Direct production of organic acids from starch by cell surface-engineered Corynebacterium glutamicum in anaerobic conditions

Yota Tsuge,Tomohisa Hasunuma,Tsutomu Tanaka,Toshihiro Tateno,Akihiko Kondo,Kengo Sasaki

doi:10.1186/2191-0855-3-72

Yota Tsuge, Tomohisa Hasunuma + Show 4 more

Open Access

https://doi.org/10.1186/2191-0855-3-72

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Journal: AMB Express	Publication Date: Dec 1, 2013
Citations: 34	License type: cc-by

Affiliation: Kobe University, Korea University

Abstract

We produced organic acids, including lactate and succinate, directly from soluble starch under anaerobic conditions using high cell-density cultures of Corynebacterium glutamicum displaying α-amylase (AmyA) from Streptococcus bovis 148 on the cell surface. Notably, reactions performed under anaerobic conditions at 35 and 40°C, which are higher than the optimal growth temperature of 30°C, showed 32% and 19%, respectively, higher productivity of the organic acids lactate, succinate, and acetate compared to that at 30°C. However, α-amylase was not stably anchored and released into the medium from the cell surface during reactions at these higher temperatures, as demonstrated by the 61% and 85% decreases in activity, respectively, from baseline, compared to the only 8% decrease at 30°C. The AmyA-displaying C. glutamicum cells retained their starch-degrading capacity during five 10 h reaction cycles at 30°C, producing 107.8 g/l of total organic acids, including 88.9 g/l lactate and 14.0 g/l succinate. The applicability of cell surface-engineering technology for the production of organic acids from biomass by high cell-density cultures of C. glutamicum under anaerobic conditions was demonstrated.

Highlights

In the new era of green chemistry, the utilization of renewable resources, such as plant biomass, and environmentally friendly chemical products are eagerly desired
PgsA-anchored α-amylase sufficiently fermented soluble starch in high-cell density cultures of C. glutamicum cells A C. glutamicum strain displaying PgsA-anchored αamylase was previously shown to efficiently produce lysine from starch by direct simultaneous saccharification and fermentation under aerobic growing conditions (Tateno et al 2007a). We investigated if this system could be applied for the production of organic acids using high cell-density cultures of C. glutamicum cells under anaerobic conditions
The concentration of lactate in the control reactor reached as high as 0.6 ± 0.3 g/l after 4 h, the concentration decreased to 0.2 ± 0.2 g/l after 10 h indicating that the lactate was utilized as carbon source after the exhaustion of glucose due to the reversible catalytic activity of lactate dehydrogenase (LDH) (Figure 1A)

Summary

Introduction

In the new era of green chemistry, the utilization of renewable resources, such as plant biomass, and environmentally friendly chemical products are eagerly desired. The cell-surface display of heterologous proteins has several potential biotechnological applications, including adsorption or degradation of environmental pollutants, recovery of rare metal ions, biosensors, and recombinant protein production (Kuroda and Ueda 2010, 2011). In addition to these applications, yeast and bacteria displaying fusion proteins composed of a cell surface-anchoring protein and a biomass-degrading protein have been effectively used for the fermentation of biomass resources, such as starch, xylan, cellobiose, and cellulose (Katahira et al 2004; Matano et al 2012; Murai et al 1997; Narita et al 2006; Yamada et al 2013). It was anticipated that the co-utilization of cell surface-engineering technology zand high cell-density systems would improve organic acid production from biomass, the efficacy of this combined approach in C. glutamicum has not been demonstrated

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