Production of pectinesterase and polygalacturonase by Aspergillus niger in submerged and solid state systems

Production of pectinesterase and polygalacturonase by Aspergillus niger was studied in submerged and solid-state fermentation systems. With pectin as a sole carbon source, pectinesterase and polygalacturonase production were four and six times higher respectively in a solid state system than in a submerged fermentation system and required a shorter time for enzyme production. The addition of glucose increased pectinesterase and polygalacturonase production in the solid state system but in submerged fermentation the production was markedly inhibited. A comparison of enzyme productivities showed that those determined for pectinesterase and polygalacturonase with pectin as a carbon source were three and five times higher by using the solid state rather than the submerged fermentation system. The productivities of the two enzymes were affected by glucose in both fermentation systems. The membranes of cells from the solid state fermentation showed increased levels of C18:1, C16:0 and C18:0 fatty acids. Differences in the regulation of enzyme synthesis by Aspergillus niger depended on the fermentation system, favoring the solid state over the submerged fermentation for pectinase production. Received 12 May 1997/ Accepted in revised form 19 September 1997     

It’s not what it looks like: molecular data fails to substantiate morphological differences in two sea hares (Mollusca,Heterobranchia, Aplysiidae) from southern Brazil

Species of sea hares have been recognized traditionally based on morphological traits, mainly the radula, external coloration, and reproductive anatomy. However, recent studies have shown substantial color variation in some sea slug species. Molecular data have been successfully used to differentiate morphologically similar species of “opisthobranchs” and resolve questions on the taxonomic value of color. The objective of this paper is to use molecular data in an attempt to elucidate whether specimens of Aplysia brasiliana with distinct colorations and morphologies are actually the same species. To this end, DNA from 14 specimens of A. brasiliana was extracted, including five specimens identified as a distinct morphotype from typical A. brasiliana. Although the two morphotypes have consistent differences in their external morphology and radula, the molecular data confirmed that there are no significant genetic differences between them. This is another example of the need to re-evaluate taxonomic decisions based on morphology in light of molecular evidence.     

Exoprotease activity of Leuconostoc oenos in stress conditions

Exoprotease activity during 48 h of total energy and nutrient starvation was examined in Leuconostoc oenos X₂L isolated from wine. Starved cells after 2 h of incubation at 30 °C in citrate buffer, 0.05 mmol 1⁻¹ pH 5, showed greater extracellular proteolytic activity than at the onset of starvation. In the presence of 60 mg l⁻¹ SO₂ and 8% or 12% ethanol, the proteolytic activity was higher ; 10 mmol l⁻¹ Ca²⁺ and Mg²⁺ produced an increase in protease activity during starvation. Glucose and 2-deoxyglucose (2-DOG) were found to repress synthesis by 80% and 100%, respectively. Cyclic adenosine 3'-5'-phosphate increased the exoprotease activity and reverted the repression by glucose and 2-DOG. De novo synthesis of proteins was required for the exoprotease activity by cells submitted to stress conditions. The absence of protease activity in the supernatant fluids from chloramphenicol-treated cells indicated that the activity is a result of deliberate release and not of passive cell lysis.     

Cardiovascular effects of 1,8-cineole,a terpenoid oxide present in many plant essential oils,in normotensive rats

