Optimizing Curdlan Synthesis: Engineering Agrobacterium tumefaciens ATCC31749 for Enhanced Production Using Dextrin as a Carbon Source

Abstract

A key goal in current research on industrial curdlan production is the expansion of carbon sources for fermentation. In this study, a recombinant bacterial strain, sp-AmyAXCC, capable of fermenting and synthesizing curdlan using dextrin as a carbon source, was produced via heterologous expression of IPTG-inducible α-amylase from Xanthomonas campestris NRRL B-1459 in Agrobacterium tumefaciens ATCC31749. External expression of the enzyme was confirmed by western blotting, and the expression levels of exogenous proteins during the fermentation process were monitored. Additionally, the properties of the curdlan product were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray diffraction. The recombinant strain produced curdlan at a titer of 30.40 ± 0.14 g/L, gel strength of 703.5 ± 34.2 g/cm2, and a molecular weight of 3.58 × 106 Da, which is 33% greater than the molecular weight of native curdlan (2.69 × 106 Da). In the batch fermentation of sp-AmyAXCC with 12% dextrin as a carbon source, the titer of curdlan was 66.7 g/L with a yield of 0.56 g/g, and a productivity rate of 0.62 g/L/h at 108 h. The results of this study expand the substrate spectrum for Agrobacterium fermentation in curdlan production and provides guidance for further industrialization of curdlan production.