0.5 s(-1), and 7.1 ± 0.2 s(-1), respectively. The Km values of AlyA, AlyB, AlyD, and AlyE toward alginate were 36 ± 7 µM, 22 ± 5 µM, 60 ± 2 µM, and 123 ± 6 µM, respectively. AlyA and AlyB were found principally to cleave the ß-1,4 bonds between ß-d-mannuronate and α-l-guluronate and subunits; AlyD and AlyE were found to principally cleave the α-1,4 bonds involving α-l-guluronate subunits. The four alginate lyases degrade alginate into longer chains of oligomers.
Assuntos
Alginatos/metabolismo , Liases/metabolismo , Vibrio/enzimologia , Ácido Glucurônico/metabolismo , Ácidos Hexurônicos/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Liases/isolamento & purificação , Modelos Moleculares , Conformação Proteica , TemperaturaRESUMO
Marine microbes use alginate lyases to degrade and catabolize alginate, a major cell wall matrix polysaccharide of brown seaweeds. Microbes frequently contain multiple, apparently redundant alginate lyases, raising the question of whether these enzymes have complementary functions. We report here on the molecular cloning and functional characterization of three exo-type oligoalginate lyases (OalA, OalB, and OalC) from Vibrio splendidus 12B01 (12B01), a marine bacterioplankton species. OalA was most active at 16°C, had a pH optimum of 6.5, and displayed activities toward poly-ß-d-mannuronate [poly(M)] and poly-α-l-guluronate [poly(G)], indicating that it is a bifunctional enzyme. OalB and OalC were most active at 30 and 35°C, had pH optima of 7.0 and 7.5, and degraded poly(M·G) and poly(M), respectively. Detailed kinetic analyses of oligoalginate lyases with poly(G), poly(M), and poly(M·G) and sodium alginate as substrates demonstrated that OalA and OalC preferred poly(M), whereas OalB preferred poly(M·G). The catalytic efficiency (kcat/Km) of OalA against poly(M) increased with decreasing size of the substrate. OalA showed kcat/Km from 2,130 mg(-1) ml s(-1) for the trisaccharide to 224 mg(-1) ml s(-1) for larger oligomers of â¼50 residues, and 50.5 mg(-1) ml s(-1) for high-molecular-weight alginate. Although OalA was most active on the trisaccharide, OalB and OalC preferred dimers. Taken together, our results indicate that these three Oals have complementary substrate scopes and temperature and pH adaptations.
Assuntos
Adaptação Fisiológica/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Polissacarídeo-Liases/metabolismo , Vibrio/enzimologia , Alginatos/metabolismo , Proteínas de Bactérias/genética , Biodegradação Ambiental , Clonagem Molecular , Meios de Cultura , Ácido Glucurônico/metabolismo , Ácidos Hexurônicos/metabolismo , Concentração de Íons de Hidrogênio , Peso Molecular , Polissacarídeo-Liases/genética , Especificidade por Substrato , Temperatura , Vibrio/genéticaRESUMO
A novel endo-ß-1,4-glucanase (EG)-producing strain was isolated and identified as Armillaria gemina KJS114 based on its morphology and internal transcribed spacer rDNA gene sequence. A. gemina EG (AgEG) was purified using a single-step purification by gel filtration. The relative molecular mass of AgEG by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 65 kDa and by size exclusion chromatography was 66 kDa, indicating that the enzyme is a monomer in solution. The pH and temperature optima for hydrolysis were 5.0 and 60 °C, respectively. Purified AgEG had the highest catalytic efficiency with carboxymethylcellulose (k(cat)/K(m) = 3,590 mg mL⻹ s⻹) unlike that reported for any fungal EG, highlighting the significance of the current study. The amino acid sequence of AgEG showed homology with hydrolases from the glycoside hydrolase family 61. The addition of AgEG to a Populus nigra hydrolysate reaction containing a commercial cellulase mixture (Celluclast 1.5L and Novozyme 188) showed a stimulatory effect on reducing sugar production. AgEG is a good candidate for applications that convert lignocellulosic biomass to biofuels and chemicals.
