Isolation of a microorganism capable of degrading poly-(L-lactide).

Abstract

Plastics are beneficial because of their facility, lightness, ease in processing, transparency, and low cost. Although some plastics are reused and recycled, the disposal of a large quantity of used plastic waste poses a great problem. Spacious land is required for burying waste material, and poisonous gas is often emitted when plastic waste is incinerated. Furthermore, abiotic plastics spoil the scenery and the ecological systems of many forms of life. Considering these problems, biodegradable plastics have been the subject of many research papers. Several kinds have been produced, such as poly (b-hydroxybutyrate), polycaprolactone, and polyglycolic acid, and depolymerases capable of degrading these materials have been reported (Benedict et al., 1983;Chu, 1981;Kemnitzer et al., 1992;Reeve et al., 1994;Tanino et al., 1982). Poly-(L-lactide) (PLA), one of these biodegradable plastics, however, is expected to be used widely since its cost has decreased recently; already it is used in the medical field (Leenslag et al., 1987;Penning et al., 1993). PLA and other lactic acid-containing polymers are synthesized chemically (Dubois et al., 1991;Kricheldorf et al., 1992;Penning et al., 1993). Apart from its biodegradability, PLA has attracted attention as a material that can be made from renewable resources such as starch because lactic acid is produced through the fermentation of starch or glucose. It is completely harmless compared with abiotic polymers when used in vessels for edible products. PLA is known to degrade slowly in natural soil, but it takes a long time for degradation to start. It can be hydrolyzed enzymatically (Ebeling et al., 1974;Fukuzaki et al., 1989;Reeve et al., 1994). Nevertheless, only a few reports have been made so far on the direct degradation of PLA by microorganisms.One report concerns a mold capable of assimilating soluble PLA-oligomer and PLA-copolymer with glycerol (Torres et al., 1996). Furthermore, Pranamuda et al. (1997) reported the degradation of PLA by Amycolatopsis sp.In the present study, we isolated a microorganism capable of efficiently degrading homo-PLA film in liquid culture. This strain differs from the one reported by Pranamuda et al. (1997), especially in terms of growth temperature and spore formation. In this report, we describe the identification of the PLA-degrading organism, the PLA-degradation conditions, and the products found in the culture supernatant. Materials and Methods Medium Isolation of a microorganism capable of degrading poly-(L-lactide)Yoko Ikura* and Toshiaki KudoInstitute of Physical and Chemical Research ( RIKEN ), Wako 351-0198, Japan (Received February 1, 1999; Accepted October 19, 1999) The isolation of poly-(L-lactide) (PLA)-degrading microorganisms was investigated. A PLA-degrading actinomycete, strain No. 3118, was isolated and tentatively identified as a member of the genus Amycolatopsis. The optimum conditions for degradation of PLA were 43°C at about pH 7 in a mineral salt medium with a low concentration of organic nutrients (0.002% yea...

Characterization of poly(L-lactide)-degrading enzyme produced by thermophilic filamentous bacteria Laceyella sacchari LP175

“…strain HT-32 (Pranamuda et al, 1997), Amycolatopsis sp. strain 3118 (Ikura and Kudo, 1999), Tritirachium album strain ATCC 22563 (Jarerat and Tokiwa, 2001), Amycolatopsis sp. strain 41 (Pranamuda et al, 2001), Amycolatopsis sp.…”

A novel poly (L-lactide) degrading thermophilic actinomycetes, Actinomadura keratinilytica strain T16-1 and pla sequencing

“…However, among these soil samples, only 10 samples were found 11 active strains isolated at 50°C and 2 isolates at 40°C. This indicates that PLA-degrading microorganisms could be regarded as having a lower population in the soil as reported by Pranamuda et al (1997) and Ikura and Kudo (1999).…”

New Insight into Biodegradation of Poly (L-Lactide), Enzyme Production and Characterization

“…HT 32 Film-weight loss; monomer production Pranamuda et al, 1997 Amycolatopsis sp. 3118 Film-weight loss; monomer production Ikura & Kudo, 1999 Amycolatopsis sp. KT-s-9 Clear zone method Tokiwa et al,1999 Amycolatopsis sp.…”

“…Amycolatopsis sp. strain 3118 was isolated and identified by Ikura & Kudo (1999). The optimum condition for degradation of PLA film were 43°C at pH about 7.0 in a mineral salt medium with a low concentration of organic nutrients (0.002% yeast extract) and PLA film disappeared within 2 weeks.…”