Katsuhiko Nakagawa

Isolation and characterization of poly(butylene succinate-co-butylene adipate)-degrading microorganism

Poly(butylene succinate-co-butylene adipate) (PBSA)-degrading bacterium, strain 1-A, was isolated from soil. Strain 1-A was identified as Bacillus pumilus on the basis of its physiological properties and partial 16S rRNA gene sequence. Strain 1-A also degraded poly(butylene succinate) (PBS) and poly(epsilon-caprolactone). On the other hand, poly(butylene adipate terephthalate) and poly(lactic acid) were minimally degraded by strain 1-A. The NMR spectra of degradation products from PBSA indicated that the adipate units were more rapidly degraded than 1,4-butanediol and succinate units. This seems to be one of the reasons why strain 1-A degraded PBSA faster than PBS.

Enzymatic degradations of copolymers of L-lactide with cyclic carbonates

Syntheses and biodegradation of random copolymers of L-lactide (L-LA) with trimethylene carbonate (TMC), 1,1-dimenthyltrimethylene carbonate (1,1-DTMC) and 2,2-dimethyltrimethylene carbonate (2,2-DTMC) were investigated at various monomer ratios using SmMe-(C 5 Me 5 ) 2 THF as an initiator at 80°C for 24 h in toluene. Enzymatic degradation of these polymers were performed using cholesterol esterase, lipoprotein lipase, and proteinase K. Poly(TMC) was effectively biodegraded by cholesterol esterase and lipoprotein lipase, while poly(2,2-DTMC) and all the copolymers were hardly degraded using these enzymes. Biodegradations of poly(L-LA-co-TMC) (97:3) and poly(L-LA-co-2,2,DTMC) (95.5) show rapid degradations using TES buffer, a compost and proteinase K. The physical properties of these copolymers were also examined.

Optochemical sensor for HCl gas based on tetraphenylporphyrin dispersed in styrene-acrylate copolymers: Effects of glass transition temperature of matrix on HCl detection

The spectral changes of tetraphenylporphyrin (TPPH2)–polymer composites in the visible region were examined in order to detect HCl gas. For TPPH2, the absorbance of the Soret and Q bands were sensitive to ppm levels of HCl. The sensing mechanism were characterized basing the protonation reaction and sorption isotherm: TPPH2+2HClfilm⇄TPPH42+·2Cl− and [HClfilm]=a[HClgas]n. The equilibrium constant of the former was decreased with increase in the working temperature and in glass transition temperature (Tg) of polymer matrix. The number of active sites (a) for HCl sorption decreased with a decrease in the Tg. The response behavior was improved by using polymer with lower Tg.

Optochemical HCl gas detection using alkoxy substituted tetraphenylporphyrin-polymer composite films: Effects of alkoxy chain length on sensing characteristics

Composite films of 5,10,15,20-tetra(4′-alkoxyphenyl)porphyrin (TP(OR)PH2) embedded in various polymer matrices were prepared and their optical responses to HCI gas were examined. The absorbance of the Soret and Q-bands for free-base TP(OR)PH2 is reversibly sensitive to sub-ppm levels of HCl. The glass transition temperature (Tg) of a matrix below the sensing temperature is more effective to the response and recovery behavior than above the sensing temperature. High sensitivity to sub-ppm levels of HCl was achieved by using a TP(OC4H9)PH2-BuMA composite film.

HCl gas sensing properties of TPPH2 dispersed in various copolymers

Abstract Composite films of tetraphenylporphyrin embedded in various of polymer matrix were prepared and their optical responses to hydrogen chloride (HCl) gas were examined. The absorbance of the Soret- and Q-bands for free-base tetraphenylporphyrin is reversibly sensitive to parts per million (ppm) levels of HCl. The lower T g of polymer matrix than the sensing temperature is effective to enhance the sensitivity of the Soret- and Q-band region.

Optochemical HCl gas sensor using substituted tetraphenylporphine–ethylcellulose composite films

Composite films of various tetraphenylporphines embedded in ethylcellulose were prepared and their optical response to gaseous HCl was investigated. The absorbance of the Soret and Q-bands for free-base tetraphenylporphines is reversibly sensitive to ppm levels of HCl. The replacement of thepara hydrogen in one phenyl group with a hydroxy group is effective in enhancing the sensitivity of the Q-band region while prolonging response time. In addition, the temperature coefficient of the sensitivity of TP(OH)(R)3PH2 is lower than that of TPPH2 . Under filtered light (>600 nm) a significant deterioration of the sensitivity was not observed for more than 50 d.

Optochemical HCl gas detection using mono-substituted tetraphenylporphin-polymer composite films

Abstract Hydroxy-/alkoxy-substituted tetraphenylporphin were synthesized and their Soret- and Q-bands’ changes with HCl gas in ppm levels were examined. Both the bands were influenced by HCl gas concentration and their changes in sub-ppm levels of HCl were decreased with an increase in the alkoxy chain length. The changes of the absorbance of the Soret- and Q(0–0)-bands were enhanced by replacing ethylcellulose with poly-hexylmethacrylate as a matrix while the recovery times prolonged. The introductions of electron donating substituents to p-phenyl positions of the porphin ring result in the basicity of pyrrole nitrogens.

An optochemical HCl gas sensor using 5,10,15,20-tetrakis (3′,5′-di-tert-butyl,4′-hydroxyphenyl) porphin-ethylcellulose composite films

The absorbance of the Soret and Q-bands of free-base tetraphenylporphins is reversibly sensitive to ppm levels of HCl. The replacement of the hydrogen para to the phenyl group with an -OH group enhances the sensitivity of the Soret and the Q-band region. While both response and recovery times of tetra 4′-OH substituted tetraphenylporphins is considerably longer than that of tetraphenylporphin, the replacing the hydrogen meta to the phenyl group with tert-butyl group is effective to improve both response and recovery times. The HCl gas sensor based on substituted-tetraphenylporphin with 4′-OH and 3′,5′-di-C(CH3)3 to the phenyl group shows superior performance for detection of emissions of ppm levels of HCl gas.

An easy access to optically pure (R)-malic acid via enantioselective hydrolysis of diethyl malate byRhizopus lipase

SummaryRacemic diethyl malate was enantioselectively hydrolyzed by crudeRhizopus lipase (Saiken) to leave optically pure (≳99% ee) (R)-(+)- malate in c.a. 20% recovery. The combination of dipropyl malate and lipase AY (Amano) also gave (R)-enantiomer with a high ee of ≥97% and about 20% recovery in a short reaction time.

Isolation and characterization of Bradyrhizobium sp. 224 capable of degrading sulfanilic acid.

A bacterial strain (strain 224), which has the ability to utilize sulfanilic acid as a sole source of carbon, was isolated from soil. 16S rRNA gene sequence obtained from strain 224 exhibited 100% identical to that of species in the genus Bradyrhizobium. Strain 224 degraded 4.7 mM of sulfanilic acid and released almost the same molar concentration of sulfate ion