Understanding the versatile roles of cellulose nanocrystals in α-amylase immobilization, starch hydrolysis, colloidal stability and printability towards advanced starch based bio-latex performance

Recently starch based bio-latexes are facing serious bottlenecks in their preparation and applications especially at the aspects of high concentration, high colloidal stability and high rheological performance. Starch paste for bio-latex production at high concentration would be prone to retrogradation and inevitably deteriorate its performance. The excessive and uncontrollable α-amylase hydrolysis behavior of starch granules at low concentration below 30 wt% could severely affect the strengthening or binding ability of bio-latex. Herein, this study proposes a practical and effective strategy by using cationic cellulose nanocrystals (CCNC) as versatile carriers of α-amylase for the preparation of starch based bio-latex (SBL) to improve starch hydrolysis efficiency even at 50 wt% concentration. CCNC immobilized α-amylase (CCNC/E) can effectively regulate starch hydrolysis behavior with controllable amylose/ amylopectin molecular weight/ distribution for enhanced colloidal stability and viscoelasticity. Furthermore, the multifunctional roles of CCNC as excellent dispersants, nano-fillers and enhancers within starch colloids could impart SBL excellent rheological property and printability in pigmented coating and printing performance, by improving the coating surface, higher printing density/ picking velocity, and lower dot gain phenomenon, compared with the control latex samples. This study proposes a promising and practical approach for efficient production of 50 wt% starch based bio-latex with advanced performance and further valorizes the cellulose nanocrystals in the starch based biomaterials applications.