Ultrasound pretreatment and enzymatic deinking by using bacterial cellulases from rice husk

Abstract

Ultrasonic pretreatment could improve the accessibility of enzymes to cellulosic fibers, hence expanding the access of enzymes to effectively remove ink from paper. In this study, enzymes were isolated from paddy rice husks and utilized for biodeinking process. The characterizations of deinking from the pulp filtrate and paper samples were carried out to understand the effect of bacterial cellulases and ultrasonic pretreatment with time variables. The results showed that cellulases from bacterial isolates had the ability to hydrolyze cellulose at 1.78 U/mL enzyme activity. Ink content measurement showed 2310 ppm of ink was removed in the paper samples with 15 min of ultrasound pretreatment and 2% cellulases. Meanwhile, morphological analysis showed significant differences in the surface areas between treated and untreated paper samples. The highest crystallinity index achieved was 70.9%, and thermal resistance was 21.0%. Other paper qualities such as stain decrease, and brightness level improvement were observed. The combination of 2% cellulases with optimum ultrasonication duration resulted in exceptional wastepaper recycling process.

Keywords:

• Cellulases
• enzymatic deinking
• paper recycling
• ultrasound pretreatment

Acknowledgments

The authors would like to thank the rector of Universitas Sumatera Utara, Medan for the research fund via Talenta Program 2019 Universitas Sumatera Utara with given contract No. 4167/UN5.1.R/PPM/2019.