Mixotrophic cultivation of green microalga Graesiella emersonii on cheese whey permeate

Mixotrophic cultivation of microalgae using dairy industry by-products as a cheap alternative media offers a sustainable method for dairy industry waste reduction and stimulation of value-added biomass synthesis. Such integration can support the principles of circular economy and promotes environmentally friendly practices within the dairy industry sector. The current study focuses on the mixotrophic cultivation of a newly isolated green microalga Graesiella emersonii MSCL 1718 strain in concentrated cheese whey permeate. It was demonstrated that G. emersonii can successfully grow in whey permeate significantly surpassing the biomass synthesis of photoautotrophic control group cultivated in modified Bold’s Basal medium. Different concentrations of permeate were assessed to determine an optimal media preparation strategy and G. emersonii lactose tolerance levels. It was shown that G. emersonii maintained significant biomass production rates with lactose exceeding 40 g L⁻¹ concentrations in the experimental media. The highest biomass productivity was observed in 20% permeate medium, reaching 0.17 ± 0.02 g L⁻¹ d-1 (dry weight). The results of this study highlight the suitability of G. emersonii for further bioconversion of dairy industry by-products into value-added biomass and commercial products. However, further assessment is required to optimise the biomass production and evaluate the bioconversion rates of various nutrients. Additionally, a pilot-scale assessment of biomass production is crucial for gaining a better understanding of the process and assessing the feasibility of the proposed approach.