Cellulose fiber size defines efficiency of enzymatic hydrolysis and impacts degree of synergy between endo- and exoglucanases

An interplay between cellulases is fundamental in biomass saccharification. Here, the synergistic action of Trichoderma harzianum Cel7A and Cel7B on two cellulosic substrates: bacterial cellulose (BC) and a much more heterogeneous filter paper (FP) was investigated by determining their saccharification yields and by analyzing both the released soluble products and the insoluble reducing ends formed in the process. Furthermore, morphological changes of the substrates were evaluated using scanning electron microscopy. Glycoside hydrolase family 7 (GH7) enzymes introduce uniform changes in BC, whereas in FP they preferentially consume thin microfibrils rather than thicker paper fibers. Thus, the size effect, which leads to a smaller surface area per unit of substrate mass for thicker fibers, seems to play a crucial role in higher enzymatic hydrolysis efficiency of BC as compared to FP. These results demonstrate that the morphology-dependent effects could be essential for the industrial breakdown of cellulose-rich plant biomass.