以批次醱酵槽生產聚麩胺酸並探討其化學衍生物 吸水性質之研究

Microbial Production of γ-Polyglutamic Acid in Fermenter and the Water Absorption Properties of Its Chemical Derivatives

聚麩胺酸是經由微生物發酵生產的天然生物性材料，其具有水溶性、生物可分解與可食等特性，且聚麩胺酸本身及其分解物對人體與環境無毒害，目前聚麩胺酸已知可應用於食品、化妝品、醫藥材料、環境保護等領域，因此工業化大量生產聚麩胺酸此一對環境友善之生物性材料相當的重要。本研究以十升發酵槽培養 Bacillus licheniformis BCRC 12826 並探討 pH、曝氣量、攪拌速率等因子對菌株生長、聚麩胺酸產量的影響，結果發現 pH 6.5、轉速 200 rpm、曝氣量為 3 L/min 較適合聚麩胺酸的生合成，最高達 25.93 g/L。本研究亦探討聚麩胺酸衍生物之吸水性，使用 B. licheniformis BCRC 12826 菌株所生產聚麩胺酸，並利用化學方法交聯偶合聚麩胺酸與環氧樹脂以得吸水凝膠，實驗發現 2.5 ﹪聚麩胺酸溶液於pH 5.33 與 150 μl 環氧樹脂進行反應 4 天，所得之凝膠可達到吸水重為乾凝膠重的 50~60倍，吸水性較其它條件製備之凝膠優越。不同吸水材料之吸水實驗中，發現 Bacillus subtilis C1 所生產之聚麩胺酸-甘油複合物於 30 分鐘吸水實驗中，吸水重為乾凝膠重之 26 倍，然而較長時間之吸水，此材料即完全溶解。

γ-Polyglutamic acid (γ-PGA) is a naturally occurring biomaterial produced by microbial fermentation. It is water soluble, biodegradable, edible, and nontoxic toward humans and the environment. γ-PGA has potential applications in food, cosmetics, medicine, and environmental protection. The development of this material is both environmentally and economically valuable. In this study, we investigated the effects of pH, aeration, and agitation on γ-PGA production by Bacillus licheniformis BCRC 12826 in a 10-L fermenter. The pH value of 6.5, an agitation speed of 200 rpm, and an aeration rate of 3 L/min were found to be the most suitable conditions for γ-PGA production by this strain, with the highest yield of γ-PGA being 25.93 g/L. The water absorption properties of γ-PGA derivatives were also investigated. The γ-PGA derivatives were prepared by coupling the γ-PGA produced by B. licheniformis BCRC 12826 (2.5 wt%) with 150 μL of diglycidyl ether of bisphenol A at pH 5.33 for 4 days. The obtained cross-linked product displayed strong water absorption activity; its specific water content was approximately 50–60. In comparison, the specific water content was approximately 26 for a γ-PGA–glycerol conjugate produced previously by B. subtilis C1. However, the γ-PGA–glycerol conjugate dissolved entirely after 30 min in water.