The literature indicates that the following factors affect the enzymatic reactivity of biomass: (1) lignin content, (2) crystallinity, (3) acetyl content, (4) degree of polymerization, (5) accessible surface area, (6) pore volume, and (7) particle size. This study focuses on the first three structural features.

A total of 147 model biomass substrates were prepared with widely different lignin contents, crystallinities, and acetyl contents. The enzymatic conversion to glucose and xylose is correlated with enzyme loading using the following empirical equation:

x = B ln (Eo) + A

where x is the conversion, Eo is the enzyme loading (FPU/g biomass), and A and B are the intercept and slope, respectively. The slope and intercept – which characterize the enzymatic reactivity of the biomass – are correlated with the three structural features. To test the validity of the correlations, the model predictions are compared to data collected for a variety of biomass feedstocks (e.g., corn stover, sugarcane bagasse) treated with a variety of industrially relevant pretreatments (e.g., AFEX, lime, dilute acid).

The significance of this work is that it allows the design of optimal pretreatment and saccharification systems that trade the costs of more extensive pretreatments against the savings of lower enzyme consumption.