(544ah) Simultaneous Cell Disruption and Semi-Quantitative Activity Assays for High-Throughput Screening of Thermostable L-Asparaginases

Authors: 
Zhang, X. Sr., Jiangnan University
Yang, T. Sr., Jiangnan University
Rao, Z. Sr., Jiangnan University
Xu, M., Jiangnan University
Yang, S. T., The Ohio State University
L-asparaginase, which catalyses the hydrolysis of L-asparagine to L-aspartate, has attracted the attention of researchers due to its expanded applications in medicine and the food industry. In this study, a novel thermostable L-asparaginase from Pyrococcus yayanosii CH1 was cloned and over-expressed in Bacillus subtilis 168. To obtain thermostable L-asparaginase mutants with higher activity, a robust high-throughput screening process was developed specifically for thermophilic enzymes. In this process, cell disruption and enzyme activity assays are simultaneously performed in 96-deep well plates. By combining error-prone PCR and screening, six brilliant positive variants and four key amino acid residue mutations were identified. Combined mutation of the four residues showed relatively high specific activity (3108 U/mg) that was 2.1 times greater than that of the wild-type enzyme. Fermentation with the mutant strain in a 5-L fermenter yielded L-asparaginase activity of 2168 U/mL.