Abstract:
Lignocellulose has economic potential as a bio-resource for the production of value-added
products (VAPs) and biofuels. The commercialization of biofuels and VAPs requires efficient enzyme
cocktail activities that can lower their costs. However, the basis of the synergism between enzymes
that compose cellulolytic enzyme cocktails for depolymerizing lignocellulose is not understood.
This review aims to address the degree of synergism (DS) thresholds between the cellulolytic enzymes
and how this can be used in the formulation of effective cellulolytic enzyme cocktails. DS
is a powerful tool that distinguishes between enzymes’ synergism and anti-synergism during the
hydrolysis of biomass. It has been established that cellulases, or cellulases and lytic polysaccharide
monooxygenases (LPMOs), always synergize during cellulose hydrolysis. However, recent evidence
suggests that this is not always the case, as synergism depends on the specific mechanism of action
of each enzyme in the combination. Additionally, expansins, nonenzymatic proteins responsible for
loosening cell wall fibers, seem to also synergize with cellulases during biomass depolymerization.
This review highlighted the following four key factors linked to DS: (1) a DS threshold at which
the enzymes synergize and produce a higher product yield than their theoretical sum, (2) a DS
threshold at which the enzymes display synergism, but not a higher product yield, (3) a DS threshold
at which enzymes do not synergize, and (4) a DS threshold that displays anti-synergy. This review
deconvolutes the DS concept for cellulolytic enzymes, to postulate an experimental design approach
for achieving higher synergism and cellulose conversion yields.
