Chikara Tsutsumi

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 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.

Incorporation of L-lactide random copolymers with Japanese cypress oil (α-pinene) using supercritical carbon dioxide

This study involved the incorporation of useful compounds, such as repellents and antibacterial agents, at high concentrations in L-lactide (L-LA) random copolymers. The amount of α-pinene released in gas from the copolymers was also evaluated. Outstanding controlled release properties were developed using random copolymers of L-lactide (L-LA) with γ-valerolactone (VL), e-caprolactone (CL), tetramethylene carbonate (TEMC) (1,3-dioxepan-2-one), and 1,5-dioxepan-2-one (DXO) using tin 2-ethyl-hexanoate [Sn(oct)2] as a catalyst at 150 °C for 24 h without solvent. Preparation of controlled release materials was accomplished using α-pinene from Japanese cypress oil and synthetic random copolymers of L-LA with cyclic monomers as base materials under supercritical carbon dioxide (scCO2). Poly(L-LA-ran-VL), poly(L-LA-ran-CL), poly(L-LA-ran-TEMC), and poly(L-LA-ran-DXO), which have lower Tm and ΔHm values than poly(L-LA) were used for the impregnation experiments. The oil content of the copolymers was greater than that in poly(L-LA). The content of oil into poly(L-LA-ran-TEMC) (80:20) was 8.1%, 2.1-fold greater than that in poly(L-LA) (Lacea H-100) (H-100), and 1.5-fold greater than that in poly(L-LA) (Lacea H-440) (H-440). Although a previous study showed that 3.2% D-limonene could be incorporated into poly(L-LA-ran-CL) (85:15) under the same conditions, results of this experiment showed that 5.8% and 6.6% oil could be incorporated into poly(L-LA-ran-CL) (81:19 or 91:9), respectively. Results from controlled release experiments demonstrated that the oil content in the polymer decreased upon copolymer degradation for all copolymers. In gas release tests, polymers H-440 and poly(L-LA-ran-VL) (85:15) released gas upon hydrolysis. Although the weight loss of H-440 was only 9% at 56 days, the calculated loss of oil in H-440 was 28%.

Synthesis and Biodegradation of Poly(l-lactide-co-β-propiolactone)

Although the copolymerizations of l-lactide (LA) with seven- or six-membered ring lactones have been extensively studied, the copolymerizations of LA with four-membered ring lactones have scarcely been reported. In this work, we studied the copolymerization of LA with β-propiolactone (PL) and the properties of the obtained copolymers. The copolymerization of LA with PL was carried out using trifluoromethanesulfonic acid as a catalyst and methanol as an initiator to produce poly(LA-co-PL) with Mn of ~50,000 and PL-content of 6–67 mol %. The Tg values of the copolymers were rapidly lowered with increasing PL-contents. The Tm and ΔHm of the copolymers gradually decreased with increasing PL-contents, indicating their decreased crystallinity. Biodegradation test of the copolymers in compost demonstrated their improved biodegradability in comparison with the homopolymer of LA.

Anodic reactions of NADH model compound by utilizing both light irradiation and riboflavin as a redox mediator

ABSTRACT Both light and a redox mediator riboflavin (RF) were utilized to promote the electro-oxidation of an NADH model compound (1-benzyl-1,4-dihydronicotinamide, BNAH), which is a key process for enzymatic biofuel cells to obtain a high performance. At the cathode, H+ ions were simultaneously reduced to produce H2 gas. To elucidate the cell reactions of this photogalvanic cell, which is significant information about the fabrication of enzymatic biofuel cells with a high performance, the effect of the BNAH and RF concentrations on the cell current, the light wavelength dependence on the current, and reduction of the RF concentration were evaluated. The obtained results strongly suggest that the anodic reactions were composed of the following reactions: 1) the photo-excitation of RF, 2) the attack of the excited RF on the BNAH and the generation of the radical species of BNAH and RF, and 3) the chain reactions between the radical species. Graphical Abstract The RF-mediated oxidation of BNAH was composed of 1) the photo-excitation of RF, 2) the attack of the excited RF on the BNAH, and 3) the chain reactions between their radicals.