Acid casein whey (ACW) is a nutrient-rich by-product of the dairy industry, with low pH, high lactose and mineral content, but its low pH represents a challenge with limited valorisation options. This study investigated the potential of ACW as a feedstock for the growth of Chlorella sp. BB-32, a marine microalga isolated from the Irish coast. Growth experiments were conducted at different heat-treatment and pH-adjustment conditions to optimise biomass production, while simultaneously monitoring the chemical oxygen demand (COD). The ACW substrate, initially at pH 4.69 with high amounts of lactose (31.68 ± 0.05 g/L) and citric acid (41.91 ± 0.16 g/L), was subjected to six pre-treatment protocols, including pH neutralisation and heat treatments ranging from 65 °C to 121 °C. Among these, ACW adjusted to pH 7.5 and heat-treated at 89 °C for 10 min supported the highest microalgal growth, resulting in significant pigment accumulation and biomass productivity. In scale-up experiments, the same pre-treatment conditions resulted in a biomass yield of 1.62 ± 0.08 g/L after 14 days, with total protein, carbohydrate, and lipid amounts reaching 34.77%, 24.2%, and 18.9% of dry weight biomass, respectively. Lipid analysis revealed valuable fatty acids, including oleic, stearic, and linolenic (α + γ) acids, suggesting potential for nutraceutical applications. A COD reduction of 24.5% was achieved, highlighting the bioremediation potential of the microalga. These results demonstrate the feasibility of using Chlorella sp. BB-32 for simultaneous valorisation and remediation of ACW, offering a sustainable route for integrating microalgal biotechnology into dairy waste management and circular bioeconomy frameworks. • Chlorella sp. BB-32 grew on heat treated (89 °C) Acid Casein Whey. • Significantly higher biomass obtained in pre-treated Acid Casein Whey (ACW). • Pre-treated ACW supported Chlorella sp. BB-32 growth better than ASN-III medium. • COD reduction of 24.5% was demonstrated in ACW by Chlorella sp. BB-32. • Chlorella sp. produced important FAs with nutraceutical benefits.
Surana et al. (Fri,) studied this question.