グルコースからポリ-_L-乳酸を工業的に製造する方法の開発

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A cultivation method called the "Hop-Step-Jump(HSJ)"method has been successfully established. In the cultivation of Lactobacillus casei B12-2, a lactic acid bacterium isolated from a tropical sample with a high sugar concentration, the HSJ method reduced the time during which the maximum lactic acid concentration is reached from 30 days to nine. In addition, 5 M sodium hydroxide and ammonia were examined as neutralizers. Tests revealed that the miximum lactic acid concentration was reached more quickly with ammonia than with sodium hydroxide. A seed culture was cultivated by a technique corresponding to HS of the HSJ method and the J cultivation was neutralized. As a result, it took 25 h to achieve a lactic acid concentration of 150 g/l. For industrial-scale fermentation, we used Lactobacillus lactis 332, which produces lactic acid of high optical purity with inexpensive corn steep liquor as the nitrogen source and performed the cultivation corresponding to HS of the HSJ method in a 200-l jar fermentor. The J cultivation was carried out industrially in a 20-m^3 jar fermentor for _L-lactic acid fermentation. In this case, it took 70 h to achieve a lactic acid concentration of 88 g/l. We have developed two approaches to purifying fermented lactic acid: electrodialysis-based enrichment and bipolar membrane-based ion exchange from ammonium lactate to lactic acid. An aqueous solution of 900 g/l _L-lactic acid was obtained at an optical purity of 95%. For the industrial production of poly-_L-lactate, _<LL>-lactide was produced from pre-polymers of poly-_L-lactate through intramolecular transesterification. In the preparation of the pre-polymers, polycondensation takes place in which the linear mono-, di-, and trimer of lactic acid are totally refluxed so that the yield of _<LL>-lactide can be improved. The temperature of the reactor is then raised in three steps to prevent racemization. A melt crystallization method without a solvent was developed for the purification of _<LL>-lactide. Ring-opening polymerization of _<LL>-lactide took place continuously, resulting in the production of high-molecular-weight poly-_L-lactate with a weight-average mol.wt.of 200, 000.
社団法人日本生物工学会の論文
2001-05-25

グルコースからポリ-_L-乳酸を工業的に製造する方法の開発

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