Enzymic Modification of Insoluble Amylose in Organic Solvents

Bruno, Ferdinando F.; Akkara, Joseph A.; Ayyagari, Madhu S.; Kaplan, David L.; Gross, Richard A.; Swift, Graham; Dordick, Jonathan S.

doi:10.1021/ma00130a028

Cited by 56 publications

(41 citation statements)

References 1 publication

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“…This approach has for example proven to be promising for the production of polymers 3,4 , anticancer and antiviral drugs 5 , aromas and fragrances 6,7 , and surfactants 8 . Performing biocatalysis in organic solvents is advantageous mainly because the solubility and stability of substrates and products are increased, thereby facilitating their transformation 1,9 , and because undesirable reactions, including hydrolysis, racemization, polymerization, and decomposition may be reduced when compared to aqueous systems 1,10 .…”

Section: Introductionmentioning

confidence: 99%

Immobilization of Candida antarctica Lipase B on fumed silica

Cruz

Pfromm

Rezac

2009

Process Biochemistry

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Enzymes are usually immobilized on solid supports or solubilized when they are to be used in organic solvents with poor enzyme solubility. We have reported previously on a novel immobilization method for s. Carlsberg on fumed silica with results that reached some of the best previously reported catalytic activities in hexane for this enzyme. Here we extend our method to Candida antarctica lipase B (CALB) as an attractive target due to the many potential applications of this enzyme in solvents. Our CALB/fumed silica preparations approached the catalytic activity of commercial Novozym 435 for a model esterification in hexane at 90wt% fumed silica (relative to the mass of the preparation). An intriguing observation was that the catalytic activity at first increases as more fumed silica was made available to the enzyme but then decreased precipitously when 90wt% fumed silica was exceeded. This was not the case for s. Carlsberg where the catalytic activity leveled off at high relative amounts of fumed silica. We determined adsorption kinetics, performed variations of the pre-immobilization aqueous pH, determined the stability, and applied fluorescence microscopy to the preparations. A comparison with recent concepts by Gross et al. may point towards a rationale for an optimum intermediate surface coverage for some enzymes on solid supports.

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Section: Introductionmentioning

confidence: 99%

Immobilization of Candida antarctica Lipase B on fumed silica

Cruz

Pfromm

Rezac

2009

Process Biochemistry

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“…The first approach employs hydrolytic enzymes (e.g., proteases or lipases) under nonaqueous conditions to catalyze condensation or acyl-transfer reactions (Rehse and Ritter, 1988;Pavel and Ritter, 1992). For instance, Bruno et al (1995) used a protease in isooctane to perform a transesterification in which a caprate (C 10 ) group was added to amylose. A general limitation to the use of proteases and lipases for polymer modification is that the reaction mechanism involves the formation of a covalently bound, acyl-enzyme intermediate which undergoes nucleophilic attack at the enzyme's active site.…”

Section: Introductionmentioning

confidence: 99%

Enzymatic grafting of a natural product onto chitosan to confer water solubility under basic conditions

Kumar

Smith

Payne

1999

Biotechnol. Bioeng.

181

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Chitosan is a natural biopolymer whose rich amine functionality confers water solubility at low pH. At higher pH's (greater than 6.5), the amines are deprotonated and chitosan is insoluble. To attain water solubility under basic conditions we enzymatically grafted the hydrophilic compound chlorogenic acid onto chitosan. Despite its name, chlorogenic acid is a nonchlorinated phenolic natural product that has carboxylic acid and hydroxyl functionality. The enzyme in this study was tyrosinase, which converts a wide range of phenolic substrates into electrophilic o‐quinones. The o‐quinones are freely diffusible and can undergo reaction with the nucleophilic amino groups of chitosan. Using slightly acidic conditions (pH = 6), it was possible to modify chitosan under homogeneous conditions. When the amount of chlorogenic acid used in the modification reaction exceeded 30% relative to chitosan's amino groups, the modified chitosan was observed to be soluble under both acidic and basic conditions, and to have a pH window of insolubility at near neutral pH. 1H NMR spectra confirmed that chitosan was chemically modified, although the degree of modification was low. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 154–165, 1999.

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“…Promising experiments for polymer synthesis (Gross and Kalra, 2002;Gross et al, 2001), anticancer and antiviral drugs (Gotor, 2002), aromas and fragrances (Barahona et al, 2006;Bartling et al, 2001), and surfactants (Bruno et al, 1995) have been reported.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective transesterification by Candida antarctica Lipase B immobilized on fumed silica

Kramer

Cruz

Pfromm

et al. 2010

Journal of Biotechnology

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Enzymatic catalysis to produce molecules such as perfumes, flavors, and fragrances has the advantage of allowing the products to be labeled "natural" for marketing in the U.S., in addition to the exquisite selectivity and stereoselectivity of enzymes that can be an advantage over chemical catalysis. Enzymatic catalysis in organic solvents is attractive if solubility issues of reactants or products, or thermodynamic issues (water as a product in esterification) complicate or prevent aqueous enzymatic catalysis. Immobilization of the enzyme on a solid support can address the generally poor solubility of enzymes in most solvents.We have recently reported on a novel immobilization method for Candida antarctica Lipase B on fumed silica to improve the enzymatic activity in hexane. This research is extended here to study the enantioselective transesterification of (RS)-1-phenylethanol with vinyl acetate. The maximum catalytic activity for this preparation exceeded the activity (on an equal enzyme amount basis) of the commercial Novozyme 435® significantly. The steady-state conversion for (R)-1-phenylethanol was about 75% as confirmed via forward and reverse reaction. The catalytic activity steeply increases with increasing nominal surface coverage of the support until a maximum is reached at a nominal surface coverage of 230%. We hypothesize that the physical state of the enzyme molecules at a low surface coverage is dominated in this case by detrimental strong enzyme-substrate interactions. Enzyme-enzyme interactions may stabilize the active form of the enzyme as surface coverage increases while diffusion limitations reduce the apparent catalytic performance again at multi-layer coverage. The temperature-, solvent-, and long-term stability for CALB/fumed silica preparations showed that these preparations can tolerate temperatures up to 70°C, continuous exposure to solvents, and long term storage.2

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Enzymic Modification of Insoluble Amylose in Organic Solvents

Cited by 56 publications

References 1 publication

Immobilization of Candida antarctica Lipase B on fumed silica

Immobilization of Candida antarctica Lipase B on fumed silica

Enzymatic grafting of a natural product onto chitosan to confer water solubility under basic conditions

Enantioselective transesterification by Candida antarctica Lipase B immobilized on fumed silica

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