Interplays of enzyme, substrate, and surfactant on hydrolysis of native lignocellulosic biomass

ABSTRACT

Tracking enzyme, substrate, and surfactant interactions to reach maximum reducing sugar production during enzymatic hydrolysis of plant biomass may provide a better understanding of factors that limit the lignocellulosic material degradation in native rice straw. In this study, enzymes (Cellic Ctec2 cellulase and Cellic Htec2 xylanase) and Triton X-100 (surfactant) were used as biocatalysts for cellulose and xylan degradation and as a lignin blocking agent, respectively. The response surface model (R² = 0.99 and R²-adj = 0.97) indicated that Cellic Ctec2 cellulase (p < 0.0001) had significant impacts on reducing sugar production, whereas Cellic Htec2 xylanase and Triton X-100 had insignificant impacts on sugar yield. Although FTIR analysis suggested binding of Triton X-100 to lignin surfaces, the morphological observation by SEM revealed similar surface features (i.e., smooth surfaces with some pores) of rice straw irrespective of Triton X-100. The reducing sugar yields from substrate hydrolysis with or without the surfactant were comparable, suggesting similar exposure of polysaccharides accessible to the enzymes. The model analysis and chemical and structural evidence suggest that there would be no positive effects on enzymatic hydrolysis by blocking lignins with Triton X-100 if high lignin coverage exists in the substrate due to the limited availability of hydrolyzable polysaccharides.

KEYWORDS:

• Nonionic surfactant
• lignin
• nonproductive binding
• cellulase
• xylanase
• response surface methodology
• lignocellulosic material

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authorship contributions

Sengthong Lee: Methodology, Investigation, Data curation, Writing-original draft;

Saengchai Akeprathumchai: Formal analysis, Validation, Writing-original draft;

Damkerng Bundidamorn: Investigation;

Lakha Salaipeth: Formal analysis, Validation;

Kanokwan Poomputsa: Conceptualization, Formal analysis;

Khanok Ratanakhanokchai: Conceptualization, Writing-review & editing;

Ken-Lin Chang: Formal analysis, Conceptualization, Writing-review & editing;

Paripok Phitsuwan: Conceptualization, Methodology, Investigation, Supervision, Data curation, Funding acquisition, Writing-original draft, review & editing.

Highlights

• Effect of interaction between enzyme and surfactant on hydrolysis of native rice straw was studied.

• The mathematical model indicates that only Cellic Ctec2 cellulase is significant for sugar release

• Triton X-100 binds onto rice straw but does not promote enzymatic hydrolysis

• Exposure of carbohydrates to enzymes is more important than lignin blocking

Additional information

Funding

This research was financially supported by Thailand Research Fund [grant number MRG6180076], Thailand Science Research and Innovation (TSRI), Basic Research Fund: Fiscal year 2021 [grant number 64A306000039], and the Program Management Unit for Human Resources & Institutional Development, Research and Innovation, Thailand [grant number B01F630003];The Program Management Unit for Human Resources & Institutional Development, Research and Innovation, Thailand [B01F630003];Thailand Research Fund [MRG6180076];