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Ryan W. Davis - One of the best experts on this subject based on the ideXlab platform.
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conversion of distiller s grains to renewable fuels and high value protein integrated techno economic and life cycle assessment
2019Co-Authors: Katherine Derose, Ryan W. Davis, Fang Liu, Blake A Simmons, Jason C QuinnAbstract:Distiller’s grains are a byproduct of corn ethanol production and provide an opportunity for increasing the economic viability and sustainability of the overall grain-to-fuels process. Typically, these grains are dried and sold as a ruminant feed adjunct. This study considers utilization of the residuals in a novel supplementary fermentation process to produce two products, enriched protein and Fusel Alcohols. The value-added proposition and environmental impact of this second fermentation step for distiller’s grains are evaluated by considering three different processing scenarios. Techno-economic results show the minimum protein selling price, assuming Fusel Alcohol products are valued at $0.79 per liter gasoline equivalent, ranges between $1.65–$2.48 kg protein–1 for the different cases. Environmental impacts of the systems were evaluated through life cycle assessment. Results show a baseline emission results of 17 g CO2-eq (MJ fuel)−1 for the fuel product and 10.3 kg CO2-eq kg protein–1 for the protei...
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integrated techno economic and life cycle assessment of the conversion of high productivity low lipid algae to renewable fuels
2019Co-Authors: Katherine Derose, Ryan W. Davis, Chad Demill, Jason C QuinnAbstract:Abstract As microalgae becomes a feedstock of interest for biofuels production, technologies have advanced to provide a variety of methods for cultivation and processing. This study explores the economic viability and environmental impact of processing high productivity, low lipid, high ash content algae into biofuels using two different production pathways. The two processing pathways explored are, 1) Biochemical processing via protein and carbohydrate fermentation to produce Fusel Alcohol products, followed by hydrothermal liquefaction to produce a biocrude, and 2) Thermal-chemical processing via whole algal hydrothermal liquefaction and used as a baseline for the biochemical process. For a feedstock, this study considered algae harvested from an algal turf scrubber, which represents a robust high productivity system, at the expense of a producing a biomass with lower lipid content and higher ash compared to conventional algae production systems. Techno-economic results show the minimum fuel selling price of $12.85 and $10.41 GGE−1 for the biochemical and thermal-chemical pathways, respectively. Life cycle assessments shows a global warming potential of 111.2 g and − 2 g CO2eq MJ fuel−1 for the biochemical and thermal-chemical pathways, respectively. Sensitivity analysis on techno-economic model inputs identifies strategic areas for further research in an effort to move towards an economically viable process. Improvements in the system based on sensitivity and techno-economic analysis results show a pathway to $3.85 GGE−1. Discussion focuses on potentials for ash removal, decrease of biomass cost and potential for higher value products.
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Development of a closed-loop process for Fusel Alcohol production and nutrient recycling from microalgae biomass
2019Co-Authors: Fang Liu, John C. Hewson, Mary B. Tran-gyamfi, Michele Hamel, Todd W. Lane, Pamela Lane, Vitalie Stavila, Ryan W. DavisAbstract:Improving the economic feasibility is necessary for algae-based processes to achieve commercial scales for biofuels and bioproducts production. A closed-loop system for Fusel Alcohol production from microalgae biomass with integrated nutrient recycling was developed, which enables the reuse of nitrogen and phosphorus for downstream application and thus reduces the operational requirement for external major nutrients. Mixed Fusel Alcohols, primarily isobutanol and isopentanol were produced from Microchloropsis salina hydrolysates by an engineered E. coli co-culture. During the process, cellular nitrogen from microalgae biomass was converted into ammonium, whereas cellular phosphorus was liberated by an osmotic shock treatment. The formation of struvite from the liberated ammonium and phosphate, and the subsequent utilization of struvite to support M. salina cultivation was demonstrated. The closed loop system established here should help overcome one of the identified economic barriers to scale-up of microalgae production, and enhance the sustainability of microalgae-based chemical commodities production.
