Identification of molecular basis that underlie enzymatic specificity of AzoRo from Rhodococcus opacus 1CP: A potential NADH:quinone oxidoreductase.

Azo dyes are important to various industries such as textile industries. However, these dyes are known to comprise toxic, mutagenic, and carcinogenic representatives. Several approaches have already been employed to mitigate the problem such as the use of enzymes. Azoreductases have been well-studied in its capability to reduce azo dyes. AzoRo from Rhodococcus opacus 1CP has been found to be accepting only methyl red as a substrate, surmising that the enzyme may have a narrow active site. To determine the active site configuration of AzoRo at atomic level and identify the key residues involved in substrate binding and enzyme specificity, we have determined the crystal structure of holo-AzoRo and employed a rational design approach to generate AzoRo variants. The results reported here show that AzoRo has a different configuration of the active site when compared with other bacterial NAD(P)H azoreductases, having other key residues playing a role in the substrate binding and restricting the enzyme activity towards different azo dyes. Moreover, it was observed that AzoRo has only about 50% coupling yield to methyl red and p-benzoquinone - giving rise to the possibility that NADH oxidation still occurs even during catalysis. Results also showed that AzoRo is more active and more efficient towards quinones (about four times higher than methyl red).

Bending is required for activation of dsz operon by the TetR family protein (DszGR).

The dsz operon responsible for the biodesulfurization of organosulfurs is under the control of a 385 bp long promoter. Recently, a TetR family protein was identified which served as an activator of operon. Here we report that the TetR family protein (WP_058249973.1), named DszGR can specifically activate the dsz operon. Direct binding of the DszGR to DNA was observed at single molecule level by AFM. It was found that the binding of DszGR to the promoter DNA induces a bend by about âˆ¼40-50° degrees which may not be enough for the activation of the promoter. Thus, bendability in the promoter sequence was analyzed. The results show that the promoter has a curvature at around -235 and -200 bp with respect to dszA start codon. On mutating this region, a decrease in activity of the promoter was observed. Our results suggest that the DszGR protein binds to the upstream sequences and induces a bend, which is facilitated by further bending of the DNA which is required for dsz promoter activity. IHF binding site present in the promoter, and a significant reduction in desulphurization activity in the absence of either IHF subunits, suggested role of IHF in regulation of the dsz operon.

Rausuquinone, a non-glycosylated pluramycin-class antibiotic from Rhodococcus.

A new pluramycin-class polyketide, rausuquinone (1), and its known congener hydramycin (2) were isolated from the culture extract of the deep-sea water-derived Rhodococcus sp. RD015140. Compound 1 possesses a γ-pyrone-fused anthraquinone core with a 3-butene-1,2-diol side chain. Structures of 1 was determined by extensive analysis of 1D and 2D NMR spectroscopic data. Compound 1 showed antimicrobial activity against Gram-positive bacteria. This is the first discovery of aromatic polyketides from the genus Rhodococcus.

Combining OSMAC Approach and Untargeted Metabolomics for the Identification of New Glycolipids with Potent Antiviral Activity Produced by a Marine Rhodococcus.

Natural products of microbial origin have inspired most of the commercial pharmaceuticals, especially those from Actinobacteria. However, the redundancy of molecules in the discovery process represents a serious issue. The untargeted approach, One Strain Many Compounds (OSMAC), is one of the most promising strategies to induce the expression of silent genes, especially when combined with genome mining and advanced metabolomics analysis. In this work, the whole genome of the marine isolate Rhodococcus sp. I2R was sequenced and analyzed by antiSMASH for the identification of biosynthetic gene clusters. The strain was cultivated in 22 different growth media and the generated extracts were subjected to metabolomic analysis and functional screening. Notably, only a single growth condition induced the production of unique compounds, which were partially purified and structurally characterized by liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). This strategy led to identifying a bioactive fraction containing >30 new glycolipids holding unusual functional groups. The active fraction showed a potent antiviral effect against enveloped viruses, such as herpes simplex virus and human coronaviruses, and high antiproliferative activity in PC3 prostate cancer cell line. The identified compounds belong to the biosurfactants class, amphiphilic molecules, which play a crucial role in the biotech and biomedical industry.

