Effects of Fed-Batch Loading of Substrate on Enzymatic Hydrolysis and Viscosity of Pretreated Barley Straw
Lisa Rosgaard1, Pavle Andric2, Kim Dam-Johansen2, Sven Pedersen1, and Anne B. S. Meyer3. (1) Starch R&D, Novozymes Inc., Krogsh°jvej 36, 2880-Bagsvaerd, Denmark, (2) Chemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark, (3) Biocentrum, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
One of the aspects of creating an economically feasible lignocellulose to ethanol process is to secure a sufficiently high enough ethanol concentration for distillation. One prerequisite of doing so is to employ high dry matter loading of the substrate and high extent of cellulose hydrolysis. However, the high viscosity of most lignocellulosic substrates makes it difficult to operate with substrate loadings much higher than 10 % by weight of dry matter. The present study provides an evaluation of a fed-batch strategy, loading multiple batches of substrate to reach 15 % by weight of dry matter, during enzymatic hydrolysis at 50 ░C, pH 5 of acid-steam exploded pretreated barley straw. The enzyme system Celluclast« (a cellulolytic enzyme preparation from Trichoderma reesei) and Novozym 188 (a β-glucosidase preparation from Aspergillus niger) was added either at the full dose for 15 % by weight of dry matter at the beginning of the hydrolytic reaction or in conjunction with the substrate during the fed-batch loading. Results regarding cellulose conversion, glucose yields, and viscosity changes during the hydrolysis are presented for several different sequential substrate loading and sequential substrate + enzyme loading regimes with the aim of providing insight into the interplay between substrate loading, viscosity and enzyme catalysed cellulose degradation of the barley straw material during the enzymatic hydrolysis reaction.