Lignocellulosic residues from bioethanol production: a novel source of biopolymers for laccase immobilization.

The full utilization of the main components in the lignocellulosic biomass is the major goal from a biorefinery point of view, giving not only environmental benefits but also making the process economically viable. In this sense the solid residue obtained in bioethanol production after steam explosion pretreatment, enzymatic hydrolysis, and fermentation of the lignocellulosic biomass, was studied for further valorization. Two different residues were analyzed, one generated by the production of cellulosic ethanol from an energy crop such as switchgrass (Panicum virgatum) and the other, from wood (Eucalyptus globulus). The chemical composition of these by-products showed that they were mainly composed of lignin with a total content range from 70 to 83% (w/w) and small amounts of cellulose and hemicellulose. The present work was focused on devising a new alternative for processing these materials, based on the ability of the ionic liquids (IL) to dissolve lignocellulosic biomass. The resulting mixture of biopolymers and IL constituted the raw material for developing new insoluble biocatalysts. Active hydrogels based on fungal laccase from Dichostereum sordulentum 1488 were attained. A multifactorial analysis of the main variables involved in the immobilization process enabled a more direct approach to improving hydrogel-bound activity. These hydrogels achieved a 97% reduction in the concentration of the estrogen ethinylestradiol, an emerging contaminant of particular concern due to its endocrine activity. The novel biocatalysts based on fungal laccase entrapped on a matrix made from a by-product of second-generation bioethanol production presents great potential for performing heterogeneous catalysis offering extra value to the ethanol biorefinery.

Microbial transformation of cholesterol: reactions and practical aspects-an update.

Cholesterol is a C27-sterol employed as starting material for the synthesis of valuable pharmaceutical steroids and precursors. The microbial transformations of cholesterol have been widely studied, since they are performed with high regio- and stereoselectivity and allow the production of steroidal compounds which are difficult to synthesize by classical chemical methods. In recent years, ongoing research is being conducted to discover novel biocatalysts and to develop biotechnological processes to improve existing biocatalysts and biotransformation reactions. The main objective of this review is to present the most remarkable advances in fungal and bacterial transformation of cholesterol, focusing on the different types of microbial reactions and biocatalysts, biotransformation products, and practical aspects related to sterol dispersion improvement, covering literature since 2000. It reviews the conversion of cholesterol by whole-cell biocatalysts and by purified enzymes that lead to various structural modifications, including side chain cleavage, hydroxylation, dehydrogenation/reduction, isomerization and esterification. Finally, approaches used to improve the poor solubility of cholesterol in aqueous media, such as the use of different sterol-solubilizing agents or two-phase conversion system, are also discussed.

Bioprospecting of whole-cell biocatalysts for cholesterol biotransformation.

Microorganisms were isolated from industrial wool scouring effluents and from the soil adjacent to the wastewater treatment lagoon, both sterols-rich environments, in order to search for novel biocatalysts able to transform cholesterol. The isolates were identified on the basis of morphological and biochemical characteristics and phylogenetic analysis. Furthermore, a rapid and accurate bacteria identification by matrix assisted laser desorption/ionization-time-of-flight mass spectrometry was carried out. Bacteria and fungi including representatives of the genera Fusarium, Talaromyces, Trichoderma, Mucor, Aspergillus, Citrobacter, Proteus, Klebsiella, Exiguobacterium, Acinetobacter, Tsukamurella, Bacillus, and Streptomyces were found and evaluated for their ability to biotransform cholesterol by whole-cell treatment system. The results show that a Trichoderma koningiopsis strain, as well as two strains of Mucor circinelloides were able to transform cholesterol into value-added products. The major products were characterized as 7ß-hydroxycholesterol, 4-cholesten-3-one, 5α,6α-epoxycholestan-3ß-ol and 5ß,6ß-epoxycholestan-3ß-ol. To the best of our knowledge, the present study is the first report of cholesterol biotransformation by representatives of Trichoderma and Mucor genera.

Aggregation Behavior of 6-Isocassine and N-Methyl-6-Isocassine: Insights into the Biological Mode of Action of Lipid Alkaloids.

The aggregation behavior of 6-isocassine and N-methyl-6-isocassine, two piperidin-3-ol alkaloids isolated respectively from the barks of Prosopis nigra and P. affinis, was investigated using a combination of NOE experiments and diffusion measurements in solvents of varying polarity and hydrogen bonding capacity. While the NOE enhancements for N-methyl-6-isocassine are positive, regardless of the solvent, those for 6-isocassine shift from negative to positive when going from chloroform-d to methanol-d(4) solution. In addition, despite the self-diffusion coefficients of both compounds being virtually identical in methanol-d4, N-methyl-6-isocassine diffuses nearly twice as fast as the non-methylated alkaloid in chloroform-d. The changes in rotational and translational dynamics observed between solvents for 6-isocassine suggest that the molecule forms dimeric head-to-head aggregates in non-polar aprotic environments, a behavior that could help explain the biological mode of action that has been proposed for this type of alkaloids.

Influence of culture conditions on the biotransformation of (+)-limonene by Aspergillus niger.

The influence of the cultivation system and of the culture medium on the biotransformation of (+)-limonene by a strain of Aspergillus niger was investigated. Biooxidation products were obtained in all conditions tested. Using a laboratory bioreactor, six terpenes were identified in every medium, predominantly terpineols and carveols, whereas terpinen-4-ol and perillyl alcohol were the only terpenes found when flasks were used for culture. Perillyl alcohol and carveols predominated when the medium was tryptic soy broth (TSB), whereas the formation of terpineols was clearly favoured in malt broth (MB). Thus, there was a marked influence of the culture conditions on the results of the biotransformation. Changes in the conditions led to variations both in the type and relative amount of products obtained.

