Rapid monomerization of poly(butylene succinate)-co-(butylene adipate) by Leptothrix sp.

For rapid monomerization of biodegradable plastics, various microorganisms were screened and TB-71 was selected as the best strain. TB-71 degraded solid poly(butylene succinate)-co-(butylene adipate) (PBSA), poly(ethylene succinate), and poly(epsilon-caprolactone) but not poly(butylene succinate), poly(2-hydroxybutylate-co-valerate) or poly(lactic acid). Esterase activity was observed in the culture broth during PBSA degradation, which was specifically induced by PBSA. Analysis of the degradation products revealed that PBSA was degraded to monomers.

Identification and characterization of novel poly(DL-lactic acid) depolymerases from metagenome.

Many poly(lactic acid) (PLA)-degrading microorganisms have been isolated from the natural environment by culture-based methods, but there is no study about unculturable PLA-degrading microorganisms. In this study, we constructed a metagenomic library consisting of the DNA extracted from PLA disks buried in compost. We identified three PLA-degrading genes encoding lipase or hydrolase. The purified enzymes degraded not only PLA, but also various aliphatic polyesters, tributyrin, and p-nitrophenyl esters. From their substrate specificities, the PLA depolymerases were classified into an esterase rather than a lipase. Among the PLA depolymerases, PlaM4 exhibited thermophilic properties; that is, it showed the highest activity at 70 degrees C and was stable even after incubation for 1 h at 50 degrees C. PlaM4 had absorption and degradation activities for solid PLA at 60 degrees C, which indicates that the enzyme can effectively degrade PLA in a high-temperature environment. On the other hand, the enzyme classification based on amino acid sequences showed that the other PLA depolymerases, PlaM7 and PlaM9, were not classified into known lipases or esterases. This is the first report on the identification and characterization of PLA depolymerase from a metagenome.

Isolation of a bacterium that degrades urethane compounds and characterization of its urethane hydrolase.

A bacterium which degrades urethane compounds was isolated and identified as Rhodococcus equi strain TB-60. Strain TB-60 degraded toluene-2,4-dicarbamic acid dibutyl ester (TDCB) and accumulated toluene diamine as the degradation product. The enzyme which cleaves urethane bond in TDCB was strongly induced by acetanilide. The purified enzyme (urethane hydrolase) was found to be homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight was estimated to be 55 kDa. The optimal temperature and pH were 45 degrees C and 5.5, respectively. The enzyme hydrolyzed aliphatic urethane compound as well as aromatic ones. The activity was inhibited by HgCl(2), p-chrolomercuribenzoic acid, and phenylmethylsulfonyl fluoride, suggesting that cysteine and/or serine residues play an important role in the activity. The enzyme catalyzed the hydrolysis of anilides, amides, and esters as well as TDCB. It was characterized as a novel amidase/esterase, differing in some properties from other known amidases/esterases.

Screening of novel cellulose-degrading bacterium and its application to denitrification of groundwater.

To establish an environmentally friendly groundwater bioremediation process using a cellulose carrier combined with cellulose-utilizing, denitrifying microorganisms, a novel psychrophilic bacterium, designated CL-5, which can degrade a commercial-based cellulose carrier as the sole carbon source, was screened. Since the denitrification capability of CL-5 is low, complex microbial systems were constructed together with other denitrifying bacteria designated NR-1 and NR-2 that were also isolated from soil. The nitrate-reducing activities of mixed cultures were much higher than those of the pure cultures of CL-5, NR-1 and NR-2. The highest N(2)O and N(2) formation activities were observed in the mixed culture of CL-5+NR-2.

Matrix metalloproteinase-2 inhibition and Zn2+-chelating activities of pyoverdine-type siderophores.

Pyoverdine-type siderophores from fluorescent Pseudomonas species were purified by Zn2+-chelate chromatography, and their matrix metalloproteinase-2 (MMP-2) inhibition and metal-ion-chelating activities were studied. Structurally different pyoverdines showed different MMP-2 inhibition activities, and the inhibition activity was correlated with Zn2+-chelating activity. The IC50 value of a pyoverdine ((P113A1)-2, MW 1187) for MMP-2 was 0.27 microg/ml (0.23 microM).

Cloning and sequencing of a poly(DL-lactic acid) depolymerase gene from Paenibacillus amylolyticus strain TB-13 and its functional expression in Escherichia coli.

The gene encoding a poly(DL-lactic acid) (PLA) depolymerase from Paenibacillus amylolyticus strain TB-13 was cloned and overexpressed in Escherichia coli. The purified recombinant PLA depolymerase, PlaA, exhibited degradation activities toward various biodegradable polyesters, such as poly(butylene succinate), poly(butylene succinate-co-adipate), poly(ethylene succinate), and poly(epsilon-caprolactone), as well as PLA. The monomeric lactic acid was detected as the degradation product of PLA. The substrate specificity toward triglycerides and p-nitrophenyl esters indicated that PlaA is a type of lipase. The gene encoded 201 amino acid residues, including the conserved pentapeptide Ala-His-Ser-Met-Gly, present in the lipases of mesophilic Bacillus species. The identity of the amino acid sequence of PlaA with Bacillus lipases was no more than 45 to 50%, and some of its properties were different from those of these lipases.