Isolation and screening of thermophilic bacilli from compost for electrotransformation and fermentation: Characterization of bacillus smithii ET 138 as a new biocatalyst

Elleke F. Bosma, Antonius H.P. van de Weijer, Martinus J.A. Daas, John van der Oost, Willem M. de Vos, Richard van Kranenburg*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Thermophilic bacteria are regarded as attractive production organisms for cost-efficient conversion of renewable resources to green chemicals, but their genetic accessibility is a major bottleneck in developing them into versatile platform organisms. In this study, we aimed to isolate thermophilic, facultatively anaerobic bacilli that are genetically accessible and have potential as platform organisms. From compost, we isolated 267 strains that produced acids from C5 and C6 sugars at temperatures of 55°C or 65°C. Subsequently, 44 strains that showed the highest production of acids were screened for genetic accessibility by electroporation. Two Geobacillus thermodenitrificans isolates and one Bacillus smithii isolate were found to be transformable with plasmid pNW33n. Of these, B. smithii ET 138 was the best-performing strain in laboratory-scale fermentations and was capable of producing organic acids from glucose as well as from xylose. It is an acidotolerant strain able to produce organic acids until a lower limit of approximately pH 4.5. As genetic accessibility of B. smithii had not been described previously, six other B. smithii strains from the DSMZ culture collection were tested for electroporation efficiencies, and we found the type strain DSM 4216T and strain DSM 460 to be transformable. The transformation protocol for B. smithii isolate ET 138 was optimized to obtain approximately 5×103 colonies per μg plasmid pNW33n. Genetic accessibility combined with robust acid production capacities on C5 and C6 sugars at a relatively broad pH range make B. smithii ET 138 an attractive biocatalyst for the production of lactic acid and potentially other green chemicals.

Original languageEnglish
JournalApplied and Environmental Microbiology
Volume81
Issue number5
Pages (from-to)1874-1883
Number of pages10
ISSN0099-2240
DOIs
Publication statusPublished - 2015
Externally publishedYes

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