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The lag phase lengthenings recorded for the proliferation ofEscherichia coli cultured in the presence of starch extracts irradiated with cobalt 60 reflect the bactericidal power of radiolysis products. The toxic effect increases with moisture content and esterification of certain hydroxyl functions of the starch, but does not vary after lipid extraction. Washing the starch before irradiation decreases lethality but lengthens the lag phase.

Fifteen yeast strains were selected for the production of food yeast from starchy substrates. From comparison with the amylolytic yeasts, a strain of Schwanniomyces castellii was selected and its characteristics are described.

The white-rot fungus Bjerkandera sp. strain BOL13 was capable of degrading toxaphene when supplied with wood chips, wheat husk or cane molasses as cosubstrates in batch culture experiments. Approximately 85% of toxaphene was removed when wheat husk was the main substrate. The production of lignin peroxidase was only stimulated when wheat husk was present in the liquid medium. Although xylanase was always detected, wheat husk supported the highest xylanase production. A negligible amount of β-glucosidase and cellulase were found in the batch culture medium. To the best of our knowledge, this is the first reported case of toxaphene degradation by white-rot fungi.

The identity of polyhydroxyalkanoates (PHA) storing bacteria selected under aerobic dynamic feeding conditions, using propionate as carbon source (reactor P), was determined by applying reverse transcriptase–polymerase chain reaction (RT-PCR) on micromanipulated cells and confirmed by fluorescence in situ hybridisation (FISH). Four genera, Amaricoccus, Azoarcus, Thauera and Paraccoccus were detected, the latter only rarely present. All the biomass was involved in PHA storage as shown by Nile Blue staining. By quantitative FISH, their specific amount was determined in this and two other systems using acetate as the carbon substrate (sequencing batch reactor [SBR] A and A1). SBR A and reactor P had the same sludge retention time (SRT, 10 days), while reactor A1 was operated with the SRT of 1 day and the double organic loading rate (OLR). Systems fed with acetate (41.1 ± 2.2 and 49.4 ± 1.4% total Bacteria, for A and A1, respectively) became enriched in Thauera independently on the SRT and OLR, while it was only present in a minor amount when propionate was used as a substrate (1.9 ± 0.2% total Bacteria). Amaricoccus was present in both reactors operated at 10 days SRT, favoured in the one fed with propionate (61.4 ± 1.9% total bacteria), and almost completely removed at the SRT of 1 day. Azoarcus cells were found in all the analysed systems (3.9 ± 0.3, 23.3 ± 1.5 and 45.9 ± 1.5 for P, A and A1, respectively), while Paracoccus was scarcely present.

Yeast cells producing the growth hormone somatomedin C (SMC) were constructed and applied in the immobilized form continuously for a period of over 10 days in a flow-through bioreactor. The construction of the MFα1-SMC fusion vector p336/1 is given as well as the results of the influence of various nutrients effecting hormone production. Immobilization of the transformed yeast cells is described and their application in a continuous bioreactor system. This study demonstrates the feasibility of a longterm and high-level hormone production by immobilized transformed yeast. The SMC productivities of free cells in batch and immobilized cells under continuous conditions were 0.2–0.3 and 0.5–0.6 mg per g wet cells and day, respectively.

The upstream region of the cellobiohydrolase gene cbhA of Clostridium thermocellum F7 was sequenced. It was found that this region contains the previously sequenced gene celK encoding an enzyme closely related to CbhA (cellulosomal subunit S3). The presence of a putative transcription terminator in the 524-bp intergenic region indicates that celK and cbhA are not cotranscribed as an operon. Sequence comparison between the two cellobiohydrolases revealed high sequence conservation in the catalytic domain and in the N-terminal cellulose-binding domain (CBD) homologous to CBD family IV, which binds specifically to amorphous cellulose and soluble cellooligosaccharides. In contrast to CbhA, CelK lacks a family III CBD capable of binding to crystalline cellulose. By partial amino acid sequence determination CelK was shown to be identical to cellulosomal subunit S5. CelK and CbhA were found to be members of subfamily E1 of cellulase family E (glycosylhydrolase family 9). Sequence comparison of catalytic domains of family E1 cellulases with C. thermocellum CelD, a family E1 endoglucanase of known three-dimensional structure, revealed a significant variation in the lengths of substrate-binding loops connecting the helices of the (α/α)6 barrel fold. The extended loops of CelK and CbhA might form an active-site tunnel, as found in the catalytic domains of fungal cellobiohydrolases.

 The paper describes some reaction engineering fundamentals of the separation of organic air pollutants (volatile organic compounds) from waste gases using fixed-bacteria monocultures (biocatalysts) in a trickle-bed reactor. In particular the influence of pollutant concentration and oxygen concentration are investigated. The separation efficiency of certain substances such as acetone and isopropanol depends strongly on the oxygen concentration. The results obtained can be described by a mathematical model based on the diffusion of oxygen into the biofilm (diffusion regime of the catalyst). The non-stationary operation of the reactor – interruption of the oxygen stream and strong fluctuation in the exhaust gas stream – showed that other components such as propionaldehyde and n-propanol could be eliminated for a certain time without oxygen. Propionic acid is formed.