Characteristic aroma compounds of cooked and fermented soybean (Chungkook-Jang) inoculated with various Bacilli.

BACKGROUND: For selecting Chungkook-jang products with a less undesirable odour, the volatile compounds that affect the overall consumer acceptance of Chungkook-jang products were analysed. The volatile compounds of Chungkook-jang were extracted by using solid phase microextraction and direct solvent extraction and were detected by using gas chromatography-olfactometry. The results were represented as the mean of the log3 flavour dilution factors; principal component analysis was used to determine the effective components. RESULTS: Fifteen and 14 volatile compounds were detected in the extracts using solid phase microextraction and direct solvent extraction, respectively. The Bacillus species 2-M1L, which has the most overall acceptance, might have a nutty initial top note and nutty and cheesy long-lasting note aromas. In correlation analysis between the characteristic aromas and the overall acceptance, trimethyl pyrazine (nutty, pungent), butanoic acid (cheesy, butyric), and methyl pyrazine (burnt, roasted) were positively correlated with overall acceptance. In contrast, 3-hydroxy-2-butanone (buttery, fatty) and 2,3-butanediol (chemical, fatty) were negatively correlated with overall acceptance. CONCLUSION: Consumers might prefer Chungkook-jang that has a more nutty and cheesy flavour and a less fatty one.

10-Gb/s direct modulation of polymer-based tunable external cavity lasers.

We demonstrate a directly-modulated 10-Gb/s tunable external cavity laser (ECL) fabricated by using a polymer Bragg reflector and a high-speed superluminescent diode (SLD). The tuning range and output power of this ECL are measured to be >11 nm and 2.6 mW (@ 100 mA), respectively. We directly modulate this laser at 10 Gb/s and transmit the modulated signal over 20 km of standard single-mode fiber. The power penalty is measured to be <2.8 dB at the bit-error rate (BER) of 10(-10).

Ring-resonator-integrated tunable external cavity laser employing EAM and SOA.

We propose and demonstrate a tunable external cavity laser (ECL) composed of a polymer Bragg reflector (PBR) and integrated gain chip with gain, a ring resonator, an electro-absorption modulator (EAM), and a semiconductor optical amplifier (SOA). The cavity of the laser is composed of the PBR, gain, and ring resonator. The ring resonator reflects the predetermined wavelengths into the gain region and transmits the output signal into integrated devices such as the EAM and SOA. The output wavelength of the tunable laser is discretely tuned in steps of about 0.8 nm through the thermal-optic effect of the PBR and predetermined mode spacing of the ring resonator.

2.5-Gb/s hybridly-integrated tunable external cavity laser using a superluminescent diode and a polymer Bragg reflector.

We presented a hybridly-integrated tunable external cavity laser with 0.8 nm mode spacing 16 channels operating in the direct modulation of 2.5-Gbps for a low-cost source of a WDM-PON system. The tunable laser was fabricated by using a superluminescent diode (SLD) and a polymer Bragg reflector. The maximum output power and the power slope efficiency of the tunable laser were 10.3 mW and 0.132 mW/mA, respectively, at the SLD current of 100 mA and the temperature of 25 degrees C. The directly-modulated tunable laser successfully provided 2.5-Gbps transmissions through 20-km standard single mode fiber. The power penalty of the tunable laser was less than 0.8 dB for 16 channels after a 20-km transmission. The power penalty variation was less than 1.4 dB during the blue-shifted wavelength tuning.

L-band tunable external cavity laser based on 1.58 µm superluminescent diode integrated with spot-size converter.

We report a 1.58 µm superluminescent diode (SLD) with a spot-size converter (SSC) designed and fabricated as a light source for a tunable external cavity laser (T-ECL). The active section of the SLD is fabricated by using a planar buried heterostructure (PBH) for low-threshold current and high-output power operation at a low injection current. The SSC structure of the SLD is designed to possess a buried deep-ridge waveguide (BD-RWG) and show a beam of less divergence. The full-width at half maximum (FWHM) of the horizontal and vertical far-field patterns (FFPs), due to the beam of the less divergence, are 14° and 13°, respectively. We also confirm that an L-band T-ECL employing the SSC SLD operates well enough to prove the characteristics of high performance.

Tunable external cavity laser employing uncooled superluminescent diode.

We have fabricated a tunable external cavity laser (T-ECL) based on a superluminescent diode and a polymeric waveguide Bragg reflector, providing a cost-effective solution for wavelength division multiplexing-passive optical network (WDM-PON) systems. The wavelength of the T-ECL is tuned through 100 GHz-spacing 16 channels by the thermo-optic tuning of the refractive index of the polymer waveguide at a low input power of 70 mW. The maximum output power and the slope efficiency of the uncooled diode at 20 (75) degrees C are 8.83 (3.80) mW and 0.107 (0.061) W/A, respectively. The T-ECL operated successfully in the direct modulation for 1.25 Gbit/s transmissions over 20 km.

Cloning of a Bacillus subtilis AMX-4 xylanase gene and characterization of the gene product.

