Production of high molecular weight pullulan by Aureobasidium pullulans HP-2001 with soybean pomace as a nitrogen source

The production of pullulan by Aureobasidium pullulans HP-2001 was enhanced by yeast extract as a nitrogen source as well as soybean pomace. The highest production of pullulan by A. pullulans HP-2001 with yeast extract was 5.5 g/l whereas that of pullulan with soybean pomace was 7.5 g/l. The gas chromatogram of pullulan produced by A. pullulans HP-2001 with soybean pomace as a nitrogen source showed that the major and minor components were glucose and mannose. The FTIR spectra of pullulans produced with yeast extract, a mixture of yeast extract and soybean pomace, and soybean pomace alone exhibited similar features. The increase in content of reducing sugars after pullulanase treatment of pullulans produced with different nitrogen sources indicated that all the pullulans had alpha-(1,6) glucosidic linkages of alpha-(1,4) linked maltotriose units. The average molecular weights of pullulans produced with various concentrations of yeast extract and soybean pomace ranged from 0.17 to 1.32x10(6) and from 1.32 to 5.66x10(6), respectively. All pullulans produced by A. pullulans HP-2001 in this study had the same basic structures, but their ratios of monomeric components were a little different, which might result in the production of pullulans with different molecular weights.

Mild, Solvent-Free ω-Hydroxy Acid Polycondensations Catalyzed byCandidaantarcticaLipase B

Immobilized Candida antarctica Lipase B (Novozyme-435) was studied for bulk polyesterifications of linear aliphatic hydroxyacids of variable chain length. The products formed were not fractionated by precipitation. The relative reactivity of the hydroxyacids was l6-hydroxyhexadecanoic acid approximately 12-hydroxydodecanoic acid approximately 10-hydroxydecanoic acid (DPavg congruent with 120, Mw/Mn <or = 1.5, 48 h, 90 degrees C) > 6-hydroxyhexanoic acid (DPavg congruent with 80, Mw/Mn < or = 1.5, 48 h, 90 degrees C). Remarkable improvements in molecular-weight buildup resulted from leaving water in the reaction. By 4 h, without application of vacuum, the DPavg for 12- and 16-carbon hydroxyacids was about 90. In contrast, with identical substrates and water removal, the DPavg at 4 h was about 23. Large differences in the molecular-weight build up of 12-hydroxydodecanoic acid were observed for catalyst concentrations (%-by-wt relative to monomer) of 0.1, 0.5, 1, and 10. Nevertheless, by 24 h, with 1% catalyst containing 0.1% lipase, poly(12-hydroxydodecanoic acid) with Mn 17 600 was formed. For 12-hydroxydodecanoic acid polymerization at 90 degrees C, the catalyst activity decreased by 7, 18, and 25% at reaction times of 4, 24, and 48 h, respectively. Furthermore, the retention of catalyst activity was invariable as a function of the substrates used.

Regioselective enzyme-catalyzed synthesis of sophorolipid esters, amides, and multifunctional monomers

Novel enzyme-mediated synthetic routes were developed to provide a new family of sophorolipid derivatives and glycolopid-based amphiphilic monomers. These compounds are of great interest for their potential use in immunoregulation, as well as for other biological properties. In the present work, an efficient lipase-catalyzed conversion of sophorolipid ethyl ester to (a) the 6'-monoacylated derivatives using Novozym 435, (b) 6' '-monoacylated derivatives using Lipase PS-C, (c) secondary amide derivatives using Novozym 435, and (d) 6',6' '-diacylated amide derivatives using Novozym 435 in an one-pot reaction and (e) the regioselective monoacylation of an amide derivative at the 6'- and 6' '-positions using Novozym 435 and Lipase PS-C, respectively, are described. The ethyl ester produced by esterification of the sophorolipid mixture with sodium ethoxide was subjected to acylation catalyzed by Novozym 435 in dry tetrahedrofuran (THF) with vinyl acetate and vinyl methacrylate to produce 6'-monoacylated derivatives. In contrast, Lipase PS-C catalyzed acylations of sophorolipid ethyl ester in dry THF with vinyl acetate and vinyl methacrylate to give the corresponding 6'-monoacylated derivatives. Novozym 435 mediated amidation of sophorolipid ethyl ester in dry THF with phenethylamine, tyramine, p-methoxyphenethylamine, 2-(p-tolyl)ethylamine, and p-fluorophenethylamine generated the corresponding secondary amides but not tertiary amides. The formation of diacyl derivatives of amides was achieved by their treatment with vinyl acetate and vinyl methacrylate in dry THF using Novozym 435 as catalyst. The conversion of sophorolipid ethyl ester to the same diacyl derivatives of amide (i.e., both amidation and acylation) in high yield was also demonstrated in dry THF by a one-pot reaction using Novozym 435. Furthermore, regioselective monoacylation of a sophorolipid amide at 6' and 6' ' in dry THF with vinyl acetate and vinyl methacrylate using Novozym 435 and Lipase PS-C was also demonstrated.