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Bioconversion of distillers’ grains hydrolysates to advanced biofuels by an Escherichia coli co-culture
2017Co-Authors: Fang Liu, Mary B. Tran-gyamfi, James D. Jaryenneh, Xun Zhuang, Ryan W. DavisAbstract:Abstract Background First generation bioethanol production utilizes the starch fraction of maize, which accounts for approximately 60% of the ash-free dry weight of the grain. Scale-up of this technology for fuels applications has resulted in a massive supply of distillers’ grains with solubles (DGS) coproduct, which is rich in cellulosic polysaccharides and protein. It was surmised that DGS would be rapidly adopted for animal feed applications, however, this has not been observed based on inconsistency of the product stream and other logistics-related risks, especially toxigenic contaminants. Therefore, efficient valorization of DGS for production of petroleum displacing products will significantly improve the techno-economic feasibility and net energy return of the established starch bioethanol process. In this study, we demonstrate ‘one-pot’ bioconversion of the protein and carbohydrate fractions of a DGS hydrolysate into C4 and C5 Fusel Alcohols through development of a microbial consortium incorporating two engineered Escherichia coli biocatalyst strains. Results The carbohydrate conversion strain E. coli BLF2 was constructed from the wild type E. coli strain B and showed improved capability to produce Fusel Alcohols from hexose and pentose sugars. Up to 12 g/L Fusel Alcohols was produced from glucose or xylose synthetic medium by E. coli BLF2. The second strain, E. coli AY3, was dedicated for utilization of proteins in the hydrolysates to produce mixed C4 and C5 Alcohols. To maximize conversion yield by the co-culture, the inoculation ratio between the two strains was optimized. The co-culture with an inoculation ratio of 1:1.5 of E. coli BLF2 and AY3 achieved the highest total Fusel Alcohol titer of up to 10.3 g/L from DGS hydrolysates. The engineered E. coli co-culture system was shown to be similarly applicable for biofuel production from other biomass sources, including algae hydrolysates. Furthermore, the co-culture population dynamics revealed by quantitative PCR analysis indicated that despite the growth rate difference between the two strains, co-culturing didn’t compromise the growth of each strain. The q-PCR analysis also demonstrated that fermentation with an appropriate initial inoculation ratio of the two strains was important to achieve a balanced co-culture population which resulted in higher total fuel titer. Conclusions The efficient conversion of DGS hydrolysates into Fusel Alcohols will significantly improve the feasibility of the first generation bioethanol process. The integrated carbohydrate and protein conversion platform developed here is applicable for the bioconversion of a variety of biomass feedstocks rich in sugars and proteins
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Cofactor engineering of ketol-acid reductoisomerase (IlvC) and Alcohol dehydrogenase (YqhD) improves the Fusel Alcohol yield in algal protein anaerobic fermentation
2016Co-Authors: Mary Tran-gyamfi, James Dekontee Jaryenneh, Ryan W. DavisAbstract:Abstract The feasibility of converting algal protein to mixed Alcohols has recently been demonstrated with an engineered E. coli strain, enabling comprehensive utilization of the biomass for biofuel applications. However, the yield and titers of mixed Alcohol production must be improved for market adoption. A major limiting factor for achieving the necessary yield and titer improvements is cofactor imbalance during the fermentation of algal protein. To resolve this problem, a directed evolution approach was applied to modify the cofactor specificity of two key enzymes (IlvC and YqhD) from NADPH to NADH in the mixed Alcohol metabolic pathway. Using high throughput screening, more than 20 YqhD mutants were identified to show activity on NADH as a cofactor. Of these 20 mutants, the four highest activity YqhD mutants were selected for combination with two IlvC mutants, both accepting NADH as a redox cofactor, for modification of the protein conversion strain. The combination of the IlvC and YqhD mutants yielded a refined E. coli strain, subtype AY3, with increased Fusel Alcohol yield of ~ 60% compared to wild type under anaerobic fermentation on amino acid mixtures. When applied to real algal protein hydrolysates, the strain AY3 produced 100% and 38% more total mixed Alcohols than the wild type strain on two different algal hydrolysates, respectively. The results indicate that cofactor engineering is a promising approach to improve the feasibility of bioconversion of algal protein into mixed Alcohols as advanced biofuels.
Jack T Pronk - One of the best experts on this subject based on the ideXlab platform.
