Tomáš Řezanka

Biodegradable plastics from renewable sources.

Plastic waste disposal is a huge ecotechnological problem and one of the approaches to solving this problem is the development of biodegradable plastics. This review summarizes data on their use, biodegradability, commercial reliability and production from renewable resources. Some commercially successful biodegradable plastics are based on chemical synthesis (i.e. polyglycolic acid, polylactic acid, polycaprolactone, and polyvinyl alcohol). Others are products of microbial fermentations (i.e. polyesters and neutral polysaccharides) or are prepared from chemically modified natural products (e.g., starch, cellulose, chitin or soy protein).

Odd-numbered very-long-chain fatty acids from the microbial, animal and plant kingdoms.

Very long chain fatty acids (FAs) are important components of different classes of lipids in all organisms from bacteria to man. They include also, usually as minor components, odd-numbered FAs. These have so far been given little attention because of technical difficulties inherent in their detection and identification. Current modern analytical methods such as GC-MS and/or LC-MS make this detection and identification possible, and should promote a study of their properties. This review brings, in a concise manner, most of the currently available information about these FAs, their occurrence in different organisms, their structure and other properties. It should provide an impetus for further research into these very interesting compounds whose chemical, biochemical and biological properties are poorly known.

Lincomycin, clindamycin and their applications

Abstract Lincomycin and clindamycin are lincosamide antibiotics used in clinical practice. Both antibiotics are bacteriostatic and inhibit protein synthesis in sensitive bacteria. They may even be bactericidal at the higher concentrations that can be reached in vivo . Clindamycin is usually more active than lincomycin in the treatment of bacterial infections, in particular those caused by anaerobic species; and it can also be used for the treatment of important protozoal diseases, e.g. malaria, most effectively in combination with primaquine. Resistance to lincomycin and clindamycin may be caused by methylation of 23S ribosomal RNA, modification of the antibiotics by specific enzymes or active efflux from the periplasmic space.

Determination of plant triacylglycerols using capillary gas chromatography, high-performance liquid chromatography and mass spectrometry.

Abstract Molecular species of triglycerides (TG) were determined in plant fats and oils, both qualitatively and quantitatively, by means of capillary gas chromatography (CGC) on a “polarizable” column, reversed-phase C18 high-performance liquid chromatography (RP-HPLC) and desorption chemical ionization mass spectrometry (DCI-MS). For the qualitative analysis values of the equivalent carbon number (ECN) and equivalent chain length (ECL) were used for the identification of individual molecular species of TG by means of RP-HPLC or CGC. Plant oils including cocoa butter with smaller numbers of double bonds can be determined without any problems by means of CGC, RP-HPLC and DCI-MS. The determination by CGC and partially also RP-HPLC failed only with oils with either a complex distribution of chain lengths, i.e., rape seed oil (high erucic acid) or a high unsaturation index (linseed oil and blackcurrant oil). However, with complementary results from all three methods it was possible to identify numerous molecular species of triglycerides in various plant oils.

Do we need new antibiotics? The search for new targets and new compounds.

Resistance to antibiotics and other antimicrobial compounds continues to increase. There are several possibilities for protection against pathogenic microorganisms, for instance, preparation of new vaccines against resistant bacterial strains, use of specific bacteriophages, and searching for new antibiotics. The antibiotic search includes: (1) looking for new antibiotics from nontraditional or less traditional sources, (2) sequencing microbial genomes with the aim of finding genes specifying biosynthesis of antibiotics, (3) analyzing DNA from the environment (metagenomics), (4) reexamining forgotten natural compounds and products of their transformations, and (5) investigating new antibiotic targets in pathogenic bacteria.

Metabolites produced by nitrogen-fixingNostoc species

This paper provides a comprehensive overview of metabolites, including lipids and lipid-like compounds, boron-containing macrocycles, arsenolipids, oligopeptides and amino acid derivatives, produced by cyanobacteria of the genusNostoc.

