Fig 1.
Postulated acarbose biosynthetic pathway.
Glucose and maltose are the carbon sources for acarbose biosynthesis.
Table 1.
Effect of culture medium initial pH on cell growth and acarbose yield during flask fermentation.
Fig 2.
Effect of pH on Streptomyces M37 fermentation.
(A) DCW, (B) specific acarbose content, (C) specific growth rate (μ), (D) specific acarbose production rate (qp), and (E) reducing sugars (glucose and maltose). Experiments were carried out in a 5-L fermentor. NaOH (2 M) and H2SO4 (2 M) were used to buffer the pH. ■ curve 1, pH 6.5; ● curve 2, pH 7.0; ▲ curve 3, pH 7.5; ▼ curve 4, pH 8.0; and ◆ curve 5, pH 8.5. Data correspond to mean ± S.D. (n = 3). Error bars were omitted for clarity.
Table 2.
Effect of the addition of reducing sugars (glucose and maltose) on Streptomyces M37 DCW and acarbose production at pH 8.0 in a 5-L fermentor.
Table 3.
Effect of the maltose-to-glucose mass ratio in the feeding medium on acarbose production by Streptomyces M37 at pH 8.0 in a 5-L fermentor a.
Fig 3.
Effect of a two-stage fermentation strategy on acarbose production by Streptomyces M37.
DCW (★), reducing sugars (■), and acarbose production (▲). Fermentations were carried out at 28°C and 200 rpm agitation speed. Glucose and maltose were fed at a 1:2 mass ratio and pH was adjusted with 2 M NaOH and 2 M H2SO4. Each value represents the mean of three separate determinations ± standard deviation (arrows indicate feeding times).
Table 4.
Effect of culture method on Streptomyces M37 acarbose fermentation in a 5-L fermentor.
Fig 4.
Specific activities of glutamate dehydrogenase (GDH) and glucose 6-phosphate dehydrogenase (G6DPH) during batch fermentation and the two-stage fermentation strategy.
Each value represents the mean of three separate determinations ± standard deviation.