Vol.:(0123456789) 1 3 Journal of Industrial Microbiology & Biotechnology (2019) 46:951–963 https://doi.org/10.1007/s10295-019-02171-9 BIOENERGY/BIOFUELS/BIOCHEMICALS - ORIGINAL PAPER Tolerance and transcriptional analysis of Corynebacterium glutamicum on biotransformation of toxic furaldehyde and benzaldehyde inhibitory compounds Pingping Zhou 1  · Imrana Khushk 1  · Qiuqiang Gao 1  · Jie Bao 1 Received: 8 September 2018 / Accepted: 1 April 2019 / Published online: 10 April 2019 © Society for Industrial Microbiology and Biotechnology 2019 Abstract Furaldehydes and benzaldehydes are among the most toxic inhibitors from lignocellulose pretreatment on microbial growth and metabolism. The bioconversion of aldehyde inhibitors into less toxic alcohols or acids (biotransformation) is the pre- requisite condition for efcient biorefnery fermentations. This study found that Corynebacterium glutamicum S9114 dem- onstrated excellent tolerance and biotransformation capacity to fve typical aldehyde inhibitors including two furaldehydes: 2-furaldehyde (furfural), 5-(hydroxymethyl)-2-furaldehyde, and three benzaldehydes: 4-hydroxybenzaldehyde, 4-hydroxy- 3-methoxybenzaldehyde (vanillin), and 4-hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde). Transcription levels of 93 genes hypothesized to be responsible for fve aldehydes biotransformation were examined by qRT-PCR. Multiple genes showed signifcantly up-regulated expression against furaldehydes or benzaldehydes. Overexpression of CGS9114_RS01115 in C. glutamicum resulted in the increased conversion of all fve aldehyde inhibitors. The signifcant oxidoreductase genes responsible for each or multiple inhibitors biotransformation identifed in this study will serve as a component of key gene device library for robust biorefnery fermentation strains development in the future biorefnery applications. Keywords Corynebacterium glutamicum S9114 · Furaldehydes · Benzaldehydes · Biotransformation · Transcriptional response Introduction Pretreatment is the crucial step for overcoming biorecal- citrance of lignocellulose to release fermentable sugars by enzymatic hydrolysis. In the harsh pretreatment process, various inhibitors are generated and severely inhibit the cell growth and metabolism of biorefnery fermentation strains in consequent fermentation step [5]. The inhibi- tors include furaldehydes: 2-furylaldehyde (furfural) and 5-(hydroxymethyl)-2-furaldehyde (HMF) from dehydration of pentose and hexose; weak organic acids: formic acid, ace- tic acid, and levulinic acid from carboxylate group hydroly- sis or furans oxidation; benzaldehydes: 4-hydroxybenzalde- hyde (HBA), 4-hydroxy-3-methoxybenzaldehyde (vanillin), and 4-hydroxy-3,5-dimethoxybenzaldehyde (syringalde- hyde) from lignin degradation [10, 22]. Furaldehydes and benzaldehydes are the most toxic inhibitors to most fermen- tation microorganisms [8, 20, 40, 41, 44] and their efective removal is the prerequisite condition for efcient biorefnery fermentations. Among the various detoxifcation methods, biological transformation of furaldehydes into less toxic alcohols and acids (biodetoxifcation) by the special biode- toxifcation microorganisms provides the most efcient way with signifcant advantages of fast, complete, and less waste water generation [12, 16, 21, 37, 43]. However, biotransfor- mation of benzaldehydes from pretreated lignocellulose bio- mass is not as efcient as furaldehydes because of their low water solubility and hydrophobicity [7, 31, 43]. Therefore, screening of robust fermentation strains to various aldehyde inhibitors is an important option in fermentation step for Pingping Zhou and Imrana Khushk are equally contributed to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10295-019-02171-9) contains supplementary material, which is available to authorized users. * Jie Bao jbao@ecust.edu.cn 1 State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China Downloaded from https://academic.oup.com/jimb/article/46/7/951/5996788 by guest on 21 February 2023