Isolation of a Poly (L-lactide) Degrading Bacterium and Improvement of its Degradation Capacity

A thermophilic bacterium capable of poly (L-lactide)(PLLA) degradation was isolated from cultivating soil in Korea. The isolate was Gram positive rod-shaped bacterium, and was identified as Geobacillus caldoxylosilyticus based on the 16S rDNA sequence analysis. The strain proved to be a new PLLA degrading bacterium which has not been reported in the open literatures yet. The degradation activity of the strain was assessed in a sterilized compost inoculated with the strain under controlled compost condition at $58^{\circ}C$ for 40 days. The strain mineralized 66%, 57%, 41% and 40% of PLLA5000, PLLA11000, PLLA34000 and PLLA256000 whose weight average molecular weights were 5000, 11000, 34000 and 256000, respectively. Incorporation of 0.1% each of gelatin, yeast extract and ammonium sulfate in the compost containing PLLA256000 as a nutritional supplement raised the biodegradation activity by 27%, 13% and 10%, respectively. Increase of the inoculum size from $10^9cfu\;g^{-1}\;to\;10^{10}cfu\;g^{-1}\;and\;10^{11}cfu\;g^{-1}$ also enhanced the biodegradation activity by 14% and 20%, respectively.

Poly(L-lactide)분해 세균의 분리 및 활성 증진

PLLA분해활성을 가진 고온성세균을 우리나라 경작토로부터 분리하였다. 분리된 균주는 그람양성 간균으로 16S rDNA 염기서열분석 결과 Geobacillus caldoxylosilyticus로 동정되었으며, 현재까지 보고되지 않은 새로운 PLLA분해세균으로 밝혀졌다. 조절화된 퇴비화조건에서 멸균퇴비에 분리균주를 접종하고 $58^{\circ}C$에서 40일간 분해활성을 측정하였다. 이 균주는 중량평균 분자량이 5000, 11000, 34000 및 256000인 PLLA5000, PLLA11000, PLLA34000 및 PLLA256000를 각각 66%, 57%, 41%및 40%생분해하였다. PLLA256000을 기질로 하여 gelatin, yeast extract 및 ammonium sulfate를 0.1%씩 첨가하여 분해활성 변화를 조사한 결과 대조군에 비하여 분해활성이 각각 27%, 13% 및 10%증진되었으며, 접종량을 $10^9cfu\;g^{-1}$로부터 $10^{10}cfu\;g^{-1}$ 및 $10^{11}cfu\;g^{-1}$로 증가시킴에 따라 PLLA256000의 생분해도는 각각 14% 및 20% 증가하였다.