Wyniki wyszukiwania - Biblioteka Nauki

1

Biocatalytic synthesis of δ-gluconolactone and ε-caprolactone copolymers

100%

Todea A. , Badea V. , Nagy L. , Kéki S. , Boeriu C. , Péter F.

Acta Biochimica Polonica

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2014

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tom 61

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nr 2

205-210

EN

The biodegradability and biocompatibility properties of ε-caprolactone homopolymers place it as a valuable raw material, particularly for controlled drug delivery and tissue engineering applications. However, the usefulness of such materials is limited by their low hydrophilicity and slow biodegradation rate. In order to improve polycaprolactone properties and functionalities, copolymerization of ε-caprolactone with δ-gluconolactone was investigated. Since enzymatic reactions involving sugars are usually hindered by the low solubility of these compounds in common organic solvents, finding the best reaction medium was a major objective of this research. The optimal copolymerization conditions were set up by using different organic media (solvent and solvents mixtures), as well as solvent free systems that are able to dissolve (completely or partially) sugars, and are nontoxic for enzymes. Native and immobilized lipases by different immobilization techniques from Candida antarctica B and Thermomyces lanuginosus have been used as biocatalyst at 80°C. Although the main copolymer amount was synthesized in DMSO:t-BuOH (20:80) medium, the highest polymerization degrees, up to 16 for the copolymer product, were achieved in solventless conditions. The products, cyclic and linear polyesters, have been characterized by FT-IR and MALDI-TOF MS analysis. The reaction product analysis revealed the formation of cyclic products that could be the major impediment of further increase of the chain length.

2

Usable products from sewage and solid waste

75%

Łebkowska M. , Załęska-Radziwiłł M.

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2011

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tom Vol. 37, no. 3

15-19

EN

Sewage and solid waste can be a valuable source of materials used directly or indirectly in manufacturing of usable products. These processes are associated with elimination of pollutants from liquid and solid wastes. The best-known methods of waste management are production of biogas and composting. This paper focuses on the possibility of obtaining biomass as a source of protein feed (whose value, in terms of the composition of aminoacids and microelements, is comparable with conventional feed, e.g. soymeal, bonemeal or fishmeal). Sewage components for bacterial, fungal, algal and vascular plants' culture are characterized as a source of protein feed. Methods of industrial scale production of enzymes, mainly proteases and lipases that have broad applications in various industries, are discussed. Development perspectives of inexpensive methods of usable products from waste production are showed. Interdisciplinary nature of presented issues, which requires cooperation of specialists in biology, chemistry and technology, is emphasized.

PL

Ścieki i odpady stałe mogą być cennym źródłem surowców wykorzystywanych bezpośrednio lub pośrednio do wytwarzania użytecznych produktów. Procesom tym towarzyszy eliminacja zanieczyszczeń z odpadów płynnych i stałych. Do najbardziej znanych sposobów zagospodarowania odpadów należy produkcja biogazu i kompostowanie. W niniejszej pracy zwrócono szczególną uwagę na możliwość pozyskiwania biomasy jako źródła białka paszowego, którego wartość pod względem składu aminokwasów i mikroelementów jest porównywalna z paszami konwencjonalnymi, między innymi z mączką sojową, kostną, rybną. Scharakteryzowano surowce ze ścieków do hodowli bakterii, grzybów, glonów i roślin naczyniowych jako źródeł białka paszowego. Omówiono sposoby produkcji na skalę przemysłową enzymów, głównie proteaz i lipaz mających szerokie zastosowanie w różnych gałęziach gospodarki. Wskazano perspektywy rozwoju metod wytwarzania użytecznych produktów z odpadów, eliminujących drogie technologie. Podkreślono interdyscyplinarny charakter przedstawionej problematyki, wymagającej współdziałania specjalistów z zakresu biologii, chemii i technologii.

3

Zastosowanie biotransformacji w syntezie optycznie czynnych laktonów

44%

Gładkowski W.

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2009

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tom [Z] 63, 5-6

361-389

EN

Compounds with lactone moiety exhibit many biological acitivities (for example antimicrobial, antifeedant, cytostatic). One of the most attractive methods to obtain optically active lactones are regio- and stereoselective biotransformations. These together with mild reaction conditions are the main advantages of the processes compared to chemical synthesis of lactones. In this review examples of such biotransformations are presented. The lactones may be obtained via direct biotransformation of substrate or in chemoenzymatic synthesis. In the second case the enzymatic step is the key one, leading to optically pure or enriched intermediate which is further transformed into desired, optically active product. As the products of direct biotransformation, lactones can be formed from fatty acids like ricinoleic or vernolic acid [1, 2], aromatic compounds (benzoic acid, mandelic acid, catechol) [3] as well as in the result of lactonization of epoxyesters by enzymatic systems of fungi or plants. In the last case the biocalysts is the apple pulp or Jerusalem artichoke pulp [4-6]. Hydrolysis of amides and nitriles is also applied to the synthesis of lactones. Especially useful in this regard are microorganisms, which exhibit both enzymatic activities [7-9]. Microbial reduction of carbonyl group in ketoesters or ketoacids is also very useful method. The reduction may occur in ? or ? position, leading to ?- or ?-hydroxyacids which cyclize to the corresponding lactones [10-13]. Reduction of carbonyl group in ?-position is the first step of a synthesis of lactones with 7- or 8-membered rings [14-16]. The application of hydrolysis or transesterification processes catalyzed by hydrolytic enzymes, mainly lipases from Pseudomonas sp., also leads to enzymatically enriched lactones. The substrates may be ?-ketoesters, ?-hydroxyamides, meso-diols or meso-diesters [10, 17-19]. Among the oxidation reaction the most known is Baeyer-Villiger reaction in which cyclic ketones are directly oxidized to the lactones by enzymes called Baeyer-Villiger monooxygenases (BVMO) [20]. The reaction is highly regioselective and can be applied to the production of unsaturated lactones [23]. In this area of research genetically modified strains of Escherichia coli are applied [21, 24], although the wild strains are also used, for example to the production of ?-caprolactone from cyclohexanone [22]. Another reaction catalyzed by oxidoreductases is the oxidation of hydroxyl group to carbonyl or carboxyl one [25-27]. In this first case horse liver alcohol dehydrogenase (HLADH) found application in the oxidation of meso-diols to lactones. The ability of different fungal strains to the regioselective hydroxylation of unactivated carbon atom found an application to the synthesis of lactones with eudesmane and germacrane systems [28-30]. Resolution of racemates is an alternative strategy used to the synthesis of lactones in optically pure forms. This aim can be achieved by enzymatic cleavage of lactone ring catalyzed by lactonases. These enzymes of microbial origin belong to esterases and are often induced during the growth of microorganisms on cyclic ketones as the carbon sources [31, 32, 34]. Enzymatic resolution of pantolactone by lactonase from Fusarium oxysporum is an example of industrial biotransformation [33]. Lipases can also be applied to the enantioselective hydrolysis of lactone ring [35-37]. The other functional groups present in the molecule can also be converted during the resolution of racemic lactones [39-44]. The examples are hydrolysis of acetoxylactones or esterification of hydroxylactones.