A gene encoding the xylanase of Bacillus subtilis AMX-4 isolated from soil was cloned into Escherichia coli, and the gene product was purified from the cell-free extract of the recombinant strain. The gene, designated xylA, consisted of 639 nucleotides encoding a polypeptide of 213 residues. The deduced amino acid sequence was highly homologous to those of xylanase belonging to glycosyl hydrolase family 11. The molecular mass of the purified xylanase was 23 kDa as estimated by SDS-PAGE. The enzyme had a pH optimum at 6.0-7.0 and a temperature optimum at 50-55 degrees C. Xylanase activity was significantly inhibited by 5 mM Cu2+ and 5 mM Mn2+, and noticeably enhanced by 5 mM Fe2+. The enzyme was active on xylans including arabinoxylan, birchwood xylan, and oat spelt xylan, but it did not exhibit activity toward carboxymethylcellulose or p-nitrophenyl-beta-xylopyranoside. The predominant products resulting from xylan and xylooligosaccharide hydrolysis were xylobiose and xylotriose. The enzyme could hydrolyze xylooligosaccharides larger than xylotriose.

Characterization of the Bacillus subtilis WL-3 mannanase from a recombinant Escherichia coli.

A mannanase was purified from a cell-free extract of the recombinant Escherichia coli carrying a Bacillus subtilis WL-3 mannanase gene. The molecular mass of the purified mannanase was 38 kDa as estimated by SDS-PAGE. Optimal conditions for the purified enzyme occurred at pH 6.0 and 60 degrees C. The specific activity of the purified mannanase was 5,900 U/mg on locust bean gum (LBG) galactomannan at pH 6.0 and 50 degrees C. The activity of the enzyme was slightly inhibited by Mg(2+), Ca(2+), EDTA and SDS, and noticeably enhanced by Fe(2+). When the enzyme was incubated at 4 degrees C for one day in the presence of 3 mM Fe(2+), no residual activity of the mannanase was observed. The enzyme showed higher activity on LBG and konjac glucomannan than on guar gum galactomannan. Furthermore, it could hydrolyze xylans such as arabinoxylan, birchwood xylan and oat spelt xylan, while it did not exhibit any activities towards carboxymethylcellulose and para-nitrophenyl-beta-mannopyranoside. The predominant products resulting from the mannanase hydrolysis were mannose, mannobiose and mannotriose for LBG or mannooligosaccharides including mannotriose, mannotetraose, mannopentaose and mannohexaose. The enzyme could hydrolyze mannooligosaccharides larger than mannobiose.

Cloning and strong expression of a Bacillus subtilis WL-3 mannanase gene in B. subtilis.

A gene encoding the mannanase of Bacillus subtilis WL-3, which had been isolated from Korean soybean paste, was cloned into Escherichia coli and the nucleotide sequence of a 2.7-kb DNA fragment containing the mannanase gene was subsequently determined. The mannanase gene, designated manA, consisted of 1,080 nucleotides encoding polypeptide of 360 amino acid residues. The deduced amino acid sequence was highly homologous to those of mannanases belonging to glycosyl hydrolase family 26. The manA gene was strongly expressed in B. subtilis 168 by cloning the gene downstream of a strong B. subtilis promoter of plasmid pJ27Delta 88U. In flask cultures, the production of mannanase by recombinant B. subtilis 168 reached maximum levels of 300 units/ml and 450 units/ml in LB medium and LB medium containing 0.3% locust bean gum, respectively. Based on the zymogram of the mannanase, it was found that the mannanase produced by recombinant B. subtilis could be maintained stably without proteolytic degradation during the culture time.

Long-Reach Transmission Characteristics of Tunable External Cavity Laser.

We report the transmission capability of a tunable external cavity laser (T-ECL) that utilizes a super-luminescent diode (SLD) and a polymer Bragg reflector (PBR) operating with a direct modulation of 2.5 Gb/s for a light source of a long-reach wavelength division multiplexed-passive optical net- work (WDM-PON). The T-ECL successfully operated at an ambient temperature of -20 °C to 70 °C when employing a cooled SLD. A tuning range of 12-nm is achieved with a tuning power of lower than 80 mW. A side mode suppression ratio of more than 35 dB was obtained for the whole tuning range. The linewidth of the lasing spectrum is less than 0.1 nm at 20 dB from the peak power. The transmission performance of the T-ECL, including an optical bandpass filter (OBPF), is better than that of the T-ECL excluding an OBPF for a long-reach transmission over 80 km of single mode fiber (SMF). The power penalty of the T-ECL is less than 1.4 dB when using an OBPF for an 80-km transmission.

Paenibacillus telluris sp. nov., a novel phosphate-solubilizing bacterium isolated from soil.

