Optimization of microalgae cultivation in food industry wastewater using microplates

The substantial generation of wastewater in the food industry has drawn worldwide attention to biological approaches, particularly microalgae, to enhance wastewater management and promote circular bioeconomy goals. Microalgae convert organic and inorganic nutrients, minerals, and CO 2 into valuable products, depending on cultivation conditions. This study focuses on optimizing bioremediation using microalgae (i.e., Chlorella vulgaris , Nannochloropsis oculata , and Scenedesmus sp.), utilizing a wastewater mixture comprising of brewery wastewater, cheese -whey and expired orange juice. Response Surface Methodology was employed to optimize the mixture proportions, aiming to maximize microalgae growth in microplate cultures. Experimental outcomes elucidated that expired orange juice exhibited the most pronounced influence on the mixture, followed by brewery wastewater. Notably, under optimum conditions, containing 43.5 %, 37.5 %, and 39.5 % expired orange juice, 31 %, 50 %, and 35 % brewery wastewater, 0.5 % cheese whey, and 25 %, 10.5 %, and 25 % water for Chlorella vulgaris , Nannochloropsis oculata , and Scenedesmus sp. respectively, microalgae growth in wastewater surpassed that in synthetic medium. Optical density monitoring revealed growth rate peaks of 1.66, 1.33, and 1.64 for Chlorella vulgaris , Nannochloropsis oculata , and Scenedesmus sp., respectively, validating the precision of the predictive model. When upscaled, cultivations in flasks under the optimal mixture proportions yielded analogous growth kinetics. Furthermore, the microalgae exhibited high removal rates of phosphate, total Kjeldahl nitrogen, ammonium nitrogen, chemical oxygen demand and total organic carbon from wastewater. Specifically, both Chlorella vulgaris and Nannochloropsis oculata achieved removal efficiencies between 80 and 90 %, emphasizing the promising role of microalgae in the remediation and valorization of food industry wastewater while promoting sustainable practices.