Isolation of microorganisms able to produce 1,3-propanediol and optimization of medium constituents for Klebsiella pneumoniae AJ4.

Microbial fermentation under anaerobic and microaerobic conditions has been used for the production of 1,3-propanediol (1,3-PD), a monomer used to produce polymers such as polytrimethylene terephthalate. In this study, we screened microorganisms using the high throughput screening method and isolated the Klebsiella pneumoniae AJ4 strain, which is able to produce 1,3-PD under aerobic conditions. To obtain the maximum 1,3-PD concentration from glycerol, the response surface methodology based on a central composite design was chosen to show the statistical significance of the effects of glycerol, peptone, and (NH(4))(2)SO(4) on 1,3-PD production by K. pneumoniae AJ4. The optimal culture medium factors for achieving maximum concentrations of 1,3-PD included glycerol, 108.5 g/L; peptone, 2.72 g/L; and (NH(4))(2)SO(4), 4.38 g/L. Under this optimum condition, the maximum concentration of 1,3-PD, 54.76 g/L, was predicted. A concentration of about 52.59 g/L 1,3-PD was obtained using the optimized medium during 26-h batch fermentation, a finding that agreed well with the predicted value.

Molecular cloning and biochemical characterization of a novel erythrose reductase from Candida magnoliae JH110.

BACKGROUND: Erythrose reductase (ER) catalyzes the final step of erythritol production, which is reducing erythrose to erythritol using NAD(P)H as a cofactor. ER has gained interest because of its importance in the production of erythritol, which has extremely low digestibility and approved safety for diabetics. Although ERs were purified and characterized from microbial sources, the entire primary structure and the corresponding DNA for ER still remain unknown in most of erythritol-producing yeasts. Candida magnoliae JH110 isolated from honeycombs produces a significant amount of erythritol, suggesting the presence of erythrose metabolizing enzymes. Here we provide the genetic sequence and functional characteristics of a novel NADPH-dependent ER from C. magnoliae JH110. RESULTS: The gene encoding a novel ER was isolated from an osmophilic yeast C. magnoliae JH110. The ER gene composed of 849 nucleotides encodes a polypeptide with a calculated molecular mass of 31.4 kDa. The deduced amino acid sequence of ER showed a high degree of similarity to other members of the aldo-keto reductase superfamily including three ER isozymes from Trichosporonoides megachiliensis SNG-42. The intact coding region of ER from C. magnoliae JH110 was cloned, functionally expressed in Escherichia coli using a combined approach of gene fusion and molecular chaperone co-expression, and subsequently purified to homogeneity. The enzyme displayed a temperature and pH optimum at 42 degrees C and 5.5, respectively. Among various aldoses, the C. magnoliae JH110 ER showed high specific activity for reduction of erythrose to the corresponding alcohol, erythritol. To explore the molecular basis of the catalysis of erythrose reduction with NADPH, homology structural modeling was performed. The result suggested that NADPH binding partners are completely conserved in the C. magnoliae JH110 ER. Furthermore, NADPH interacts with the side chains Lys252, Thr255, and Arg258, which could account for the enzyme's absolute requirement of NADPH over NADH. CONCLUSIONS: A novel ER enzyme and its corresponding gene were isolated from C. magnoliae JH110. The C. magnoliae JH110 ER with high activity and catalytic efficiency would be very useful for in vitro erythritol production and could be applied for the production of erythritol in other microorganisms, which do not produce erythritol.

Cloning and characterization of thermostable esterase from Archaeoglobus fulgidus.