Assuntos
Armillaria/enzimologia , Celulase/isolamento & purificação , Celulase/metabolismo , Populus/metabolismo , Armillaria/classificação , Armillaria/genética , Armillaria/isolamento & purificação , Biomassa , Metabolismo dos Carboidratos , Celulase/química , Cromatografia em Gel , DNA Fúngico/química , DNA Fúngico/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Hidrólise , Dados de Sequência Molecular , Peso Molecular , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , TemperaturaRESUMO
Enhanced catalytic activities of different lignocellulases were obtained from Armillaria gemina under statistically optimized parameters using a jar fermenter. This strain showed maximum xylanase, endoglucanase, cellobiohydrolase, and ß-glucosidase activities of 1,270, 146, 34, and 15 U mL(-1), respectively. Purified A. gemina xylanase (AgXyl) has the highest catalytic efficiency (k (cat)/K (m) = 1,440 mg mL(-1) s(-1)) ever reported for any fungal xylanase, highlighting the significance of the current study. We covalently immobilized the crude xylanase preparation onto functionalized silicon oxide nanoparticles, achieving 117 % immobilization efficiency. Further immobilization caused a shift in the optimal pH and temperature, along with a fourfold improvement in the half-life of crude AgXyl. Immobilized AgXyl gave 37.8 % higher production of xylooligosaccharides compared to free enzyme. After 17 cycles, the immobilized enzyme retained 92 % of the original activity, demonstrating its potential for the synthesis of xylooligosaccharides in industrial applications.
Assuntos
Armillaria/enzimologia , Endo-1,4-beta-Xilanases/isolamento & purificação , Endo-1,4-beta-Xilanases/metabolismo , Enzimas Imobilizadas/metabolismo , Armillaria/genética , DNA Fúngico/química , DNA Fúngico/genética , Endo-1,4-beta-Xilanases/genética , Dados de Sequência Molecular , Nanopartículas/química , Oligossacarídeos/metabolismo , Análise de Sequência de DNA , Dióxido de Silício/químicaRESUMO
Lipomyces tetrasporous is an oleaginous yeast that can utilize a variety of plant-based sugars. It accumulates lipids during growth on lignocellulosic biomass hydrolysates. We present the annotated genome sequence of L. tetrasporous NRRL Y-64009 to aid in its development as a platform organism for producing lipids and lipid-based bioproducts.
RESUMO
Yarrowia lipolytica is an oleaginous yeast that produces high titers of fatty acid-derived biofuels and biochemicals. It can grow on hydrophobic carbon sources and lignocellulosic hydrolysates. The genome sequence of Y. lipolytica NRRL Y-64008 is reported to aid in its development as a biotechnological chassis for producing biofuels and bioproducts.
RESUMO
Enhanced yields of different lignocellulases were obtained under statistically-optimized parameters using Pholiota adiposa. The k (cat) value (4,261 s(-1)) of purified xylanase under standard assay conditions was the highest value ever reported. On covalent immobilization of the crude xylanase preparation onto functionalized silicon oxide nanoparticles, 66 % of the loaded enzyme was retained on the particle. Immobilized enzyme gave 45 % higher concentrations of xylooligosaccharides compared to the free enzyme. After 17 cycles, the immobilized enzyme retained 97 % of the original activity, demonstrating its prospects for the synthesis of xylooligosaccharides in industrial applications.
Assuntos
Enzimas Imobilizadas/metabolismo , Nanopartículas , Oligossacarídeos/metabolismo , Pholiota/enzimologia , Dióxido de Silício/metabolismo , Xilosidases/metabolismo , Ligação ProteicaRESUMO
The halotolerant and osmotolerant yeast Zygosaccharomyces rouxii can produce multiple volatile compounds and has the ability to grow on lignocellulosic hydrolysates. We report the annotated genome sequence of Z. rouxii NRRL Y-64007 to support its development as a platform organism for biofuel and bioproduct production.
