Production of algal biomass, chlorophyll, starch and lipids using aquaculture wastewater under axenic and non-axenic conditions

Although co-cultivation of algae with aquaculture products has the potential to reduce water use and pollutant discharges while producing energy feedstocks and other end-products, little research has been carried out in this area. Maintaining axenic conditions (algal monocultures without other microorganisms) in algal culturing systems using aquaculture wastewater as a nutrient source would not be practical. This study examined the effects of the use of aquaculture wastewater as a nutrient source on biomass development of three algae cultures (indigenous mixed species consortium, Chlorella sp. and Scenedesmus) under axenic and non-axenic conditions. Biomass development was assessed by cell growth, chlorophyll, starch and lipid production. The presence of aquaculture microorganisms decreased biomass productivity in Chlorella but not in the other algae cultures. Non-axenic conditions had no effect on overall starch and chlorophyll production; however, significantly higher lipid contents were achieved under non-axenic conditions for Chlorella and the indigenous culture. The higher algal lipid content for these cultures under non-axenic conditions may have been due to competition with bacteria for nutrients. The presence of bacteria was required for effective removal of organics, while effective nitrogen removal was observed in all systems containing algae. Results from this study also show that algae harvesting should be timed to coincide with the peak production of the desired target end-product (biomass, chlorophyll, starch or lipid). (C) 2014 Elsevier B.V. All rights reserved.