Optimization of fermentation conditions for the anti-cyanobacterial substances production by Streptomyces sp. HJC-D1 using response surface methodology

To investigate the influence of fermentation conditions such as temperature, initial pH, volume and agitation rate on anti-cyanobacterial active substances production, response surface methodology (RSM) was carried out to optimize the fermentation conditions of an anti-cyanobacterium Streptomyces sp. HJC-D1, and the anti-cyanobacterial effect was evaluated. Most common and widespread bloom-forming cyanobacterium Microcystis aeruginosa that is associated with microcystic toxins secretion was used as indicator cyanobacterium. The central composite design (CCD) was applied to evaluate the combined effects of the four factors, that is, temperature, initial pH, volume and agitation rate. Based on the analysis of 30 performed experiments, the best optimum level of operating parameters was 33.1°C for temperature, 11.8 for initial pH, 91.2 mL for volume and 337.5 rpm for agitation rate. Additionally, the maximum removal efficiency of chlorophyll a under the optimized culture conditions in flask cultures was 93.7%. It is noteworthy that the yield of the anti-cyanobacterial active substances produced by Streptomyces sp. HJC-D1 was significantly improved using response surface methodology and suggested the potential to develop a commercial biological control agent against M. aeruginosa.