RESUMO
BACKGROUND: Sugar alcohols are widely used as low-calorie sweeteners in the food and pharmaceutical industries. They can also be transformed into platform chemicals. Yarrowia lipolytica, an oleaginous yeast, is a promising host for producing many sugar alcohols. In this work, we tested whether heterologous expression of a recently identified sugar alcohol phosphatase (PYP) from Saccharomyces cerevisiae would increase sugar alcohol production in Y. lipolytica. RESULTS: Y. lipolytica was found natively to produce erythritol, mannitol, and arabitol during growth on glucose, fructose, mannose, and glycerol. Osmotic stress is known to increase sugar alcohol production, and was found to significantly increase erythritol production during growth on glycerol. To better understand erythritol production from glycerol, since it was the most promising sugar alcohol, we measured the expression of key genes and intracellular metabolites. Osmotic stress increased the expression of several key genes in the glycerol catabolic pathway and the pentose phosphate pathway. Analysis of intracellular metabolites revealed that amino acids, sugar alcohols, and polyamines are produced at higher levels in response to osmotic stress. Heterologous overexpression of the sugar alcohol phosphatase increased erythritol production and glycerol utilization in Y. lipolytica. We further increased erythritol production by increasing the expression of native glycerol kinase (GK), and transketolase (TKL). This strain was able to produce 27.5 ± 0.7 g/L erythritol from glycerol during batch growth and 58.8 ± 1.68 g/L erythritol during fed-batch growth in shake-flasks experiments. In addition, the glycerol utilization was increased by 2.5-fold. We were also able to demonstrate that this strain efficiently produces erythritol from crude glycerol, a major byproduct of the biodiesel production. CONCLUSIONS: We demonstrated the application of a promising enzyme for increasing erythritol production in Y. lipolytica. We were further able to boost production by combining the expression of this enzyme with other approaches known to increase erythritol production in Y. lipolytica. This suggest that this new enzyme provides an orthogonal route for boosting production and can be stacked with existing designs known to increase sugar alcohol production in yeast such as Y. lipolytica. Collectively, this work establishes a new route for increasing sugar alcohol production and further develops Y. lipolytica as a promising host for erythritol production from cheap substrates such as glycerol.
RESUMO
Simultaneous co-fermentation of glucose and xylose is a key desired trait of engineered Saccharomyces cerevisiae for efficient and rapid production of biofuels and chemicals. However, glucose strongly inhibits xylose transport by endogenous hexose transporters of S. cerevisiae. We identified structurally distant sugar transporters (Lipomyces starkeyi LST1_205437 and Arabidopsis thaliana AtSWEET7) capable of co-transporting glucose and xylose from previously unexplored oleaginous yeasts and plants. Kinetic analysis showed that LST1_205437 had lenient glucose inhibition on xylose transport and AtSWEET7 transported glucose and xylose simultaneously with no inhibition. Modelling studies of LST1_205437 revealed that Ala335 residue at sugar binding site can accommodates both glucose and xylose. Docking studies with AtSWEET7 revealed that Trp59, Trp183, Asn145, and Asn179 residues stabilized the interactions with sugars, allowing both xylose and glucose to be co-transported. In addition, we altered sugar preference of LST1_205437 by single amino acid mutation at Asn365. Our findings provide a new mechanistic insight on glucose and xylose transport mechanism of sugar transporters and the identified sugar transporters can be employed to develop engineered yeast strains for producing cellulosic biofuels and chemicals.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/enzimologia , Glucose , Lipomyces/enzimologia , Proteínas de Transporte de Monossacarídeos/genética , Xilose , Arabidopsis/genética , Fermentação , Cinética , Lipomyces/genética , Saccharomyces cerevisiae/genéticaRESUMO
Biohydrogen is a clean and renewable source of energy. It can be produced by using technologies such as thermochemical, electrolysis, photoelectrochemical and biological, etc. Among these technologies, the biological method (dark fermentation) is considered more sustainable and ecofriendly. Dark fermentation involves anaerobic microbes which degrade carbohydrate rich substrate and produce hydrogen. Lignocellulosic biomass is an abundantly available raw material and can be utilized as an economic and renewable substrate for biohydrogen production. Although there are many hurdles, continuous advancements in lignocellulosic biomass pretreatment technology, microbial fermentation (mixed substrate and co-culture fermentation), the involvement of molecular biology techniques, and understanding of various factors (pH, T, addition of nanomaterials) effect on biohydrogen productivity and yield render this technology efficient and capable to meet future energy demands. Further integration of biohydrogen production technology with other products such as bio-alcohol, volatile fatty acids (VFAs), and methane have the potential to improve the efficiency and economics of the overall process. In this article, various methods used for lignocellulosic biomass pretreatment, technologies in trends to produce and improve biohydrogen production, a coproduction of other energy resources, and techno-economic analysis of biohydrogen production from lignocellulosic biomass are reviewed.
