A sustainable cultivation of microalgae using dairy and fish wastes for enhanced biomass and bio-product production

In this study, the growth, biomass, and bio-constituents of Chroococcus sp., Haematococcus pluvialis, Dunaliella sp., Coelastrella saipanensis, and Chlorella sp. grown in dairy wastewater and fish waste as nutrients were assessed. As both wastes constitute organic and inorganic nutrients, dairy wastes contain proportionately higher amount of K, Na, and sugars than the fish wastes which contains nitrogen, phosphorus, organic carbon, and protein as nutrients. Algae grown among different dilutions of wastes showed that medium supplemented with 50% dairy waste significantly increased the growth, biomass, carbohydrates, and protein content in algae such as Chroococcus sp., H. pluvialis, C. saipanensis, and Chlorella sp., whereas in Dunaliella sp. by addition of 10% dairy waste showed maximum growth and other bio-constituents, but 50% fish waste used for Chroococcus sp., C. saipanensis, and Chlorella sp. growth medium. A total of 25% fish waste used for Dunaliella sp. and H. pluvialis. The enhanced growth and bio-constitute accumulation in microalgae grown using waste nutrients was further confirmed by increased growth observed in nitrogen-depleted waste supplemented medium over control (only medium). Despite increased growth and bio-constituent accumulation in algae grown by waste nutrients, Chroococcus sp., H. pluvialis, and Chlorella sp. grown by waste nutrients showing significant decrease in chlorophyll content were found as efficient in absorbing waste nutrients by heterotrophic mode. The Chroococcus sp. and Dunaliella sp. grown in dairy waste and Chlorella sp., H. pluvialis, and C. saipanensis grown in fish waste accumulated intracellular non-polar storage lipids identified through fluorescence study were recognised as suitable biorefinery candidates for lipid sequestration by utilizing waste nutrients, besides high value pigments. This study concludes that dairy and fish wastes are cost-effective nutrient resource for enhanced growth, bio-constituents, lipids, and high values pigments accumulation in microalgae as biorefinery.