Abstract
Sugar refinery washing water (SRWW) contains abundant levels of carbon sources and lower levels of contaminants than other types of wastewater, which makes it ideal for heterotrophic cultivation of microalgae. Here, carbon sources in SRWW were utilized for conversion into the form of value-added docosahexaenoic acid (DHA) using Aurantiochytrium sp. KRS101. Since SRWW is not a defined medium, serial optimizations were performed to maximize the biomass, lipid, and DHA yields by adjusting the nutrient (carbon, nitrogen, and phosphorus) concentrations as well as the application of salt stress. Optimum growth performance was achieved with 30% dilution of SRWW containing a total organic carbon of 95,488 mg L−1. Increasing the nutrient level in the medium by supplementation of 9 g L−1 KH2PO4 and 20 g L−1 yeast extract further improved the biomass yield by an additional 14%, albeit at the expense of a decrease in the lipid content. Maximum biomass, lipid, and DHA yields (22.9, 6.33, and 2.03 g L−1, respectively) were achieved when 35 g L−1 sea salt was applied on a stationary phase for osmotic stress. These results demonstrate the potential of carbon-rich sugar refinery washing water for DHA production using Aurantiochytrium sp. KRS101 and proper cultivation strategy.
Highlights
Among an estimated total of over 300,000 species of microalgae[1], numerous species have been found to have commercially desirable phenotypes including high biomass production, lipid content, and potential for value-added products[2,3]
The glucose and sucrose concentrations in sugar refinery washing water (SRWW) were measured separately and estimated to be 69,100 ± 930 and 5,050 ± 212 mg L−1, respectively. These results show that SRWW contained sufficient carbon sources to previous researches using 5 to 80 g L−1 of only glucose or combination with fructose, and sucrose for the heterotrophic cultivation of Aurantiochytrium sp
SRWW containing high levels of organic carbon in the form of saccharides was applied to the heterotrophic cultivation of Aurantiochytrium sp
Summary
Among an estimated total of over 300,000 species of microalgae[1], numerous species have been found to have commercially desirable phenotypes including high biomass production, lipid content, and potential for value-added products[2,3]. DHA is a key omega-3 fatty acid that has beneficial health effects, including reducing the risks of human cardiovascular diseases, cancer, schizophrenia, and Alzheimer’s disease[9]. It plays an important role as a structural lipid in cell membranes and it is necessary for proper visual and neurological development in infants[10]. The wastewaters arise from various uses ranging from washing the sugar cane, melting, concentrating, filtering, purifying the sugar and washing the vessel and line This wastewater contains high levels of organic carbons which are in most cases recycled to be used in molasses or yeast production systems[22]. The advantage of using SRWW for low-cost fermentation processes is apparent, though, careful characterization and optimization will be needed for application on specific target strains and products
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