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Escherichia coli was selected as the sample to study the toxicity of arsenite in the presence of saccharides. The effect of glucosamine, N-acetylglucosamine, glucose, lactose, sucrose, glucosamine and cyclodextrin on the toxicity of arsenite against E. coli was investigated by microcalorimetry. The glucosamine and the tested chitooligomer decreased the toxicity of arsenite on cells of E. coli, and the effect of glucosamine was stronger than that of the chitooligomer. These results suggest that the glucosamine and chitooligomer may be employed as the assistant antidote for arsenite.

Chitosan is a renewable resource for the production of nitrogen-containing aromatic heterocyclics. It was found that chitosan started to decompose and produce some volatile compounds at around 525 K in a nitrogen atmosphere, the volatiles were characterized by Fourier transform infrared spectrometer. The apparent activation energy for the thermal degradation of chitosan was determined. To further investigate the degradation, chitosan was pyrolyzed under vacuum at 553 K for 1 h, and the volatile compounds were analyzed by gas chromatography/mass spectrometry. The volatile compounds included aromatic heterocyclics such as pyrazines, pyridines, pyrroles and furans, and the pyrazines were the major products. The pyrolysis mechanism of chitosan was also proposed.

Dietary chitosans with different molecular weight M w and the degree of deacetylation DDA (high molecular weight chitosan HCS with M w 7.60 × 10 5 and DDA 85.5%, middle molecular weight chitosan MCS with M w 3.27 × 10 4 and DDA 85.2%, chito-oligomer COS with M w 0.99 × 10 3 and DDA 85.7% and water-soluble chitosan WSC with M w 3.91 × 10 4 and DDA 52.6%) were used at the 1.05% level to feed mice for 90 days. Afterwards no pathological symptoms, clinical signs or deaths were observed. The body weight of mice in chitosan group and control group showed no significant difference. Although HCS, COS and WSC had no significant effect on the level of Fe, Zn and Cu in the tested mice’s liver, spleen, heart and kidney, MCS significantly increased the level of Fe, Zn and Cu in liver. Therefore dietary ingestion of chitosan did not depress the level of Fe, Zn and Cu in mice.

Four chitosan samples with different molecular weight Mw and the degree of deacetylation DD (HCS 7.60 × 105 and 85.5%, MCS 3.27 × 104 and 85.2%, COS 0.99 × 103 and 85.7%, WSC 3.91 × 104 and 52.6%) were prepared, and labeled by fluorescein isothiocyanate. These labeled samples were used to investigate the absorption and distribution in mice after oral administration. The results indicated that the absorption and distribution of chitosan was significantly influenced by its Mw and water-solubility. The absorption of chitosan molecules increased with the decrease of the Mw and the increase of the water-solubility. The absorbed chitosan molecules were distributed to all tested organs such as liver, kidney, spleen, thymus, heart and lung. The chitooligomer molecules were easily absorbed and metabolized. The absorbed chitosan molecules from water-soluble WSC in all tested tissues maintained high concentration for a long period. The results suggest that different chitosan may be employed for different functional food.

Chitooligomers have attracted much interest due to their unique biological activities. However, chitooligomers easily turn brown during shelf life. The factors influencing the browning of chitooligomers were investigated. The results indicated that the browning was attributed to the structure change of chitooligomers. The water-solubility, thermal stability and moisture-adsorption of chitooligomers decreased with the increase of browning. The time, temperature, pH, moisture, oxygen and reductant all had effect on the browning of chitooligomers. The optimal preservation condition for chitooligomers should be at low temperature and humidity, at pH below 4 or above 10, and in absence of oxygen.