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substrate specificity of thiamine pyrophosphate dependent 2 oxo acid decarboxylases in saccharomyces cerevisiae
2012Co-Authors: Gabriele Romagnoli, Jack T Pronk, Marijke A H Luttik, Peter Kotter, Jeanmarc DaranAbstract:Fusel Alcohols are precursors and contributors to flavor and aroma compounds in fermented beverages, and some are under investigation as biofuels. The decarboxylation of 2-oxo acids is a key step in the Ehrlich pathway for Fusel Alcohol production. In Saccharomyces cerevisiae, five genes share sequence similarity with genes encoding thiamine pyrophosphate-dependent 2-oxoacid decarboxylases (2ODCs). PDC1, PDC5, and PDC6 encode differentially regulated pyruvate decarboxylase isoenzymes; ARO10 encodes a 2-oxo-acid decarboxylase with broad substrate specificity, and THI3 has not yet been shown to encode an active decarboxylase. Despite the importance of Fusel Alcohol production in S. cerevisiae, the substrate specificities of these five 2ODCs have not been systematically compared. When the five 2ODCs were individually overexpressed in a pdc1? pdc5? pdc6? aro10? thi3? strain, only Pdc1, Pdc5, and Pdc6 catalyzed the decarboxylation of the linear-chain 2-oxo acids pyruvate, 2-oxobutanoate, and 2-oxo-pentanoate in cell extracts. The presence of a Pdc isoenzyme was also required for the production of n-propanol and n-butanol in cultures grown on threonine and norvaline, respectively, as nitrogen sources. These results demonstrate the importance of pyruvate decarboxylases in the natural production of n-propanol and n butanol by S. cerevisiae. No decarboxylation activity was found for Thi3 with any of the substrates tested. Only Aro10 and Pdc5 catalyzed the decarboxylation of the aromatic substrate phenylpyruvate, with Aro10 showing superior kinetic properties. Aro10, Pdc1, Pdc5, and Pdc6 exhibited activity with all branched-chain and sulfur-containing 2-oxo acids tested but with markedly different decarboxylation kinetics. The high affinity of Aro10 identified it as a key contributor to the production of branched-chain and sulfur-containing Fusel Alcohols.
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the ehrlich pathway for Fusel Alcohol production a century of research on saccharomyces cerevisiae metabolism
2008Co-Authors: Lucie A Hazelwood, Jack T Pronk, Jeanmarc Daran, Antonius J A Van Maris, Richard J DickinsonAbstract:Saccharomyces cerevisiae has been used for at least eight millennia in the production of Alcoholic beverages (41). Along with ethanol and carbon dioxide, fermenting cultures of this yeast produce many low-molecular-weight flavor compounds. These Alcohols, aldehydes, organic acids, esters, organic sulfides, and carbonyl compounds have a strong impact on product quality. Indeed, the subtle aroma balance of these compounds in fermented foods and beverages is often used as an organoleptic fingerprint for specific products and brands (42). Food fermentation by yeast and lactic acid bacteria is accompanied by the formation of the aliphatic and aromatic Alcohols known as Fusel Alcohols. Fusel oil, which derives its name from the German word Fusel (bad liquor), is obtained during the distillation of spirits and is enriched with these higher Alcohols. While Fusel Alcohols at high concentrations impart off-flavors, low concentrations of these compounds and their esters make an essential contribution to the flavors and aromas of fermented foods and beverages. Fusel Alcohols are derived from amino acid catabolism via a pathway that was first proposed a century ago by Ehrlich (13). Amino acids represent the major source of the assimilable nitrogen in wort and grape must, and these amino acids are taken up by yeast in a sequential manner (23, 32). Amino acids that are assimilated by the Ehrlich pathway (valine, leucine, isoleucine, methionine, and phenylalanine) are taken up slowly throughout the fermentation time (32). After the initial transamination reaction (Fig. (Fig.1),1), the resulting α-keto acid cannot be redirected into central carbon metabolism. Before α-keto acids are excreted into the growth medium, yeast cells convert them into Fusel Alcohols or acids via the Ehrlich pathway. FIG. 1. The Ehrlich pathway. Catabolism of branched-chain amino acids (leucine, valine, and isoleucine), aromatic amino acids (phenylalanine, tyrosine, and trytophan), and the sulfur-containing amino acid (methionine) leads to the formation of Fusel acids and ... Current scientific interest in the Ehrlich pathway is supported by increased demands for natural flavor compounds such as isoamyl Alcohol and 2-phenylethanol, which can be produced from amino acids in yeast-based bioconversion processes (14), as well as by the need to control flavor profiles of fermented food products. The goal of this paper is to present a concise centenary overview of the biochemistry, molecular biology, and physiology of this important pathway in S. cerevisiae.
