Cellulases, Hemicellulases, and Pectinases

The study of cellulases is important from the standpoint of microbial conversion of biomass to feeds and chemical feed stock. The complex structure of hemicelluloses has dictated a correspondingly diverse array of hemicellulases. The concentration (or actually dilution) of enzyme preparation required to effect this level of depolymerization is converted, through a somewhat indirect procedure, to the cellulase activity in filter paper units (FPU) per milliliter. Rather than being an exact representation of the saccharification process that occurs in simultaneous saccharification and fermentation (SSF), diafiltration saccharification assay (DSA) data were useful for comparison with SSF data in efforts to identify the influences of factors other than product inhibition on the performance of cellulases in SSF. Cellulases may also be detected in slab gels using either Western blotting or enzyme-linked immunosorbent assay, as reported for enzymes from Trichoderma reesei. When preparing enzyme-treated substrates, care must be taken to employ phenolic acid esterase-free cellulases. Hemicellulose-depolymerizing enzymes are divided into three classes; the endoacting, exoacting, and oligomer-hydrolyzing. The process of detecting and verifying exoglucanases (cellobiohydrolases [CBHs] in context of the fungal cellulose systems) has long been controversial. If purified proteins are available, careful comparisons of reducing-sugar yields and fluidity values from carboxymethylcellulose (CMC) hydrolysis as a function of enzyme concentration can be used to judge whether an enzyme is more endoglucanase-like or CBH-like. Recent reviews by Kashyap and Naidu and Panda outline the pectinase enzymes in detail. Ruthenium red staining in plates and zymograms has also been used for assay of pectinase enzymes.