Efficient preparation of β-1,3-glucooligosaccharides by microwave-assisted hydrothermal degradation of curdlan and preliminary exploration of its antibacterial activity

The study focuses on the efficient production of curdlan β-1,3-glucooligosaccharides (CDOS) through microwave-assisted hydrothermal hydrolysis of curdlan. The optimal condition was identified as 170 °C and 30 min, resulting in a curdlan liquefaction yield of over 96%, mainly contains CDOS along with minor amounts of glucose and 5-hydroxymethylfurfural (5-HMF). Oligosaccharides with a low degree of polymerization (DP), specifically DP2 to DP6, were isolated. The yields for DP2 to DP6 were 15.87%, 8.33%, 6.00%, 3.13%, and 1.83%, respectively, with purities over 70%. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analysis demonstrated that the dense triple helix structure of the crystalline structure was disrupted during degradation. Additionally, CDOS at a concentration of 2.5 mg/mL partially inhibited the growth of <i>Escherichia coli</i>. This study concludes that the combination of microwave-assisted hydrothermal hydrolysis with gel filtration chromatography provides an efficient method for producing and purifying CDOS.