Amare Gessesse | PubMed Health

PubMed2006

Nesterenkonia aethiopica sp. nov., an alkaliphilic, moderate halophile isolated from an Ethiopian soda lake.

Strain DSM 17733(T), isolated from the shore of Lake Abjata in Ethiopia, is a heterotrophic, alkaliphilic, moderately halophilic, Gram-positive, strictly aerobic, non-motile,non-endospore-forming bacterium. The organism grows optimally at 30-37 degrees C, pH 9 and 3 % (w/v) NaCl. Analysis of the cell wall showed the presence of murein of the type L-lys-gly-L-Glu, variation A4alpha. The G + C content of the genomic DNA was 69.0 mol%. Sequence analysis of 16S rRNA gene sequence of strain DSM 17733(T) placed the isolate in the genus Nesterenkonia. DNA-DNA hybridization of DSM 17733(T) with those organisms with the closest phylogenetic affiliation, i.e. Nesterenkonia halobia, Nesterenkonia lacusekhoensis and Nesterenkonia xinjiangensis, gave relatedness values of 48.5 %, 63.7 % (repetition, 57.2 %) and 35.7 % (repetition, 29.3 %), respectively. On the basis of both phenotypic and phylogenetic criteria and the low levels of DNA-DNA relatedness with the phylogenetically closest species N. xinjiangensis and N. halobia, it is proposed that the isolate be classified in a novel species, Nesterenkonia aethiopica sp. nov. The type strain is DSM 17733(T) (=CCUG 48939(T)).

Ethiopia↗

PubMed2003

Lipase and protease extraction from activated sludge.

In the process of wastewater treatment hydrolysis of polymeric substances is the first and rate-limiting step. A closer study of the enzymes catalysing these reactions is essential for a better understanding of the microbial activity in the wastewater treatment process. Therefore, development of gentle and efficient enzyme extraction methods from environmental samples is very important. In this study we present a method for the extraction of lipases and proteases from activated sludge using the non-ionic detergent Triton X-100, EDTA, and cation exchange resin (CER), alone or in combination for the extraction of lipases and proteases from activated sludge. The sludge was continuously stirred in the presence of either buffer alone or in the presence of detergent and/or chelating agents. In all cases, a marked reduction in floc size was observed upon continuous stirring. However, no lipase activity and negligible protease activity was extracted in the presence of buffer alone, indicating that enzyme extraction was not due to shear force alone. The highest lipase activity was extracted using 0.1% Triton X-100 above which the activity was gradually decreasing. For proteases, the highest activity was obtained in the presence of 0.5% Triton X-100 and no decrease in activity was observed. Differences observed in the extraction efficiency of the two enzymes indicate the need for optimisation of the extraction process for the different enzymes or the extracellular polymeric substances from activated sludge.

Cation Exchange Resins↗