Screening and Comparative Characterization of Microorganisms from Iranian Soil Samples Showing ω-Transaminase Activity toward a Plethora of Substrates

Abstract

In this study, soil microorganisms from Iran were screened for ω-transaminase (ω-TA) activity based on growth on minimal media containing (rac)-α-methylbenzylamine (rac-α-MBA) as a sole nitrogen source. Then, for the selection of strains with high enzyme activity, a colorimetric o-xylylendiamine assay was conducted. The most promising strains were identified by 16S rDNA sequencing. Five microorganisms showing high ω-TA activity were subjected to determine optimal conditions for ω-TA activity, including pH, temperature, co-solvent, and the specificity of the ω-TA toward different amine donors and acceptors. Among the five screened microorganisms, Bacillus halotolerans turned out to be the most promising strain: Its cell-free extract showed a highly versatile amino donor spectrum toward aliphatic, aromatic chiral amines and a broad range of pH activity. Transaminase activity also exhibited excellent solvent tolerance, with maximum turnover in the presence of 30% (v/v) DMSO.

Transaminases for industrial biocatalysis: novel enzyme discovery

“…stercoris were isolated from a petroleum refinery and an oil field respectively. The resulting enzymes showed tolerance to organic solvents, performing best in 30% DMSO, as well as an acidophilic profile (optimum activity at pH 5, with 70% activity remaining at pH 3) (Noshahri et al 2019). Recent examples like this serve to reinforce the benefits of continuing to use activity-guided methods for enzyme discovery, in particular when the advantages of this approach can be extended to previously untapped and extreme environments.…”

“…While a number of other discovery approaches have emerged in recent years, such as culture-independent metagenome screening, novel enzymes continue to be discovered in this way ( Fig. 1) (Wilding et al 2015(Wilding et al , 2016Wu et al 2017;Noshahri et al 2019). In the latter example by Noshahri et al, the decades-old approach of using enrichment media with 1-PEA as the sole nitrogen source was given a new lease of life by applying this method to microorganisms from challenging environments.…”

Growth optimization and identification of an ω-transaminase by a novel native PAGE activity staining method in a Bacillus sp. strain BaH isolated from Iranian soil

“…Among them, Bacillus sp. strain BaH (IBRC-M 11337) exhibited ω-TA activity towards several amine donors and acceptors with broad pH tolerance from 5 to 9 (Gord Noshahri et al 2019 ).…”

Counterbalance of Stability and Activity Observed for Thermostable Transaminase from Thermobaculum terrenum in the Presence of Organic Solvents

“…The changes in non-covalent interactions and conformational flexibility as well as the influence of a solvent on particular steps of the catalyzed reactions seem to facilitate the catalysis and underlie the enzyme activation in water-solvent media [15,22,32,35]. Recently, the increase of transaminase activity in cell-free lysates in the presence of organic solvents was demonstrated [36].…”