These compound concentrations were established according to the purpose of each experiment. Experimental procedure Spore germination and inoculum preparation consisted of two pre-cultures with 24-hour cultivation each in shake flasks. Inoculum volume comprised 10% of suspension cell volume per culture medium volume throughout this study. Submerged cultures for cephamycin C production were selleck compound performed Cilengitide in 500 ml Erlenmeyer
shake flasks at 28°C and 260 rpm (5 cm eccentricity). To prevent problems of oxygen limitation during the shake-flask procedure, the broth volume was kept under 10% of the Erlenmeyer flask nominal volume. Samples were collected at 24-hour intervals. Experiments in the bench-scale bioreactor (New Brunswick Bioflo 2000; 5 l working volume) were performed at 1.0 vvm aeration rate, 6.8 ± 0.1 pH, 28°C temperature, and 50% dissolved oxygen saturation level automatically
controlled by varying the agitation speed. Analytical methods The supernatant was obtained after centrifugation of the culture medium at 15,550 x g for 10 min, 4°C, for further analyses. The cell density was quantified as grams Selleck KPT-8602 of dry weight per liter of sample (gDWC l-1). Cephamycin C was determined by means of the agar-diffusion assay method using cephalosporin C zinc salt (Sigma) as standard. Penase® (BD Difco) was employed at 20 μL per ml of sample, reacting at 25°C for 20 min to degrade penicillin N. In this method, the measure of cephamycin C represents the total amount of cephalosporins in the sample (in mg l-1) . A calibration curve was performed using ten cephalosporin C concentration values from 5 to 120 mg l-1 and 24 replicates for each concentration. Antibiotic analyses were also carried out via high-performance liquid chromatography as described in Baptista
Neto et Acetophenone al. . Lysine and alpha-aminoadipic acid analyses were conducted by means of the post-column derivatization method with orthophtalaldehyde and quantified in a fluorescence detector . The starch concentration was determined after acid hydrolysis, by quantifying the total reducing sugars by the dinitrosalicylic acid method . Experimental design CCF experimental designs, including four replicates of an experiment under the same conditions, were employed to investigate individual and combined effects of lysine and compounds, one at a time, putrescine, 1,3-diaminopropane, cadaverine, and alpha-aminoadipic acid, on cephamycin C production. The response surface methodology was used to investigate the relationship between cephamycin C production (response variable) and the compounds that enhance beta-lactam antibiotic production (independent variables) [40, 41].