Biotransformation Of Organic Compounds Research Articles

Biochemical characterization of a recombinant laccase from Halalkalibacterium halodurans C-125 and its application in the biotransformation of organic compounds

ObjectivesThis study aimed to produce an engineered recombinant laccase from extremophilic Halalkalibacterium halodurans C-125 (Lac-HhC-125) with higher protein yield, into a more active conformation and with properties that meet the fundamental needs of biotechnological application.ResultsThe rLac-HhC125 was partially purified by size exclusion chromatography and concentrated by ultrafiltration (10 kDa) with a yield of 57.6%. Oxidation reactions showed that adding 2 mM CuSO4 to the assay solution led to activating the laccase. To increase its initial activity, the rLac-HhC125 was treated at 50 °C for 20 min before the assays, improving its performance by fourfold using the syringaldazine as a substrate. When treated with EDTA, methanol, ethanol, and DMSO, the rLac-HhC125 maintained more than 80% of its original activity. Interestingly, the acetonitrile induced a twofold activity of the rLac-HhC125. The putative rLac-HhC125 demonstrated a capability of efficient transformation of different organic compounds at pH 6, known as dye precursors, into coloured molecules.ConclusionThe rLac-HhC125 was active at high temperatures and alkaline pH, exhibited tolerance to organic solvents, and efficiently transformed different hydroxy derivatives into coloured compounds, which indicates that it can be used in various biotechnological processes.

Biotransformation of emerging pollutants in groundwater by laccase from P. sanguineus CS43 immobilized onto titania nanoparticles

Biotransformation of organic compounds by using biocatalysts such as laccases provides an environmentally attractive alternative to supplement conventional wastewater treatment. However, loss and inactivation of enzymes are challenges to solve for their potential use in water treatment applications. Titania presents a high chemical stability and easy functionalization, which are important characteristics in a support used for immobilization processes. Therefore, in this study, the immobilization of laccase enzymes produced by Pycnoporus sanguineus CS43 onto titania nanoparticles (∼21 nm) was optimized. Surface modification of the support was carried out by using different weight% (wt%) of 3-aminopropyltriethoxysilane (APTES) as a coupling agent and the cross-linker glutaraldehyde (GLU) as a laccase binder. Free and immobilized enzymatic activity were measured based on 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays and were compared regarding apparent activity and activity recovery. In addition, the effect of ionic strength on the immobilization process was studied, finding that low ionic strength (25 mM phosphate buffer) promote a high activity recovery, greater than 90% and even higher than previous reports. Immobilized laccases showed high thermostability at 50 and 60 °C (half-lives of 45.7 and 3.7 h, respectively), and high stability at low pH values of 2 and 3 (half-lives of 31.8 and 107.1 h respectively). Furthermore, the biocatalyst was assessed in the biotransformation of emerging pollutants such as acetaminophen and diclofenac by using 100 UL−1 of immobilized laccase at pH 4; the maximum biotransformation percentage of DCF was 68% after 8 h, and more than 90% biotransformation of ACE was reached after 2 h of treatment.

Biotransformation of organic compounds in vivo using larvae of beetles (Allomyrina dichotoma) as biocatalysts

The biotransformation of organic compounds using the larvae of the Japanese rhinoceros beetle (Allomyrina dichotoma) as a biocatalyst is described. When phenyl alkanediones were administered by mouth (p.o) or subcutaneous injection (s.c) to the beetle, asymmetric reduction occurred to yield the corresponding diols in varying optical yields: 1-phenyl-1,2-propandione or 1-phenyl-1,3-butanedione reduced to (1R,2S)- and (1S,2S)-1,2-phenylpropanediols in high optical yields or (1R,3S)- and (1R,3R)-1-phenyl-1,3-butanediols in low to high optical yields, respectively. By administrating 1-phenyl-1-propanone, 1-phenyl-1-butanone or 4-phenyl-2-butanone, redox reactions occurred to give 1-phenyl-1,2-propanediols or 1-phenyl-1,3-butanediols in lower optical yields. The administrations of β-ionone and cinnamyl chloride resulted in regioselective allylic oxidations producing enone and cinnamic acid, respectively. However, when (R)-(-)-carvone was administered, regiospecific dihydroxylation at the isopropenyl group occurred to give (4R,8R)- and (4R,8S)-8,9-dihydroxy-8,9-dihydrocarvone as diastereoisomers. These results appear to demonstrate similar reaction tendency with the case of a microorganism. It is possible that these reactions were due in part to bacteria in the intestine of the larva: however, regio- and stereoselectivities of the reactions were sometimes unique. Thus, it is supposed that these biotransformations were accomplished by the ensemble of the larva׳s own enzymes with several bacteria. The results obtained in this study might show the possibility of using such enzymes derived from insects, including beetle larvae, as a biocatalyst.

