Abstract
The production of rifamycin B using the gene amplified variant of Amycolatopsis mediterranei (NCH) was initially optimized in shake flasks through medium modifications and fed-batch addition of uracil. The yield was increased by 21.7% (from 11.7 to 14.3 g/l) when F2m1 medium was used. The production was further verified and optimized in fedbatch- mode in a laboratory fermentor using F2m3 medium and the optimized conditions (agitation 500 rpm, aeration; 1.5 for 3 days then control DO at 30% thereafter, pH; 6.5 for 3 days then 7 thereafter and control temperature at 28°C). Fed-batching of glucose syrup (5% v/v at day 3) and glucose (1% at days 6 and 8) increased the yield from 17.8 to 20.9 g/l (17.3%) at day 10. A yield of upto 20 g/l was recorded when 0.1% uracil was fed-batched at day 2. Integration of the most optimum conditions for fed-batching glucose syrup, glucose and uracil further increased the yield from 17.8 to 24.8 g/l (39%) in 10 days. The overall optimization of rifamycin B production increased the yield almost 2 folds. Statistical analysis revealed that there is a significant increase in rifamycin B production by using One-Way ANOVA at p<0.05 in all the tested fed-batch addition regimes.
Highlights
Fermentation media, cultural conditions and operation modes are the most important factors in a production process, providing the main environment of the organism
In case of rifamycin B production, the consumption of the reducing sugar is common in the stationary phase the mycelium growth almost stopped
This consumption is usually directed for rifamycin B biosynthesis and mycelium maintenance; fed-batching of carbon source such as glucose to maintain the reduced sugar at 1-1.5% is recommended [3]
Summary
Fermentation media, cultural conditions and operation modes are the most important factors in a production process, providing the main environment of the organism. Media composition especially with the critical components shall be optimized to produce the maximum yield of product and minimal yield of undesired products In these regards, fed-batch fermentation is an important operation mode to optimize and increase the productivity of secondary metabolites, such as antibiotics [2]. In case of rifamycin B production, the consumption of the reducing sugar is common in the stationary phase the mycelium growth almost stopped This consumption is usually directed for rifamycin B biosynthesis and mycelium maintenance; fed-batching of carbon source such as glucose to maintain the reduced sugar at 1-1.5% is recommended [3]. The addition of organic nitrogen compounds is generally recognized to be essential for high yields of rifamycin B production by serving either as a precursor or stimulant for antibiotic biosynthesis [4]
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