Extraction and characterization of chitin and chitosan from molts and Eupolyphaga sinensis Walker: Influence of chemical and ultrasound-assisted enzymatic processing

Abstract

Chitin was extracted from molts and different life-stages of Eupolyphaga sinensis Walker (ESW) using both chemical and ultrasound-assisted enzymolysis (UAE) methods, followed by deacetylation to produce chitosan. The physicochemical and structural properties of extracted chitosan were characterized and compared with commercially available chitosan (CAC), to validate the methods used. Results illustrated changes in chitosan structure, referencing the growth-stages of ESW, with more significant differences observed between UAE and chemical approaches. UAE method remarkably increased the chitin and chitosan yields, particularly in male nymphs (66.42 %-increase in chitin) and adult males (56.42 %-increase in chitosan), with molts showing the highest chitin (30.49 %) and chitosan (17.16 %). FTIR and XRD spectra indicated that the transmission peaks of the extracted chitosan were consistent with CAC, but the UAE-prepared chitosan (UMC) exhibited higher acetylation (81.00 %-81.82 %) and lower viscosity-average molecular weight compared to chemical method. Scanning electron microscopy showed the surface of ESW chitosan had several pores, whereas the CAC had no voids, implying ESW chitosan possessed higher water- and fat-binding capacity. Furthermore, differential scanning calorimetry analysis showed better homogeneity and thermal stability in UMC. This study suggests that ESW could be used as an alternative source for chitosan production, especially following the application of UAE method.