Thermostable esterase gene was cloned (Est-AF) from extremophilic microorganisms, Archaeoglobus fulgidus DSM 4304. The protein analysis result showed that Est-AF is monomer with total 247 amino acids and molecular weight of estimated 27.5 kDa. It also showed repeating units G-X-S-X-G (GHSLG) (residues 86 approximately 90) which is reported as active site of known esterases, and the putative catalytic triad composed of Ser88, Asp198 and His226. The esterase activity test with various acyl chain length of rho-nitrophenol resulted that Est-AF showed highest specific activity with rho-nitrophenylbutyrate (pNPC4) and rapidly decrease with rho-nitrophenyl ester contain more than 8 carbon chain. These results represent that cloned enzyme is verified as a carboxylesterase but not a lipase because esterase activity is decreased with rho-nitrophenyl ester contains more than 8 carbon chains but lipase activity does not affected with carbon chain length. Optimum temperature of esterase reaction with rho-nitrophenylbutyrate (pNPC4) was 80 degrees C. When ketoprofen ethyl ester was used as a substrate, activity of Est-AF showed the highest value at 70 degrees C, and 10% of activity still remains after 3 h of incubation at 90 degrees C. This result represents Est-AF has high thermostability with comparison of other esterases that have been reported. However, Est-AF showed low enantioselectivity with ketoprofen ethyl ester. Optimum pH of Est-AF is between pH 7.0 and pH 8.0. Km value of ketoprofen ethyl ester is 1.6 mM and, Vmax is 1.7 micromole/mg protein/min. Est-AF showed similar substrate affinity but slower reaction with ketoprofen ethyl ester compare with esterase from mesophilic strain P. fluorescens.

Proteomic analysis of fructophilic properties of osmotolerant Candida magnoliae.

Candida magnoliae, an osmotolerant and erythritol producing yeast, prefers D-fructose to D-glucose as carbon sources. For the investigation of the fructophilic characteristics with respect to sugar transportation, a sequential extraction method using various detergents and ultracentrifugation was developed to isolate cellular membrane proteins in C. magnoliae. Immunoblot analysis with the Pma1 antibody and twodimensional electrophoresis analysis coupled with MS showed that the fraction II was enriched with membrane proteins. Eighteen proteins out of 36 spots were identified as membrane or membrane-associated proteins involved in sugar uptake, stress response, carbon metabolism, and so on. Among them, three proteins were significantly upregulated under the fructose supplying conditions. The hexose transporter was highly homologous to Ght6p in Schizosaccharomyces pombe, which was known as a predominant transporter for the fructose uptake of S. pombe because it exhibited higher affinity to D-fructose than D-glucose. The physicochemical properties of the ATP-binding cassette transporter and inorganic transporter explained their direct or indirect associations with the fructophilic behavior of C. magnoliae. The identification and characterization of membrane proteins involved in sugar uptake might contribute to the elucidation of the selective utilization of fructose to glucose by C. magnoliae at a molecular level.

Two threonine residues required for role of AfsKav in controlling morphogenesis and avermectin production in Streptomyces avermitilis.

AfsKav is a eukaryotic-type serine/threonine protein kinase, required for sporulation and avermectin production in Streptomyces avermitilis. In terms of their ability to complement SJW4001 (DeltaafsK-av), afsK-av mutants T165A and T168A were not functional, whereas mutants T165D and T168D retained their ability, indicating that Thr-165 and Thr-168 are the phosphorylation sites required for the role of AfsKav. Expression of the S-adenosylmethione synthetase gene promoted avermectin production in the wild-type S. avermitilis, yet not in the mutant harboring T168D or T165D, demonstrating that tandem phosphorylation on Thr-165 and Thr-168 in AfsKav is the mechanism modulating avermectin production in response to S-adenosylmethione accumulation in S. avermitilis.

Suppression of mast cell degranulation by a novel ceramide kinase inhibitor, the F-12509A olefin isomer K1.

