Table 1 Selecting a biocatalyst for biomass valorization

(A) Source of biocatalyst

 Whole cell or free enzyme

Whole cells can also be used in permeabilized form [52]

 Wild type or mutant enzyme produced by rDNA technology

Some organisms are frequently used as the source for industrial enzymes [53]

 Refolded from IBs or use of IBs itself

Choice of the host is important. For enzymes where activity depends upon post translational modification, higher organisms are used as host expression systems [54]

(B) Free or immobilized form

 Soluble conjugates

For insoluble substrates (which is often the case with biomass), soluble conjugates [55] or enzymes in membrane reactors are preferred [56]

 Carrier free or insoluble support

Enzyme aggregates like CLEA [57] or CLEC [58] have high volumetric activity

(C) Operational stability

This may be different from storage stability [36]

(D) Reaction medium

The use of co-solvents is under exploited [59]

(E) Normal or promiscuous activity

As more enzymes, engineered for better promiscuous activity, become available, this application may increase [60, 61]