Development of a new L-lactate purification process via chitosan lactate

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04675
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22060:Environmental systems for civil engineering-related
• Research Institution: Doshisha University
• Principal Investigator: Akao Satoshi 同志社大学, 理工学部, 教授 (30448196)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: キトサン乳酸塩 / ポリ乳酸 / 乳酸発酵 / 包括固定化法 / 貧溶媒添加法 / 乳酸アンモニウム / キトサン再利用

Outline of Final Research Achievements

Optically pure lactate is a raw material for biodegradable polylactic resin. Such lactate is produced by fermentation, and lactate purification from cultivation broth remains a critical issue for reducing the production cost of polylactic resin. Crystallization of calcium lactate is a popular process for its purification; however, the process requires condensed calcium lactate solution, and calcium sulfate is produced as waste in the final step for liberation of lactic acid. This study investigated the purification process via chitosan lactate. Chitosan l-lactate was made using chitosan as a neutralizer in lactate fermentation. Anti-solvent crystallization was applied to recover chitosan lactate, and acetone was worked as an anti-solvent to precipitate lactate chitosan. Finally, ammonium lactate and chitosan were obtained separately by adding chitosan lactate into aqueous ammonia. The recovery ratio of lactate and chitosan was almost 100% when using high molecular chitosan.

Free Research Field

有機性廃棄物利用

Academic Significance and Societal Importance of the Research Achievements

本研究は，バイオマスプラスチックであるポリ乳酸の製造コスト低減化に資するものとして実施した．カルシウムを用いた乳酸精製法の課題であった濃縮に伴う不純物混入や廃棄物（石膏）の生成を解決するため，カルシウムに代わってキトサンを用いたプロセスの検討，濃縮を必要としない塩沈殿法の検討，廃棄物を避けるべくキトサン再利用プロセスの検討を行った．結果として，乳酸生成菌によるキトサン乳酸塩の生成，アセトンを用いたキトサン乳酸塩の沈殿回収，アンモニア水を用いたキトサンと乳酸アンモニウムの分離回収を示し，キトサン乳酸塩を経由する新規の乳酸精製法が提案できた．