Efficient production and secretion of pyruvate from Halomonas sp. KM-1 under aerobic conditions.

Yoshikazu Kawata,Isao Matsushita,Jun Tsubota,Taku Nishimura

doi:10.1186/s13568-016-0195-y

Yoshikazu Kawata, Isao Matsushita + Show 2 more

Open Access

https://doi.org/10.1186/s13568-016-0195-y

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Abstract

The alkaliphilic, halophilic bacterium Halomonas sp. KM-1 can utilize both hexose and pentose sugars for the intracellular storage of bioplastic poly-(R)-3-hydroxybutyric acid (PHB) under aerobic conditions. In this study, we investigated the effects of the sodium nitrate concentration on PHB accumulation in the KM-1 strain. Unexpectedly, we observed the secretion of pyruvate, a central intermediate in carbon- and energy-metabolism processes in all organisms; therefore, pyruvate is widely used as a starting material in the industrial biosynthesis of pharmaceuticals and is employed for the production of crop-protection agents, polymers, cosmetics, and food additives. We then further analyzed pyruvate productivity following changes in culture temperature and the buffer concentration. In 48-h batch-cultivation experiments, we found that wild-type Halomonas sp. KM-1 secreted 63.3 g/L pyruvate at a rate of 1.32 g/(L·h), comparable to the results of former studies using mutant and recombinant microorganisms. Thus, these data provided important insights into the production of pyruvate using this novel strain.

Highlights

Pyruvate is a central intermediate in carbon and energy metabolism in all organisms; pyruvate is widely used as a starting material in the industrial biosynthesis of pharmaceuticals and is employed for production of crop-protection agents, polymers, cosmetics, and food additives (Li et al 2001)
To increase poly-(R)-3-hydroxybutyric acid (PHB) productivity, we examined the effects of increasing sodium nitrate concentrations (15.0, 20.0, 25.0, and 30.0 g/L) in simple batch cultivations of the KM-1 strain under aerobic conditions
Increasing the concentration of sodium nitrate in batch culture medium was expected to increase the production of both Cell dry mass (CDM) and PHB; the production of CDM and PHB decreased compared with the levels observed in previous studies (Fig. 1a, b) (Kawata et al 2013, 2014)

Summary

Introduction

Pyruvate is a central intermediate in carbon and energy metabolism in all organisms; pyruvate is widely used as a starting material in the industrial biosynthesis of pharmaceuticals and is employed for production of crop-protection agents, polymers, cosmetics, and food additives (Li et al 2001). Alkaliphilic and halophilic bacteria are appropriate candidates for industrial production of pure organic acids. The KM-1 strain secretes pure (R)-3-hydroxybutyric acid ([R]-3-HB) under microaerobic conditions (Kawata et al 2012a). The KM-1 strain can utilize a variety of carbon sources; surprisingly the KM-1 strain can utilize C6 and C5 sugars in parallel, without glucose catabolite repression (Kawata et al 2012a, 2013) This strain has already been employed to produce PHB from biodiesel waste glycerol and saccharified wood (Kawata and Aiba 2010; Kawata et al 2013). In this study, we further explored this observation and investigated changes in pyruvate production with different nitrate concentrations, culture temperatures, and buffer salinities in simple batch cultivations of the KM-1 strain under aerobic conditions

Materials and methods

Results

Discussion

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