Tetracycline production with sweet potato residue by solid state fermentation

Abstract For saving energy in antibiotic production and reducing the amount of agricultural wastes, solid state fermentation was used in this study to produce tetracycline with sweet potato residue by Streptomyces viridifaciens ATCC 11989. It was found that the optimal media for tetracycline production were sweet potato residue 100 g, organic nitrogen (rice bran, wheat bran, or peanut meal) 20 g, (NH 4 ) 2 SO 4 2.4 g, KH 2 PO 4 0.4 g, CaCO 3 1.8 g, NaCl 0.6 g, MgCl 2 0.8 g, soluble starch 10 g, methionine 0.2 g, histidine 0.8 g, and monosodium glutamate 1.6 g with initial moisture content 68–72%, and initial pH 5.8–6.0. Each gram of dry weight substrate was inoculated with 1.0 × 10 8 conidia and incubated at 26°C for 5–7 days, producing 4720 μg of total tetracycline equivalent potency. When incubated at 26°C with the initial moisture content 68%, the conidia in solid media germinated on the second day, mycelia grew abundantly on the third day and reached stationary phase on the sixth day. The antibiotic production was consistent with the morphogenesis of S. viridifaciens : activity could be detected on the third day, had the maximal potency on the sixth day, and decreased slightly on the tenth day. (11‐3‐88 tly).