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The implementation of a stereoselective Michael addition with water as substrate is still a major challenge by classical, chemical means. Inspired by nature's ability to carry out this attractive reaction with both high selectivity and efficiency, the interest in hydratases (EC 4.2.1.x) to accomplish a selective water addition is steadily rising. The gram-positive bacterial genus Rhodococcus is known as biocatalytic powerhouse and has been reported to hydrate various Michael acceptors leading to chiral alcohols. This study aimed at the in-depth re-investigation of the hydration potential of Rhodococcus whole-cells towards Michael acceptors. Here, two concurrent effects responsible for the hydration reaction were found: while the majority of substrates was hydrated in an oxygen-independent manner by amino-acid catalysis, an enzyme-catalysed water addition to (E)-4-hydroxy-3-methylbut-2-enoic acid was proven to be oxygen-dependent. 18O2-labelling studies showed that no 18O2 was incorporated in the product. Therefore, a novel O2-dependent hydratase distinct from all characterised hydratases so far was found.

1,3-Diphenyl-2(13C)-hydroxy-3-methoxypropan-1-one was synthesised and used to probe the mechanism of a benzilic ester rearrangement (BER). Computational studies suggest that the preferred site of attack of the nucleophile in this benzilic ester rearrangement is on C-14. On the basis of these results a new reaction mechanism is proposed. Copyright © 2009 John Wiley & Sons, Ltd.

Anaerobic growth of Thermotoga neapolitana led maximum to hydrogen yield of 3.85 ± 0.07 mol H2/mol glucose and production rate of 51 ml/l/h. This productivity is strongly affected by stirring, pH buffering, N2 sparging and culture/headspace volume ratio. Embden–Meyerhoff pathway is the only glycolytic route in T. neapolitana but, under the conditions used in this study, about 12–15% of the biogas requires consumption of protein source. Reduction of the hydrogen yields below the theoretical 4 mol H2/mol glucose is mainly due to production of lactate and alanine that affect the availability of pyruvate/NADH for the hydrogenase, as well as to loss of part of glucose by conversion to fructose that is eventually released in the medium. Hydrogen productivity is modulated during the bacterial growth and major biogas synthesis is recorded in the stationary phase in concomitance with reduction of lactate synthesis. Apparently, this event is not consistent with an equal increase in acetate production. In agreement with the hydrogenase model recently proposed for the sister species Thermotoga maritima, this suggests that cellular NADH+ ratio has a crucial role on biogas synthesis.

Structural diversity of polypropionates arises from the amazing combination of acetate and propionate units. Feeding experiments with single and doubly 13 C -labelled precursors prove that the Mediterranean slug Placida dendritica utilizes intact C 3 -units for the biosynthesis of placidenes (e.g., 1 – 5 ), prototypes of a family of pyrone-containing polypropionates largely represented in fungi and marine invertebrates. These results show that fungi and molluscs have elaborated two distinct polyketide pathways for the synthesis of similar or even identical compounds.