Prenylated isoflavonoids: Botanical distribution, structures, biological activities and biotechnological studies. An update (1995-2006).

In contrast with the parent class of flavonoids, the distribution of the isoflavonoid class in the plant kingdom is relatively limited, probably owing to the sporadic occurrence of isoflavone synthase. Isoflavonoids have been mostly found in the subfamily Fabaceae/Papilionoideae of the Leguminosae family. Isoprenoid-substituted (also called complex) isoflavonoids are expressed from a smaller number of plants, as a result of the similarly restricted distribution of prenyltransferases (PT-ase). After the reviews of Tanara & Ibrahim (1995), Boland & Donnelly (1997), the Handbook of Flavonoids by Harborne & C ( Handbook of Flavonoids, 1999), and the paper by Harborne and Williams (2000) few other reports concern the distribution and the biological activity of complex isoflavonoids, except a list of isoflavonoids produced from non leguminous plants. This review deals with an update of the literature on isoprenylated isoflavonoids in the years 1995-2006 and is focused on the following highlights. 1. Natural sources of complex isoflavonoids (2000-2006); 2. Chemical structure variety: new entries (2000-2006) 3. Biological activities and a possible structure-activity relationship (1995-2006) 4. In vitro production and microbial metabolism (1995-2006).

The contribution of oxazolidinone frame to the biological activity of pharmaceutical drugs and natural products.

The development of resistance by the antibiotics in the Gram-positive pathogenic bacteria over the last twenty years and continuing today has created a need for new antibiotic classes, which may be unaffected by existing bacterial resistance. The oxazolidin-2-ones represent not only a new class with a novel mechanism of action, but also satisfy the requirement for overcoming the resistance mechanisms. Both linezolid and eperozolid, the first chemical candidates, arose from the piperazine subclass, with the first one being chosen further development because of its enhanced pharmacokinetic properties. The main attractive traits of the oxazolidinone series has encouraged further work in the area, and the patent literature reveals that extensive chemical investigation is currently being made. The unexpected early resistance development emphasizes the need for further exploration of features of the oxazolidinone to eliminate these deficiencies. Recently, several changes, involving the C5 side chain as well the N-phenyl heterocyclic ring, give promise for such improvement. Oxazolidinone antibacterial agents comprise also ketolides, derivatives of macrolides, such as erythromycin A, with a newly formed carbamate cycle, with a largely unexplored potential. The oxazolidinone nucleus does not appear only in the structures of antimicrobial drugs, but a number of biological activities are connected with frameworks including the oxazolidinone ring. A partial list of these activities comprises enzyme inhibitors, agonists and antagonists, with a particular citation for a new generation of selective monoamino oxidase inhibitors (befloxatone). The oxazolidinone moiety was found in the structure of few biologically active natural products, such as (-)-cytoxazone and streptazolin. Moreover, in some cases the oxazolidinone ring has been chosen for the preparation of isosteric aza analogues of natural compounds (podophyllotoxin, pilocarpine) that can be more easily synthesised and more hardly inactivated. Finally, the participation of oxazolidinone chiral auxiliaries to several syntheses of natural products must be acknowledged.

Biotransformation of 1,8-cineole, the main product of Eucalyptus oils

The forest industry in Uruguay has grown considerably during the last decade. Eucalyptus plantations account for 74 percent of the forested land, with Eucalyptus globulus being the most widely distributed species. This industry is dedicated exclusively to the production of wood without exploiting the by-products (leaves and small branches). Eucalyptus leaves are known to contain important amounts of essential oils composed primarily of 1,8-cineole (1,3,3-trymethyl-2-oxabicyclo[2.2.2]octane). In this work, the biotransformation of 1,8-cineole, is achieved using a native bacterium (Rhodococcus sp.) which was isolated from the soil of Eucalyptus forest. A 98 percent of bioconversion was achieved. Three different optically pure compounds were obtained, and they were identified as 2-endo-hydroxy-1,8-cineole, 2-exo-hydroxy-1,8-cineole and 2-oxo-1,8-cineole.

Novel prenyltransferase enzymes as a tool for flavonoid prenylation.

The recent identification of genes encoding a novel family of soluble aromatic prenyltransferases from Streptomyces species and the structural characterization of one of these proteins are challenging discoveries in the biochemistry of natural compounds. In addition to their notable physiological role in the biosynthesis of aminocoumarin antibiotics, these enzymes represent an advanced tool for exploring novel isoprenoid substitutions in aromatic compounds and are expected to foster the emerging pharmacological applications of prenylated flavonoids.

Prenylated flavonoids: pharmacology and biotechnology.

Within the flavonoid class of natural products the prenylated sub-class is quite rich in structural variety and pharmacological activity. In the last twenty years a huge number of new structures has been reported, mostly from Leguminosae and Moraceae, with few coming from other genera. The presence, in different forms, of the isoprenoid chain can lead to impressive changes in biological activity, mostly attributed to an increased affinity for biological membranes and to an improved interaction with proteins. Molecules, such as xanthohumol and sophoraflavanone G, while being very structurally simple, show numerous pharmacological applications and are ideal candidates for SAR aimed to the discovery of new drugs. Only recently the biogenesis of these compounds has been more extensively studied and much attention has been focused on the enzymes involved in the modification and transfer of the prenyl unit.