Bioconversion to chitosan: a two stage process employing chitin deacetylase from Penicillium oxalicum SAEM-51

Chitin deacetylase from Penicillium oxalicum SAEM-51 was evaluated for bioconversion of chitin to chitosan in a two stage chemical and enzymatic process. Variations in morphology, crystallinity and thermal properties following chemical treatment were evaluated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. Degree of deacetylation of the substrates was determined using FT-IR and elemental analysis. The pretreatment of substrate led to the decrease in crystallinity and formation of amorphous chitinous substrates to facilitate enzyme reaction. The treated chitin was further subjected to enzymatic deacetylation employing chitin deacetylase from P. oxalicum SAEM-51 to produce chitosan with considerably higher degree of deacetylation. Maximum deacetylation (79.52%) was achieved using superfine chitin, owing to its porous structure and low crystallinity. Further, derivation of reaction variables, i.e. substrate amount and enzyme dose through full-factorial central composite design led to enhanced degree of deacetylation with formation of 90% deacetylated chitosan.