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pyruvate decarboxylase catalyzes decarboxylation of branched chain 2 oxo acids but is not essential for Fusel Alcohol production by saccharomyces cerevisiae
1998Co-Authors: Eelko G Ter Schure, Marcel T Flikweert, Johannes P Van Dijken, Jack T Pronk, Theo C VerripsAbstract:The Fusel Alcohols 3-methyl-1-butanol, 2-methyl-1-butanol, and 2-methyl-propanol are important flavor compounds in yeast-derived food products and beverages. The formation of these compounds from branched-chain amino acids is generally assumed to occur via the Ehrlich pathway, which involves the concerted action of a branched-chain transaminase, a decarboxylase, and an Alcohol dehydrogenase. Partially purified preparations of pyruvate decarboxylase (EC 4.1.1.1) have been reported to catalyze the decarboxylation of the branched-chain 2-oxo acids formed upon transamination of leucine, isoleucine, and valine. Indeed, in a coupled enzymatic assay with horse liver Alcohol dehydrogenase, cell extracts of a wild-type Saccharomyces cerevisiae strain exhibited significant decarboxylation rates with these branched-chain 2-oxo acids. Decarboxylation of branched-chain 2-oxo acids was not detectable in cell extracts of an isogenic strain in which all three PDC genes had been disrupted. Experiments with cell extracts from S. cerevisiae mutants expressing a single PDC gene demonstrated that both PDC1- and PDC5-encoded isoenzymes can decarboxylate branched-chain 2-oxo acids. To investigate whether pyruvate decarboxylase is essential for Fusel Alcohol production by whole cells, wild-type S. cerevisiae and an isogenic pyruvate decarboxylase-negative strain were grown on ethanol with a mixture of leucine, isoleucine, and valine as the nitrogen source. Surprisingly, the three corresponding Fusel Alcohols were produced in both strains. This result proves that decarboxylation of branched-chain 2-oxo acids via pyruvate decarboxylase is not an essential step in Fusel Alcohol production.
Jeanmarc Daran - One of the best experts on this subject based on the ideXlab platform.
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substrate specificity of thiamine pyrophosphate dependent 2 oxo acid decarboxylases in saccharomyces cerevisiae
2012Co-Authors: Gabriele Romagnoli, Jack T Pronk, Marijke A H Luttik, Peter Kotter, Jeanmarc DaranAbstract:Fusel Alcohols are precursors and contributors to flavor and aroma compounds in fermented beverages, and some are under investigation as biofuels. The decarboxylation of 2-oxo acids is a key step in the Ehrlich pathway for Fusel Alcohol production. In Saccharomyces cerevisiae, five genes share sequence similarity with genes encoding thiamine pyrophosphate-dependent 2-oxoacid decarboxylases (2ODCs). PDC1, PDC5, and PDC6 encode differentially regulated pyruvate decarboxylase isoenzymes; ARO10 encodes a 2-oxo-acid decarboxylase with broad substrate specificity, and THI3 has not yet been shown to encode an active decarboxylase. Despite the importance of Fusel Alcohol production in S. cerevisiae, the substrate specificities of these five 2ODCs have not been systematically compared. When the five 2ODCs were individually overexpressed in a pdc1? pdc5? pdc6? aro10? thi3? strain, only Pdc1, Pdc5, and Pdc6 catalyzed the decarboxylation of the linear-chain 2-oxo acids pyruvate, 2-oxobutanoate, and 2-oxo-pentanoate in cell extracts. The presence of a Pdc isoenzyme was also required for the production of n-propanol and n-butanol in cultures grown on threonine and norvaline, respectively, as nitrogen sources. These results demonstrate the importance of pyruvate decarboxylases in the natural production of n-propanol and n butanol by S. cerevisiae. No decarboxylation activity was found for Thi3 with any of the substrates tested. Only Aro10 and Pdc5 catalyzed the decarboxylation of the aromatic substrate phenylpyruvate, with Aro10 showing superior kinetic properties. Aro10, Pdc1, Pdc5, and Pdc6 exhibited activity with all branched-chain and sulfur-containing 2-oxo acids tested but with markedly different decarboxylation kinetics. The high affinity of Aro10 identified it as a key contributor to the production of branched-chain and sulfur-containing Fusel Alcohols.