Antigen-induced degranulation of mast cells plays a pivotal role in allergic and inflammatory responses. Recently, ceramide kinase (CERK) and its phosphorylated product ceramide 1-phosphate (C1P) have emerged as important players in mast cell degranulation. Here, we describe the synthesis of a novel F-12509A olefin isomer, K1, as an effective CERK inhibitor. In vitro kinase assays demonstrated that K1 effectively inhibits CERK without inhibiting sphingosine kinase and diacylglycerol kinase. Treating RBL-2H3 cells with K1 reduced cellular C1P levels to 40% yet had no effect on cell growth. Furthermore, treatment with K1 significantly suppressed both calcium ionophore- and IgE/antigen-induced degranulation, indicating that K1 interferes with signals that happen downstream of Ca(2+) mobilization. Finally, we show that K1 affects neither IgE/antigen-induced global tyrosine phosphorylation nor subsequent Ca(2+) elevation, suggesting a specificity for CERK-mediated signals. Our novel CERK inhibitor provides a useful tool for studying the biological functions of CERK and C1P. Moreover, to our knowledge, this is the first report demonstrating that inhibition of CERK suppresses IgE/antigen-induced mast cell degranulation. This finding suggests that CERK inhibitors might be a potential therapeutic tool in the treatment of allergic diseases.

Selective utilization of fructose to glucose by Candida magnoliae, an erythritol producer.

Candida magnoliae isolated from honeycomb is an industrially important yeast with high erythritol-producing ability. Erythritol has been used as functional sugar substitute for various foods. In order to analyze the physiological properties of C. magnoliae, a study on sugar utilization pattern was carried out. The fermentation kinetics of glucose and fructose revealed that C. magnoliae has the discrepancy in glucose and fructose utilization when it produces erythritol. In contrast to most yeasts, C. magnoliae showed preference for fructose to glucose as a carbon source, deserving the designation of fructophilic yeast. Such a peculiar pattern of sugar utilization in C. magnoliae seems to be related to the evolutionary environment.

Proteomics and physiology of erythritol-producing strains.

In-depth knowledge bases on physiological properties of microbes are required to design a better microbial system at a gene level and to develop an industrially viable process in an optimized scheme. Proteomic analyses of industrially useful microorganisms are particularly important for achieving such objectives. In this review, industrial application of erythritol in food and pharmaceutical areas and proteomic techniques for erythritol-producing microbes were presented. Proteomic technologies for erythritol-producing strains such as Candida magnoliae contained protein or peptide sample preparation for two-dimensional electrophoresis and mass spectrometry, analysis of proteome with matrix assisted laser desorption-ionization/time-of-flight mass spectrometry, liquid chromatography/electrospray ionization/tandem mass spectrometry and similarity searching algorithms. The proteomic information was applied to predict the carbon metabolism of erythritol-synthesizing microorganisms.

Complete genome sequence of Klebsiella oxytoca M1, isolated from Manripo area of South Korea.

Here we report the full genome sequence of Klesiella oxytoca M1, isolated from Manripo area of South Korea. The strain K. oxytoca M1 is able to produce either 2,3-butanediol or acetoin selectively by controlling the pH and temperature.

Widespread activation of antibiotic biosynthesis by S-adenosylmethionine in streptomycetes.

The effect of S-adenosylmethionine (SAM) on the production of various antibiotics was investigated to determine whether SAM-dependent methylation is required in biosynthetic pathways of antibiotics. Pristinamycin II(B) and granaticin do not require SAM-dependent methylation in their biosynthesis pathways, and production of these two antibiotics was increased about 2-fold when a low concentration (50 and 10 microM, respectively) of SAM was treated; in contrast, oleandomycin and avermectin B1a require SAM as a methyl donor in their biosynthesis, and production of these two antibiotics was increased 5-fold and 6-fold, depending on the SAM concentration within a certain range. We also found that the transcription of a pathway-specific regulator, gra-ORF9, was activated by exogenous SAM treatment. Production of oleandomycin and avermectin B1a was decreased by using a methyltransferase inhibitor, sinefungin, but the production levels of these antibiotics were restored to the control level by simultaneously adding SAM and sinefungin. Interestingly, we have found a similar stimulatory effect of S-adenosylhomocysteine (SAH), the methylation product of SAM, on antibiotic production in the four strains. Our results clearly demonstrate the widespread activation of antibiotic production using SAM in streptomycetes.

Study on persistent infection of Japanese encephalitis virus Beijing-1 strain in serum-free Sf9 cell cultures.

