Optimization of flask culture medium and conditions for hyaluronic acid production by a streptococcus equisimilis mutant nc2168

A mutant designated NC2168, which was selected from wild-type Streptococcus equisimilis CVCC55116by ultraviolet ray combined with60Co-γ ray treatment and does not produce streptolysin, was employed to produce hyaluronic acid (HA). In order to increase the output of HA in a flask, the culture medium and conditions for NC2168 were optimized in this study. The influence of culture medium ingredients including carbon sources, nitrogen sources and metal ions on HA production was evaluated using factional factorial design. The mathematical model, which represented the effect of each medium component and their interaction on the yield of HA, was established by the quadratic rotary combination design and response surface method. The model estimated that, a maximal yield of HA could be obtained when the concentrations of yeast extract, peptone, glucose, and MgSO4 were set at 3 g/100 mL, 2 g/100 mL, 0.5 g/100 mL and 0.15 g/100 mL, respectively. Compared with the values obtained by other runs in the experimental design, the optimized medium resulted in a remarkable increase in the output of HA and the maximum of the predicted HA production was 174.76 mg/L. The model developed was accurate and reliable for predicting the production of HA by NC2168.Cultivation conditions were optimized by an orthogonal experimental design and the optimal conditions were as follows: temperature 33ºC, pH 7.8, agitation speed 200 rpm, medium volume 20 mL.

Comparison of Mycobacterial Growth in Dubos Medium, Hyaluronate Supplemented Medium and Umbilical Cord Extract Based Medium

This is a report of attempts to compare the growth yields of various species of fastidious mycobacterium inch1ding human pathogens and non-pathogens in the conventional Dubos liquid medium and two simple media formulated recently; one is a medium containing 0.1% hyaluronic acid and 6.0% bovine serum albumin and the other is a semisyntheic medium made of umbilical cord extract supplemented with 10% sheep serum as a final concentration. All mycobacterial strains employed in experiments gave the heaviest growth yields in the hyaluronic acid-bovine serum albumin medium (HAS medium), among the three media. Dubos liquid medium seemed to be inferior to a medium made of umbilical cord extract (UCE medium) in supporting mycobacterial growth. There were three-to seven-fold increases in dry weight of the bacteria grown in the HAS medium as compared with those in the Dubos liquid medium. We also looked for the possible effect of bovine serum albumin (BSA)in the HAS medium on mycobacterial growth. As a result, we found that the amount of BSA in the HAS medium, ranging from zero to 6.0% in the medium, showed no substantial effect on the mycobacteria1 growth.