Vancomycin antibiotic production and TCA-glyoxalate pathways depending on the glucose concentration in Amycolatopsis orientalis

Abstract

In order to identify the aspects of intermediary metabolism relevant to vancomycin production, the correlation between vancomycin antibiotic production and intra-extracellular tricarboxylic acid cycle (TCA) intermediate products, α-ketoglutarate dehydrogenase and glyoxalate shunt isocitrate lyase activities, all of which play key roles in the carbon metabolism, were investigated depending on the glucose concentration of Amycolatopsis orientalis medium with respect to incubation period. The intracellular levels of citrate, α-ketoglutarate, fumarate and malate, which are TCA pathway intermediates, reached maximum levels on the 36th and 48th hours for 5 and 10–20 g/L of glucose range, respectively. The levels of these intermediates increased with increasing glucose concentrations up to 12.5 and/or 15.0 g/L and decreased at 20 g/L of glucose. On the other hand, the levels of succinate, another TCA intermediate, increased up to 32nd hour for 5 g/L of glucose and 60th hour for the range of 10–20 g/L of glucose. The maximum intracellular citrate, α-ketoglutarate, fumarate, malate and succinate levels were determined as 1205, 702, 865, 2275 and 1269 ppm, respectively. The activity of α-ketoglutarat dehydrogenase, one of the main enzymes of TCA pathway, increased with increasing glucose levels up to 10 g/L of glucose, while the activity of the key enzyme of glyoxalate shunt, isocitrate lyase increased significantly with increase in glucose concentration especially after 36th hour of incubation. The α-ketoglutarate dehydrogenase and isocitrate lyase activities reached maximum levels at the 48th hour and were 172 and 1006 IU/mg, respectively. The continuation of increases in isocitrate lyase activity with decreases in TCA cycle intermediates after 48th hour is an indication of the correlation between TCA and glyoxalate cycles. The highest level of extracellular vancomycin production of A. orientalis in relation with TCA intermediates were determined at 15 g/L of glucose as 7.8 ppm at the 48th hour.