Biotransformation of Cortisone with Rhodococcus rhodnii: Synthesis of New Steroids.

Cortisone is a steroid widely used as an anti-inflammatory drug able to suppress the immune system, thus reducing inflammation and attendant pain and swelling at the site of an injury. Due to its numerous side effects, especially in prolonged and high-dose therapies, the development of the pharmaceutical industry is currently aimed at finding new compounds with similar activities but with minor or no side effects. Biotransformations are an important methodology towards more sustainable industrial processes, according to the principles of "green chemistry". In this work, the biotransformation of cortisone with Rhodococcus rhodnii DSM 43960 to give two new steroids, i.e., 1,9ß,17,21-tetrahydoxy-4-methyl-19-nor-9ß-pregna-1,3,5(10)-trien-11,20-dione and 1,9ß,17,20ß,21-pentahydoxy-4-methyl-19-nor-9ß-pregna-1,3,5(10)-trien-11-one, is reported. These new steroids have been fully characterized.

Expression, Rapid Purification and Functional Analysis of DnaK from Rhodococcus ruber.

BACKGROUND: Heat shock proteins (HSPs) represent a group of important proteins which are produced by all kinds of organisms especially under stressful conditions. DnaK, an Hsp70 homolog in prokaryotes, has indispensable roles when microbes was confronted with stress conditions. However, few data on DnaK from Rhodococcus sp. were available in the literature. In a previous study, we reported that toluene and phenol stress gave rise to a 29.87-fold and 3.93-fold increase for the expression of DnaK from R. ruber SD3, respectively. Thus, we deduced DnaK was in correlation with the organic solvent tolerance of R. ruber SD3. OBJECTIVE: To elucidate the role of DnaK in the organic solvent tolerance of R. ruber SD3, expression, purification and functional analysis of Dnak from R. ruber SD3 were performed in the present paper. METHODS: In this article, DnaK from R. ruber SD3 was heterologously expressed in E. coli BL21(DE3) and purified by affinity chromatography. Functional analysis of DnaK was performed using determination of kinetics, docking, assay of chaperone activity and microbial growth. RESULTS: The recombinant DnaK was rapidly purified by affinity chromatography with the purification fold of 1.9 and the recovery rate of 57.9%. Km, Vmax and Kcat for Dnak from R. ruber SD3 were 80.8 µM, 58.1 nmol/min and 374.3 S-1, respectively. The recombinant protein formed trimer in vitro, with the calculated molecular weight of 214 kDa. According to in-silico analysis, DnaK interacted with other molecular chaperones and some important proteins in the metabolism. The specific activity of catalase in the presence of recombinant DnaK was 1.85 times or 2.00 times that in the presence of BSA or Tris-HCl buffer after exposure to 54 °C for 1h. E. coli transformant with pET28-dnak showed higher growth than E. coli transformant with pET28 at 43°C and in the presence of phenol, respectively. CONCLUSION: The biochemical properties and the interaction analysis of DnaK from R. ruber SD3 deepened our understanding of DnaK function. DnaK played an important role in microbial growth when R. ruber was subjected to various stress such as heating and organic solvent.

Enhanced polyhydroxybutyrate (PHB) production by newly isolated rare actinomycetes Rhodococcus sp. strain BSRT1-1 using response surface methodology.

