Assessing process variable effects on laccase-mediated treatment for enhanced saccharification efficiency

Lignocellulosic materials (LCM) have gained popularity as a substitute for petroleum, enabling the production of biofuels and various compounds. Eucalyptus bark residue (EBR), generated by pulp and paper mills, is a prime illustration of such materials. The conversion of holocellulose in these materials typically involves the application of enzymes. Nevertheless, these materials may still contain lignin, widely recognized as hindering enzymatic processes. In this work, laccase was evaluated as an accessory enzyme on the hydrolysis of EBR. It underwent autohydrolysis with a severity (S0) of 3.84. The pretreated solid was then hydrolyzed using Cellic CTec2 in conjunction with a laccase-mediated treatment (LMT) employing an in-house produced laccase extract by Lentinus sajor-caju. The potential effects of this enzyme were assessed through the glucose released over time and the enzyme adsorption onto the solid substrate. No positive effects were observed when laccase was added simultaneously with cellulases; however, adding laccase 24 h before cellulases increased glucose production by 11 %. Increasing the laccase load notably resulted in a visible decrease in hydrolysis efficiency, suggesting potential toxicity or inhibition effects. Implementing a washing step proved effective in removing phenolics (inhibitors). LMT apparently suffered mass transfer issues and showed differences in enzyme adsorption for different solids, as verified by the free Cel7A levels. However, when an efficient laccase treatment preceded the washing step, with reduced mass transfer limitations, subsequent enzymatic hydrolysis yielded nearly 30 % more glucose. The utilization of laccase in the hydrolysis of LCM can be promising for enhancing the efficiency and cost-effectiveness of related processes, however process design, particularly the timing of enzyme addition and inhibitor removal, plays a critical role in optimizing enzymatic hydrolysis.