We used the same procedure as described elsewhere (Pauchet et al. 2020 (link)). Briefly, open reading frames (ORFs) of GH5_2, excluding the stop codon, were amplified by polymerase chain reaction (PCR) using RACE-ready cDNA generated in our previous study (Shin et al. 2021 ). A Kozak sequence was added at the 5′-end of the PCR product by integrating it into the forward PCR primer. The resulting PCR products were cloned into pIB/V5-His TOPO/TA (Invitrogen, Waltham, MA, USA) in an ORF with a V5-(His)6 epitope at the carboxyl-terminus, and constructs in the correct orientation were selected after colony PCR. For two constructs (RBIC5 and RBIC9), codon-optimized synthetic constructs cloned into pIB/V5-His TOPO/TA were obtained from the company GenScript (Piscataway, NJ, USA). Insect Sf9 cells (Invitrogen) were routinely cultured in SF-900 II serum-free medium (Gibco, Paisley, UK). Cells were transfected in six-well plates using FUGENE HD (Promega, Madison, WI, USA) as the transfection reagent. After 72 h, the culture medium of transfected cells was harvested, and cell debris was removed by centrifugation. Recombinant GH5_2 proteins were recovered by immunoprecipitation using anti-V5 agarose beads (V5-Trap, ChromoTek, Planegg-Martinsried, Germany). After immunoprecipitation, agarose beads were resuspended in 150 µl of double-distilled water.