Direct incorporation of glucosamine and N-acetylglucosamine into exopolymers by Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245: production of chitosan-cellulose and chitin-cellulose exopolymers

Abstract

Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245 incorporated 2-amino-2-deoxy-D-glucose (glucosamine) and 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine), but not 3-O-methyl-D-glucose or 2-deoxy-D-glucose into exopolymers. Incorporation was confirmed by gas chromatography with and without mass spectrometry, Fourier transform infrared, and 1H nuclear magnetic resonance. The average molar percentage of glucosamine and N-acetylglucosamine in the exopolymers was about 18%.

FIG. 1

Procedure to purify and fractionate exopolymers synthesized with glucosamine. AIGGCP, acetic acid-insoluble glucose-coglucosamine copolymer; ASGGCP, acetic acid-soluble glucose-coglucosamine copolymer; DW, distilled water.

FIG. 2

GC chromatograms of trimethylsilylated (TMS) sugar components of (A) exopolymer made with glucose, (B) 10% acetic acid-insoluble fraction of exopolymer made with glucosamine (the molar ratio of glucose to glucosamine was 6.0 to 1.0), (C) 10% acetic acid-soluble fraction of exopolymer made with glucosamine (the molar ratio of glucose to glucosamine was 0.6 to 1.0), (D) water-insoluble fraction of exopolymer made with N-acetylglucosamine (the molar ratio of glucose to N-acetylglucosamine was 6.2 to 1.0), and (E) water-soluble fraction of exopolymer made with N-acetylglucosamine (the molar ratio of glucose to N-acetylglucosamine was 0.8 to 1.0). Glu, glucose; N-AcGlu, N-acetylglucosamine.

FIG. 3

GC chromatograms of trimethylsilylated (TMS) sugar components of (A) 10% acetic acid-soluble fraction of exopolymer made with glucosamine (the molar ratio of glucose to glucosamine was 0.6 to 1.0) and (B) water-soluble fraction of exopolymer made with N-acetylglucosamine (the molar ratio of glucose to N-acetylglucosamine was 0.8 to 1.0). Glu, glucose; N-AcGlu, N-acetylglucosamine.

FIG. 4

FTIR spectra of (A) cellulose, (B) chitin, (C) chitosan (DS = 0.1, measured by ¹H-NMR), (D) 10% acetic acid-soluble fraction of exopolymer made with glucosamine as the carbon source, and (E) water-soluble fraction of exopolymer made with N-acetylglucosamine as the carbon source.

FIG. 5

Production of exopolymers with glucose (●), glucosamine (■), and N-acetylglucosamine (□) as a function of cultivation time of G. xylinum ATCC 10245. Each point represents the average of three samples; standard deviations ranged from 0.002 to 0.005 for the glucosamine and N-acetylglucosamine samples and 0.01 to 0.05 for the glucose samples.