2-keto-3-deoxy sugar acid 2-keto-3-deoxy-l-galactonate 3,6-anhydro-l-galactose ARPE-19 Codium fragile Ecklonia maxima Ecklonia radiata N,N′-diacetylchitobiose N-acetylated chitosan oligosaccharide Nrf2 Pseudoalteromonas RAW 264.7 cells Sargassum elegans Ulva Vibrio activity adhesion agarose alginate lyase alkaliphilic anti-inflammatory activity biochemical characterization cancer carbohydrate-binding domain catalytic mechanism chitinases chitooligosaccharides chitosan oligosaccharide cold-adaption cold-tolerant