Lipase-catalyzed polycondensations: effect of substrates and solvent on chain formation, dispersity, and end-group structure

The effects of substrates and solvent on polymer formation, number-average molecular weight (M(n)), polydispersity, and end-group structure for lipase-catalyzed polycondensations were investigated. Diphenyl ether was found to be the preferred solvent for the polyesterification of adipic acid and 1,8-octanediol giving a M(n) of 28 500 (48 h, 70 degrees C). The effect of varying the alkylene chain length of diols and diacids on the molecular weight distribution and the polymer end-group structure was assessed. A series of diacids (succinic, glutaric, adipic, and sebacic acid) and diols (1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol) were polymerized in solution and in bulk. It was found that reactions involving monomers having longer alkylene chain lengths of diacids (sebacic and adipic acid) and diols (1,8-octanediol and 1,6-hexanediol) give a higher reactivity than reactions of shorter chain-length diacids (succinic and glutaric acid) and 1,4-butanediol. The bulk lipase-catalyzed condensation reactions were feasible, but the use of diphenyl ether gave higher M(n) values (42,400 g/mol in 3 days at 70 degrees C). The polydispersity varied little over the conditions studied giving values </=2. No specific trend with respect to end-group structure as a function of time was observed. At 70 degrees C, the retention of catalyst activity in the bulk was independent of substrate structure but was higher when reactions were conducted in diphenyl ether than in bulk.

Increased mitotic activity in the dentate gyrus of the hippocampus of adult C57BL/6J mice exposed to the flurothyl kindling model of epileptogenesis

Repeated flurothyl-induced generalized forebrain seizures result in a progressive and permanent lowering of the generalized seizure threshold in mice and an increase in the percentage of animals expressing forebrain-brainstem seizures, when rechallenged with flurothyl, after a stimulation-free period. Since this seizure paradigm serves as an excellent model for examining changes in seizure threshold and seizure propagation, we were interested in examining mitotic activity in hippocampal progenitors following flurothyl-induced epileptogenesis. In the present studies, we investigated (1). the effect of one or eight flurothyl-induced seizures on mitotic activity in the hippocampal dentate gyrus of adult mice measured by 5-bromo-2'-deoxyuridine incorporation, (2). the time course of change in hippocampal mitotic activity, (3). the cellular phenotype of these mitotically active cells, and (4). the relationship of changes in mitotic activity to changes in seizure threshold and phenotype. Significant increases in hippocampal mitotic activity were observed in mice exposed to either one or eight flurothyl-induced seizures. Increases were observed at 1 and 3 days following one seizure, and at 0, 1, 3, and 7 days following eight seizures. Confocal analyses, using neuronal and glial markers, suggest that the majority of these mitotic cells are neurons. In addition, no correlation was observed between hippocampal mitotic activity and the final seizure type that animals expressed following incubation and flurothyl retest. A significant correlation was observed between hippocampal mitotic activity and seizure threshold in flurothyl-kindled mice. Overall, these results indicate that both one and eight flurothyl-induced seizures are potent inducers of hippocampal neurogenesis in adult mice. Results further suggest that the increases in hippocampal neurogenesis are not directly related to the processes that underlie the shift in behavioral seizure phenotype, but may be involved in either the establishment or the maintenance of seizure threshold in this flurothyl model of epileptogenesis.

Activity of Candida rugosa lipase immobilized on gamma-Fe2O3 magnetic nanoparticles

We report the stability and enzymatic activity of Candida rugosa Lipase (E.C.3.1.1.3) immobilized on gamma-Fe2O3 magnetic nanoparticles. The immobilization strategies were either reacting the enzyme amine group with a nanoparticle surface acetyl, or amine groups. In the former, the enzyme was attached through a C=N bond, while in the latter it was connected using glutaraldehyde. AFM images show an average particle size of 20 +/- 10 nm after deconvolution. The enzymatic activity of the immobilized lipase was determined by following the ester cleavage of p-nitrophenol butyrate. The covalently immobilized enzyme was stabile and reactive over 30 days.

Imaging the distribution and secondary structure of immobilized enzymes using infrared microspectroscopy

Synchrotron infrared microspectroscopy (SIRMS) was used for the first time to image the distribution and secondary structure of an enzyme (lipase B from Candida antarctica, CALB) immobilized within a macroporous polymer matrix (poly(methyl methacrylate)) at 10 microm resolution. The beads of this catalyst (Novozyme435) were cut into thin sections (12 microm). SIRMS imaging of these thin sections revealed that the enzyme is localized in an external shell of the bead with a thickness of 80-100 microm. Also, the enzyme was unevenly distributed throughout this shell. Furthermore, by SIRMS-generated spectra, it was found that CALB secondary structure was not altered by immobilization. Unlike CALB, polystyrene molecules of similar molecular weight diffuse easily throughout Novozyme435 beads. Scanning electron micrograph (SEM) images of the Novozyme435 beads showed that the average pore size is 10 times larger than CALB or polystyrene molecules, implying that there is no physical barrier to enzyme or substrate diffusion throughout the bead. Thus, the difference between polystyrene and enzyme diffusivity suggests that protein-matrix and protein-protein interactions govern the distribution of the enzyme within the macroporous resin.

Biodegradable polymers for the environment

Biodegradable polymers are designed to degrade upon disposal by the action of living organisms. Extraordinary progress has been made in the development of practical processes and products from polymers such as starch, cellulose, and lactic acid. The need to create alternative biodegradable water-soluble polymers for down-the-drain products such as detergents and cosmetics has taken on increasing importance. Consumers have, however, thus far attached little or no added value to the property of biodegradability, forcing industry to compete head-to-head on a cost-performance basis with existing familiar products. In addition, no suitable infrastructure for the disposal of biodegradable materials exists as yet.