Study On Screening Of Daptomycin Producing Strains And Fermentation Conditions Of Optimization

Daptomycin is a new type composed of multiple amino acids lipid peptide antibiotics, it is produced by Streptomyces roseosporus, and its activity limited to gram-positive organisms, including anaerobic bacteria and enterococcus resistant bacteria, especially the antibiotic-resistant bacteria such as staphvlococcus aureus(MRSA), vancomycin-resistant enterococci(VRE), and has a broad application prospect in medicine.In this paper, optimization of fermentation conditions for screening of high yield strains as the main purpose, breeding of production strains, shake flask, 50 L fermentation medium optimization are studied, we got the following conclusions:1. Streptomyces roseosporus DT-04-11 was used as an original strain. A mutant strain DT-117 was screened out by using ultraviolet mutagenesis and streptomycin resistant breeding. The production of A21978 C was 6952μg/mL, and the strain is genetically stable.2. Through shaking flask experiment, we got the initial seed and fermentation culture medium formula. Seed culture medium formula: maltodextrin 5%, glucose 2%, soybean flour 2%, six hydrated ferrous sulfate 0.1%, ammonia 0.1%, defoaming agent0.1%.pH7.0.Fermentation culture medium formula: maltodextrin 20%, yeast powder 4%, six hydrated ferrous sulfate 0.1%, ammonia 0.1%, defoaming agent 0.1%,pH7.5.3. Through the experiment exploration, 50 L automatic fermentation tank fermentation conditions were determined as follows:Using the optimized medium formula, medium load 30 L, seeds of age for 36 h, quantity of 10%, ventilation 1:1(v:v), control the DO the process in 25~50%, precursor adding time for 25 to 30 h fermentation, adding flow is 0.25 to 0.3 mL/h, fermented liquid culture 8~9 days, using ammonia fermentation process control pH around 7.5.