Sf9 cells have obvious advantages for the conventional production technology of vaccine. They are useful tools for high concentration and large-scale cultures. Sf9 cells were grown to maximal concentration, 8 x 10(6) cells/ml in a 500ml spinner flask, with a doubling time at the exponentially growing phase of 24.5 hours, using serum-free media. To explore the ability of Sf9 cells to be infected by the Japanese encephalitis (JE) virus Beijing-1 strain, Sf9 cells were infected with the virus. By 4-5 days post-infection, 10-15% of the Sf9 cells showed cytopathic effect (CPE), from granularity to the formation of syncytia and multinucleated giant cells continuously observed over a period of 35 days. Positive fluorescent reactions were detected in 30-40% of cells infected with the JE virus Beijing-1 strain, and the uninfected Sf9 cells were completely negative. Virus particles, propagated in Sf9 and Vero cells, were concentrated by sedimentation on 40% trehalose cushions by ultracentrifugation, and showed identical patterns of viral morphogenesis. Complete virus particles, 40 to 50 nm in diameter, were observed, and JE virus envelope (E) proteins, at 53 kDa, were found in the western blot analysis to the anti-JE virus E protein monoclonal antibody and reacted as a magenta band in the same position to the glycoprotein staining. To evaluate whether the infectious virus was produced in Sf9 cells inoculated with the JE virus Beijing-1 stain, Sf9 cells were inoculated with the virus, and sample harvested every 5 days. The titers of the JE virus Beijing-1 strain rose from 1.0 x 10(5) to 1.5 x 10(6) pfu/ml. The infected Sf9 cells could be sub-cultured in serum-free medium, with no change in the plaque sizes formed by the JE virus Beijing-1 strain in the plaque assay. It is suggested that the ability of the JE virus Beijing-1 strain to infect Sf9 cells in serum-free media will provide a useful insect cell system, where the JE virus replication, cytopathogenicity and vaccine immunogen can be studied.

Use of waste Chinese cabbage as a substrate for yeast biomass production.

The possibility of using waste Chinese cabbage (Brassica campestris) as a substrate for microbial biomass production was investigated. The juice from waste Chinese cabbage contains relatively high amounts of reducing sugars suitable for yeast culture. The cell mass and protein content of four species of yeast, Candida utilis, Pichia stipitis, Kluyveromyces marxianus, and Saccharomyces cerevisiae, were determined when cultured in juice extracted from cabbage waste. Compared to YM broth containing the same level of sugar, all the strains except C. utilis showed higher total protein production in cabbage juice medium (CJM).

Role of osmotic and salt stress in the expression of erythrose reductase in Candida magnoliae.

The osmotolerant yeast, Candida magnoliae, which was isolated from honeycomb, produces erythritol from sugars such as fructose, glucose, and sucrose. Erythrose reductase in C. magnoliae (CmER) reduces erythrose to erythritol with concomitant oxidation of NAD(P)H. Sequence analysis of the 5'-flanking region of the CmER gene indicated that one putative stress response element (STRE, 5'-AGGGG- 3'), found in Saccharomyces cerevisiae, exists 72 nucleotides upstream of the translation initiation codon. An enzyme activity assay and semiquantitative reverse transcription polymerase chain reaction revealed that the expression of CmER is upregulated under osmotic and salt stress conditions caused by a high concentration of sugar, KCl, and NaCl. However, CmER was not affected by osmotic and oxidative stress induced by sorbitol and H(2)O(2), respectively. The basal transcript level of CmER in the presence of sucrose was higher than that in cells treated with fructose and glucose, indicating that the response of CmER to sugar stress is different from that of GRE3 in S. cerevisiae, which expresses aldose reductase in a sugar-independent manner. It was concluded that regulation of CmER differs from that of other aldose reductases in S. cerevisiae.

Synergistic effects of chromosomal ispB deletion and dxs overexpression on coenzyme Q(10) production in recombinant Escherichia coli expressing Agrobacterium tumefaciens dps gene.

