The effect of catalase on enzymatic saccharification of wheat straw slurry

Abstract

Enzyme inactivation during enzymatic saccharification is a problem because it causes a slowdown in saccharification before the substrate is completely converted into sugars. Lytic polysaccharide monooxygenases can, under certain conditions, produce hydrogen peroxide which causes release of reactive oxygen species. These reactive oxygen species can interact either directly or indirectly with enzymes, causing their inactivation. Another reason for enzyme inactivation is precipitation. It has been shown that up to 30% of proteins can precipitate during standard saccharification conditions. This project investigated the effect of catalase on both enzymatic saccharification and enzyme precipitation. During saccharification of 10% dry matter wheat straw slurry the addition of catalase decreased enzyme inactivation, and thereby the glucose release by 9.5% at a CTec3 loading of 15 mg/g DW. It was also found that acidifying reactions taking place during enzymatic saccharification were reduced by the addition of catalase meant that less KOH was needed to adjust the pH during the saccharification process. It was shown that at least part of the enzyme inactivation during saccharification can be caused by precipitation. In this project it was found that enzyme precipitation is higher at pH 4 than at pH 5 and 6. The results also showed that catalase can partially mitigate this precipitation. The enzyme cocktail used in this project is CTec3.