Development of porous membranes of poly (lactic acid) via thermally induced phase separation and its application to bioprocesses

可生物降解的聚酯，例如，聚（L-乳酸）在自然环境中可被微生物降解，在人体中可降解，近年来在生物工程中受到越来越多的关注。在这项研究中，我们已经开发了微孔膜的生物降解聚酯通过热致相分离。首先，聚合物的特性和相分离的条件（稀释剂、聚合物浓度和热历史）对相分离中液滴的生长以及所形成的多孔材料的结构和孔径的影响。在此基础上，制备了聚L-乳酸、聚ε-己内酯及其共混物的微孔膜。聚乳酸膜对酵母细胞悬浮液的过滤表现出筛网过滤的特性。聚（L-乳酸）和聚（ε-己内酯）的聚合物共混物的膜显示出深层过滤器的膜。后一种膜的过滤通量远高于前一种膜。我们还将聚L-乳酸膜应用于白色腐菌Trametesversicolor的膜表面液体培养中，以生产一种氧化酶漆酶。该膜在28℃条件下稳定性好，在重复使用的情况下，膜表面液体培养的产酶量明显高于液体表面培养。生物可降解多孔膜将有助于生物工业和生物医学工程的可持续发展。

Biodegradable polyesters, e.g., poly(_L-lactic acid), which are degraded by microorganisms in natural environment and degradable in human bodies, have recently received increased attention in bioengineering. In this study we have developed microporous membranes of biodegradable polyesters via thermally induced phase separation. At first effect of characteristics of polymers and conditions of phase separation (diluent, polymer concentration, and thermal history) on the growth of the droplet in phase separation and the structures and pore sizes of the formed porous materials. Then, we made microporous membranes of poly(_L-lactic acid), poly(ε-caprolactone), and their blends. The poly(_L-lactic acid) membrane showed the characteristics of a screen filter in the filtration of yeast cell suspensions. The membrane of a polymer blend of poly(_L-lactic acid) and poly(ε-caprolactone) showed that of a depth filter. The filtration flux with the latter membrane was much higher than that with the former. We also applied poly(_L-lactic acid) membrane to the production of an oxidase, laccase, by membrane-surface liquid culture of white rot fungus, Trametes versicolor. The membrane was stable at 28℃ and the fungus grown on the membrane secreted much more enzyme in the repeated use of membrane-surface liquid culture than in liquid surface culture. The porous biodegradable membranes would contribute to the development of sustainable bioindustry and biomedical engineering.