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- ItemA Photoclick-Based High-Throughput Screening for the Directed Evolution of Decarboxylase OleT(Weinheim : Wiley-VCH, 2021) Markel, Ulrich; Lanvers, Pia; Sauer, Daniel F.; Wittwer, Malte; Dhoke, Gaurao V.; Davari, Mehdi D.; Schiffels, Johannes; Schwaneberg, UlrichEnzymatic oxidative decarboxylation is an up-and-coming reaction yet lacking efficient screening methods for the directed evolution of decarboxylases. Here, we describe a simple photoclick assay for the detection of decarboxylation products and its application in a proof-of-principle directed evolution study on the decarboxylase OleT. The assay was compatible with two frequently used OleT operation modes (directly using hydrogen peroxide as the enzyme's co-substrate or using a reductase partner) and the screening of saturation mutagenesis libraries identified two enzyme variants shifting the enzyme's substrate preference from long chain fatty acids toward styrene derivatives. Overall, this photoclick assay holds promise to speed-up the directed evolution of OleT and other decarboxylases. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemPrecultures Grown under Fed-Batch Conditions Increase the Reliability and Reproducibility of High-Throughput Screening Results(Weinheim : Wiley-VCH, 2019) Keil, Timm; Landenberger, Markus; Dittrich, Barbara; Selzer, Sebastian; Büchs, JochenOne essential task in bioprocess development is strain selection. A common screening procedure consists of three steps: first, the picking of colonies; second, the execution of a batch preculture and main culture, e.g., in microtiter plates (MTPs); and third, the evaluation of product formation. Especially during the picking step, unintended variations occur due to undefined amounts and varying viability of transferred cells. The aim of this study is to demonstrate that the application of polymer-based controlled-release fed-batch MTPs during preculture eliminates these variations. The concept of equalizing growth through fed-batch conditions during preculture is theoretically discussed and then tested in a model system, namely, a cellulase-producing Escherichia coli clone bank containing 32 strains. Preculture is conducted once in the batch mode and once in the fed-batch mode. By applying the fed-batch mode, equalized growth is observed in the subsequent main culture. Furthermore, the standard deviation of cellulase activity is reduced compared to that observed in the conventional approach. Compared with the strains in the batch preculture process, the first-ranked strain in the fed-batch preculture process is the superior cellulase producer. These findings recommend the application of the fed-batch MTPs during preculture in high-throughput screening processes to achieve accurate and reliable results. © 2019 The Authors. Biotechnology Journal Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim