Preparation of chitooligosaccharides from fungal waste mycelium by recombinant chitinase

• A new method for enzymatic production of chitin oligosaccharides was developed.
• Fungal chitin from waste mycelia is a good source of chitin.
• The main product of hydrolysis with recombinant chitinase was N,N′-diacetylchitobiose.
• The highest yield of chitobiose after 5 d of hydrolysis was 24%.

This study aimed to develop an enzymatic method for conversion of chitin from fungal waste mycelia to chitooligosaccharides. The recombinant chitinase LlChi18A from Lactococcus lactis was over-expressed by Escherichia coli BL21 (DE3) and purified by affinity chromatography. The enzymatic properties of the purified enzyme were studied by chitin oligosaccharides. Waste mycelium was pre-treated by alkaline. The optimal conditions for hydrolysis of fungal chitin by recombinant chitinase were determined by Schales method. HPLC/ESI-MS was used to determine the content of N-acetylglucosamine and chitooligosaccharides after hydrolysis. The level of reducing sugar released from pretreated mycelium by chitinase increased with the reaction time during 6 days. The main product in the hydrolysates was N,N′-diacetylchitobiose. After hydrolysis by chitinase for 5 d, the yield of N,N′-diacetylchitobiose from waste mycelium was around 10% with estimated purity of around 70%. Combination of chitinase and snailase remarkably increased the yield to 24% with purity of 78%. Fungal mycelium which contains chitin is a new potential source for obtaining food grade chitooligosaccharides.

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