Poly-ß-hydroxybutyrate (PHB) is a biodegradable polymer, synthesized as carbon and energy reserve by bacteria and archaea. To the best of our knowledge, this is the first report on PHB production by a rare actinomycete species, Rhodococcus pyridinivorans BSRT1-1. Response surface methodology (RSM) employing central composite design, was applied to enhance PHB production in a flask scale. A maximum yield of 3.6 ± 0.5 g/L in biomass and 43.1 ± 0.5 wt% of dry cell weight (DCW) of PHB were obtained when using RSM optimized medium, which was improved the production of biomass and PHB content by 2.5 and 2.3-fold, respectively. The optimized medium was applied to upscale PHB production in a 10 L stirred-tank bioreactor, maximum biomass of 5.2 ± 0.5 g/L, and PHB content of 46.8 ± 2 wt% DCW were achieved. Furthermore, the FTIR and 1H NMR results confirmed the polymer as PHB. DSC and TGA analysis results revealed the melting, glass transition, and thermal decomposition temperature of 171.8, 4.03, and 288 °C, respectively. In conclusion, RSM can be a promising technique to improve PHB production by a newly isolated strain of R. pyridinivorans BSRT1-1 and the properties of produced PHB possessed similar properties compared to commercial PHB.

Characterization of alkylguaiacol-degrading cytochromes P450 for the biocatalytic valorization of lignin.

Cytochrome P450 enzymes have tremendous potential as industrial biocatalysts, including in biological lignin valorization. Here, we describe P450s that catalyze the O-demethylation of lignin-derived guaiacols with different ring substitution patterns. Bacterial strains Rhodococcus rhodochrous EP4 and Rhodococcus jostii RHA1 both utilized alkylguaiacols as sole growth substrates. Transcriptomics of EP4 grown on 4-propylguaiacol (4PG) revealed the up-regulation of agcA, encoding a CYP255A1 family P450, and the aph genes, previously shown to encode a meta-cleavage pathway responsible for 4-alkylphenol catabolism. The function of the homologous pathway in RHA1 was confirmed: Deletion mutants of agcA and aphC, encoding the meta-cleavage alkylcatechol dioxygenase, grew on guaiacol but not 4PG. By contrast, deletion mutants of gcoA and pcaL, encoding a CYP255A2 family P450 and an ortho-cleavage pathway enzyme, respectively, grew on 4-propylguaiacol but not guaiacol. CYP255A1 from EP4 catalyzed the O-demethylation of 4-alkylguaiacols to 4-alkylcatechols with the following apparent specificities (kcat/KM): propyl > ethyl > methyl > guaiacol. This order largely reflected AgcA's binding affinities for the different guaiacols and was the inverse of GcoAEP4's specificities. The biocatalytic potential of AgcA was demonstrated by the ability of EP4 to grow on lignin-derived products obtained from the reductive catalytic fractionation of corn stover, depleting alkylguaiacols and alkylphenols. By identifying related P450s with complementary specificities for lignin-relevant guaiacols, this study facilitates the design of these enzymes for biocatalytic applications. We further demonstrated that the metabolic fate of the guaiacol depends on its substitution pattern, a finding that has significant implications for engineering biocatalysts to valorize lignin.

Effects of Monoacyltrehalose Fraction of Rhodococcus Biosurfactant on the Innate and Adaptive Immunity Parameters In Vivo.

The biosurfactant monoacyltrehalose fraction isolated from Rhodococcus ruber IEGM 231 actinobacterium suppresses antibody production, bactericidal potential, and production of IL-1ß by mouse peritoneal cells after intraperitoneal and intramuscular injection and stimulates the production of IL-10 after intraperitoneal injection. The data of in vitro experiments attest to an important role of bacterial glycolipids in the regulation of the functions of splenocytes and peritoneal macrophages.

Can Halophilic and Psychrophilic Microorganisms Modify the Freezing/Melting Curve of Cold Salty Solutions? Implications for Mars Habitability.

