The Experts below are selected from a list of 14487 Experts worldwide ranked by ideXlab platform

Atri D Tripathi - One of the best experts on this subject based on the ideXlab platform.

M R Othman - One of the best experts on this subject based on the ideXlab platform.

Christopher J Petzold - One of the best experts on this subject based on the ideXlab platform.

  • Methyl Ketone production by pseudomonas putida is enhanced by plant derived amino acids
    Biotechnology and Bioengineering, 2019
    Co-Authors: Jie Dong, Yan Chen, Veronica T Benites, Edward E K Baidoo, Christopher J Petzold
    Abstract:

    Plants are an attractive sourceof renewable carbon for conversion to biofuels and bio-based chemicals. Conversion strategies often use a fraction of the biomass, focusing on sugars from cellulose and hemicellulose. Strategies that use plant components, such as aromatics and amino acids, may improve the efficiency of biomass conversion. Pseudomonas putida is a promising host for its ability to metabolize a wide variety of organic compounds. P. putida was engineered to produce Methyl Ketones, which are promising diesel blendstocks and potential platform chemicals, from glucose and lignin-related aromatics. Unexpectedly, P. putida Methyl Ketone production using Arabidopsis thaliana hydrolysates was enhanced 2-5-fold compared with sugar controls derived from engineered plants that overproduce lignin-related aromatics. This enhancement was more pronounced (~seven-fold increase) with hydrolysates from nonengineered switchgrass. Proteomic analysis of the Methyl Ketone-producing P. putida suggested that plant-derived amino acids may be the source of this enhancement. Mass spectrometry-based measurements of plant-derived amino acids demonstrated a high correlation between Methyl Ketone production and amino acid concentration in plant hydrolysates. Amendment of glucose-containing minimal media with a defined mixture of amino acids similar to those found in the hydrolysates studied led to a nine-fold increase in Methyl Ketone titer (1.1 g/L).

  • Methyl Ketone production by pseudomonas putida is enhanced by plant derived amino acids
    bioRxiv, 2018
    Co-Authors: Jie Dong, Yan Chen, Veronica T Benites, Edward E K Baidoo, Christopher J Petzold
    Abstract:

    ABSTRACT Plant biomass is an attractive source of renewable carbon for conversion to biofuels and bio-based chemicals. Conversion strategies often use a fraction of the total biomass, focusing on sugars from cellulose and hemicellulose. Strategies that use plant components such as plant-derived aromatics and amino acids have the potential to improve the efficiency of overall biomass conversion. Pseudomonas putida is a promising host for biomass conversion for its ability to metabolize a wide variety of organic compounds, including aromatics derived from lignin. P. putida was engineered to produce medium chain Methyl Ketones, which are promising diesel blendstocks and potential platform chemicals, from glucose and lignin-related aromatics, 4-hydroxybenzoate (4-HB) and protocatechuate (PCA). Unexpectedly, P. putida Methyl Ketone production was enhanced 2-to 5-fold compared to sugar controls when Arabidopsis thaliana hydrolysates derived from engineered plants that overproduce 4-HB and PCA, while E. coli production was lowered in these hydrolysates. This enhancement was more pronounced (~7-fold increase) with hydrolysates derived from non-engineered switchgrass (Panicum virgatum L.) suggesting it did not arise from overproduction of 4-HB and PCA. Global proteomic analysis of the Methyl Ketone-producing P. putida suggested that plant-derived amino acids may be the source of this enhancement. Mass spectrometry-based measurements of plant-derived amino acids demonstrated a high correlation between Methyl Ketone production and amino acid concentration in plant hydrolysates. Amendment of glucose-containing minimal media with a defined mixture of amino acids similar to those found in the hydrolysates studied led to a 9-fold increase in Methyl Ketone titer (1.1 g/L).

Harry R Beller - One of the best experts on this subject based on the ideXlab platform.

