Using Seawater And Monosodium Glutamate Wastewater To Cultivate Freshwater Algae And Produce Biomass At Scale

Microalgae,as a kind of renewable biological resource,has attracted extensive attention that have the competitive advantages of short doubling time,high photosynthetic efficiency and strong environmental adaptability.However,due to the high production cost of freshwater resources and chemical nutrients,the industrial development and application of microalgae bioenergy are restricted.It has become a hot research topic that cultivates microalgae with high density and lipid content at low cost and on a large scale.In recent years,the cultivation of microalgae with abundant seawater has become a new breakthrough in the field of microalgae bioenergy.Using abundant seawater for cultivating microalgae saves freshwater.However,seawater has low nitrogen,phosphorus content and high salinity which makes it difficult to cultivate microalgae directly.Therefore,it is crucial to seek cheap nutrient source and salt-tolerant microalgae in seawater.In this study,two kinds of low-proportion wastewater were added into seawater:anaerobically digested effluent from kitchen waste(S+ADE-KW)and monosodium glutamate wastewater(S+MSG)to culture Scenedesmus sp.SDEC-8,Golenkinia sp.SDEC-16 and Chlorella Sorokiniana SDEC-18.The study mainly investigated the growth characteristics,cell morphology and photosynthetic system changes of freshwater microalgae under the cultivation conditions of seawater with different wastewater.The response of main metabolites of freshwater microalgae was analyzed,and the production process of cultivating freshwater microalgae was established with seawater added low proportion of wastewater.The size of cylindrical photobioreactor was optimized and the feasibility of large-scale cultivation of freshwater microalgae by seawater was clarified.The main studies and conclusions reached in the present study are as follows:(1)Morphology and pigment changes revealed that spherical,single-celled SDEC-16 and SDEC-18 had better adaptation to the seawater-based media than multiple-celled SDEC-8.The highest biomass of SDEC-16 and SDEC-18 was in S+MSG medium which achieved 0.76 g/L and 0.80 g/L,respectively;the highest biomass of SDEC-8 was in BG11 medium which was 0.47 g/L.(2)Due to the salt stress from seawater,the lipid productivities of SDEC-16 and SDEC-18 obtained 47.99 and 35.90 mg/L/d in S+MSG,respectively.In addition to lipid,the protein of SDEC-16 and SDEC-18 might be potential biomass resources that could attain 13.11 and 18.09 mg/L/d in S+MSG.(3)Compared to S+ADE-KW,more suitable phosphorus concentration(5.51 mg/L)and lower free ammonia concentration(11.48 mg/L)in S+MSG were the main influencing factors for higher biomass concentration and lipid yield of SDEC-16 and SDEC-18.(4)When the size of the cylindrical reactor was optimized to 20 cm in diameter and 2 m in height,the maximum biomass concentration and productivity of SDEC-16 were 2.08 g/L and 0.25 g/L/d by adding monosodium glutamate wastewater to seawater,respectively.Compared with carbohydrate and protein production,lipid was the dominant metabolite of SDEC-16.The lipid content and productivity by adding monosodium glutamate wastewater to seawater were 60.50%and 98.99 mg/L/d,respectively.This study proved that the spherical,single-celled Golenkinia sp.SDEC-16 and Chlorella sorokiniana SDEC-18 had better adaptability to seawater medium.Adding low proportion of monosodium glutamate wastewater into seawater to cultivate Golenkinia sp.SDEC-16 could achieve low-cost,large-scale and stable production of biomass with high density and high lipid content,and has positive significance for the development of microalgae bioenergy field.