Assuntos
Hidrogênio , Tecnologia , Biocombustíveis , Biomassa , Características da Família , Fermentação , Hidrogênio/análise , LigninaRESUMO
Lignocellulosic biomass is an inexpensive renewable source that can be used to produce biofuels and bioproducts. The recalcitrance nature of biomass hampers polysaccharide accessibility for enzymes and microbes. Several pretreatment methods have been developed for the conversion of lignocellulosic biomass into value-added products. However, these pretreatment methods also produce a wide range of secondary compounds, which are inhibitory to enzymes and microorganisms. The selection of an effective and efficient pretreatment method discussed in the review and its process optimization can significantly reduce the production of inhibitory compounds and may lead to enhanced production of fermentable sugars and biochemicals. Moreover, evolutionary and genetic engineering approaches are being used for the improvement of microbial tolerance towards inhibitors. Advancements in pretreatment and detoxification technologies may help to increase the productivity of lignocellulose-based biorefinery. In this review, we discuss the recent advancements in lignocellulosic biomass pretreatment technologies and strategies for the removal of inhibitors.
Assuntos
Biocombustíveis , Lignina , Biomassa , BiotecnologiaRESUMO
Yarrowia lipolytica has been used to produce both citric acid and lipid-based bioproducts at high titers. In this study, we found that pH differentially affects citric acid and lipid production in Y. lipolytica W29, with citric acid production enhanced at more neutral pH's and lipid production enhanced at more acid pH's. To determine the mechanism governing this pH-dependent switch between citric acid and lipid production, we profiled gene expression at different pH's and found that the relative expression of multiple transporters is increased at neutral pH. These results suggest that this pH-dependent switch is mediated at the level of citric acid transport rather than changes in the expression of the enzymes involved in citric acid and lipid metabolism. In further support of this mechanism, thermodynamic calculations suggest that citric acid secretion is more energetically favorable at neutral pH's, assuming the fully protonated acid is the substrate for secretion. Collectively, these results provide new insights regarding citric acid and lipid production in Y. lipolytica and may offer new strategies for metabolic engineering and process design.
Assuntos
Biotecnologia/métodos , Ácido Cítrico/metabolismo , Glucose/metabolismo , Lipídeos/biossíntese , Yarrowia/metabolismo , Ácido Cítrico/análise , Meios de Cultura/química , Meios de Cultura/metabolismo , Concentração de Íons de Hidrogênio , Lipídeos/análise , Nitrogênio/metabolismo , Yarrowia/fisiologiaRESUMO
BACKGROUND: Sugar alcohols are commonly used as low-calorie sweeteners and can serve as potential building blocks for bio-based chemicals. Previous work has shown that the oleaginous yeast Rhodosporidium toruloides IFO0880 can natively produce arabitol from xylose at relatively high titers, suggesting that it may be a useful host for sugar alcohol production. In this work, we explored whether R. toruloides can produce additional sugar alcohols. RESULTS: Rhodosporidium toruloides is able to produce galactitol from galactose. During growth in nitrogen-rich medium, R. toruloides produced 3.2 ± 0.6 g/L, and 8.4 ± 0.8 g/L galactitol from 20 to 40 g/L galactose, respectively. In addition, R. toruloides was able to produce galactitol from galactose at reduced titers during growth in nitrogen-poor medium, which also induces lipid production. These results suggest that R. toruloides can potentially be used for the co-production of lipids and galactitol from galactose. We further characterized the mechanism for galactitol production, including identifying and biochemically characterizing the critical aldose reductase. Intracellular metabolite analysis was also performed to further understand galactose metabolism. CONCLUSIONS: Rhodosporidium toruloides has traditionally been used for the production of lipids and lipid-based chemicals. Our work demonstrates that R. toruloides can also produce galactitol, which can be used to produce polymers with applications in medicine and as a precursor for anti-cancer drugs. Collectively, our results further establish that R. toruloides can produce multiple value-added chemicals from a wide range of sugars.