The cardiovascular effects of i.v. treatment with 1,8-cineole, a monoterpenic oxide present in many plant essential oils, were investigated in normotensive rats. This study examined (i) whether the autonomic nervous system is involved in the mediation of 1,8-cineole-induced changes in mean aortic pressure (MAP) and heart rate (HR) and (ii) whether the hypotensive effects of 1,8-cineole could result from its vasodilatory effects directly upon vascular smooth muscle. In both pentobarbital-anesthetized and conscious, freely moving rats, bolus injections of 1,8-cineole (0.3-10 mg/kg, i.v.) elicited similar and dose-dependent decreases in MAP. Concomitantly, 1,8-cineole significantly decreased HR only at the highest dose (10 mg/kg). Pretreatment of anesthetized rats with bilateral vagotomy significantly reduced the bradycardic responses to 1,8-cineole (10 mg/kg) without affecting hypotension. In conscious rats, i.v. pretreatment with methylatropine (1 mg/kg), atenolol (1.5 mg/kg), or hexamethonium (30 mg/kg) had no significant effects on the 1,8-cineole-induced hypotension, while bradycardic responses to 1,8-cineole (10 mg/kg) were significantly reduced by methylatropine. In rat isolated thoracic aorta preparations, 1,8-cineole (0.006-2.6 mM) induced a concentration-dependent reduction of the contraction induced by potassium (60 mM). This is the first physiological evidence that i.v. treatment with 1,8-cineole in either anesthetized or conscious rats elicits hypotension; this effect seems related to an active vascular relaxation rather than withdrawal of sympathetic tone.     

Selenium nanoparticles from Lactobacillus paracasei HM1 capable of antagonizing animal pathogenic fungi as a new source from human breast milk

The current study was performed to develop a simple, safe, and cost-effective technique for the biosynthesis of selenium nanoparticles (SeNPs) from lactic acid bacteria (LAB) isolated from human breast milk with antifungal activity against animal pathogenic fungi. The LAB was selected based on their speed of transforming sodium selenite (Na₂SeO₃) to SeNPs. Out of the four identified LAB isolates, only one strain produced dark red color within 32 h of incubation, indicating that this isolate was the fastest in transforming Na₂SeO₃ to SeNPs; and was chosen for the biosynthesis of LAB-SeNPs. The superior isolate was further identified as Lactobacillus paracasei HM1 (MW390875) based on matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and phylogenetic tree analysis of 16S rRNA sequence alignments. The optimum experimental conditions for the biosynthesis of SeNPs by L. paracasei HM1 were found to be pH (6.0), temperature (35˚C), Na₂SeO₃ (4.0 mM), reaction time (32 h), and agitation speed (160 rpm). The ultraviolet absorbance of L. paracasei-SeNPs was detected at 300 nm, and the transmission electron microscopy (TEM) captured a diameter range between 3.0 and 50.0 nm. The energy-dispersive X-ray spectroscopy (EDX) and the Fourier-transform infrared spectroscopy (FTIR) provided a clear image of the active groups associated with the stability of L. paracasei-SeNPs. The size of L. paracasei-SeNPs using dynamic light scattering technique was 56.91 ± 1.8 nm, and zeta potential value was −20.1 ± 0.6 mV in one peak. The data also revealed that L. paracasei-SeNPs effectively inhibited the growth of Candida and Fusarium species, and this was further confirmed by scanning electron microscopy (SEM). The current study concluded that the SeNPs obtained from L. paracasei HM1 could be used to prepare biological antifungal formulations effective against major animal pathogenic fungi. The antifungal activity of the biologically synthesized SeNPs using L. paracasei HM1 outperforms the chemically produced SeNPs. In vivo studies showing the antagonistic effect of SeNPs on pathogenic fungi are underway to demonstrate the potential of a therapeutic agent to treat animals against major infectious fungal diseases.     

Environmental Scanning Electron Microscopy characterization of the adhesion of conidia from <Emphasis Type="Italic">Penicillium expansum</Emphasis> to cedar wood substrata at different pH values

Initial microbial adhesion to surfaces is a complicated process that is affected by a number of factors. An important property of a solution that may influence adhesion is pH. The surface properties of the cedar wood were characterized by the sessile drop technique. Moreover, the interfacial free energy of surface adhesion to the cedar wood was determined under pH values (2, 3, 5, 7, 9 and 11). The results showed that cedar wood examined at different pH levels could be considered hydrophobic ranged from Giwi = ?13.1 mJ/m² to Giwi = ?75 mJ/m². We noted that the electron-donor character of cedar wood was important at both basic and limit acidic conditions (pH 11 and pH 3) and it decreased at intermediate pH (pH 5). The cedar wood substratum presents a weak electron acceptor under various pH’s. In addition, the adhesion of conidia from Penicilllium expansum to the cedar wood surfaces at different pH values (2, 3, 5, 7, 9 and 11) was investigated using Environmental Scanning Electron Microscopy and image analysis was assessed with the Mathlab^® program. The data analysis showed that the conidia from P. expansum were strongly influenced by the pH. The maximum adhesion occurs in the pH 11 and pH 3 and decreased to 24% at pH 5.     

