Application of heat compensation calorimetry to an E. coli fed-batch process.

The application of biocalorimetry to fermentation processes offers advantageous insights, while being less complex compared to other, sophisticated PAT solutions. Although the general concept is established, calorimetric methods vary in detail. In this work, a special approach, called heat compensation calorimetry, was applied to an E. coli fed-batch process. Much work has been done for batch processes, proving the validity and accuracy of this calorimetric mode. However, the adaption of this strategy to fed-batch processes has some implications. In the first section of this work, batch fermentations were performed, comparing heat capacity calorimetry to the compensation mode. Both processes showed very good agreement by means of growth behavior. The heat related differences, e.g. temperature profiles, were obvious. In addition, the impact of the chosen mode on the calculation of in-process heat transfer coefficients was shown. Finally, a fed-batch fermentation was performed. The compensation mode was kept sufficiently, up to the point where the metabolic heat production accelerated strongly. Controller tuning was a neuralgic point, which would have needed further optimization under these conditions. Nevertheless, in the present work it was possible to realize a working compensation process while demonstrating critical aspects that must be considered when establishing such approach.

Measurement of heat transfer coefficients in stirred single-use bioreactors by the decay of hydrogen peroxide.

Single-use bioreactors are barely described by means of their heat transfer characteristics, although some of their properties might affect this process. Steady-state methods that use external heat sources enable precise investigations. One option, commonly present in stirred, stainless steel tanks, is to use adjustable electrical heaters. An alternative are exothermic chemical reactions that offer a higher flexibility and scalability. Here, the catalytic decay of hydrogen peroxide was considered a possible reaction, because of the high reaction enthalpy of -98.2 kJ/mole and its uncritical reaction products. To establish the reaction, a proper catalyst needed to be determined upfront. Three candidates were screened: catalase, iron(III)-nitrate and manganese(IV)-oxide. Whilst catalase showed strong inactivation kinetic and general instability and iron(III)-nitrate solution has a pH of 2, it was decided to use manganese(IV)-oxide for the bioreactor studies. First, a comparison between electrical and chemical power input in a benchtop glass bioreactor of 3.5 L showed good agreement. Afterwards the method was transferred to a 50 L stirred single-use bioreactor. The deviation in the final results was acceptable. The heat transfer coefficient for the electrical method was 242 W/m2/K, while the value achieved with the chemical differed by less than 5%. Finally, experiments were carried out in a 200 L single-use bioreactor proving the applicability of the chemical power input at technical relevant scales.

Aerobic biodegradation of the brominated flame retardants, dibromoneopentyl glycol and tribromoneopentyl alcohol.

Halogenated organic compounds constitute one of the largest and most diverse groups of chemicals in the environment. Many of these compounds are toxic, persistent and, as a result of their often limited biodegradability, tend to bioaccumulate in the environment. Dibromoneopentyl glycol (DBNPG) and tribromoneopentyl alcohol (TBNPA) are brominated flame retardants commonly used as additives during the manufacture of plastic polymers and as chemical intermediates in the synthesis of other flame retardants. Both are classified as not readily biodegradable. In this paper, we demonstrate the biodegradation of both DBNPG and TBNPA by a common bacterial consortium under aerobic conditions in enrichment cultures containing yeast extract. DBNPG and TBNPA biodegradation is accompanied by a release of bromide into the medium, due to a biological debromination reaction. Molecular analysis of the clone library PCR amplified 16S rRNA gene was used to characterize the bacterial consortium involved in the biodegradation.

Biotechnological production and bioactivities of mollisin and two new, structurally related fungal naphthoquinone metabolites.

The antibiotic and fungicidal deuteromycete Mollisia caesia Sacc. was cultivated on a large scale. Mollisin (1; = 8-(dichloroacetyl)-5-hydroxy-2,7-dimethylnaphthalene-1,4-dione) and two new tri- and tetrahalogenated metabolites, mollisin A (2) and mollisin B (3) were isolated from M. caesia. The formation of 2 and 3 indicates that the biosynthesis of these compounds starts from a C(16) polyketide (Scheme). Mollisin (1) shows strong fungicidal activities against Sclerophoma pityophila (Corda) v. Höhn and Heterobasidion annosum (Fr.) Bref., which is one of the most-destructive basidiomycetes in coniferous forests. The metabolites 1-3 possess interesting pharmacological activities in assays in search of anti-inflammatory and antiproliferative drugs.