A strategy of experimental design using a fractional factorial design (FFD) and a central composite rotatable design (CCRD) were carried out with the aim to obtain the best conditions of temperature (20-30 degrees C), agitation rate (100-300 rpm), initial pH (5.0-7.0), inoculum concentration (5-15%), and glucose concentration (30-70 g/l) for glutathione (GSH) production in shake-flask culture by Saccharomyces cerevisiae ATCC 7754. By a FFD (2(5-2)), the agitation rate, temperature, and pH were found to be significant factors for GSH production. In CCRD (2(2)) was obtained a second-order model equation, and the percent of variation explained by the model was 95%. The results showed that the optimal culture conditions were agitation rate, 300 rpm; temperature, 20 degrees C; initial pH, 5; glucose, 54 g/l; and inoculum concentration, 5%. The highest GSH concentration (154.5 mg/l) was obtained after 72 h of fermentation.

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ABSTRACT

In this work, the effects of different carbon:nitrogen (C:N) ratios, carbon source and initial carbon concentration, in liquid medium used for submerged fermentation, on biomass growth, succinic acid production and yield of product in substrate (YP/S) were studied. It was used three carbon sources as substrate such as glucose, xylose and sucrose and the C:N ratios studied were in the range of 2.5-35. The succinic acid production was best at a C:N ratio of 12.5:1, as much for the succinic acid production as for the yield of product in relation to the substrate (YP/S). For the biomass growth the C:N ratios of 2.5:1, 5:1 and 10:1 had only presented significant difference with regards to the too much assays. The substrate that presents the best results was the glucose with succinic acid concentrations up to 7.5 g.L-1.

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