  • engineering e coli for simultaneous glucose xylose utilization during Methyl Ketone production
    Microbial Cell Factories, 2018
    Co-Authors: Xi Wang, Eebeen Goh, Harry R Beller
    Abstract:

    We previously developed an E. coli strain that overproduces medium-chain Methyl Ketones for potential use as diesel fuel blending agents or as flavors and fragrances. To date, the strain’s performance has been optimized during growth with glucose. However, lignocellulosic biomass hydrolysates also contain a substantial portion of hemicellulose-derived xylose, which is typically the second most abundant sugar after glucose. Commercialization of the Methyl Ketone-producing technology would benefit from the increased efficiency resulting from simultaneous, rather than the native sequential (diauxic), utilization of glucose and xylose. In this study, genetic manipulations were performed to alleviate carbon catabolite repression in our most efficient Methyl Ketone-producing strain. A strain engineered for constitutive expression of xylF and xylA (involved in xylose transport and metabolism) showed synchronized glucose and xylose consumption rates. However, this newly acquired capability came at the expense of Methyl Ketone titer, which decreased fivefold. Further efforts were made to improve Methyl Ketone production in this strain, and we found that two strategies were effective at enhancing Methyl Ketone titer: (1) chromosomal deletion of pgi (glucose-6-phosphate isomerase) to increase intracellular NADPH supply and (2) downregulation of CRP (cAMP receptor protein) expression by replacement of the native RBS with an RBS chosen based upon mutant library screening results. Combining these strategies resulted in the most favorable overall phenotypes for simultaneous glucose–xylose consumption without compromising Methyl Ketone titer at both 1 and 2% total sugar concentrations in shake flasks. This work demonstrated a strategy for engineering simultaneous utilization of C6 and C5 sugars in E. coli without sacrificing production of fatty acid-derived compounds.

  • Engineering E. coli for simultaneous glucose–xylose utilization during Methyl Ketone production
    'Springer Science and Business Media LLC', 2018
    Co-Authors: Xi Wang, Eebeen Goh, Harry R Beller
    Abstract:

    Abstract Background We previously developed an E. coli strain that overproduces medium-chain Methyl Ketones for potential use as diesel fuel blending agents or as flavors and fragrances. To date, the strain’s performance has been optimized during growth with glucose. However, lignocellulosic biomass hydrolysates also contain a substantial portion of hemicellulose-derived xylose, which is typically the second most abundant sugar after glucose. Commercialization of the Methyl Ketone-producing technology would benefit from the increased efficiency resulting from simultaneous, rather than the native sequential (diauxic), utilization of glucose and xylose. Results In this study, genetic manipulations were performed to alleviate carbon catabolite repression in our most efficient Methyl Ketone-producing strain. A strain engineered for constitutive expression of xylF and xylA (involved in xylose transport and metabolism) showed synchronized glucose and xylose consumption rates. However, this newly acquired capability came at the expense of Methyl Ketone titer, which decreased fivefold. Further efforts were made to improve Methyl Ketone production in this strain, and we found that two strategies were effective at enhancing Methyl Ketone titer: (1) chromosomal deletion of pgi (glucose-6-phosphate isomerase) to increase intracellular NADPH supply and (2) downregulation of CRP (cAMP receptor protein) expression by replacement of the native RBS with an RBS chosen based upon mutant library screening results. Combining these strategies resulted in the most favorable overall phenotypes for simultaneous glucose–xylose consumption without compromising Methyl Ketone titer at both 1 and 2% total sugar concentrations in shake flasks. Conclusions This work demonstrated a strategy for engineering simultaneous utilization of C6 and C5 sugars in E. coli without sacrificing production of fatty acid-derived compounds

Bernard Cote - One of the best experts on this subject based on the ideXlab platform.

  • 1 5 asymmetric induction in boron mediated β alkoxy Methyl Ketone aldol addition reactions
    ChemInform, 2004
    Co-Authors: David A. Evans, Bernard Cote, Paul J Coleman, Brian T Connell
    Abstract:

    This article presents studies that illustrate β-alkoxy Methyl Ketone-derived boron enolates undergo diastereoselective aldol addition to afford the 1,5-anti diol relationship. The stereochemical outcome of this reaction is documented to be general for a variety of β-alkoxy Methyl Ketone analogues and aldehyde partners. The double stereodifferentiating reactions of these enolates with chiral β-alkoxy aldehydes have also been investigated in conjunction with the possibility of controlling the absolute stereochemistry of the aldol process. With the proper selection of reaction conditions, the proximal alkoxy substituent on either the aldehyde (1,3-induction) or the enolate fragment (1,5-induction) can be employed to control facial selectivity of the aldol addition. Selection of a boron enolate ensures dominant 1,5-anti induction from the β-alkoxy Methyl Ketone-derived enolate partner while negating any influence of the β-alkoxy aldehyde substituent. Conversely, if stereochemical control from the β-alkoxy ald...

