Determination of the kinetic parameters in continuous cultivation byDebaryomyces hansenii grown on D-xylose

Summary The kinetic parameters of the yeastDebaryomyces hansenii grown in continous cultivation on D-xylose were determined by different methods. While the values obtained for μ_m by the steady state and the washout methods only gave a 3% difference, the determined K_s values by the steady state and the maximal biomass output methods led a to a 305% difference. The latter method was suggested to overestimate the K_s value.     

Partition behaviour of horseradish peroxidase isoenzymes in aqueous two-phase poly(ethyleneglycol)/phosphate systems

Summary Partition of purified horseradish peroxidase isoenzymes in aqueous two-phase systems was not affected by pH changes, but tie-line length and NaCl addition greatly increased the partition coefficient of all three isoenzymes, the former having more influence than the latter. In all systems, K were higher for acidic than those for neutral and basic isoenzymes, and K for basic were the lowest.     

Microbial production and purification of arachidonic acid

Summary Mortierella alpina S-17 cultivated in shaker flasks in the semisynthetic liquid medium with 3% glucose at 28 °C for 14 days accumulated 2.1 g/l of intracellular lipid rich in arachidonic acid (ARA). The content of ARA was 50 % of the total fatty acids. The simple method for high pure methyl arachidonate preparation was developed.     

Simultaneous high-biomass protein production and nutrient removal using Spirulina maxima in sea water supplemented with anaerobic effluents

Maximum protein accumulation (71%, w/w) and nutrient removal by a mutant strain of Spirulina maxima growing on sea water supplemented with anaerobically treated pig slurry was achieved at 30°C with constant illumination (60 to 70 Em^-2s^-1), using a flow rate of 14.5 cm s^-1 (20 rev. min^-1 of a paddle wheel). Total phosphates were decreased by 99% and all ammonia-N was removed under these conditions.The authors are with the Department of Environmental Biotechnology, Institute of Ecology, Aptd Postal 63, Xalapa, Ver., Mexico     

Desulphurization of dibenzothiophene by bacteria

Four out of 187 strains, from enrichment cultures of dibenzothiophene (DBT), grew on DBT or thiophene 2-carboxylate as S sources. The four isolates, presumptively identified as Agrobacterium sp., Xanthomonas sp. and Corynebacterium spp., individually and together desulphurized DBT, producing 2-hydroxybiphenyl and sulphate.M. Constanti and A. Bordons are with the Departament de Bioquímica i Biotecnologia, and J. Giralt is with the Departament d'Enginyeria Química, both of the Universitat Rovira i Virgili, Pl. Imperial Tarraco 1, 43005 Tarragona, Catatonia, Spain     

Sandhoff disease in Argentina: high frequency of a splice site mutation in the HEXB gene and correlation between enzyme and DNA-based tests for heterozygote detection

The level of -hexosaminidase activity in plasma and leukocytes and the frequency of three known HEXB mutations were studied in an Argentinean deme with high incidence of infantile Sandhoff disease. Two mutations were previously identified in one of two Sandhoff patients from the region, a splice mutation, IVS-2+1 GA, and a 4-bp deletion, CTTT_782–785. These mutations, and a 16kb deletion from the 5' end of the HEXB gene common in non-Argentineans, were screened in 9 Sandhoff patients (all unrelated), 24 obligate heterozygotes, 33 additional individuals belonging to families with affected members, and 64 randomly ascertained individuals from the high risk region. Of 31 independent alleles examined, including those of the two patients previously reported, 30 had the IVS-2 splice mutation and only the originally reported patient had the CTTT deletion. The 16-kb deletion was not observed. Further, among the 57 unaffected members of families with a previous history of Sandhoff disease, and absolute correlation was found between carrier diagnosis by enzyme assay of leukocytes and the DNA-based tests for mutation. One of the 64 controls was classified as a carrier by enzyme assay but did not have one of the three mutations screened. We conclude that a single mutation predominates in this Argentinean population and that the DNA-based test can be an effective supplement or alternative to enzyme-based testing.     

Self-fertility and associated flower head traits in the Iberian taxa ofLactuca and related genera (Asteraceae: Lactuceae)

Sexual reproduction is the main reproduction mechanism among the 14 wild Iberian taxa ofLactuca, Prenanthes, Cicerbita, andMycelis. High levels of self-fertilization occur inLactuca, as well as facultative and obligate xenogamy. Xenogamy is strongly correlated with large capitula having blue or bright yellow colouration, high P/O ratios, and long anthesis, whereas self-fertilization is correlated with smaller capitula having pale yellow colouration, small P/O ratios, and short anthesis. Large variations occur in P/O index among taxa showing similar fertilization mechanism, probably in relation to the number of florets included in flower heads. Interesting differences in reproductive systems have been detected between subspecies ofLactuca viminea.     

A descriptive study of some Antarctic notaspidean opisthobranchs (Gastropoda), with description of a new genus and species

During the expedition “ANTARTIDA 9101”, organized by the Spanish Oceanographic Institute to the South Orkney Islands, four specimens of notaspidean gastropods were collected. Three of them have been identified as Bathyberthella antarctica Willan and Bertsch, 1987. However, one specimen, although externally similar to B. antarctica, had an internal anatomy exhibiting features that have enabled us to consider it to be a new genus and species. This new taxon is characterized by the presence of jaws without mandibular elements, and a vaginal gland that partially surrounds the distal region of the vaginal duct. In this paper the new genus and species is described. Additional anatomical data of the specimens of B. antarctica collected during the expedition are also included.     

Determination of ammonium and L-Glutamine in hybridoma cell cultures by sequential flow injection analysis

A flow injection anlytical system based on a gas diffusion membrane module for ammonia and an ammonium flow-through potentiometric detector has been set up for measurement of L-glutamine and ammonium ions in hybridoma cell cultures. The main feature of the system is that the same basic analytical concept and equipment is used in both measurements, the only difference being for the determination of L-glutamine, in which the sample flows through an immobilized glutaminase cartridge. The conditions to enable the performance of both analysis consecutively, avoiding potential interferences by unwanted deamination of other compounds in the samples, have been determined. Finally, the proposed system has been compared with reference analytical methods for batch hybridoma cell culture experiments.     

Importance of fungi in the diet of Gammarus pulex and Asellus aquaticus

An important component of the interaction between macroinvertebrates and leaf litter in streams in the extent to which consumers can differentiate between undecomposed and decomposing leaves. The detritivores Gammarus pulex and Asellus aquaticus fed preferentially on conditioned rather on unconditioned leaf material. Growth in A. aquaticus was significantly reduced when unconditioned leaves were provided, but in G. pulex no significant effect of conditioning on growth was observed. The capacity of G. pulex to tolerate reductions in food quality seems to be a consequence of a compensatory system in which respiration rates change to compensate for reductions in food quality. In this way a constant growth rate is maintained. Increases in ingestion rates to compensate for low quality food were not observed.