We present the hypothesis that microorganisms can change the freezing/melting curve of cold salty solutions by protein expression, as it is known that proteins can affect the liquid-to-ice transition, an ability that could be of ecological advantage for organisms on Earth and on Mars. We tested our hypothesis by identifying a suitable candidate, the well-known psycrophile and halotolerant bacteria Rhodococcus sp. JG3, and analyzing its response in culture conditions that included specific hygroscopic salts relevant to Mars-that is, highly concentrated magnesium perchlorate solutions of 20 wt % and 50 wt % Mg(ClO4)2 at both end members of the eutectic concentration (44 wt %)-and subfreezing temperatures (263 K and 253 K). Using a combination of techniques of molecular microbiology and aqueous geochemistry, we evaluated the potential roles of proteins over- or underexpressed as important players in different mechanisms for the adaptability of life to cold environments. We recorded the changes observed by micro-differential scanning calorimetry. Unfortunately, Rhodococcus sp. JG3 did not show our hypothesized effect on the melting characteristics of cold Mg-perchlorate solutions. However, the question remains as to whether our novel hypothesis that halophilic/psychrophilic bacteria or archaea can alter the freezing/melting curve of salt solutions could be validated. The null result obtained after analyzing just one case lays the foundation to continue the search for proteins produced by microorganisms that thrive in very cold, high-saline solutions, which would involve testing different microorganisms with different salt components. The immediate implications for the habitability of Mars are discussed.

Facile and Green Production of Human Milk Fat Substitute through Rhodococcus opacus Fermentation.

Human milk fat substitute (HMFS) is a class of structured lipids widely used in infant formulas. Herein, HMFS was prepared by Rhodococcus opacus fermentation. The substrate oils suitable for HMFS production were coconut oil (66.1-57.5%), soybean oil (17.5-26.5%), high oleic acid sunflower oil (5.4-4.5%), Antarctic krill oil (9-9.5%), and fungal oil (2%). Six HMFSs were prepared, among which HMFS V and VI were similar to human milk fat from Chinese in terms of fatty acid composition and triacylglycerol species. The sn-2 position of HMFS was occupied by palmitic acid (49.31 and 43.48% in HMFS V and VI, respectively). The major triacylglycerols were OPL, OPO, and LPL, accounting for 15.90, 9.49, and 6.84 and 17.52, 8.44, and 8.55% in HMFS V and VI, respectively. This study is the first to prepare structured lipids intended for infant formula through fermentation, providing a novel strategy for the edible oil industry.

Application of Thin-Layer Chromatography-Flame Ionization Detection (TLC-FID) to Total Lipid Quantitation in Mycolic-Acid Synthesizing Rhodococcus and Williamsia Species.

In addition to cell membrane phospholipids, Actinobacteria in the order Corynebacteriales possess a waxy cell envelope containing mycolic acids (MA). In optimized culture condition, some species can also accumulate high concentrations of intracellular triacylglycerols (TAG), which are a potential source of biodiesel. Bacterial lipid classes and composition alter in response to environmental stresses, including nutrient availability, thus understanding carbon flow into different lipid classes is important when optimizing TAG synthesis. Quantitative and qualitative analysis of lipid classes normally requires combinations of different extraction, derivatization, chromatographic and detection methods. In this study, a single-step thin-layer chromatography-flame ionization detection (TLC-FID) technique was applied to quantify lipid classes in six sub-Antarctic Corynebacteriales strains identified as Rhodococcus and Williamsia species. A hexane:diethyl-ether:acetic acid solvent system separated the total cellular lipids extracted from cells lysed by bead beating, which released more bound and unbound MA than sonication. Typical profiles included a major broad non-polar lipid peak, TAG and phospholipids, although trehalose dimycolates, when present, co-eluted with phospholipids. Ultra-performance liquid chromatography-tandem mass-spectrometry and nuclear magnetic resonance spectroscopy detected MA signatures in the non-polar lipid peak and indicated that these lipids were likely bound, at least in part, to sugars from cell wall arabinogalactan. Waxy esters were not detected. The single-solvent TLC-FID procedure provides a useful platform for the quantitation and preliminary screening of cellular lipid classes when testing the impacts of growth conditions on TAG synthesis.

