Most industrial enzymes today are produced from batch fermentation using organisms including various fungi, bacteria and yeasts. During fermentation, the microorganisms multiply in industrial bioreactors and the enzyme is typically excreted into the culture medium (extracellular).
After fermentation, extraction and purification are important steps for enzyme recovery from the biomass. In this first step, the fermenter broth is clarified to remove the spent cells and other suspended solids from the fermenter contents. The steps and clarification techniques employed will depend on the nature of the enzyme and the desired purity.
Enzyme Extraction and Purification
After fermentation, the liquid broth contains a high density of microorganisms that must be separated from the liquid phase containing the enzyme (and others dissolved solids). This separation step is called fermentation broth clarification and consists of a physical separation of suspended solids from the liquid phase. The two main solutions industrially applied for fermentation broth clarification are centrifugation and filtration.
Centrifugation produces a concentrate of suspended solids in the range of 10 to 15% dry suspended solids and a clarified stream still containing some haze and residual microorganisms. The level of clarification depends on the centrifuge design and the rotational speed of the bowl or plates.
The centrifuge overflow needs to be further clarified to remove residual suspended solids to protect downstream processing steps. This can be achieved using traditional technologies like depth filter media or by filtration through filter aids, like Diatomaceous Earth filters.
Alternatively, modern methods are also available for fermentation broth clarification using crossflow filtration in a single step. Advantageously, this solution is a fully enclosed process and highly automated, offering a physical barrier to prevent microorganisms from leaching into the filtrate.
Moreover, due to the high permeate quality, the final enzyme liquid concentrate can be delivered with much lower concentration of preservatives resulting in a higher selling price.