Modification of paper properties using carbohydrate-binding module 3 from the Clostridium thermocellum CipA scaffolding protein produced in Pichia pastoris: elucidation of the glycosylation effect

The carbohydrate-binding modules (CBMs) have emerged as an interesting alternative to enzymes for fibers modification, e.g. of pulp and paper. Glycosylation in CBMs is thought to have a key role in the improvement of cellulose fibers. Thus, in this work the non-glycosylated (CBM3mt) and glycosylated (CBM3wt) recombinant versions of CBM3 from Clostridium thermocellum CipA-both produced in Pichia pastoris-were studied. Binding assays showed that CBM3mt had a higher affinity for microcrystalline cellulose (Avicel) than CBM3wt. In addition, CBM3mt produced a much higher hydrophobization of Whatman paper than CBM3wt. However, the effects of the two CBM3s on pulp and paper were identical. The CBM3s did not affect the drainability of Eucalyptus globulus or a mixture of E. globulus and Pinus sylvestris pulps. On the other hand, both improved significantly strength-related properties of E. globulus papersheets, namely burst (up to 12 %) and tensile strength (up to 10 %) indexes. This is the first report showing the capacity of CBM3 from C. termocellum CipA to modify paper properties. The results showed that glycosylation did not influence the drainage of CBM3-treated pulps nor the properties of the produced papers. Thus, glycans in glycosylated CBM3 may not be related with fiber improvement, namely superior pulp drainage.