Takashi Ohmoto

Biodegradation of bisphenol A and related compounds by Sphingomonas sp. strain BP-7 isolated from seawater.

A bacterium capable of assimilating 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), strain BP-7, was isolated from offshore seawater samples on a medium containing bisphenol A as sole source of carbon and energy, and identified as Sphingomonas sp. strain BP-7. Other strains, Pseudomonas sp. strain BP-14, Pseudomonas sp. strain BP-15, and strain no. 24A, were also isolated from bisphenol A-enrichment culture of the seawater. These strains did not degrade bisphenol A, but accelerated the degradation of bisphenol A by Sphingomonas sp. strain BP-7. A mixed culture of Sphingomonas sp. strain BP-7 and Pseudomonas sp. strain BP-14 showed complete degradation of 100 ppm bisphenol A within 7 d in SSB-YE medium, while Sphingomonas sp. strain BP-7 alone took about 40 d for complete consumption of bisphenol A accompanied by accumulation of 4-hydroxyacetophenone. On a nutritional supplementary medium, Sphingomonas sp. strain BP-7 completely degraded bisphenol A and 4-hydroxyacetophenone within 20 h. The strain degraded a variety of bisphenols, such as 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, and 1,1-bis(4-hydroxyphenyl)cyclohexane, and hydroxy aromatic compounds such as 4-hydroxyacetophenone, 4-hydroxybenzoic acid, catechol, protocatechuic acid, and hydroquinone. The strain did not degrade bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)sulfone, or bis(4-hydroxyphenyl)sulfide.

Degradation of bisphenol A by Bacillus pumilus isolated from kimchi, a traditionally fermented food

Novel bisphenol A (BPA)-degrading bacterial strains, designated as BP-2CK, BP-21DK, and BP-22DK, were isolated from kimchi, a traditionally fermented food. These isolates were identified as Bacillus pumilus and efficiently degraded BPA in a medium supplemented with nutrients such as peptone, beef extract, and yeast extract. Strains BP-2CK, BP-21DK, and BP-22DK successfully degraded 25, 25, and 50 ppm of BPA, respectively, and all strains exhibited BPA-degrading activity in the presence of 10% NaCl. Accumulation of the metabolites including 4-hydroxyacetophenone, one of the intermediates produced by the other BPA-degrading bacteria, was not observed in BPA degradation by the isolated strains. These results indicate that the isolated food-derived bacteria are applicable for the construction of efficient and safer systems for the removal of BPA.

Efficient Microbial Degradation of Bisphenol A in the Presence of Activated Carbon

The biodegradation of bisphenol A (BPA) was carried out with Sphingomonas sp. strain BP-7 and Sphingomonas yanoikuyae BP-11R in the presence of activated carbon (AC). When AC was present, both BPA-degrading bacteria efficiently degraded 300 mg/l BPA without releasing 4-hydroxyacetophenone, the major intermediate produced in BPA degradation, into the medium. The biological regeneration of AC was possible using the BPA-degrading bacteria, suggesting that an efficient system for BPA removal can be constructed by introducing BPA-degrading bacteria into an AC treatment system.

Purification and Characterization of an Endo-1,4-β-glucanase from Neisseria sicca SB that Hydrolyzes β-1,4 Linkages in Cellulose Acetate

An enzyme catalyzing hydrolysis of β-1,4 bonds in cellulose acetate was purified 18.3-fold to electrophoretic homogeneity from a culture supernatant of Neisseria sicca SB, which can assimilate cellulose acetate as the sole carbon and energy source. The molecular mass of the enzyme was 41 kDa and the isoelectric point was 4.8. The pH and temperature optima of the enzyme were 6.0–7.0 and 60°C. The enzyme catalyzed hydrolysis of water-soluble cellulose acetate (degree of substitution, 0.88) and carboxymethyl cellulose. The K m and V max for water-soluble cellulose acetate and carboxymethyl cellulose were 0.242% and 2.24 μmol/min/mg, and 2.28% and 12.8 μmol/min/mg, respectively. It is estimated that the enzyme is a kind of endo-1,4-β-glucanase (EC 3.2.1.4) from the substrate specificity and hydrolysis products of cellooligosaccharides. The enzyme and cellulose acetate esterase from Neisseria sicca SB degraded water-insoluble cellulose acetate by synergistic action.

