Pollutant Removal And Phycocyanin Production In The Cultivation Of Spirulina Platensis By Food Industry Wastewater

The phycocyanin contained in Spirulina platensis is a high-value compound that can be used in food and cosmetics.It also has antioxidant,anti-inflammatory,anticancer and neuroprotective effects.Currently,photoautotrophic culture of Spirulina platensis is the only commercial source of phycocyanin,while it grows slowly and consumes lots of water and nutrients,which makes the production of phycocyanin costly.Food industry wastewater is rich in nutrients,low toxicity and large discharge,suitable for the culture of Spirulina platensis,it helps reduce the production costs of phycocyanin.However,there are few studies combining using food industry wastewater to culture Spirulina platensis with the production of phycocyanin.In this study,6 methods were used to extract phycocyanin crudely from Spirulina platensis,and the type of extraction agent,operation frequency and operation time were optimized.The growth of Spirulina platensis,the removal efficiency of pollutants in molasses fermentation wastewater,and the production of phycocyanin was the evaluation standards of screening the cultivation of Spirulina platensis FACHB314,FACHB439 and FACHB791 in molasses fermentation wastewater and pH optimization.As an extractant,phosphate buffer is better than water mostly.The optimal operating conditions of each phycocyanin crude extraction method are,vortex shaking: 2 shaking;swelling: 16 h;freezing-thawing: 6 freezing-thawing;ultrasonic: 480 W,continuous ultrasound for 15 minutes;ultrasonic+swelling: ultrasonic power 480 W,continuous ultrasound for 15 minutes,swelling 16 h;ultrasonic+freezingthawing: ultrasonic power 480 W,continuous ultrasound for 15 minutes,freezingthawing 8 times.During the operation of the vortex shaking,the temperature of extract rise rapidly,which could lead to denaturation and inactivation of phycocyanin,therefore,it was not used in this experiment.The composite methods are better than the single method,and the ultrasonic+swelling method is the best.Among all processes,the ultrasonic with swelling method is the best for the extraction of phycocyanin from Spirulina platensis.Its optimal process parameters are: ultrasonic power 480 W,continuous ultrasound 15 min,swelling 16 h.Spirulina platensis carried out mixotrophic growth in simulated molasses wastewater.Although there was microbial contamination throughout the cultivation cycle,Spirulina platensis maintained dominant in wastewater systems.FACHB314 grew best,with max biomass concentration,specific growth rate and biomass productivity of 2.13 ± 0.01 g/L,1.14 ± 0.02 d-1 and 0.59 ± 0.003 g/L/d,respectively.Spirulina platensis has excellent ability to remove ammonia nitrogen and nitrate nitrogen in molasses fermentation wastewater,while its ability to remove chemical oxygen demand and phosphate phosphate are ordinary.Nitrogen and phosphorus in wastewater are effectively recovered.Taken together: FACHB314 has the best treatment effect on wastewater,which is 82.11 ± 0.13%(chemical oxygen demand),99.75 ± 0.06%(ammonia nitrogen),94.71 ± 0.08%(nitrate nitrogen)and 78.51 ± 0.04%(phosphate phosphate).The content,purity and productivity of phycocyanin in Spirulina platensis reached the maximum during the nitrogen depletion;FACHB314 had the highest content,purity and productivity of phycocyanin,which were 4.42 ± 0.07%,0.37 ± 0.02 and 28.0 ± 0.73 mg/L/d,respectively.FACHB314 is the best algae strain for treating molasses wastewater and producing phycocyanin.When the pH ranges 8.5-9.0,the growth of FACHB314,the removal efficiency of pollutants and the production of phycocyanin are the best.The max biomass concentration,specific growth rate and biomass productivity were 4.27 ± 0.01 g/L,2.17 ± 0.11 d-1 and 1.37 ± 0.03 g/L/d,respectively.The removal efficiency of chemical oxygen demand,ammonia nitrogen,nitrate nitrogen and phosphate phosphorus were 83.78 ± 0.26 %,94.68 ± 0.79 %,99.29 ± 0.08% and 96.86 ± 1.60 %,the minimum concentration was 381.24 ± 6.04 mg/L,0.81 ± 0.07 mg/L,5.32 ± 0.04 mg/L and 0.72 ± 0.03 mg/L.The pH optimization enhance the removal efficiency of phosphate phosphorus in wastewater significantly;FACHB314 recovered more than 85% of nitrogen and almost all of the phosphorus removed from wastewater.The highest content,purity and productivity of phycocyanin were 5.53 ± 0.26 %,0.34 ± 0.01 and 71.74 ± 4.24 mg/L/d,respectively,and the phycocyanin productivity was more than doubled compared with before.The pH ranging 8.5-9.0 is the best solution.