How can microorganisms be used to manufacture alternative (milk) proteins? This can be achieved in two ways, explained Julia Keppler of Wageningen University & Research at the spring congress of the Society for the Advancement of Dairy Science.

The first is the cellular method, in which animal stem cells are incubated to create a type of 'laboratory udder' that produces 'milk'. The other is the acellular method, in which (genetic) microorganisms in a bioreactor are used to convert substrates into new milk proteins”, explained Julia Keppler, Associate Professor of Functionality Driven Protein Processing at WUR. The latter method is also known as precision fermentation.

Stem Cells

As an example of protein produced by stem cells, Keppler referred to recombined β-lactoglobulin (the main whey protein in cows: editor). She compared its properties to the animal variant, through which several variants could be ascertained. The functionality of the variants was determined, and the structure was found to differ from that of cow-derived proteins and those from cells.

Physiochemical and Emulsifying Properties

The physio chemical and emulsifying properties of both types of β-lactoglobulin were also compared and found to be similar. The protein was subsequently purified from a solution containing various reaction products. An example of purification with polyphosphate was demonstrated. Mannans (polysaccharides that yield glucose and mannose on hydrolysis) were still present, but did not affect emulsion stability. This needs to be cost-efficient, but requires further investigation, Keppler noted.

Cheese

Keppler: “It is a matter of whether phosphate is necessary to achieve the structure and/or whether micelles are needed to make cheese. Fat is also needed, and it is a question of whether the isolated proteins are sustainable. A carbon source is needed to produce casein, and chromatography is required to separate the proteins from other reaction products. The process requires further optimisation to make it more sustainable than animal proteins." She believes that this method could offer consumers a choice between animal-produced proteins, plant-based proteins and proteins produced by microorganisms. “However, there is still work to be done in the areas of safety, EU legislation, sustainability and sensory properties", Keppler told us.

www.genootschapmelkkunde.nl and www.wur.nl