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the ehrlich pathway for Fusel Alcohol production a century of research on saccharomyces cerevisiae metabolism
2008Co-Authors: Lucie A Hazelwood, Jack T Pronk, Jeanmarc Daran, Antonius J A Van Maris, Richard J DickinsonAbstract:Saccharomyces cerevisiae has been used for at least eight millennia in the production of Alcoholic beverages (41). Along with ethanol and carbon dioxide, fermenting cultures of this yeast produce many low-molecular-weight flavor compounds. These Alcohols, aldehydes, organic acids, esters, organic sulfides, and carbonyl compounds have a strong impact on product quality. Indeed, the subtle aroma balance of these compounds in fermented foods and beverages is often used as an organoleptic fingerprint for specific products and brands (42). Food fermentation by yeast and lactic acid bacteria is accompanied by the formation of the aliphatic and aromatic Alcohols known as Fusel Alcohols. Fusel oil, which derives its name from the German word Fusel (bad liquor), is obtained during the distillation of spirits and is enriched with these higher Alcohols. While Fusel Alcohols at high concentrations impart off-flavors, low concentrations of these compounds and their esters make an essential contribution to the flavors and aromas of fermented foods and beverages. Fusel Alcohols are derived from amino acid catabolism via a pathway that was first proposed a century ago by Ehrlich (13). Amino acids represent the major source of the assimilable nitrogen in wort and grape must, and these amino acids are taken up by yeast in a sequential manner (23, 32). Amino acids that are assimilated by the Ehrlich pathway (valine, leucine, isoleucine, methionine, and phenylalanine) are taken up slowly throughout the fermentation time (32). After the initial transamination reaction (Fig. (Fig.1),1), the resulting α-keto acid cannot be redirected into central carbon metabolism. Before α-keto acids are excreted into the growth medium, yeast cells convert them into Fusel Alcohols or acids via the Ehrlich pathway. FIG. 1. The Ehrlich pathway. Catabolism of branched-chain amino acids (leucine, valine, and isoleucine), aromatic amino acids (phenylalanine, tyrosine, and trytophan), and the sulfur-containing amino acid (methionine) leads to the formation of Fusel acids and ... Current scientific interest in the Ehrlich pathway is supported by increased demands for natural flavor compounds such as isoamyl Alcohol and 2-phenylethanol, which can be produced from amino acids in yeast-based bioconversion processes (14), as well as by the need to control flavor profiles of fermented food products. The goal of this paper is to present a concise centenary overview of the biochemistry, molecular biology, and physiology of this important pathway in S. cerevisiae.
Theo C Verrips - One of the best experts on this subject based on the ideXlab platform.
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bat2p is essential in saccharomyces cerevisiae for Fusel Alcohol production on the non fermentable carbon source ethanol
2005Co-Authors: Sung A Schoondermarkstolk, Maria Tabernero, J W Chapman, Eelko G Ter Schure, Theo C Verrips, A J Verkleij, Johannes BoonstraAbstract:Branched-chain amino acids (BCAAs) are key substrates in the formation of Fusel Alcohols, important flavour components in fermented foods. The first step in the catabolic BCAA degradation is a transaminase step, catalyzed by a branched-chain amino acid transaminase (BCAAT). Saccharomyces cerevisiae possesses a mitochondrial and a cytosolic BCAAT, Bat1p and Bat2p, respectively. In order to study the impact of the BCAATs on Fusel Alcohol production derived from the BCAA metabolism, S. cerevisiae BCAAT-deletion mutants were constructed. The BCAA l-leucine was exogenously supplied during cultivations with mutants of S. cerevisiae. BAT1 deletion is not essential for Fusel Alcohol production, neither under glucose nor under ethanol growth conditions. The 3-methyl-1-butanol production rate of bat1Δ-cells on ethanol was decreased in comparison with that of wild-type cells, but the cells were still able to produce 3-methyl-1-butanol. However, drastic effects in Fusel Alcohol production were obtained in cells lacking BAT2. Although the constructed bat2Δ-single deletion strain and the bat1Δbat2Δ-double deletion strain were still able to produce 3-methyl-1-butanol when grown on glucose, they were incapable of producing any 3-methyl-1-butanol when ethanol was the sole carbon source available. In the circumstances used, gene expression analysis revealed a strong upregulation of BAT2 gene activity in the wild type, when cells grew on ethanol as carbon source. Apparently, the carbon metabolism is able to influence the expression of BCAATs and interferes with the nitrogen metabolism. Furthermore, analysis of gene expression profiles shows that the expression of genes coding for other transaminases present in S. cerevisiae was influenced by the deletion of one or both BCAATs. Several transaminases were upregulated when a BCAAT was deleted. Strikingly, none of the known transaminases was significantly upregulated when BAT2 was deleted. Therefore we conclude that the expression of BAT2 is essential for 3-methyl-1-butanol formation on the non-fermentable carbon source, ethanol.
