Effects of glycerol on the production of poly(γ-glutamic acid) by Bacillus licheniformis

The effect of glycerol on poly(gamma-glutamic acid) (gamma-PGA) fermentation was studied. The addition of glycerol as a co-substrate with L-glutamic acid and citric acid enhanced the production of gamma-PGA. The investigation on phospholipid composition of the cell membrane showed that, among the five major phospholipids including phosphatidylethanolamine (PE), phosphatidyl serine (PS), phosphatidic acid (PA), cardiolipin (CL) and phosphatidyl glycerol (PG), the syntheses of PG, PE, PS and CL were greatly influenced by the addition of glycerol. The further investigation of phospholipids ester-linked fatty acids showed that the existence of glycerol in medium caused the obvious decrease in C16:1 and C18:1 fatty acids and the increase in C10:0 and C12:0 fatty acids. It is concluded that the addition of glycerol led to an effective excretion of gamma-PGA resulting from the influences on the synthesis of cell membrane phospholipids and their ester-linked fatty acids. (c) 2004 Elsevier Ltd. All rights reserved.