Co-encapsulation of slow release compounds and Rhodococcus rhodochrous ATCC 21198 in gellan gum beads to promote the long-term aerobic cometabolic transformation of 1,1,1-trichloroethane, cis-1,2-dichloroethene and 1,4-dioxane.

Rhodococcus rhodochrous ATCC 21198 (strain ATCC 21198) was successfully co-encapsulated in gellan gum beads with orthosilicates as slow release compounds (SRCs) to support aerobic cometabolism of a mixture of 1,1,1-trichloroethane (1,1,1-TCA), cis-1,2-dichloroethene (cis-DCE), and 1,4-dioxane (1,4-D) at aqueous concentrations ranging from 250 to 1000 µg L-1. Oxygen (O2) consumption and carbon dioxide (CO2) production showed the co-encapsulated cells utilized the alcohols that were released from the co-encapsulated SRCs. Two model SRCs, tetrabutylorthosilicate (TBOS) and tetra-s-butylorthosilicate (T2BOS), which hydrolyze to produce 1- and 2-butanol, respectively, were encapsulated in gellan gum (GG) at mass loadings as high as 10% (w/w), along with strain ATCC 21198. In the GG encapsulated beads, TBOS hydrolyzed 26 times faster than T2BOS and rates were ∼4 times higher in suspension than when encapsulated. In biologically active reactors, the co-encapsulated strain ATCC 21198 effectively utilized the SRC hydrolysis products (1- and 2-butanol) and cometabolized repeated additions of a mixture of 1,1,1-TCA, cis-DCE, and 1,4-D for over 300 days. The transformation followed pseudo-first-order kinetics. Vinyl chloride (VC) and 1,1-dichloroethene (1,1-DCE) were also transformed in the reactors after 250 days. In the long-term treatment, the batch reactors with co-encapsulated T2BOS GG beads achieved similar transformation rates, but at much lower O2 consumption rates than those with TBOS. The results demonstrate that the co-encapsulation technology can be a passive method for the cometabolic treatment of dilute groundwater plumes.

Structural Determination of a New Peptidolipid Family from Rhodococcus opacus and the Pathogen Rhodococcus equi by Multiple Stage Mass Spectrometry.

The cell walls of the genus Rhodococcus including the pathogenic bacterium Rhodococcus equi (R. equi) and biotechnologically important bacterium Rhodococcus opacus (R. opacus) contain an abundant peptidolipid (or termed lipopeptide) family whose structures have not been reported previously. Here, we describe a linear ion-trap multiple-stage mass spectrometric (LIT MSn) approach with high resolution mass spectrometry (HRMS), in conjunction with NMR spectroscopy, chemical reactions, and GC/MS analysis to define the structures of these compounds. We employed LIT MSn (n = 2-8) on the [M + Na]+ ion species to establish the peptide sequence, the identity of the fatty acyl substituent, and its location within the molecule, while NMR spectroscopy and GC/MS were used to recognize the Leu and Ile moieties. The major new lipopeptide found in R. opacus is defined as C17H35CH(OH)CH2CO-NHLeu-Ser-Leu-Ile-Thr-Ile-PheCOOH, where a ß-OH fatty acyl (C18-C22) substituent is attached to the N-terminal of the LSLITIF peptide chain via a NH-CO bond. By contrast, the main peptidolipids found in R. equi belong to the cyclopeptidolipid family, which possesses the same peptide sequence and lipid chain, but the ß-OH group of the fatty acyl moiety and the C-terminus of the peptide (i.e., the -COOH) are cyclized by an ester bond formation to a lactone, with a structure similar to iturin-A (Peypoux, F. et al. Biochemistry 1978, 17, 3992-3996). The antibiotic activity test of these new lipids did not reveal an activity against any of seven microorganisms tested.

Pb2+ biosorption from aqueous solutions by live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2.