For biotechnological production of coenzyme Q(10) (CoQ(10)) in recombinant Escherichia coli, three genetic manipulations were performed: heterologous expression of decaprenyl diphosphate synthase (Dps) from Agrobacterium tumefaciens, deletion of endogenous octaprenyl diphosphate synthase (IspB), and overexpression of 1-deoxy-d-xylulose synthase (Dxs). Expression of the dps gene and deletion of the ispB gene in E. coli BL21(DE3)DeltaispB/pAP1 allowed production of CoQ(10) only. Furthermore, coexpression of the dxs gene increased the specific content of CoQ(10) from 0.55-0.89mgg(-1) to 1.40mgg(-1). For mass production of CoQ(10), fed-batch fermentation of E. coli BL21(DE3)DeltaispB/pAP1+pDXS was carried out in a defined medium with 20gl(-1) initial glucose and by the glucose-feeding strategy of pH-stat. Finally, 99.4mgl(-1) CoQ(10) concentration, 1.41mgg(-1) specific CoQ(10) content and 3.11mgl(-1)h(-1) productivity were obtained in 33h of the fermentation, which were 78, 1.9, and 19 times higher than those for E. coli BL21(DE3)/pAP1 without the ispB deletion and dxs overexpression.

Cloning and characterization of CmGPD1, the Candida magnoliae homologue of glycerol-3-phosphate dehydrogenase.

Glycerol-3-phosphate dehydrogenase (GPDH) plays a central role in glycerol metabolism. A genomic CmGPD1 gene encoding NADH-dependent GPDH was isolated from Candida magnoliae producing a significant amount of glycerol. The gene encodes a polypeptide of 360 amino acids, which shows high homology with known NADH-dependent GPDHs of other species. The CmGPD1 gene was expressed in recombinant Escherichia coli with the maltose-binding protein (MBP) fusion system and purified to homogeneity using simple affinity chromatography. The purified CmGpd1p without the MBP fusion displayed an apparent molecular mass of 40 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The CmGpd1p enzyme exhibited a K(cat)/K(m) value of 195 min(-1) mM(-1) for dihydroxyacetone phosphate whereas K(cat)/K(m) for glycerol-3-phosphate is 0.385 min(-1) mM(-1). In a complementation study, CmGpd1p rescued the ability of glycerol synthesis and salt tolerance in a Saccharomyces cerevisiae GPD1DeltaGPD2Delta mutant strain. The overall results indicated that CmGPD1 encodes a functional homologue of S. cerevisiae GPDH.

Amplification of 1-deoxy-D-xyluose 5-phosphate (DXP) synthase level increases coenzyme Q10 production in recombinant Escherichia coli.

For the enhancement of coenzyme Q(10) (CoQ(10)) production, 1-deoxy-D-xylulose 5-phosphate (DXP) synthase of Pseudomonas aeruginosa was constitutively coexpressed in a recombinant Escherichia coli strain, which harbors the ddsA gene from Gluconobacter suboxydans encoding decaprenyl diphosphate synthase. It was found that the expression of the ddsA gene caused depletion of the isopentenyl diphosphate (IPP) pool in E. coli. Amplification of DXP synthase level by installing P. aeruginosa DXP synthase restored the diminished IPP pool and concomitantly resulted in approximately a twofold increase in relative content and productivity of CoQ(10). Maximum CoQ(10) concentration of 46.1 mg l(-1) was achieved from glucose-limited fed-batch cultivation of the recombinant E. coli strain simultaneously harboring the ddsA and dxs genes.

Screening and characterization of a novel esterase from a metagenomic library.

