The alterations of organic acids citrate, alpha-ketoglutarate, succinate, fumarate, malate production together with isocitrate lyase activity as a glyoxalate shunt enzyme, and antibiotic production of Streptomyces sp M4018 were investigated in relation to changes in the glucose, glycerol and starch concentrations (5-20 g/L) after identification as a strain of Streptomyces hiroshimensis based on phenotypic and genotypic characteristics. The highest intracellular citrate and alpha-ketoglutarate levels in 20 g/l of glucose, glycerol, and starch mediums were 399.47 +/- 4.78, 426.93 +/- 6.40, 355.84 +/- 5.38 ppm and 444.81 +/- 5.12, 192.96 +/- 2.26, 115.20 +/- 2.87 ppm, respectively. The highest succinate, malate, and fumarate levels were also determined in 20 g/l of glucose medium as 548.9 +/- 11.21, 596.15 +/- 8.26, and 406.42 +/- 6.59 ppm and the levels were significantly higher than the levels in glycerol and starch. Extracellular organic acid levels measured also showed significant correlation with carbon source concentrations by showing negative correlation with pH levels of the growth medium. The antibiotic production of Streptomyces sp. M4018 was also higher in glucose medium as was the case also for organic acids when compared with glycerol. On the other hand, there is no production in starch.