막 분리 기반 고효율 젖산 분리 공정

Abstract

본 연구에서는 발효액에서 젖산을 회수하기 위한 분리막 기반의 유기산 정제 공정을 도입하고, 순도가 높은 젖산을 회수하였다. 도입된 정제 공정은 한외 여과, 나노 여과, 이온 교환 그리고 감압 증발의 총 4단계 공정이 연계되어 각 단계별로 최종 산물인 젖산을 제외한 발효액 내 다양한 성분 (미생물, 고형분, 글루코오스, 무기 이온) 의 효과적인 배제가 가능하였다. 먼저 한외 여과 공정을 통해 발효액 내 미생물 및 고형물이 효과적으로 배제되는 것을 확인하였다. 고형물의 배제 성능 확인뿐 아니라 막 오염 현상에 대한 부분에 대한 연구도 함께 진행하였다. 나노 여과 공정을 통해 발효액 내 글루코오스와 젖산을 선택적으로 분리하였다. 분리막 표면의 기공 크기와 표면 전하를 통해 젖산은 적은 손실로 투과하는 반면 글루코오스 및 무기 이온 성분들은 대부분 배제되었다. 나노 여과 공정에서 배제되지 못한 일부 무기 이온 성분들은 이온 교환 공정을 통해 제거하였다. 최종적으로 감압 증발법을 통해 물을 제거함으로써 고순도 (99.5% 이상)의 젖산을 회수하였다. |Lactic acid is a chemical compound used for polymer precursors, food, pharmaceutical, and cosmetic applications. Lactic acid can be produced from fermentation processes followed by separation processes such as precipitation, distillation and reactive extraction. However, these conventional separation processes have drawbacks from the viewpoint of cost and energy efficiency. In this study, we proposed integrated membrane separation process to recover lactic acid from fermentation broth, consisting of ultrafiltration (UF), nanofiltration (NF), ion exchange (IEX), and vacuum-assisted evaporation (VE). As a pretreatment step, microbes and colloidal particles can be successfully rejected by UF membrane, while severe membrane fouling occurred due to high concentration in the fermentation broth. Effect of various UF membrane properties on membrane fouling during fermentation broth filtration was studied to enhance the separation efficiency. Effective purification of lactic acid was performed by NF process due to size exclusion and Donnan exclusion of NF membrane. Finally, residual inorganic salt ions were removed by IEX followed by VE for the concentration of the lactic acid aqueous solution. By using a stepwise separation processes, various components (e.g., microbes, glucose and inorganic salt ions) in the fermentation broth were successfully separated, resulting in the recovery of lactic acid with high purity (> 99.5%).; Lactic acid is a chemical compound used for polymer precursors, food, pharmaceutical, and cosmetic applications. Lactic acid can be produced from fermentation processes followed by separation processes such as precipitation, distillation and reactive extraction. However, these conventional separation processes have drawbacks from the viewpoint of cost and energy efficiency. In this study, we proposed integrated membrane separation process to recover lactic acid from fermentation broth, consisting of ultrafiltration (UF), nanofiltration (NF), ion exchange (IEX), and vacuum-assisted evaporation (VE). As a pretreatment step, microbes and colloidal particles can be successfully rejected by UF membrane, while severe membrane fouling occurred due to high concentration in the fermentation broth. Effect of various UF membrane properties on membrane fouling during fermentation broth filtration was studied to enhance the separation efficiency. Effective purification of lactic acid was performed by NF process due to size exclusion and Donnan exclusion of NF membrane. Finally, residual inorganic salt ions were removed by IEX followed by VE for the concentration of the lactic acid aqueous solution. By using a stepwise separation processes, various components (e.g., microbes, glucose and inorganic salt ions) in the fermentation broth were successfully separated, resulting in the recovery of lactic acid with high purity (> 99.5%).