Enhanced phenolic compounds tolerance response of Clostridium beijerinckii NCIMB 8052 by inactivation of Cbei_3304

Jun Liu,Qinlu Lin,Yunchuan Luo,Xueying Chai,Ting Guo

doi:10.1186/s12934-018-0884-0

Abstract

BackgroundPhenolic compounds generated in hydrolysis of lignocellulosic materials are major limiting factors for biological production of solvents by Clostridia, but it lacks the attention on the study of adaptation or resistance mechanisms in response to phenolic compounds.ResultsGene Cbei_3304, encoding a hypothetical membrane transport protein, was analyzed by bioinformatic method. After insertional inactivation of the functionally uncertain gene Cbei_3304 in Clostridium beijerinckii NCIMB 8052, resulted in enhanced phenolic compounds tolerance. Compared to the parent strain C. beijerinckii NCIMB 8052, evaluation of toxicity showed the recombination stain C. beijerinckii 3304::int had a higher level of tolerance to four model phenolic compounds of lignocellulose-derived microbial inhibitory compounds. A comparative transcriptome analysis showed that the genes were involved in membrane transport proteins (ABC and MFS family) and were up-regulated expression after disrupting gene Cbei_3304. Additionally, the adaptation of C. beijerinckii NCIMB 8052 in response to non-detoxified hemicellulosic hydrolysate was improved by disrupting gene Cbei_3304.ConclusionToxicity evaluation of lignocellulose-derived phenolic compounds shows that Cbei_3304 plays a significant role in regulating toxicities tolerance for ABE fermentation by C. beijerinckii, and the adaptation of non-detoxified hemicellulosic hydrolysate is significantly improved after inactivation of Cbei_3304 in wild-type strain C. beijerinckii NCIMB 8052. It provided a potential strategy for generating high inhibitor tolerance strains for using lignocellulosic materials to produce solvents by clostridia in this study.

Highlights

Phenolic compounds generated in hydrolysis of lignocellulosic materials are major limiting factors for biological production of solvents by Clostridia, but it lacks the attention on the study of adaptation or resistance mechanisms in response to phenolic compounds
The group of toxic compounds metabolism: Furfural and 5-hydroxymethyl-furfural (HMF) are converted into alcohol dependent on the intracellular energy and reducing power (NADH/NADPH) to reduce the toxicity [4, 8, 9]; Phenolic compounds such as ρ-coumaric acid, ferulic acid, and caffeic acid are metabolized by phenolic acid decarboxylase and reductase in Lactobacillus spp. and Saccharomyces cerevisiae [10, 11]; Our previous research reported that the gene Cbei_4693, probably encoded a NADPH-dependent FMN reductase, plays an important role in regulating ferulic acid tolerance of the ABE fermentation by C. beijerinckii, and ferulic acid could be completely converted into the less toxic phenolic compound–hydroferulic acid [12]
The group of regulation factors involved in the tolerance of toxic compounds: Overexpression of groES and groEL genes, encoding head shock proteins, dramatically improved the production of acetone and butanol even under 0.5 g/L of ferulic acid stressed condition [13]; The Multiple antibiotic resistance Regulator (MarR) family, a transcription factor such as hosA protein, is associated with the regulation of genes that are involved in antibiotic resistance and detoxification noxious compounds to Enterobacteriaceae spp. [14]; In addition, there are two major types of efflux pump involved in microorganism resistance of toxicities: ATP-binding cassette (ABC) transporters and major facilitator superfamily (MFS) transporters

Summary

Introduction

Phenolic compounds generated in hydrolysis of lignocellulosic materials are major limiting factors for biological production of solvents by Clostridia, but it lacks the attention on the study of adaptation or resistance mechanisms in response to phenolic compounds. The group of toxic compounds metabolism: Furfural and 5-hydroxymethyl-furfural (HMF) are converted into alcohol dependent on the intracellular energy and reducing power (NADH/NADPH) to reduce the toxicity [4, 8, 9]; Phenolic compounds such as ρ-coumaric acid, ferulic acid, and caffeic acid are metabolized by phenolic acid decarboxylase and reductase in Lactobacillus spp. and Saccharomyces cerevisiae [10, 11]; Our previous research reported that the gene Cbei_4693, probably encoded a NADPH-dependent FMN reductase, plays an important role in regulating ferulic acid tolerance of the ABE fermentation by C. beijerinckii, and ferulic acid could be completely converted into the less toxic phenolic compound–hydroferulic acid [12]. There is a lack of attention to study adaptation or resistance mechanisms of phenolic compounds in the C. beijerinckii fermentation

Methods

Results

Conclusion