Toxicological effects of primary-treated urban wastewaters, before and after ozone treatment, on freshwater mussels ( Elliptio complanata)

This study examined the toxic potential of a primary-treated municipal effluent, before and after ozonation, in freshwater mussels. Animals were exposed to various concentrations (0, 1, 3, 10 and 20% v/v) of a primary-treated effluent and also after a treatment with ozone at 10 mg/L in continuous flow-through mode for seven weeks. A suite of biomarkers was used to assess the potential toxic effects of various contaminants typically present in municipal wastewaters: heavy metal metabolism (metallothioneins and labile zinc), cytochrome P4501A1 and 3A4, glutathione S-transferase activities (biotransformation of organic compounds), lipid peroxidation and xanthine oxidoreductase (oxygen radical scavenging), DNA damage, mitochondrial electron transport activity at various temperatures and gonad lipid levels (cellular energy allocation) and aspartate transcarbamoylase and dihydrofolate reductase (gonad activity). On the one hand, some biomarkers, including metallothioneins, labile zinc, glutathione S-transferase, cytochrome P4503A4 activity, dehydrofolate reductase and aspartate transcarbamoylase, were readily decreased. In contrast, these biomarkers, cytochrome P4501A1, gill lipid peroxidation, DNA strand breaks in gills and digestive gland, mitochondrial electron transport at high and low temperatures (temperature-dependent activity) and total gonad lipids, were readily increased. In general, ozone treatment reduced adverse effects by either decreasing the intensity of the toxic responses or increasing the threshold concentration. For gill lipid peroxidation, however, intensity was greater at a higher threshold concentration. Ozone treatment eliminated the temperature sensitivity of the mitochondrial electron transport system, indicating a loss of interaction between temperature and urban pollution in terms of energy expenditure in mussels. Ozone treatment could significantly decrease either the toxic potency or intensity of urban pollutants at the expense of increased oxidative stress in gills of freshwater mussels.

Biotransformation of Citrinin to Decarboxycitrinin Using an Organic Solvent-Tolerant Marine Bacterium, Moraxella sp. MB1

Organic solvent tolerant microorganisms (OSTMs) are novel group of extremophilic microorganisms that have developed resistance to withstand solvent toxicity. These organisms play an important role in biotransformation of organic compounds. In the present study, we used an organic solvent-tolerant marine bacterium, Moraxella sp. MB1. 16S rRNA sequencing revealed that the bacterium shows 98% similarity with an uncultured marine bacterium with GenBank accession no. AY936933. This bacterium was used for the transformation of a toxin, citrinin, into decarboxycitrinin in a biphasic system. This transformation was affected by decarboxylase enzyme produced by MB1. Transformation of citrinin to decarboxycitrinin was monitored by thin-layer chromatography (TLC) and spectrophotometrically. Citrinin decarboxylase activity responsible for transformation was studied in cell-free growth medium and cell lysate of Moraxella sp. MB1. Citrinin decarboxylase was found to be intracellular in nature. The biotransformed product was purified and identified as decarboxycitrinin using electrospray ionization mass spectrometry (ESI-MS/MS) and nuclear magnetic resonance (NMR) spectrometry. The antibiotic activity of both citrinin and decarboxycitrinin is also reported.

Metabolism of drugs by the kidney

The kidneys have many clearly defined physiologic functions. Although their role as an excretory organ for drugs and chemicals and their polar metabolites is well described, their involvement in the biotransformation of xenobiotics is relatively poorly understood. It is accurate to state that our present understanding of the metabolic processes of drugs is based largely on studies carried out in the liver. Only recently have detailed investigations into drug metabolism in the kidney been carried out. These studies have shown that the kidney is meta-bolically very active in effecting the biotransformation of a variety of chemicals and drugs and, in some cases, surpasses the liver. It is important to understand the role of the kidney in drug and chemical biotransformation for a variety of reasons. Because the kidney receives a substantial portion of the cardiac output, it is reasonable to expect that it may make a significant contribution to the total metabolic alteration of drugs in the body. Furthermore, it is now known that the toxic effects of many drugs and chemicals are attributable to their metabolic conversion to reactive electrophilic intermediates, which, on reaction with cellular nucleophiles, lead to a variety of deleterious effects. Perhaps most important is the appreciation that this interaction between reactive intermediates and critical cellular macromolecules is intimately involved in mutagenic and carcinogenic changes. In addition, necrotic changes may also be associated with cellular alkylation. Thus, a complete perspective on the role of the kidney in pharmacologic and toxicologic processes is dependent on a thorough understanding of the drug and chemical metabolic capabilities of this organ. The biotransformation of organic compounds can be conveniently divided into oxidative, reductive, hydrolytic, and synthetic or conjugation reactions. The first three reactions are based on the type of chemical change produced. Synthetic or conjugation reactions usually involve the enzyme-catalyzed combination of a chemical or a metabolite and a carbohydrate or an amino acid, and they yield highly polar, readily excretable metabolites. Furthermore, multiple metabolic alterations are very common. Williams, in his classic book, Detoxication Mechanisms, suggests that the metabolism of many xenobiotics occurs in two steps [1]. The first, termed I reactions, includes oxidative, reductive, and hydrolytic reactions; the second, termed II reactions, consists of conjugative reactions and includes, for example, glucuronide, sulfate, and hippuric acid formation. It should be noted that although the metabolites produced in phase I reactions are frequently less toxic or less active pharmacologically than the parent compound is, abundant examples can be cited where the metabolites are more toxic and more active pharmacologically. By the same token, although the conjugates produced in phase II reactions are usually very polar and less toxic, notable exceptions exist; for example, the sulfate conjugate of N-hydroxyacetyl-aminofluorene is thought to be the proximate carcinogen in the case of this compound [5].