Biochemical characterization of a novel L-asparaginase from Paenibacillus barengoltzii being suitable for acrylamide reduction in potato chips and mooncakes.

A novel L-asparaginase gene (PbAsnase) from Paenibaeillus barengoltzii CAU904 was cloned and expressed in Escherichia coli. The L-asparaginase gene was 1011bp encoding 336 amino acids. Multiple sequence alignment of PbAsnase with other known L-asparaginases revealed that the enzyme showed high similarities with some Rhizobial-type L-asparaginases, sharing the highest identity of 32% with a characterized L-asparaginase from Rhizobium etli CFN 42, suggesting that it should be a novel L-asparaginase. The recombinant L-asparaginase (PbAsnase) was purified to homogeneity and biochemically characterized. The purified enzyme was optimally active at pH 8.5 and 45°C, respectively. It was stable within pH 5.5-10.0 and at temperatures below 55°C. PbAsnase exhibited strict substrate specificity towards L-asparagine (35.2U/mg), with Km and Vmax values of 3.6mM and 162.2μmol/min/mg, respectively, but displayed trace activity towards L-glutamine. Moreover, the application potential of PbAsnase on acrylamide migration in potato chips and mooncakes was evaluated. The pretreatment by PbAsnase significantly decreased the acrylamide contents in potato chips and mooncakes by 86% and 52%, respectively. The unique properties of PbAsnase may make it a good candidate in industries, especially in food safety.