Metagenomes from various environmental soils were screened using alpha-naphthyl acetate and Fast Blue RR for a novel ester-hydrolyzing enzyme on Escherichia coli. Stepwise fragmentations and subcloning of the initial insert DNA (30-40 kb) using restriction enzymes selected to exclude already known esterases with subsequent screenings resulted in a positive clone with a 2.5-kb DNA fragment. The cloned sequence included an open reading frame consisting of 1089 bp, designated as est25, encoding a protein of 363 amino acids with a molecular mass of about 38.3 kDa. Amino acid sequence analysis revealed only moderate identity (< or = 48%) to the known esterases/lipases in the databases containing the conserved sequence motifs of esterases/lipases, such as HGGG (residues 124-127), GxSxG (residues 199-203), and the putative catalytic triad composed of Ser201, Asp303, and His333. Est25 was functionally overexpressed in a soluble form in E. coli with optimal activity at pH 7.0 and 25 degrees C. The purified Est25 exhibited hydrolyzing activity toward p-nitrophenyl (NP)-fatty acyl esters with short-length acyl chains (< or = C6) with the highest activity toward p-NP-acetate (Km=1.0 mM and Vmax = 63.7 U/mg), but not with chain lengths > or = C8, demonstrating that Est25 is an esterase originated most likely from a mesophilic microorganism in soils. Est25 efficiently hydrolyzed (R,S)-ketoprofen ethyl ester with Km of 16.4 mM and Vmax of 59.1 U/mg with slight enantioselectivity toward (R)-ketoprofen ethyl ester. This study demonstrates that functional screening combined with the sequential uses of restriction enzymes to exclude already known enzymes is a useful approach for isolating novel enzymes from a metagenome.

Selective utilization of fructose to glucose by Candida magnoliae, an erythritol producer.

Candida magnoliae isolated from honeycomb is an industrially important yeast with high erythritol-producing ability. Erythritol has been used as functional sugar substitute for various foods. In order to analyze the physiological properties of C. magnoliae, a study on sugar utilization pattern was carried out. The fermentation kinetics of glucose and fructose revealed that C. magnoliae has the discrepancy in glucose and fructose utilization when it produces erythritol. In contrast to most yeasts, C. magnoliae showed preference for fructose to glucose as a carbon source, deserving the designation of fructophilic yeast. Such a peculiar pattern of sugar utilization in C. magnoliae seems to be related to the evolutionary environment.

Biotechnological production and applications of coenzyme Q10.

Coenzyme Q10 is widely used as an essential component of ATP generation in the oxidative phosphorylation process and as an antioxidant preventing lipid peroxidation and scavenging superoxide. It is also recommended as a supplement to 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. Research efforts on the production of coenzyme Q10 by microorganisms focus on the development of potent strains by conventional mutagenesis and metabolic engineering, analysis and modification of the key metabolic pathways and optimization of fermentation strategies. Especially, random mutants with drugs resistance show a high coenzyme Q10 concentration. Metabolic engineering techniques have been applied to improve coenzyme Q10 production. The key enzymes involved in the coenzyme Q10 biosynthesis pathway have been cloned and expressed in Escherichia coli. The rational design of metabolic pathways in combination with engineering optimization of fermentation processes could facilitate the development of viable bioconversion processes.

Homomeric and heteromeric interactions of the extracellular domains of death receptors and death decoy receptors.

Death receptors (DRs) can induce apoptosis by oligomerization with TRAIL, whereas death decoy receptors (DcRs) cannot, due to their lack of functional intracellular death domains. However, it is not known whether DRs and DcRs can interact with one another to form oligomeric complexes prior to TRAIL binding. To address this issue, the extracellular domains (ECDs) of DR4 (sDR4), DR5 (sDR5), DcR1 (sDcR1), and DcR2 (sDcR2) were expressed in a soluble, monomeric form, and their binding interactions were quantified by surface plasmon resonance. The purified sDRs and sDcRs exhibited native-like secondary structure and bound to TRAIL with binding affinities in the nanomolar range (K(D)= approximately 10-62 nM), suggesting that they were properly folded and functional. The soluble receptors interacted homophilically and heterophilically with similar micromolar range affinities (K(D)= approximately 1-9 microM), with the exception that sDR5 did not interact with the sDcRs. Our results suggest that most DRs and DcRs can laterally interact through their ECDs to form homomeric and/or heteromeric complexes in the absence of TRAIL binding.