A phosphate-solubilizing bacterial strain designated PS38(T) was isolated from farm soil. The isolate was a Gram-positive, motile, endospore-forming, rod-shaped bacterium. It grew optimally at 37°C and pH 7.5. The predominant cellular fatty acids were anteiso-C(15:0), anteiso-C(17:0), and iso-C(16:0). The DNA G+C content was 49.5 mol% and the predominant menaquinone was MK-7. Phylogenese analyses based on 16S rRNA gene sequences showed that the strain PS38(T) belonged to the genus Paenibacillus and was most closely related to Paenibacillus chibensis JCM 9905(T), P. barengoltzii SAFN-016(T), P. timonensis 2301032(T), and P. motobuensis MC10(T) with 96.3%, 96.0%, 95.9%, and 95.5% 16S rRNA gene sequence similarity, respectively. On the basis of morphological, chemotaxonomic, physiological, and phylogenetic properties, strain PS38(T) represents a novel species of the genus Paenibacillus, for which the name Paenibacillus telluris sp. nov. is proposed. The type strain is PS38(T) (=KCTC 13946(T) =CGMCC 1.10695(T)).

Characterization of a Paenibacillus woosongensis beta-Xylosidase/alpha-Arabinofuranosidase produced by recombinant Escherichia coli.

A gene encoding the beta-xylosidase/alpha-arabinofuranosidase (XylC) of Paenibacillus woosongensis was cloned into Escherichia coli. This xylC gene consisted of 1,425 nucleotides, encoding a polypeptide of 474 amino acid residues. The deduced amino acid sequence exhibited an 80% similarity with those of both Clostridium stercorarium beta-xylosidase/alpha-N-arabinosidase and Bacillus cellulosilyticus alpha-arabinofuranosidase, belonging to the glycosyl hydrolase family 43. The structural gene was subcloned with a Cterminal His-tag into a pET23a(+) expression vector. The His-tagged XylC, purified from a cell-free extract of a recombinant E. coli BL21(DE3) Codon Plus carrying a xylC gene by affinity chromatography, was active on paranitrophenyl- alpha-arabinofuranoside (pNPA) as well as paranitrophenyl- beta-xylopyranoside (pNPX). However, the enzymatic activities for the substrates were somewhat incongruously influenced by reaction pHs and temperatures. The enzyme was also affected by various chemicals at different levels. SDS (5 mM) inhibited the enzymatic activity for pNPX, while enhancing the enzymatic activity for pNPA. Enzyme activity was also found to be inhibited by addition of pentose or hexose. The Michaelis constant and maximum velocity of the purified enzyme were determined for hydrolysis of pNPX and pNPA, respectively.

Paenibacillus woosongensis sp. nov., a xylanolytic bacterium isolated from forest soil.

A novel xylan-degrading bacterium, YB-45(T), was isolated from forest soil. The organism is a facultatively anaerobic, Gram-variable, motile, endospore-forming, rod-shaped bacterium. It grew optimally at 37 degrees C and pH 7.5 in the presence of 3 % (w/v) NaCl. The predominant cellular fatty acids were anteiso-C(15 : 0), iso-C(15 : 0) and C(16 : 0). The DNA G+C content was 51.7 mol% and the predominant menaquinone was MK-7. Growth was observed with many carbohydrates, including xylan, as sole carbon sources. Strain YB-45(T) produces a wide variety of hydrolytic enzymes, such as xylanase, cellulase, amylase, beta-mannanase, beta-mannosidase, beta-xylosidase, alpha-galactosidase, beta-galactosidase and beta-glucosidase. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain YB-45(T) belongs to the genus Paenibacillus, sharing sequence similarity that was <96 %. It was related most closely to Paenibacillus jamilae DSM 13815(T), with 95.7 % sequence similarity. On the basis of morphological, chemotaxonomic, physiological and phylogenetic properties, strain YB-45(T) represents a novel species of the genus Paenibacillus, for which the name Paenibacillus woosongensis sp. nov. is proposed. The type strain is YB-45(T) (=KCTC 3953(T)=DSM 16971(T)).

Production of teicoplanin by a mutant of Actinoplanes teicomyceticus.

Teicoplanin, a glucopeptide antibiotic, was produced by a mutant of Actinoplanes teicomyceticus at 300 mg l-1 using mannose and yeast extract as carbon and nitrogen sources in flask culture and at 500 mg l-1 in 5-1 jar fermenter. Teicoplanin production was 25-fold higher than in the parent strain.

Characterization of a thermostable D-stereospecific alanine amidase from Brevibacillus borstelensis BCS-1.

A gene encoding a new thermostable D-stereospecific alanine amidase from the thermophile Brevibacillus borstelensis BCS-1 was cloned and sequenced. The molecular mass of the purified enzyme was estimated to be 199 kDa after gel filtration chromatography and about 30 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that the enzyme could be composed of a hexamer with identical subunits. The purified enzyme exhibited strong amidase activity towards D-amino acid-containing aromatic, aliphatic, and branched amino acid amides yet exhibited no enzyme activity towards L-amino acid amides, D-amino acid-containing peptides, and NH(2)-terminally protected amino acid amides. The optimum temperature and pH for the enzyme activity were 85 degrees C and 9.0, respectively. The enzyme remained stable within a broad pH range from 7.0 to 10.0. The enzyme was inhibited by dithiothreitol, 2-mercaptoethanol, and EDTA yet was strongly activated by Co(2+) and Mn(2+). The k(cat)/K(m) for D-alaninamide was measured as 544.4 +/- 5.5 mM(-1) min(-1) at 50 degrees C with 1 mM Co(2+).