Use of date products in production of oxytetracycline by Streptomyces rimosus

The use of date waste for lactic acid production by a fed-batch culture using Lactobacillus casei subsp. rhamnosus

The production of lactic acid from date juice by Lactobacillus caseisubsp. rhamnosus in batch and fed-batch cultures has been investigated. The fed-batch culture system gave better results for lactic acid production and volumetric productivity. The aim of this work is to determine the effects of the feeding rate and the concentration of the feeding medium containing date juice glucose on the cell growth, the consumption of glucose and the lactic acid production by Lactobacillus casei subsp. rhamnosus in fed-batch cultures. For this study, two concentrations of the feeding medium (62 and 100 g/L of date juice glucose) were tested at different feeding rates (18, 22, 33, 75 and 150 mL/h). The highest volumetric productivity (1.3 g/L.h) and lactic acid yield (1.7 g/g) were obtained at a feeding rate of 33 mL/h and a date juice glucose concentration of 62 g/L in the feeding medium. As a result, most of the date juice glucose was completely utilised (residual glucose 1 g/L), and a maximum lactic acid production level (89.2 g/L) was obtained.

Enhancement of oxytetracycline production after gamma irradiation-induced mutagenesis of Streptomyces rimosus CN08 strain

Streptomyces rimosus CN08 isolated from Tunisian soil produced 8.6 mg l(-1) of oxytetracycline (OTC) under submerged fermentation (SmF). Attempts were made for enhancing OTC production after irradiation-induced mutagenesis of Streptomyces rimosus CN08 with Co(60)-γ rays. 125 OTC-producing colonies were obtained after screening on kanamycin containing medium. One mutant called Streptomyces rimosus γ-45 whose OTC production increased 19-fold (165 mg l(-1)) versus wild-type strain was selected. γ-45 mutant was used for OTC production under solid-state fermentation (SSF). Wheat bran (WB) was used as solid substrate and process parameters influencing OTC production were optimized. Solid-state fermentation increased the yield of antibiotic production (257 mg g(-1)) when compared with submerged fermentation. Ammonium sulphate as additional nitrogen source enhanced OTC level to 298 mg g(-1). Interestingly, OTC production by γ-45 mutant was insensitive to phosphate which opens the way to high OTC production even in medium containing phosphate necessary for optimal mycelia growth.