Sensitivity And Biodegradation Of Spirulina Plantensis To Silfa Antibiotics

Sulfonamides (SAs), as one kind of broad spectrum antimicrobial drug, play a major role in livestock industries, aquaculture industries and pharmaceuticals industries. These drugs are widely used as specific therapeutics and prophylactics and growth promoters in animal feed. SAs are harmful to the bacteria, single-cell algae, invertebrates, plants and fish act as competitive inhibitors of p-aminobenzoate in folate biosynthesis, even destroy the balance of the ecosystem.Photosynthetic algae, exiting at the beginning of the food chain, can provide essential nutrition in its simplest form for the survival of fish and invertebrates in most aquatic ecosystems, its species diversity and primary production immediately affect the function and structure of aquatic ecosystems. In conclusion, photosynthetic algae are of great significance in aquatic ecosystems. In the mean time, algae are used in a biological indicator for monitoring and evaluating water quality. The major aim of the present study is to preliminarily investigate the toxicity of SAs towards Spirulina platensis, along with the feasibility of SAs removal by Spirulina platensis in waste water. The experimental results showed that:(1) Spirulina platensis was cultivated in Zarrouk culture medium. The algae were in the logarithmic phase of growth at the beginning of the experiment and reproduced at very rapid rates. The results showed that the activity of Spirulina platensis was damaged seriously by exposure to continuous light, even gone to dead quickly. However, the growth of Spirulina platensis was not increased by continuous dark exposure, but its activity was keep. In other word, the normal growth of Spirulina platensis was the best under a regular alternative light-dark regimen (12h light and12h dark). The pH constantly increased with incubation times, which in the culture medium with Spirulina platensis rised faster than without Spirulina platensis. Moreover, the pH rate of change had nothing to do with the initial cell concentration, depending on the rate of Spirulina platensis growth.(2) The growth-inhibition effect of SAs was investigated with Spirulina platensis. In acute toxicity tests, the results showed that the growth of Spirulina platensis was observably stimulated by low concentrations of sulfadiazine (<4mg/L), then the inhibition appeared gradually with the increasing of concentrations. One of the most remarkable things was that sulfamethazine and sulfamethoxazole had pernicious effect on Spirulina platensis growth at lower concentrations (>0.4mg/L). The inhibition of chlorophyll a contents of Spirulina platensis was dependent on the concentrations of sulfadiazine, sulfamethazine and sulfamethoxazole, the higher the concentration the stronger the inhibition. In contrast, the inhibition of chlorophyll a contents of Spirulina platensis enlarged at first and reduced thereafter, and the summit was at the48h, showing a typical "bell" curves, suggesting an adaptive response of Spirulina platensis to the sulfadiazine, sulfamethazine and sulfamethoxazole. Our results revealed that the effect on specific growth rate constant was similar to chlorophyll a contents of Spirulina platensis. EC50in48h of sulfadiazine, sulfamethazine and sulfamethoxazole was12.10mg/L,6.06mg/L and5.33mg/L respectively, declined with the number of1-octanol-water partition coefficient (-0.08,0.26and0.89) rising.(3) The removal rate of sulfadiazine, sulfamethazine and sulfamethoxazole was4.42%,3.50%and7.24%higher in the culture solution with Spirulina platensis than that of without of Spirulina platensis in96h, respectively. Besides, the constant of sulfadiazine, sulfamethazine and sulfamethoxazole removal rate with Spirulina platensis in the nutrient solution was1.29×10-41/h,3.27×10-41/h and3.55×10-41/h, respectively. However, the value decreased to0.72×10-41/h,1.37×10-41/h and1.35×10-41/h in the absence of Spirulina platensis. This phenomenon implied that Spirulina platensis was able to be more effective in removing the sulfadiazine, sulfamethazine and sulfamethoxazole. The constant of sulfadiazine, sulfamethazine and sulfamethoxazole removal rate was1.79,2.39and2.63times in the culture solution with Spirulina platensis as that of without Spirulina platensis. This showed that Spirulina platensis had certain ability to promote the degradation of sulfadiazine, sulfamethazine and sulfamethoxazole. In the nutrient solution with Spirulina platensis, the first-order degradation rate constant of sulfadiazine, sulfamethazine and sulfamethoxazole increased with the value of the1-octanol-water partition coefficient of sulfadiazine, sulfamethazine and sulfamethoxazole increasing. The results indicated that the stronger the lipophilicity of antibiotic was the easier antibiotic would be removed by Spirulina platensis. If, once inhibition had occurred, the possibility of using Spirulina platensis to biologically remove aqueous sulfadiazine, sulfamethazine and sulfamethoxazole was reduced. Experimental data revealed that Spirulina platensis might enhance the sulfamethazine and sulfamethoxazole removal via degradation and accumulation. Accumulation of sulfamethazine and sulfamethoxazole in the first24h reached the maximum, and then gradually declined over the time. Similarly, bioconcentration factor index (BCF) was higher in24h and then declined from24h to96h. However, a time-dependent study showed that degradation of sulfamethazine and sulfamethoxazole was progressively growing over the time, with the maximum value of degradation in96h. The research result indicated that Spirulina platensis had the potential to degrade sulfadiazine, sulfamethazine and sulfamethoxazole and habitat the environment polluted with sulfadiazine, sulfamethazine and sulfamethoxazole.