ChbG is essential for growth on the acetylated chitooligosaccharides chitobiose and chitotriose but is dispensable for growth on cellobiose and chitosan dimer, the deacetylated form of chitobiose. Deacetylation of chitobiose-6-P and chitotriose-6-P is necessary for both the activation of the chb promoter by the regulatory protein ChbR and the hydrolysis of phosphorylated beta-glucosides by the phospho-beta-glucosidase ChbF. Catalyzes the removal of only one acetyl group from chitobiose-6-P to yield monoacetylchitobiose-6-P, the inducer of ChbR and the substrate of ChbF. It can also use chitobiose and chitotriose as substrates. H2O + N,N'-diacetylchitobiose = acetate + N-acetyl-beta-D-glucosaminyl-(1->4)-D-glucosamine diacetylchitobiose-6'-phosphate + H2O = acetate + N'-monoacetylchitobiose-6'-phosphate Glycan degradation; chitin degradation. Homodimer. By N,N'-diacetylchitobiose. Cells lacking this gene are unable to grow on chitobiose and chitotriose. Belongs to the YdjC deacetylase family. ChbG subfamily. Was originally (PubMed:8121401 and PubMed:2179047) characterized as part of a cryptic cel operon for a cellobiose degradation system. The Cel+ phenotype is due to mutations making expression chitobiose-independent and altering the substrate specificity.