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For microorganisms to live under extreme physical conditions requires important adaptations of the cells. In many organisms the use of Na instead of protons as coupling ion in energy transduction is associated with such adaptation. This review focuses on the enzymes that are responsible for the generation and utilization of Na gradients in extremophilic microorganisms. Aspects that are dealt with include: bioenergetics and ion homeostasis in extremophilic Bacteria and Archaea; the molecular mechanism of Na translocation; and (dis)advantages of Na as coupling ion in energy transduction. [ABSTRACT FROM AUTHOR]

A newly isolated solvent-tolerant Pseudomonas putida strain converts (+)-limonene to high concentrations of a single and stable product, perillic acid. The presence of a cosubstrate is necessary for growth and perillic acid production. Glycerol appears to be the most suitable cosubstrate among those tested. An optimal combination of 150 mM limonene and 50 mM glycerol was found. Other factors that improve the extent and/or rate of bioconversion are the use of ammonia or urea as the nitrogen source, control of temperature at 30–34 °C and of pH at 7.0, as well as the use of emulsifiers to increase the bioavailability of limonene. Up to 18 mM (3.0 g · l−1) perillic acid is produced, a concentration that is not growth inhibitory. The observations that a single product is formed in high concentrations and that it is not further metabolized make this limonene bioconversion of commercial interest. [ABSTRACT FROM AUTHOR]