Pseudomonas biofilms: possibilities of their control

Genus Pseudomonas includes a large number of species that can be encountered in biotechnological processes as well as in the role of serious human or plant pathogens. Pseudomonads easily form biofilms on various types of surfaces. The biofilm phenotype is characterized by an increased resistance to environmental influences including resistance to antibiotics and other disinfectants, causing a number of problems in health care, food industry, and other areas. Considerable attention is therefore paid to the possibilities of eradication/destruction of pseudomonads biofilms both in terms of understanding the mechanisms of biofilm formation and at the level of finding suitable antibiofilm tools applicable in practice. The first part of this review is devoted to an overview of the regulatory mechanisms that are directly or indirectly involved in the formation of biofilm. The most effective approaches to suppressing the formation of biofilm that do not cause the development of resistance are based on the application of substances that interfere with the regulatory molecules or block the appropriate regulatory mechanisms involved in biofilm development by the cells. Pseudomonads biofilm formation is, similar to other microorganisms, a sophisticated process with many regulatory elements. The suppression of this process therefore also requires multiple antibiofilm tools.

Characterization of rhamnolipids produced by non-pathogenic Acinetobacter and Enterobacter bacteria

Rhamnolipid production by two non-pathogenic bacterial strains Acinetobacter calcoaceticus and Enterobacter asburiae, and established rhamnolipid producer Pseudomonas aeruginosa was investigated. Rhamnolipids were separated from supernatant and further purified by thin-layer chromatography. Mass spectrometry with negative electrospray ionization revealed rhamnolipid homologues varying in chain length and unsaturation. Tandem mass spectrometry identified mono-rhamnolipid and di-rhamnolipid homologues containing one or two 3-hydroxy fatty acids. Several media differing in carbon (sunflower oil, glycerol and sodium citrate), nitrogen (ammonium ions, nitrate) and phosphorus (total content) source, respectively, were tested to obtain enhanced rhamnolipid production. The best production (0.56g/l) was obtained when nitrate was used as a nitrogen source. Both strains produced rhamnolipids that exhibited excellent emulsification activity with aromatic and aliphatic hydrocarbons and several plant oils. Unlike P. aeruginosa the two strains, i.e. Acinetobacter and Enterobacter, are not pathogenic to humans.

Gas chromatography—mass spectrometry and desorption chemical ionization mass spectrometry of triacylglycerols from the green alga chlorella kessleri

Abstract The distribution of triacyglycerols in the green alga Chlorella Kessleri cultivated heterotropically were determined by means of gas chromatography-mass spectrometry and desorption chemical ionization mass spectrometry. Quantitative and qualitative results obtained by the two methods are correlated.

Effect of nitrogen and phosphorus starvation on the polyunsaturated triacylglycerol composition, including positional isomer distribution, in the alga Trachydiscus minutus

The yellow-green alga Trachydiscus minutus (Eustigmatophyceae, Heterocontophyta) was cultivated in a standard medium and under nitrogen- and phosphorus-starvation and its triacylglycerols were analyzed by RP-HPLC/MS-APCI. The molecular species of triacylglycerols included a total of 74 triacylglycerols having at least one polyunsaturated fatty acid. Polyunsaturated triacylglycerols were identified for the first time in a yellow-green alga. N-starvation brought about a nearly 50% drop in TAGs containing EPA, and also decreased TAGs containing ARA, while P-starvation had a sizable effect on those TAGs that contain two or three arachidonic acids. In four TAGs containing PUFA, i.e. EEE, EEA, EAA and AAA, N-starvation caused a rapid fivefold increase in ARA content and the ratio of TAGs containing ARA, i.e. AEE to AAA increased tenfold relative to control. Regioisomeric characterization of triacylglycerols containing palmitic, arachidonic (ARA) and eicosapentaenoic acids (EPA) showed that the proportion of positional isomers is affected by N- and P-starvation. N- and P-starvation also changed the ratio of symmetrical to asymmetrical TAGs. Positional isomers exhibited identical ratios of symmetrical and asymmetrical TAGs irrespective of the type of FAs. In control cultivation the major TAGs with a single PUFA were symmetrical ones (PEP or PAP) whose ratio to asymmetrical counterparts (PPE or PPA) was about 3:1, whereas N- and P-starvation yielded opposite ratios, 1:3-1:5. The control cultivation yielded ~90% asymmetrical TAGs with two PUFAs (i.e. PEE and PAA), whereas with N- and P-starvation the ratio of symmetrical to asymmetrical TAGs increased to 2:1 and 3:2, respectively.