Lipase catalyzed reactions of aliphatic and arylaliphatic carbonic acid esters

Symmetrical dialkyl carbonates and dibenzyl carbonates reacted with various nucleophiles in the presence of Candida antarctica lipase B in organic solvents. For example, reaction of dibutyl and dibenzyl carbonate with an alcohol gave a mixture of the mono- and disubstituted products. Aminolysis, however, afforded only the carbamates, without subsequent reaction to the ureum derivatives. The reaction rates were rather low compared with carboxylic esters; the reactivity increased in the order dimethyl相似文献   

Fatty Acid Specificity in Lipase-Catalyzed Synthesis of Glucoside Esters

The fatty acid specificity of the B-lipase derived from Candida antarctica was investigated in the synthesis of esters of ethyl D-glucopyranoside. The specificity was almost identical with respect to straight-chain fatty acids with 10 to 18 carbon atoms. However, lower fatty acids such as hexanoic and octanoic acid and the unsaturated 9-cis-octadecenoic acid were found to be poor substrates of the enzyme. As a consequence of this selectivity, these fatty acids were accumulated in the unconverted fraction when ethyl D-glucopyranoside was esterified with an excess of a mixture of fatty acids. This accumulation can reduce the overall effectiveness of the process as the activity of the lipase was found to be reduced when exposed to high concentrations of short-chain fatty acids. Finally, using a simplified experimental set-up, the specificity of the C. antarctica B-lipase was compared to the specificity of lipases derived from C. rugosa, Mucor miehei, Humicola, and Pseudomonas. Apart from the C. rugosa lipase, which exhibited a very poor performance, all the enzymes showed a very similar specificity with respect to fatty acids longer than octanoic acid while only the C. antarctica B-lipase showed activity towards sort-chain fatty acids.     

Effect of Planting Unit Size and Sediment Stabilization on Seagrass Transplants in Western Australia

Abstract The effect of increasing planting unit size and stabilizing sediment was examined for two seagrass planting methods at Carnac Island, Western Australia in 1993. The staple method (sprigs) was used to transplant Amphibolis griffithii (J. M. Black) den Hartog and the plug method was used to transplant A. griffithii and Posidonia sinuosa Cambridge and Kuo. Transplant size was varied by increasing the number of rhizomes incorporated into a staple and increasing the diameter of plugs. Planting units were transplanted into bare sand, back into the original donor seagrass bed, or into a meadow of Heterozostera tasmanica, which is an important colonizing species. Sprigs of A. griffithii were extracted from a monospecific meadow; tied into bundles of 1, 2, 5, and 10 rhizomes; and planted into unvegetated areas. Half the units were surrounded by plastic mesh and the remainder were unmeshed. All treatments were lost within 99 days after transplanting, and although larger bundles survived better than smaller ones, no significant differences could be attributed to the effects of mesh or sprig size. Plugs of P. sinuosa and A. griffithii were extracted from monospecific meadows using polyvinyl chloride pipe of three diameters, 5, 10, and 15 cm, and planted into unvegetated areas nearby. Half the units were surrounded by plastic mesh and the remainder were unmeshed. Posidonia sinuosa plugs were also placed within a meadow of H. tasmanica (Martens ex Aschers.) den Hartog. Only 60% of A. griffithii plug sizes survived 350 days after transplanting back into the donor bed; however, survival of transplants at unvegetated areas varied considerably, and analysis of variance indicated a significant two‐way interaction between treatment and plug size. Transplants survived better when meshed (90% survived) and survival improved with increasing plug size. Posidonia sinuosa transplants survived poorly (no plugs survived beyond 220 days in bare or meshed treatments) regardless of size. Survival of 10‐ and 15‐cm plugs was markedly better than the 5‐cm plugs in vegetated areas, including the H. tasmanica meadow. The use of large seagrass plugs may be appropriate for transplantation in high‐energy wave environments.     

Immobilization to prevent enzyme incompatibility with proteases

Abstract

Enzyme incompatibility is a problem in multi-enzyme processes that involve a non-specific protease, such as Alcalase. An example is the one-pot enzymatic synthesis of peptides catalyzed by a lipase and a protease. The incompatibility between lipase B from Candida antarctica (CalB) and Alcalase was studied. To what extent immobilization of both or either CalB or Alcalase onto macroporous beads helps to prevent hydrolysis of CalB by Alcalase was evaluated. The rate of activity loss of native and immobilized CalB in the absence and presence of native and immobilized Alcalase was calculated from the rate of triacetin hydrolysis. Immobilization of both or either CalB or Alcalase onto macroporous beads was found to be effective in largely preventing hydrolysis of CalB by Alcalase.     

Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68–90% and of 9.5×10^?2–72×10^?2 mmol l^?1 h^?1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^?2 mmol l^?1 h^?1), with these acids the conversion yields and initial rates were lower and in the range of 10–45% and of 0.7×10^?2 to 12.1×10^?2 mmol l^?1 h^?1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^?2 mmol l^?1 h^?1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

PTP1B inhibitory effects of tridepside and related metabolites isolated from the Antarctic lichen Umbilicaria antarctica

The selective inhibition of PTP1B has been widely recognized as a potential drug target for the treatment of type 2 diabetes and obesity. In the course of screening for PTP1B inhibitory natural products, the MeOH extract of the dried sample of the Antarctic lichen Umbilicaria antarctica was found to exhibit significant inhibitory effect, and the bioassay-guided fractionation and purification afforded three related lichen metabolites 1-3. Compounds 1-3 were identified as gyrophoric acid (1), lecanoric acid (2), and methyl orsellinate (3) mainly by analysis of NMR and MS data. These compounds inhibited PTP1B activity with 50% inhibitory concentration values of 3.6 ± 0.04 μM, 31 ± 2.7 μM, and 277 ± 8.6 μM, respectively. Furthermore, the kinetic analysis of PTP1B inhibition by compound 1 suggested that the compound inhibited PTP1B activity in a non-competitive manner.     

