Genetic sensor-regulators functional in Clostridia
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GENETICS AND MOLECULAR BIOLOGY OF INDUSTRIAL ORGANISMS - ORIGINAL PAPER
Genetic sensor‑regulators functional in Clostridia SongI Han1 · Younghwan Kim2 · Mukund Karanjikar2 · Ka‑Yiu San1,3 · George N. Bennett3,4 Received: 9 June 2020 / Accepted: 18 August 2020 © Society for Industrial Microbiology and Biotechnology 2020
Abstract This study addressed the functionality of genetic circuits carrying natural regulatory elements of Clostridium acetobutylicum ATCC 824 in the presence of the respective inducer molecules. Specifically, promoters and their regulators involved in diverse carbon source utilization were characterized using mCherryOpt or beta-galactosidase as a reporter. Consequently, most of the genetic circuits tested in this study were functional in Clostridium acetobutylicum ATCC 824 in the presence of an inducer, leading to the expression of reporter proteins. These genetic sensor-regulators were found to be transferable to another Clostridium species, such as Clostridium beijerinckii NCIMB 8052. The gradual expression of reporter protein was observed as a function of the carbohydrates of interest. A xylose-inducible promoter allows a titratable and robust expression of a reporter protein with stringency and efficacy. This xylose-inducible circuit was seen to enable induction of the expression of reporter proteins in the presence of actual sugar mixtures incorporated in woody hydrolysate wherein glucose and xylose are present as predominant carbon sources. Keywords Sensor · Regulator · Clostridium acetobutylicum · mCherryOpt · Beta-galactosidase
Introduction Clostridium acetobutylicum ATCC 824 (C. acetobutylicum ATCC 824) is a gram-positive and spore-forming obligate anaerobe [38]. It has been known to metabolize a wide variety of carbon sources to produce acetone, butanol, ethanol (ABE), and other chemicals [36]. Depending on the type of carbon sources supplemented, it reveals a distinct solvent production profile. Butanol has a high energy content as well as low vapor pressure, and it can be manufactured on a large Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10295-020-02303-6) contains supplementary material, which is available to authorized users. * George N. Bennett [email protected] 1
Department of Bioengineering, Rice University, Houston, TX 77005, USA
2
Technology Holding LLC, West Valley City, UT 84119, USA
3
Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, USA
4
Department of BioSciences, Rice University, Houston, TX 77005, USA
scale by anaerobic fermentation [28]. The metabolism of this organism can be characterized as two distinct phases initiated from the acidogenic phase, followed by the solventogenic phase [1]. Rapid cell growth is observed in the acidogenic phase producing acetate and butyrate accompanied by a pH decrease, which triggers the solventogenic phase where ABE is produced, leading to the uptake of acids and a pH increase [44]. An advantage of Clostridia as a host orga
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