In this study, the Pb2+ biosorption potential of live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2 was analyzed. Optimal biosorption conditions were determined via single factor optimization, which were as follows: temperature, 25°C; pH, 5.0, and biosorbent dose, 0.75 g L-1. A response surface software (Design Expert 10.0) was used to analyze optimal biosorption conditions. The biosorption data for live and dead biosorbents were suitable for the Freundlich model at a Pb2+ concentration of 200 mg L-1. At this same concentration, the maximum biosorption capacity was 88.74 mg g-1 (0.428 mmol g-1) for live biosorbents and 125.5 mg g-1 (0.606 mmol g-1) for dead biosorbents. Moreover, in comparison with the pseudo-first-order model, the pseudo-second-order model seemed better to depict the biosorption process. Dead biosorbents seemed to have lower binding strength than live biosorbents, showing a higher desorption capacity at pH 1.0. The order of influence of competitive metal ions on Pb2+ adsorption was Cu2+ > Cd2+ > Ni+. Fourier-transform infrared spectroscopy analyses revealed that several functional groups were involved in the biosorption process of dead biosorbents. Scanning electron microscopy showed that Pb2+ attached to the surface of dead biosorbents more readily than on the surface of live biosorbents, whereas transmission electron microscopy confirmed the transfer of biosorbed Pb2+ into the cells in the case of both live and dead biosorbents. It can thus be concluded that dead biosorbents are better than live biosorbents for Pb2+ biosorption, and they can accordingly be used for wastewater treatment.

Purification, characterization and anticancer activities of exopolysaccharide produced by Rhodococcus erythropolis HX-2.

In the present study, an exopolysaccharide (EPS) producer Rhodococcus erythropolis HX-2 was isolated from Xinjiang oil field, China. The HX-2 EPS (name HPS) production reached 8.957 g/L by RSM in MSM medium. The HPS was purified by ethanol precipitation and fractionation by DEAE-Cellulose and Sepharose column, the yield of HPS was 3.736 g/L. HPS composed by glucose, galactose, fucose, mannose and glucuronic acid. FT-IR spectroscopy indicated the presence of a large amount of hydroxyl groups. NMR spectroscopy indicated the existence of both α and ß-configuration for sugar moieties present in HPS. The degradation temperature (255.4 °C) of the HPS was determined by thermogravimetric analysis (TGA). A reticular structure of HPS was observed by SEM and the AFM analysis of the HPS revealed straight chains line. Meanwhile, the WSI and WHC of HPS were 92.15 ± 3.05% and 189.45 ± 5.65%, respectively. Finally, In vitro anticancer activity purified EPS was evaluated on L929 normal cells, A549 cancer cells, SMMC-7721 liver cancer cells and Hela cervical cancer cell. HPS inhibited the growth of cancer cells in a certain concentration without damage to normal cells. These characteristics indicate that its potential application value in food, industry and pharmaceutical application.

Novel waste-derived biochar from biomass gasification effluent: preparation, characterization, cost estimation, and application in polycyclic aromatic hydrocarbon biodegradation and lipid accumulation by Rhodococcus opacus.

This study evaluated an enhancement of simultaneous polycyclic aromatic hydrocarbon (PAH) biodegradation and lipid accumulation by Rhodococcus opacus using biochar derived cheaply from biomass gasification effluent. The chemical, physical, morphological, thermal, and magnetic properties of the cheaply derived biochar were initially characterized employing different techniques, which indicated that the material is easy to separate, recover, and reuse for further application. Batch experiments were carried out to study biochar-aided PAH biodegradation by R. opacus clearly demonstrating its positive effect on PAH biodegradation and lipid accumulation by the bacterium utilizing the synthetic media containing 2-, 3- or 4-ring PAH compounds, at an initial concentration in the range 50-200 mg L-1, along with 10% (w/v) inoculum. An enhancement in PAH biodegradation from 79.6 to 92.3%, 76.1 to 90.5%, 74.1 to 88.2%, and 71.6 to 82.3% for naphthalene, anthracene, phenanthrene, and fluoranthene, respectively, were attained with a corresponding lipid accumulation of 68.1%, 74.2%, 72.4%, and 63% (w/w) of cell dry weight (CDW). From contact angle measurements carried out in the study, enhancement in PAH biodegradation and lipid accumulation due to the biochar was attributed to an improved bioavailability of PAH to the degrading bacterium.

