title: High-throughput screening of B factor saturation mutated Rhizomucor miehei lipase thermostability based on synthetic reaction.
abstract: Conventional lipase screening methods are mostly based on hydrolytic activity, which may not always be the best method to assess the enzyme activity, especially for evaluating synthetic activity. Here we developed a high throughput and visual method to screen clones with high synthetic activity and used it to assess lipases thermostability. All mutants' lipase synthetic activity were identified through esterification of caprylic acid and ethanol with methyl red as the pH indicator adding in the substrates on according to the color change halo around the colony on culture plates since synthetic reaction was often accompanied with a rise in pH. After two rounds operation with the pH indicator screening method, we obtained a double mutant Asn120Lys/Lys131Phe from the Rhizomucor miehei lipase saturation mutated library based on amino acid residue B factors. The mutant's initial synthetic activity was a little higher than wild type and its thermostability in synthetic reaction was enhanced, which remained 63.1% residual activity after being heated at 70°C for 5h comparing to 51.0% of wild type. The double mutant with the two residue replacements balanced well between stability and activity. Yeast surface display technology and the pH indicator method, combined with colony screening were shown to facilitate high-throughput screening for lipase synthetic activity.
authors.affiliation: Guangdong Key Laboratory of Fermentation and Enzyme Engineering, School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510006, PR China.
authors.forename: Jun-hui
authors.initials: JH
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Lin
authors.forename: Yu-fei
authors.initials: YF
authors.lastname: Sun
authors.forename: Yan-rui
authors.initials: YR
authors.lastname: Ye
authors.forename: Sui-ping
authors.initials: SP
authors.lastname: Zheng
authors.forename: Shuang-yan
authors.initials: SY
authors.lastname: Han
mesh_terms: D001709:Biotechnology / Q000379:methods; D002210:Caprylates / Q000378:metabolism*; D003470:Culture Media; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004951:Esterification; D000431:Ethanol / Q000378:metabolism*; D057166:High-Throughput Screening Assays / Q000379:methods*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D020103:Rhizomucor / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D002210:Caprylates; D003470:Culture Media; D004800:Enzymes, Immobilized; D000431:Ethanol; D008049:Lipase; C031492:octanoic acid