Enhanced Antimicrobials Production by Streptomyces sundarbansensis sp. nov. in a Novel Extended Surface Biofilm Reactor

A newly designed extended surface biofilm reactor (ESBR) with an inner configuration consisting of eight equidistantly spaced polymethylmethacrylate rectangular strips placed radially on a circular disk to provide additional surface area for microbial growth was used for antimicrobials production by the biofilm-forming marine isolate Streptomyces sundarbansensis sp nov.. Antimicrobials production by Streptomyces sundarbansensis sp nov. is studied in small scale polymethylmethacrylate conico-cylindrical flask (PMMA-CCF), as well as in a 4.2 L ESBR. The best pH and temperature for antimicrobials production are determined (pH 10, 30C) through a designed experimental study using PMMA-CCF. Consequently, operating conditions in the ESBR are studied using a 3 experimental design wherein each of two (n = 2) parameters viz. aeration and inner configuration submergence are considered at three levels viz. high, medium, and low: 0.75, 0.50, and 0.25 L/min for aeration rate; and 75, 50, and 25 % for inner configuration submergence, (while maintaining the rotational speed at 140rpm). The 50% submergence condition together with maximum permissible aeration is found to be most favorable for antimicrobials production peak antimicrobial activity (PAMA) attaining its highest value, 47 mm. PAMA increases with increasing aeration at all operating conditions studied particularly, at 50% submergence condition, a threefold increase in aeration rate (0.25~0.75 L/min) causes PAMA to increase by 74%, thus showing the strong aeration dependence of this antimicrobials producer. Again, compare to the best values obtained in the 420 mL PMMA-CCF experiments, corresponding ESBR value is 15% higher for PAMA – strong evidence for applying this novel bioreactor for cultivation of antimicrobial-producing marine microbes.