Metabolism of Naphthalenesulfonic Acids by Pseudomonas sp. TA-2

A 2-naphthylamine-1-sulfonate (tobias acid)-degrading Pseudomonas strain was isolated from soil. This organism degraded 1-naphthalenesulfonate and 2-naphthol-1-sulforiate as well as tobias acid. When the cells grown on a nutrient medium were incubated with tobias acid, 1-naphthalenesulfonate, and 2-naphthol-1-sulfonate, salicylate was temporarily accumulated in the culture medium. A salicylate-degrading enzyme and a gentisate-degrading enzyme were induced by salicylate and gentisate, respectively. On the other hand, the enzymes which degrade sulfonated naphthalenes to salicylate were constitutive. Ammonia, sulfate, and a small amount of sulfite were detected in the course of degradation of tobias acid. 2-Naphthol-8-sulfonate or 1-naphthol-5-sulfonate was converted into 2,4-dihydroxybenzoate or 2,6-dihydroxybenzoate respectively. Both cis-1,2-dihydroxy-1,2-dihydro-3-naphthalenesulfonate and sulfate were formed when the cells were incubated with 2-naphthalenesulfonate. It is suggested that tobias acid was d...

Mode of Action on Deacetylation of Acetylated Methyl Glycoside by Cellulose Acetate Esterase from Neisseria sicca SB

The regioselective deacetylation of purified cellulose acetate esterase from Neisseria sicca SB was investigated on methyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside and 2,3,4,6-tetra-O-acetyl-β-D-galactopyranoside. The substrates were used as model compounds of cellulose acetate in order to estimate the mechanism for deacetylation of cellulose acetate by the enzyme. The enzyme rapidly deacetylated at position C-3 of methyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside to accumulate 2,4,6-triacetate as the main initial reaction product in about 70% yield. Deacetylation was followed at position C-2, and generated 4,6-diacetate in 50% yield. The enzyme deacetylated the product at positions C-4 and C-6 at slower rates, and generated 4- and 6-monoacetates at a later reaction stage. Finally, it gave a completely deacetylated product. For 2,3,4,6-tetra-O-acetyl-β-D-galactopyranoside, CA esterase deacetylated at positions C-3 and C-6 to give 2,4,6- and 2,3,4-triacetate. Deacetylation proceeded sequentially at positions C-3 and C-6 to accumulate 2,4-diacetate in 55% yield. The enzyme exhibited regioselectivity for the deacetylation of the acetylglycoside.

Role of Endo-1,4-β-glucanases from Neisseria sicca SB in Synergistic Degradation of Cellulose Acetate

An enzyme hydrolyzing β-1,4 bonds in cellulose acetate was purified 10.5-fold to electrophoretic homogeneity from a culture supernatant of Neisseria sicca SB, which assimilate cellulose acetate as the sole carbon and energy source. The enzyme was an endo-1,4-β-glucanase, to judge from the substrate specificity and hydrolysis products of cellooligosaccharides, we named it endo-1,4-β-glucanase I (EG I). Its molecular mass was 50 kDa, 9 kDa larger than EG II from this strain, and its isoelectric point was 5.0. Results of N-terminal and inner-peptide sequences of both enzymes, and a similarity search, suggested that EG I contained a carbohydrate-binding module at the N-terminus and that EG II lacked this module. The pH and temperature optima of EG I were 5.0-6.0 and 45°C. It hydrolyzed water-soluble cellulose acetate (degree of substitution, 0.88) and carboxymethyl cellulose. The K m and V max for these compounds were 0.296% and 1.29 μmol min-1 mg-1, and 0.448% and 13.6 μmol min-1 mg-1, respectively. Both glucanases and cellulose acetate esterase from this strain degraded water-insoluble cellulose acetate synergistically.

Conversion of naphthoates to cis-dihydrodiols by naphthalenesulfonate-assimilating Pseudomonas sp. TA-2

A naphthalenesulfonate-assimilating bacterium, Pseudomonas sp. TA-2, was found to convert 2-naphthoate to cis-1,2-dihydroxv-1,2-dihydronaphthalene-2-carboxylate (DDN2C) and cis-l,2-dihydroxy-l,2-dihydronaphthalene-3-carboxylate (DDN3C), and converted 1-naphthoate to as-l,2-dihydroxy-l,2-dihydronaphthalene-l-carboxylate (DDN1C). It was suggested that conversion of naphthoates was done by a dioxvgenase with relaxed regioselectivity.