Recovery

The purpose of the recovery process is to separate the enzyme from the biomass and to produce a solution that contains the enzyme at a purity that can be used for formulation of the final product.

Recovery processes are designed to handle large product volumes in a fast and cost-effective way. To ensure this Novozymes has state-of-the-art pilot plants where suitable methods are developed before we scale up the processes to production.
 
Recovery
 
 
The type and sequence of unit operations are selected so that the product reaches the desired quality with a high enzyme yield and low production costs. An expert’s description can be found here.
 

The main factors that influence the design of an enzyme recovery process are:

 
1. The properties of the production organism
2. The characteristics of the enzyme
3. Product quality demands
4. The type of product to be produced
5. The environmental impact of the process

Influence of the production organism   

Almost all our enzymes are produced by submerged fermentation of a microorganism.
The type of production organism (bacterium or fungus) has a major impact on the design of the process, and even within the two types of producer hosts there are significant differences. Primarily, the difference in size of the microorganisms is an issue, but the differences in the composition of the fermentation media, for example well defined versus complex, will also influence the design of the processes. 
 
 

Enzyme characteristics 

Most enzymes are monocomponents, meaning that only one enzyme protein contributes to the overall activity. In a few cases the enzyme product can be a multicomponent mixture of several enzyme proteins. In these cases the recovery process must be designed to ensure that the ratio between the enzyme proteins important for the application is maintained throughout the recovery process.
 
The properties of the enzyme have an impact on the design of the conditions for the recovery process, especially characteristics like temperature and pH stability, solubility of the enzyme protein, and hydrophobicity. The enzyme activity as a function of pH and temperature also influences the choice of process conditions. When processing proteases, for example, it can be advantageous to select process conditions where the enzyme has low activity in order to avoid self-digestion (autoproteolysis) of the enzyme. 


Demand for product quality

The product quality demands are highly dependent on the application of the enzyme. Most enzymes have requirements for their physical appearance (color, odor). Impurities related to the process (e.g., the presence of unfermented sugar from the media) and the microorganism (e.g., metabolites produced during the fermentation) can influence the quality of the product. Dealing with these issues usually requires the incorporation of one or more purification steps in the process.
Typical requirements also include protein purity, germ count, and absence of other enzyme activities. The presence of other enzyme activities can interfere with the application or, more commonly, negatively affect the product stability, for example proteases present in the product degrading the enzyme of interest.
 

Type of product

The result of the recovery process is an enzyme contained in a solution that serves as the starting point for the formulation of the final product. The recovery process therefore needs to take the different formulation requirements into account. An enzyme concentrate to be used for a liquid enzyme formulation needs to have an enzyme concentration high enough to allow for dilution by formulation chemicals. Furthermore, the demand for physical and enzymatic stability of the liquid enzyme product typically requires that the recovery process reduces compounds (salts) that can precipitate or degrade the enzyme (e.g. proteases). Enzyme concentrates to be used for a dry formulation (granulate), need to fill the requirements on activity and dry matter content. A low activity to dry matter ratio will make it difficult to obtain sufficiently high enzyme concentration.

 

The environmental impact of the process 

The recovery process generates waste in the form of sludge, for example used biomass and liquid waste (e.g., in the form of cleaning liquids). A significant cost of the recovery process is therefore the disposal of these materials, and the design of the recovery process needs to consider this aspect. The environmental impact can be reduced by considering reuse of process liquids, by selecting unit operations that have low impact, or by producing valuable products from the waste. An example of the latter is the use of the utilized biomass as fertilizer on farmland or as animal feed.
An example of reuse/recycling of process liquids is the use of permeate from the ultrafiltration for dilution in the first steps of the recovery process. The benefit of this approach is not only that generation of wastewater is reduced, but also that the dry matter returned with the permeate can be expected to have a stabilizing effect on the enzyme (e.g., proteases).