Efficient Expression and Characterization of an Endo-Type Lyase HCLase_M28 and Its Gradual Scale-Up Fermentation for the Preparation of Chondroitin Sulfate Oligosaccharides.

Glycosaminoglycan (GAG) lyases have been critical in structural and functional studies of GAGs. HCLase_M28, a lyase identified from the genome of Microbacterium sp. M28 was heterologously expressed, enzymatically characterized, and prepared in large-scale fermentation for the production of chondroitin sulfate (CS) oligosaccharides. Results showed that the expression of HCLase_M28 in Escherichia coli BL21 (DE3)-pET24a-HCLase_M28 opt1 and Bacillus subtilis W800-pSTOP1622-HCLase_M28 opt2 were 108-fold and 25-fold that of wide strain. The optimal lytic reaction of HCLase_M28 happened in 20 mM Tris-HCl (pH 7.2) at 50 °C with a specific activity of 190.9 U/mg toward CS-A. The degrading activity was slightly simulated in presence of 1 mM Ca 2+ and Mn 2+ while severely inhibited by Hg + , Cu 2+ , Fe 3+ , and SDS. TLC and ESI-MS analysis proved HCLase_M28 was an endolytic lyase and degraded CS and hyaluronic acid into unsaturated disaccharides. Through a gradual scale-up of fermentation in 5 L, 100 L, and 1000 L, a highly efficient intracellular expression of HCLase_M28 with an activity of 3.88 × 10 5  U/L achieved within a 34 h of cultivation. Through ultrafiltration, CS oligosaccharides with DP of 2 to 8 as the main components could be controllably prepared. The successful large-scale fermentation made HCLase_M28 a promising enzyme for industrial production of CS oligosaccharides.