Conversion of α-chitin Substrates with Varying Particle Size and Crystallinity Reveals Substrate Preferences of the Chitinases and Lytic Polysaccharide Monooxygenase of Serratia Marcescens

Industrial depolymerization of chitinous biomass generally requires numerous steps and the use of deleterious substances. Enzymatic methods provide an alternative, but fundamental knowledge that could direct potential development of industrial enzyme cocktails is scarce. We have studied the contribution of monocomponent chitinases (ChiA, -B, and -C) and the lytic polysaccharide monooxygenase (LPMO) from Serratia marcescens on depolymerization of α-chitin substrates with varying particle size and crystallinity that were generated using a converge mill. For all chitinases activity was positively correlated to a decline in particle size and crystallinity. Especially ChiC, the only nonprocessive endochitinase from the S. marcescens chitinolytic machinery, benefited from mechanical pretreatment. Combining the chitinases revealed clear synergies for all substrates tested. CBP21, the chitin-active LPMO from S. marcescens, increased solubilization of substrates with high degrees of crystallinity when combined with each of the three chitinases, but this synergy was reduced upon decline in crystallinity.