Valorisation of Whey Permeate in Sequential Bioprocesses towards Value-Added Products–Optimisation of Biphasic and Classical Batch Cultures of Kluyveromyces marxianus

Whey permeate is categorised as hazardous wastewater for aquatic environments, mainly due to its high lactose content. Therefore, it must be valorised before being released into the environment. One pathway for whey permeate management is its use in biotechnological processes. Herein, we present roads for whey permeate valorisation with the K. marxianus WUT240 strain. The established technology is based on two bioprocesses. During first, 2.5 g/L 2-phenylethanol and fermented plant oils enriched with different flavourings are obtained after 48 h biphasic cultures at 30 °C. The second process leads to a maximum of 75 g ethanol/L (Y(P/S) = 0.53 g/g) after 96 h at 30 °C. Moreover, established whey permeate valorisation pathways reduced its biochemical oxygen demand and chemical oxygen demand values by 12- to 3-fold, respectively. Together, the present study reports a complete, effective, and environmentally friendly whey permeate management strategy while simultaneously enabling the acquisition of valuable compounds with substantial application potential.