Earticle

초록

영어

Polylactide (PLA), which is one of the most important biodegradable and biocompatible polyesters that are derived from annually renewable biomass such as corn and sugar beets, has attracted much attention for its favorable material properties. The most efficient method for preparation of PLA is the ring-opening polymerization of the dimeric cyclic ester of lactic acid, lactide. Lactic acid is widely used in the food, pharmaceutical and cosmetic industries. It is also a major raw material for the production of polylactic acid (PLA) that is a biodegradable, environmentfriendly polymer which could be a substitute for synthetic plastics derived from petroleum feedstocks. Fermentative production of lactic acid offers the great advantage of producing optically pure L-or D- lactic acid depending upon the strains selected for fermentation. The optical purity of lactic acid is crucial for the physical properties of PLA. Though L-lactic acid can be polymerized to give crystalline (PLLA) suited to commercial uses, its application is limited by its low melting point. Complexing PLLA with poly D-lactic acid (PDLA), however, increases the melting point thus presenting an attractive solution to the heat sensitivity of PLA. However, fermentation of sugars to D-lactic acid is little studied and its microbial productivity is not well known. Therefore, we investigated D-lactic acid fermentation with a view to obtaining improved strains capable of producing D-lactic acid with enhanced productivities and finally we got a maximum lactic acid production 60 g/l. Fermentation based process requires maintenance of near neutral pH for high productivity and this necessitates addition of alkali in most of the cases. Alkali addition produces salt of lactic acid instead of lactic acid itself. To overcome this salt problem, we tested the electrodialysis based processes that do not require addition of acid or alkali again to convert lactate salts into lactic acid. Electrodialysis technology which is shown in Fig. 1 is based on electromigration of ions through a stack of cation and anion exchange membranes. Basically, it involves two steps. The first step called conventional electrodialysis (CED) separates and concentrates lactate salts. The second step called bipolar electrodialysis (BED) converts lactate salts into lactic acid. We adopted this two process and produced D-lactic aicd. Lactide is prepared by a two-step process: first, the lactic acid is converted into oligo (lactic acid) by a polycondensation reaction; second, the oligo(lactic acid) is thermally depolymerized to form the cyclic lactide via a unzipping mechanism. Through catalyst screening test for polycondensation and unzipping depolymerization reaction, we got a new method which shorten the whole reaction time as 50% level compared to the conventional method. Poly(L-lactide) was obtained from the ring-opening polymerization of L-lactide. We investigated various catalysts and polymerization conditions. Finally we got the best catalyst system and the scale-up technology.

키워드

저자

• Chae Hwan HONG [ CAE & Materials Research Team, Central Advanced R&E Institute ]
• Si Hwan KIM [ CAE & Materials Research Team, Central Advanced R&E Institute ]
• Ji Yeon SEO [ CAE & Materials Research Team, Central Advanced R&E Institute ]
• Do Suck HAN [ CAE & Materials Research Team, Central Advanced R&E Institute ]

참고문헌

발행기관

간행물

표지보기 관심저널 등록

• 간행물명

  한국생물공학회 학술대회

• 간기

  반년간

• 수록기간

  1985~2013

• 십진분류

  KDC 476 DDC 576