1,720,974 research outputs found
Production in sea-water of thermostable alkaline proteases by a halotolerant strain of Bacillus licheniformis
No full textA halotolerant strain of Bacillus licheniformis, previously isolated from marine sediments, produced high protease activity during the early stationary phase of growth. The use of sea-water in the fermentation medium enhanced the production of this activity of 150%. After a partial purification, three different proteolytic enzymes could be detected, which were alkaline serine proteases, exhibiting optimal activity at pH 9.0 and at 70°C. The proteases were activated by NaCl, with a two, three-fold increase in activity and were stable in presence of 0.7% NaBO3, 0.5% NaClO and 3% H2 O2
PROTEINASE PRODUCTION BY HALOPHILIC ISOLATES FROM MARINE-SEDIMENTS
No full textTwenty-one strains of spore-forming bacteria were isolated from marine sediments of the Tyrrhenian seaboard (Livorno, Italy) and identified asBacillus licheniformis by their morphological, physiological and biochemical characteristics. All strains were able to grow at 15% NaCl and on media prepared with 100% seawater. In these conditions 75% of the strains were able to produce a bacitracin-like antibiotic and 100% of the strains showed proteolytic activity. Particularly, all strains showed proteinase production with an activity optimum at pH 8.5 and 60°C. Three strains produced high levels of proteolytic activity only when cultured in the presence of seawater
PROPERTIES OF 2 PECTIN LYASES PRODUCED BY AUREOBASIDIUM-PULLULANS LV-10
No full textTwo pectic lyases, L1 and L2, from culture liquids of Aureobasidium pullulans LV 10 were partially purified by ultrafiltration, CM-Sepharose 6B, DEAE-cellulose and/or Sephadex G 100 column chromatography, and characterized. L1 and L2 showed optimum activity at pH 5 and 7.5 respectively, and at 40°C. The molecular weights of the enzymes determined by gel filtration were estimated to be 89000 1000 and 55000 1000 for L1 and L2 respectively. Both lyases were activated by Ca2+ ions. L1 attacked highly esterified pectins, L2 attacked low methoxy-pectins in preference to polygalacturonic acid
Genotypic characterization of thermophilic bacilli: a study on new soil isolates and several reference strains
No full textA genotypic study using amplified ribosomal DNA restriction analysis (ARDRA), random amplified polymorphic DNA fingerprinting (RAPD) and ribosomal spacer analysis (RSA) in comparison with DNA-DNA reassociation experiments was carried out with 85 thermophilic Bacillus isolates from uncultivated soil of 14 different geographical areas and seventeen reference strains representing defined thermophilic Bacillus species. This approach permitted the attribution of 51 % of the new isolates to the Bacillus thermoleovorans group and the identification of 40% of the new isolates as B. “thermodenitrificans”. Moreover, 2 strains were assigned to B. pallidus species and 1 isolate to B. thermosphaericus species. The remaining 6% of our thermophilic isolates from soil, constituting 2 DNA-DNA homology groups, are still unidentified. A detailed genotypic characterization of the heterogeneous species of B. thermoleovorans and B. stearothermophilus was also presented
DETECTION AND CHARACTERIZATION OF NATURALLY-OCCURRING PLASMIDS IN BACILLUS-LICHENIFORMIS
No full textTwenty-two Bacillus licheniformis strains, freshly isolated from pasture-land, were studied for the presence of plasmid DNA. Among these strains, 14 were shown to harbor one or more plasmids of different size. Southern-hybridization experiments showed a high homology between all plasmids investigated and a 2.2-kb PvuII/HindIII fragment of pBL1, a B. licheniformis plasmid previously isolated. Three fragments of pBL1, including the 2.2-kb PvuII/HindIII region, were cloned into pJH101 vector. The resulting chimeras were able to transform Bacillus subtilis. The fragment with high homology probably contains the region with the replicative functions of plasmids from B. licheniformis species
Production of laccase by Botrytis cinerea and fermentation studies with strain F226
No full textAfter induction, seven strains ofBotrytis cinerea released into the culture broth considerable amounts of laccase in a brief production time. The set-up of a suitable production process was studied with a selected strain in a 10-L fermenter. The optimum fermentation conditions were a 3% inoculum with a high degree of sporulation, a simple medium containing 20 g L–1 of glucose and 2 g L–1 of yeast extract at pH 3.5, 2 g L–1 gallic acid as inducer, added after 2 days of growth, an agitation speed of 300 rpm, an aeration rate of 1.2 vvm and a temperature of 24°C. By optimizing the culture conditions, the enzyme activity reached 28 U ml–1 in 5 days with a specific activity of 560 U mg–1 protein. The best procedure to obtain a suitable crude enzyme preparation was concentration of the supernatant medium to 10% of the initial volume by ultrafiltration, followed by a fractional precipitation with ethanol. The optimum pH and temperature for laccase activity were 5.5 and 40°C, respectively, with syringaldazine as the substrate
Specific identification of Lactobacillus helveticus by PCR with pepC, pepN and htrA targeted primers
No full textSpecific regions in three genes coding for aminopeptidases C and N, and a trypsin-like serine protease were selected as species-specific
primer sequences for rapid and reliable identification of Lactobacillus helveticus strains. The PCR procedures carried out gave specific 524-,
726- and 918-bp amplificates, with DNA isolated from L. helveticus. No PCR product was generated for closely related bacteria. The
amplification products were also screened for their species specificity in dot blot hybridization with representatives of the most closely
related genera and species and a number of other bacterial species
PCR fingerprinting of whole genomes: the spacers between the 16S and 23S rRNA genes and of intergenic tRNA gene regions reveal a different intraspecific genomic variability of Bacillus cereus and Bacillus licheniformis
No full textGenomic diversity in 21 strains of Bacillus cereus and 10 strains of Bacillus licheniformis was investigated by random amplified polymorphic DNA (RAPD) analysis, which samples the whole genome, and by two PCR fingerprinting techniques sampling the hypervariable spacers between the conserved 16S and 23S rRNA genes of the rRNA gene operon (ITS-PCR) and regions between tRNA genes (tDNA-PCR). RAPD analysis showed a remarkable diversity among strains of B. cereus that was not observed with the rRNA and tRNA intergenicspacer-targeted PCR, where all the strains showed practically identical fingerprints. A wide variability among the B. cereus strains was also observed in the plasmid profiles, suggesting that the genetic diversity within B. cereus species can arise from plasmid transfer. One contribution to the diversity detected by RAPD analysis was determined by the presence of large extrachromosomal elements that were amplified during RAPD analysis as shown by Southern hybridization experiments, In contrast to the strains of B. cereus, the 10 strains of B. licheniformis were grouped into two clusters which were the same with all the methods employed, The 16S rRNA genes were identical in all 10 strains when examined using single strand conformation polymorphism analysis after digestion with Alul and Rsal. From these data we hypothesize two different evolutionary schemes for the two species
MAPPING OF 3 PLASMIDS FROM LACTOBACILLUS-HELVETICUS ATCC-15009
No full textThree plasmids isolated from Lactobacillus helveticus ATCC 15009 were analysed by restriction digestion. A restriction map of the 22.0, 6.0 and 3.5 kb plasmids is presented. The existence of genetic markers such as carbohydrate fermentation, lactose metabolism, antibiotics and heavy metal ions resistance was also investigated but the plasmids remain cryptic
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