Overexpression of the primary sigma factor gene sigA improved carotenoid production by Corynebacterium glutamicum: Application to production of β-carotene and the non-native linear C50 carotenoid bisanhydrobacterioruberin

Hironori Taniguchi,Nadja A Henke,Volker F Wendisch,Sabine A.E Heider

doi:10.1016/j.meteno.2017.01.001

Hironori Taniguchi, Nadja A Henke + Show 2 more

Open Access

https://doi.org/10.1016/j.meteno.2017.01.001

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Abstract

Corynebacterium glutamicum shows yellow pigmentation due to biosynthesis of the C50 carotenoid decaprenoxanthin and its glycosides. This bacterium has been engineered for production of various non-native cyclic C40 and C50 carotenoids such as β-carotene, astaxanthin or sarcinaxanthin. In this study, the effect of modulating gene expression more broadly by overexpression of sigma factor genes on carotenoid production by C. glutamicum was characterized. Overexpression of the primary sigma factor gene sigA improved lycopene production by recombinant C. glutamicum up to 8-fold. In C. glutamicum wild type, overexpression of sigA led to 2-fold increased accumulation of the native carotenoid decaprenoxanthin in the stationary growth phase. Under these conditions, genes related to thiamine synthesis and aromatic compound degradation showed increased RNA levels and addition of thiamine and the aromatic iron chelator protocatechuic acid to the culture medium enhanced carotenoid production when sigA was overexpressed. Deletion of the gene for the alternative sigma factor SigB, which is expected to replace SigA in RNA polymerase holoenzymes during transition to the stationary growth phase, also increased carotenoid production. The strategy of sigA overexpression could be successfully transferred to production of the non-native carotenoids β-carotene and bisanhydrobacterioruberin (BABR). Production of the latter is the first demonstration that C. glutamicum may accumulate a non-native linear C50 carotenoid instead of the native cyclic C50 carotenoid decaprenoxanthin.

Highlights

Carotenoids are natural pigments which show various colors from yellow to red depending on their chemical structures (Britton et al, 2004)
Genes related to thiamine synthesis and aromatic compound degradation showed increased RNA levels and addition of thiamine and the aromatic iron chelator protocatechuic acid to the culture medium enhanced carotenoid production when sigA was overexpressed
In the lycopene producing strain LYC5 sigma factor genes were overexpressed and their influence on lycopene production was evaluated in Biolector microscale cultivations

Summary

Introduction

Carotenoids are natural pigments which show various colors from yellow to red depending on their chemical structures (Britton et al, 2004). Because of versatile applications especially in food and feed industries, the demand for bio-based carotenoid production is increasing (Breithaupt, 2007; Scotter, 2011). In order to increase the production and efficiency, metabolic engineering has been applied in the natural carotenoid producers as well as in non-carotenogenic organisms (Ausich, 2009; Ye and Bhatia, 2012). IPP (Isopentenyl pyrophosphate) and DMAPP (Dimethylallyl pyrophosphate) are synthesized either by the mevalonate (MEV) pathway or the methylerythritol phosphate (MEP) pathway (Chang et al, 2013). IPP and its isomer DMAPP are condensed to geranylgeranyl pyrophosphate (GGPP), of which lycopene is synthesized (Moise et al, 2014). Lycopene is a red C40 carotenoid that serves as precursor for the synthesis of other C40 and C50 carotenoids such as β-carotene, lutein or astaxanthin (Heider et al, 2014a; Misawa and Shimada, 1997)

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