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KMID : 1094720090140060775
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Biotechnology and Bioprocess Engineering
2009 Volume.14 No. 6 p.775 ~ p.780
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Antibiotic Production by a Marine Isolate (MS 310) in An Ultra-low-speed Rotating Disk Bioreactor
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Sreyashi Sarkar
Joydeep Mukherjee
Debashis Roy
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Abstract
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Actinomycin-D production by a biofilm-forming estuarine isolate viz. Streptomyces sp. MS 310 is studied in smallscale shaken cultures, as well as in a 25 L rotating disk bioreactor, (RDBR) which, when operated at a disk rotational speed of 1 revolution/day with 50% disk submergence, mimics the intertidal conditions of the microbe뭩 niche estuarine habitat- alternating 12 h periods of inundation and exposure. The ideal pH and temperature for antibiotic production are determined (pH 10, 30oC) through a designed experimental study using shaken flasks. Subsequently, operating conditions in the RDBR are investigated employing a 3n experimental design wherein each of two (n = 2) parameters 翟? aeration and disk submergence are considered at three levels 翟? high, medium, and low: 9.0, 6.0, and 3.0 L/min for aeration rate; and 75, 50, and 25% for disk submergence, (while maintaining the rotational speed at 1.0 rev/day). The niche-mimic condition along with maximum permissible aeration is found to be most favorable for antibiotic production - peak antibiotic activity (PAA) and peak activity attainment rate (PAAR) simultaneously attaining their highest values: 40 mm and 2.13 mm/h, respectively. Both PAA and PAAR increase with increasing aeration at all operating conditions examined - particularly, at the niche-mimic condition, a threefold increase in aeration rate (3~9 L/min) causes PAA to increase by 33%, whereas PAAR increases by 2.5 times, thus pointing to the strong aeration dependence of this actinomycin-D producer. Again, compared to the best values obtained in the 500 mL shaken flask experiments, corresponding RDBR values are 16% higher for PAA and more than 5 times higher for PAAR - strong evidence for employing these novel bioreactors for cultivation of antibiotic-producer marine microbes.
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KEYWORD
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actinomycin-D, niche-mimic, rotating disk bioreactor, productivity
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