Enzymatic production of fully deacetylated chitooligosaccharides and their neuroprotective and anti-inflammatory properties

Among several commercial enzymes screened for chitosanolytic activity, Neutrase 0.8L (a protease from Bacillus amyloliquefaciens) was selected in order to obtain a product enriched in deacetylated chitooligosaccharides (COS). The hydrolysis of different chitosans with this enzyme was followed by size exclusion chromatography (SEC-ELSD), mass spectrometry (ESI-Q-TOF), and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Neutrase 0.8L converted 10 g/L of various chitosans into mostly deacetylated oligosaccharides, yielding approximately 2.5 g/L of chitobiose, 4.5 g/L of chitotriose, and 3 g/L of chitotetraose. We found out that the neutral protease was not responsible for the chitosanolytic activity in the extract, while it could participate in the deacetylating process. The synthesized COS were tested in vitro for their neuroprotective (toward human SH-S5Y5 neurons) and anti-inflammatory (in RAW macrophages) activities, and compared with other functional ingredients, namely fructooligosaccharides.