The effect of glycerol on poly(g-glutamic acid) (g-PGA) fermentation was studied. The addition of glycerol as a co-substrate with Lglutamic acid and citric acid enhanced the production of g-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 g-PGA resulting from the influences on the synthesis of cell membrane phospholipids and their ester-linked fatty acids. # 2004 Elsevier Ltd. All rights reserved.

Dissolved oxygen (DO) concentration is one of the most important environmental factors affecting cell growth and product formation. The effect of different DO concentration produced by changing the agitation speed or aeration rate the on batch production of microbial transglutaminase (MTG) with Streptoverticillium mobaraense was studied. Based on the kinetic analysis of the batch fermentation process, a two-stage agitation speed control strategy was developed, in which the agitation speed was controlled at 450 rpm in the first 24 h to achieve a DO level of up to 35%, and then switched to 350 rpm after 24 h to maintain a DO level at 15-25%. By applying this two-stage agitation speed control strategy in MTG fermentation, the maximal MTG activity and productivity reached 3.32 U/ml and 83.0 U/(l h), respectively, which were 15.3% higher than the best results in which the agitation speed was controlled at 350 rpm (2.88 U/ml and 72.0U/(lh)).

Acetic acid, propionic acid, lactic acid, butyric acid, and a kind of the mixed four were used as carbon sources for Ralstonia eutropha to biosynthesize polyhydroxyalkanoates (PHAs) in this study. Lactic acid was used up the first among the four organic acids, acetic acid, butyric acid and propionic acid subsequently. Furthermore, acetic acid was produced when propionic acid was used as carbon source for the biosynthesis of PHAs by Ralstonia eutropha, and which was never reported before. In the fed-batch culture, the mole rate of HV component of the PHAs were relatively lower than that of the batch culture, however, the maximum yield of dry cell weight (DCW) and PHAs increased.

筛选和分离得到的多株脱氮微生物,能在完全好氧条件下将氨氮转化为NO2-，随即在好氧反硝化菌的作用下还原为N排放，整个生物脱氮过程历时较短，30h内对200mg/L的氨氮去除率达99%，而且无中间产物NO2-的积累。混合脱氮微生物菌群生长的适宜pH范围为7～10，探索实现混合脱氮微生物菌群高密度培养的pH: 发酵前期补酸控制pH≤8，发酵中后期不控制pH值，可缩短菌体的生长周期，提高菌体的氨氮降解速率。细胞质量浓度达3.9g/L，比自然pH条件下提高了62.5%.