Rhodococcus and Yarrowia-Based Lipid Production Using Lignin-Containing Industrial Residues.

Improvement in biorefining technologies coupled with development of novel fermentation strategies and analysis will be paramount in establishing supplementary and sustainable biofuel pathways. Oleaginous microorganisms that are capable of accumulating triacylglycerides (TAGs) and fatty acid methyl esters (FAMEs), such as Rhodococcus and Yarrowia species, can be used to produce second-generation biofuels from non-food competing carbon sources. These "microbiorefineries" provide a pathway to upgrade agricultural and industrial waste streams to fungible fuels or precursors to chemicals and materials. Here we provide a general overview on cultivating Rhodococcus and Yarrowia on agro-waste/industrial biomass pretreatment waste streams to produce single-cell oils/lipids and preparing samples for FAME detection.

Potential TSPO Ligand and Photooxidation Quencher Isorenieratene from Arctic Ocean Rhodococcus sp. B7740.

Due to its special aromatic structure, isorenieratene is thought to be an active natural antioxidant and photo/UV damage inhibitor. In this work, isorenieratene that was extracted from Rhodococcus sp. B7740 isolated from the Arctic Ocean, showed excellent scavenging ability of both singlet oxygen and hydroxyl radical in the UVB-induced auto-oxidation process using the EPR method. Within an ARPE-19 cell model damaged by UVB radiation, isorenieratene showed fine protective effects (1.13 ± 0.03 fold) compared with macular xanthophylls (MXs) through upregulating of tspo. The molecular docking was firstly performed to investigate the interaction of isorenieratene with TSPO as a special ligand. Results showed isorenieratene might form a better binding conformation (S-score -8.5438) than MXs and indicate that isorenieratene not only can function as a direct antioxidant but also activate tspo in ARPE-19 cells. Thus, isorenieratene might ease the UV-related damages including age-related macular degeneration (AMD).

An effective immobilized haloalkane dehalogenase DhaA from Rhodococcus rhodochrous by adsorption, crosslink and PEGylation on meso-cellular foam.

Haloalkane dehalogenase DhaA catalyzes the hydrolysis of halogenated compounds by cleavage of the carbon-halogen bond. However, DhaA suffers from poor environmental stability and difficult recovery, which significantly increase the cost of DhaA. Here, an effective enzyme immobilization strategy was developed to overcome the disadvantages of DhaA. DhaA was physically absorbed with amine-functionalized meso-cellular foam (MCF). The MCF-absorbed DhaA (MD) was intermolecularly crosslinked with 8-arm PEG N­hydroxysuccinimide ester and then PEGylated by maleimide-thiol chemistry. DhaA from Rhodococcus rhodochrous was absorbed at a loading capacity of 100 mg/g in MD. The bulk crystallinity and morphology of MCF were largely maintained. The immobilized DhaA (MD-P1-P2) showed a lower Michaelis constant (Km, 0.588 mM) than DhaA (0.905 mM), along with an extremely low leaching ratio of DhaA (1.1%) from MCF. MD-P1-P2 exhibited a high stability in the extreme environmental conditions, as reflected by the remaining activity of 99.8% in 40% (v/v) DMSO for 5 h, 87.3% in 3 M urea solution for 1 h, 25.9% at pH 3.0, and 51.8% at room temperature for 30 days. Thus, our study was expected to develop an effective immobilized DhaA for practical application.