Effect of Additives on Polysaccharide Retention in Green Liquor Pretreatment of Loblolly Pine for Enzymatic Hydrolysis

Abstract

In order to improve polysaccharide retention during pretreatment and increase enzymatic hydrolysis efficiency, green liquor (GL) pretreatment was performed at: (1) higher GL sulfidity; (2) higher sulfidity with the addition of sodium polysulfide; (3) higher sulfidity with the addition of sodium borohydride; or (4) higher sulfudity with the addition of sodium tetraborate. The results indicate that green liquor pretreatment with the higher sulfidity, with the addition of polysulfide and with the addition of sodium borohydride, is effective in increasing enzymatic conversion of the pretreated pulps. The addition of sodium tetraborate, on the other hand, is not effective. These measures can be combined with oxygen delignification and/or mechanical refining to further improve the enzymatic hydrolysis efficiency. Up to 80% of the polysaccharides in softwood can be converted to fermentable sugars, but only with the addition of 40 FPU enzyme dose.

Keywords:

• Green liquor
• sodium borohydride
• polysulfide
• sulfidity
• enzymatic hydrolysis

Acknowledgments

This research was financially supported by a consortium of industrial members (Wood to Ethanol Consortium I) through a grant to North Carolina State University. The authors are grateful to the members of the consortium. The experiments were carried out in the Department of Forest Biomaterials, North Carolina State University.