Antioxidative Effect of an Isolate from a Culture Filtrate of Aspergillus niger

D-Ins(1,3,4,5)P₄ and unnatural L-Ins(1,3,4,5)P₄ were prepared in gram-quantities from D- and L-2,6-di-O-benzyl-myo-inositol by a chemical phosphorylation and deprotection step in high yield and purity without extensive purification. The optically pure benzyl derivatives were obtained by enzyme-catalyzed resolution of racemic 2,6-di-O-benzyl-myo-inositol under acyl-transfer conditions in vinyl acetate as the acyl donor. The lipase of Candida antarctica only acetylated regio- and enantio-selectively the L-enantiomer, providing exclusively L-5-acetyl-2,6-di-O-benzyl-myo-inositol, whereas the D-enantiomer remained unchanged.     

南极假丝酵母脂肪酶B在离子液体/超临界流体体系中的稳定性模拟

脂肪酶在离子液体/超临界流体体系中的结构稳定性是影响其活性的重要因素。本文采用分子动力学方法分别研究了南极假丝酵母脂肪酶B(CALB)在离子液体CYPHOS IL-201/极性超临界流体CHF_3两相体系和离子液体CYPHOS IL-201/非极性超临界流体CO_2两相体系中的结构稳定性,揭示影响CALB结构稳定性的因素。研究结果表明,在超临界CHF_3中,CHF_3破坏蛋白维持α螺旋结构的氢键是蛋白结构不稳定的主要原因;在超临界CO_2中,CALB蛋白的结构紧密性降低,有序二级结构发生了变化,导致稳定性下降。离子液体和两种超临界流体均形成了两相体系,蛋白处于离子液体相中,离子液体不溶于超临界流体,但超临界流体部分进入离子液体相,降低了离子液体相的黏度。其中,相比于CYPHOS IL-201/CO_2体系,CYPHOS IL-201/CHF_3体系的黏度降低多。在离子液体CYPHOS IL-201与超临界流体(CHF_3、CO_2)形成的两相体系中,离子液体CYPHOS IL-201具有保护蛋白结构的作用,使CALB蛋白结构更加稳定。     

Construction of a Pseudozyma antarctica strain without foreign DNA sequences (self-cloning strain) for high yield production of a biodegradable plastic-degrading enzyme

ABSTRACT

The basidiomycetous yeast Pseudozyma antarctica GB-4(0) esterase (PaE) is a promising candidate for accelerating degradation of used biodegradable plastics (BPs). To increase safety and reduce costs associated with the use of PaE, we constructed a self-cloning strain with high-PaE productivity. A Lys12 gene (PaLYS12)-deleted lysine auxotroph strain GB4-(0)-L1 was obtained from GB-4(0) by ultraviolet mutagenesis and nystatin enrichment. Subsequently, the PaE gene (PaCLE1) expression cassette consisting of GB-4(0)-derived PaCLE1, under the control of a xylose-inducible xylanase promoter with PaLYS12, was randomly introduced into the GB4-(0)-L1 genome. A PaE high-producing strain, PGB474, was selected from among the transformants by high throughput double-screening based on its ability to degrade emulsified polybutylene succinate-co-adipate. Quantitative PCR revealed that four copies of the PaE gene expression cassette were introduced into the PGB474 genome. PGB474 produced 2.0 g/L of PaE by xylose-fed-batch cultivation using a 3-L jar fermentor for 72 h.     

Natural hybridization between a deciduous (Nothofagus antarctica, Nothofagaceae) and an evergreen (N. dombeyi) forest tree species: evidence from morphological and isoenzymatic traits

BACKGROUND AND AIMS: Trees with a partial leaf-shedding pattern and other morphological features a priori considered intermediate between those of the deciduous Nothofagus antarctica (G. Forster) Oersted and the evergreen N. dombeyi (Mirb.) Oersted (Nothofagaceae) were found in natural stands. The hybridization between a deciduous and an evergreen species of Nothofagus has not been reported so far in natural communities. METHODS: The putative hybrids and the two presumed parental species were compared using 14 enzyme systems as well as shoot, leaf and reproductive morphology. KEY RESULTS: Six enzyme systems showed good resolution (MDH-B, IDH, SKDH, 6-PGDH, GOT and PGI) and in four of them (PGI, MDH-B, SKDH and 6-PGDH) the putative hybrids showed intermediate zymogram patterns between N. antarctica and N. dombeyi. Both principal coordinates analysis on isozyme data and principal components analysis (PCA) on quantitative morphological traits of shoots and leaves separated both parental species and located the putative hybrids closer to N. antarctica than to N. dombeyi. In the PCA, the number of basal cataphylls and the length : width ratio of leaves were the variables most discriminating among shoots of the three entities. The putative hybrids were intermediate between both species regarding leaf vernation, outline and venation, variation in leaf shape (length/width) with position on the parent shoot and in staminate inflorescence and cupule morphology. For other morphological traits, the putative hybrids resembled one of the parental species or differed from both species (e.g. valve morphology). CONCLUSIONS: Isoenzymatic and morphological data sets support the idea of the hybrid nature (probably F1 generation) of the semi-deciduous trees found. Nothofagus antarctica and N. dombeyi are probably more closely related than previously assumed. The relevance of pollen type in revealing evolutionary relationships between Nothofagus species is supported, and that of leaf-shedding pattern is rejected.