The characterization of size-controlled nanocrystalline cellulose from soy hulls with ultrasonic assisted extraction

Soybean is a crop of important economic significance and soy hull is the residual by-product of soybean processing industry. In this study, cellulose nanocrystals were extracted from soy hull using a combined acid hydrolysis-ultrasonic treatment process, and its structure, properties, and antimicrobial activity were investigated. Fourier-transform infrared spectroscopy revealed the presence of hydrogen and ester bonds in the soy hull nanocrystalline cellulose (SHNC), whereas scanning electron microscopy showed that the SHNC was globular or short-rod shaped with diameters in the range of 20–50 nm. The molecular weight of SHNC was 213,935 Da and the extraction yield was 11.42%. Meanwhile, SHNC also had high crystallinity (55.59%), thermal stability, transparency (80%), and UV resistance. Notably, SHNC exhibited an excellent bacteriostatic effect against Escherichia coli and Staphylococcus aureus , whose bacteriostatic percentage reached 69.33%. Meanwhile, this study provided a new idea for the high value utilization of waste soy hull.