Optimization of macroelement concentrations, pH and osmolarity for triacylglycerol accumulation in Rhodococcus opacus strain PD630.

Helge Jans Janßen,Mohammad H A Ibrahim,Alexander Steinbüchel,Daniel Bröker

doi:10.1186/2191-0855-3-38

Helge Jans Janßen, Mohammad H A Ibrahim + Show 2 more

Open Access

https://doi.org/10.1186/2191-0855-3-38

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Abstract

The refinement of biodiesel or renewable diesel from bacterial lipids has a great potential to make a contribution for energy production in the future. This study provides new data concerning suitable nutrient concentrations for cultivation of the Gram-positive Rhodococcus opacus PD630, which is able to accumulate large amounts of lipids during nitrogen limitation. Enhanced concentrations of magnesium have been shown to increase the final optical density and the lipid content of the cells. Elevated phosphate concentrations slowed down the onset of the accumulation phase, without a clear effect on the final optical density and the cell’s lipid content. A robust growth of R. opacus was possible in the presence of ammonium concentrations of up to 1.4 g l-1 and sucrose concentrations of up to 240 g l-1, with an optimum regarding growth and lipid storage observed in the range of 0.2 to 0.4 g l-1 ammonium and 20 to 40 g l-1 sucrose, respectively. Moreover, R. opacus showed tolerance to high salt concentrations.

Highlights

Due to the expected depletion of fossil fuel sources in the near future, increasing attention is paid to the development of alternative sources of energy
The culture that was grown in presence of 240 g l-1 sucrose stored even less fatty acids than the culture grown in presence of 5 g l-1 though at the latter concentration all carbon was depleted during the exponential growth phase
Due to the very low growth inhibition of sucrose even at concentrations as high as 240 g l-1, it seems unlikely that the bacterial metabolism is strongly affected

Summary

Introduction

Due to the expected depletion of fossil fuel sources in the near future, increasing attention is paid to the development of alternative sources of energy. Bioethanol and biodiesel (fatty acid alkyl ester, FAAE) are among others the most interesting organic compounds, currently comprising about 90% of the biofuel market (Antoni et al.2007; Uthoff et al 2009). Today the industrial production of biodiesel is restricted to the transesterification of fatty acids derived from oleaginous plants like rapeseed, oil palm and soya or from animal fats (Luque et al.2008). Because of the low price for methanol, fatty acid methyl esters are mostly produced (Al-Zuhair 2007), but other short-chain length alcohols can be used as well for the production of biodiesel with altered properties (Röttig et al 2010). The transesterification can be done either by chemical or enzymatic catalysis or in vivo, by the use of microbial cells (Adamczak et al 2009).

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