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pyruvate decarboxylase catalyzes decarboxylation of branched chain 2 oxo acids but is not essential for Fusel Alcohol production by saccharomyces cerevisiae
1998Co-Authors: Eelko G Ter Schure, Marcel T Flikweert, Johannes P Van Dijken, Jack T Pronk, Theo C VerripsAbstract:The Fusel Alcohols 3-methyl-1-butanol, 2-methyl-1-butanol, and 2-methyl-propanol are important flavor compounds in yeast-derived food products and beverages. The formation of these compounds from branched-chain amino acids is generally assumed to occur via the Ehrlich pathway, which involves the concerted action of a branched-chain transaminase, a decarboxylase, and an Alcohol dehydrogenase. Partially purified preparations of pyruvate decarboxylase (EC 4.1.1.1) have been reported to catalyze the decarboxylation of the branched-chain 2-oxo acids formed upon transamination of leucine, isoleucine, and valine. Indeed, in a coupled enzymatic assay with horse liver Alcohol dehydrogenase, cell extracts of a wild-type Saccharomyces cerevisiae strain exhibited significant decarboxylation rates with these branched-chain 2-oxo acids. Decarboxylation of branched-chain 2-oxo acids was not detectable in cell extracts of an isogenic strain in which all three PDC genes had been disrupted. Experiments with cell extracts from S. cerevisiae mutants expressing a single PDC gene demonstrated that both PDC1- and PDC5-encoded isoenzymes can decarboxylate branched-chain 2-oxo acids. To investigate whether pyruvate decarboxylase is essential for Fusel Alcohol production by whole cells, wild-type S. cerevisiae and an isogenic pyruvate decarboxylase-negative strain were grown on ethanol with a mixture of leucine, isoleucine, and valine as the nitrogen source. Surprisingly, the three corresponding Fusel Alcohols were produced in both strains. This result proves that decarboxylation of branched-chain 2-oxo acids via pyruvate decarboxylase is not an essential step in Fusel Alcohol production.
Kenneth W Nickerson - One of the best experts on this subject based on the ideXlab platform.
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quorum sensing activity in ophiostoma ulmi effects of Fusel oils and branched chain amino acids on yeast mycelial dimorphism
2012Co-Authors: Alexander Berrocal, Jose Navarrete, Claudia Oviedo, Kenneth W NickersonAbstract:Aims: For Ophiostoma (Ceratocystis) ulmi, the ability to undergo morphological change is a crucial factor for its virulence. To gain an understanding of quorum-sensing activity in O. ulmi as it relates to yeast-mycelium dimorphism control, this study examines the effects of branched-chain amino acids as well as their Fusel Alcohols and Fusel acids as quorum sensing molecules. Methods and Results: In a defined medium containing glucose, proline and salts, O. ulmi grew as yeasts when the culture was inoculated with a high density of spores (2 × 107 CFU ml−1) and as mycelia when inoculated with a low spore density (4 × 105 CFU ml−1). The cultures displaying yeast morphology secreted a quorum-sensing factor that shifted the morphology from mycelia to yeast. This quorum-sensing molecule was lipophilic and extractable by organic solvents from the spent medium. Using GC/MS analysis, it was determined that the major compound in the extract was 2-methyl-1-butanol. A similar effect was observed when the branched-chain amino acids (Fusel Alcohol precursors) were used as the nitrogen source. E, E-farnesol had no effect on the morphology of O. ulmi. Conclusions: Addition of the branched-chain amino acids or one of the compounds detected in the spent medium, 2-methyl-1-butanol or 4-hydroxyphenylacetic acid, or methylvaleric acid, decreased germ tube formation by more than 50%, thus demonstrating a quorum sensing molecule behaviour in O. ulmi cultures. Significance and impact of the study: This study presents advances in the investigation of dimorphism in O. ulmi, complementing the existing scientific basis, for studying, understanding and controlling this phenomenon.
