A short abstract of the doctoral research

Global protein demand is increasing, but animal protein production remains resource-intensive and environmentally damaging. Microbial protein offers a more sustainable alternative because it can be produced without agricultural land and can convert low-value industrial side streams into valuable biomass.

This dissertation examines how cheese whey permeate —a low-value dairy by-product—can be upgraded into microbial protein through either direct lactose utilization or a two-step process with lactic acid fermentation as intermediate process. Cheese whey permeate can be efficiently fermented into lactic acid under non-sterile conditions and that using lactic acid as an intermediate improves biomass and protein yields, compared to lactose. Techno-economic and environmental assessments indicate that the two-step process is both cheaper and has a lower environmental footprint, especially when implemented close to dairy producers to avoid transport costs. Moreover, resource efficiency can be improved by recycling nitrogen-rich side streams, such as heat-treatment centrate produced during nucleic acid reduction, which reduces the need for external nitrogen sources. Overall, cheese whey permeate can be efficiently converted into microbial protein following appropriate process optimisation.