  • 1 5 asymmetric induction in Methyl Ketone aldol addition reactions
    Journal of Organic Chemistry, 1997
    Co-Authors: David A. Evans, And Paul J Coleman, Bernard Cote
    Abstract:

    In the addition of enol derivatives to â-alkoxy aldehydes, the influence of the â-heteroatom substituent may be regulated by the nature of the aldol process selected (eq 1). For example, good levels of 1,3-anti induction may be realized in the Lewis acid-promoted addition with enol silanes. In contrast, this same substituent possesses no control over the analogous enol borinate nucleophilic additions.2 We have speculated that the principal bias exerted by the â-alkoxy substituent is electrostatic in nature. Given the importance of these remote effects on the π-facial selectivity of aldehyde electrophiles, we have now probed the analogous polar effect of a â-heteroatom substituent on the enolate facial bias in these acetate aldol processes (eq 2).3,4 In this paper, Methyl Ketone enolates that undergo highly 1,5-diastereoselective aldol addition are identified, and the integration of this control element into double-stereodifferentiating aldol reactions is presented. This study was initiated with an examination of the aldol reactions of unsubstituted Ketone enolates 1 (M ) TMS, Li, BR2) that contain a â-alkoxy substituent (Table 1). To isolate the contribution of electrostatic effects to the diastereoselectivity of these addition processes, enolates 1 were selected bearing â-substituents of similar steric size (-OCH2Ar vs -CH2CH2Ar) but different electronic properties. Unlike our previous study on 1,3induction (eq 1),2 the dialkylboron enolates5 displayed good levels of asymmetric induction with dihydrocinnamaldehyde, consistently favoring the 1,5-anti diol product 2 (Table 1, entries 1-5). Due to the similar steric requirements of the â-substituents, electrostatic effects might be at least partially responsible for enolate face selectivity. The enolate facial bias may be further enhanced by a decrease in reaction temperatures (Table 1, entry 5). In contrast to our previous study on 1,3induction (eq 1),2 the Lewis acid-mediated aldol reaction in this system demonstrated no asymmetric induction (Table 1, entry 6).6 Similarly, the aldol reactions of metal enolates capable of internal chelation with the â-heteroatom were also nonselective (Table 1, entry 7).7 (1) For general approaches to the synthesis of 1,3-diol relationships in conjunction with C-C bond formation see: (a) Rychnovsky, S. D.; Hoye, R. C. J. Am. Chem. Soc. 1994, 116, 1753-1765. (b) Mora, Y.; Asai, M.; Okumura, A.; Furukawa, H. Tetrahedron 1995, 51, 52995314. (c) Knochel, P.; Brieden, W.; Rozema, M. J.; Eisenberg, C. Tetrahedron Lett. 1993, 34, 5881-5884. (2) (a) Evans, D. A.; Duffy, J. L.; Dart, M. J. Tetrahedron Lett. 1994, 35, 8537-8540. (b) Evans, D. A.; Dart, M. J.; Duffy, J. L.; Yang, M. G. J. Am. Chem. Soc., 1996, 118, 4322-4343. (3) (a) Blanchette, M. A.; Malamas, M. S.; Nantz, M. H.; Roberts, J. C.; Somfai, P.; Whritenour, D. C.; Masamune, S. J. Org. Chem. 1989, 54, 2817-2825. (b) Seebach, D.; Misslitz, U.; Uhlmann, P. Angew. Chem., Int. Ed. Engl. 1989, 28, 472-473. (4) For 1,4-induction in acetate aldol reactions see: (a) Zibuck, R.; Liverton, N. J.; Smith, A. B. J. Am. Chem. Soc. 1986, 108, 2451-2453. (b) Braun, M. Angew. Chem., Int. Ed. Engl. 1987, 26, 24-37. (c) Paterson, I.; Goodman, J. M.; Isaka, M. Tetrahedreon Lett. 1989, 30, 7121-7124. (d) Trost, B. M.; Urabe, H. J. Org. Chem. 1990, 55, 39823983. (e) Roush, W. R.; Bannister, T. D. Tetrahedron Lett. 1992, 33, 3587-3590. (f) Lagu, B. R.; Liotta, D. C. Tetrahedron Lett. 1994, 35, 4485-4488. (5) Evans, D. A.; Nelson, J. V.; Vogel, E.; Taber, T. R. J. Am. Chem. Soc. 1981, 103, 3099-3111. The regiochemistry (CH3 vs CH2) of the enolization process with Bu2BOTf and Chx2BCl with these Methyl Ketone substrates is high (>95:5). In certain cases, 9-BBNOTf is nonselective in this enolization process. Table 1. 1,5-Induction with Various Metal Enolates