The key to acetate: metabolic fluxes of acetic acid bacteria under cocoa pulp fermentation-simulating conditions.

Acetic acid bacteria (AAB) play an important role during cocoa fermentation, as their main product, acetate, is a major driver for the development of the desired cocoa flavors. Here, we investigated the specialized metabolism of these bacteria under cocoa pulp fermentation-simulating conditions. A carefully designed combination of parallel 13C isotope labeling experiments allowed the elucidation of intracellular fluxes in the complex environment of cocoa pulp, when lactate and ethanol were included as primary substrates among undefined ingredients.

Core fluxome and metafluxome of lactic acid bacteria under simulated cocoa pulp fermentation conditions.

In the present work, simulated cocoa fermentation was investigated at the level of metabolic pathway fluxes (fluxome) of lactic acid bacteria (LAB), which are typically found in the microbial consortium known to convert nutrients from the cocoa pulp into organic acids. A comprehensive (13)C labeling approach allowed to quantify carbon fluxes during simulated cocoa fermentation by (i) parallel (13)C studies with [(13)C6]glucose, [1,2-(13)C2]glucose, and [(13)C6]fructose, respectively, (ii) gas chromatography-mass spectrometry (GC/MS) analysis of secreted acetate and lactate, (iii) stoichiometric profiling, and (iv) isotopomer modeling for flux calculation. The study of several strains of L.

Debottlenecking recombinant protein production in Bacillus megaterium under large-scale conditions--targeted precursor feeding designed from metabolomics.

In the present work the impact of large production scale was investigated for Bacillus megaterium expressing green fluorescent protein (GFP). Specifically designed scale-down studies, mimicking the intermittent and continuous nutrient supply of large- and small-scale processes, were carried out for this purpose. The recombinant strain revealed a 40% reduced GFP yield for the large-scale conditions.

On the origin of the electrostatic surface potential of Aspergillus niger spores in acidic environments.

The electrostatic surface potential of fungal spores is generally regarded as potentially influencing spore aggregation and pellet formation in submerged cultures of filamentous fungi. Spores of Aspergillus niger are typically characterized by negative zeta potentials over a wide range of pH values. In this study, this particular behavior is ascribed to the presence of an extensive melanin coating.