Linkage between bacterial and fungal rhizosphere communities in hydrocarbon-contaminated soils is related to plant phylogeny

Phytoremediation is an attractive alternative to excavating and chemically treating contaminated soils. Certain plants can directly bioremediate by sequestering and/or transforming pollutants, but plants may also enhance bioremediation by promoting contaminant-degrading microorganisms in soils. In this study, we used high-throughput sequencing of bacterial 16S rRNA genes and the fungal internal transcribed spacer (ITS) region to compare the community composition of 66 soil samples from the rhizosphere of planted willows (Salix spp.) and six unplanted control samples at the site of a former petrochemical plant. The Bray–Curtis distance between bacterial communities across willow cultivars was significantly correlated with the distance between fungal communities in uncontaminated and moderately contaminated soils but not in highly contaminated (HC) soils (>2000 mg kg⁻¹ hydrocarbons). The mean dissimilarity between fungal, but not bacterial, communities from the rhizosphere of different cultivars increased substantially in the HC blocks. This divergence was partly related to high fungal sensitivity to hydrocarbon contaminants, as demonstrated by reduced Shannon diversity, but also to a stronger influence of willows on fungal communities. Abundance of the fungal class Pezizomycetes in HC soils was directly related to willow phylogeny, with Pezizomycetes dominating the rhizosphere of a monophyletic cluster of cultivars, while remaining in low relative abundance in other soils. This has implications for plant selection in phytoremediation, as fungal associations may affect the health of introduced plants and the success of co-inoculated microbial strains. An integrated understanding of the relationships between fungi, bacteria and plants will enable the design of treatments that specifically promote effective bioremediating communities.     

Purification and characterization of a thermostable α-galactosidase from Thielavia terrestris NRRL 8126 in solid state fermentation

Several seeds and husks of some plants belonging to leguminosae, Graminae, Compositae and Palmae were evaluated as carbon substrates to produce α-galactosidase (α-Gal) by the thermophilic fungus, Thielavia terrestris NRRL 8126 in solid substrate fermentation. The results showed that Cicer arietinum (chick pea seed) was the best substrate for α-Gal production. The crude enzyme was precipitated by ammonium sulphate (60%) and purified by gel filtration on sephadex G-100 followed by ion exchange chromatography on DEAE-Cellulose. The final purification fold of the enzyme was 30.42. The temperature and pH optima of purified α-Gal from Thielavia terrestris were 70 °C and 6.5, respectively. The enzyme showed high thermal stability at 70 °C and 75 °C and the half-life of the α-Gal at 90 °C was 45 min. Km of the purified enzyme was 1.31 mM. The purified enzyme was inhibited by Ag2+, Hg2+, Zn2+, Ba2+, Mg2+, Mn2+ and Fe2+ at 5 mM and 10 mM. Also, EDTA, sodium arsenate, L-cysteine and iodoacetate inhibited the enzyme activity. On the other hand, Ca2+, Cu2+, K+ and Na+ slightly enhanced the enzyme activity at 5 mM while at 10 mM they caused inhibition. The molecular weight of the α-Gal was estimated to be 82 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This enzyme displays a number of biochemical properties that make it a potentially strong candidate for biotechnological and medicinal applications.     

Preliminary Observations on the Pathogenesis of a Virulent Strain of Newcastle Disease Virus in Chickens

Development of Newcastle disease, after experimental and natural infection with the virulent strain VLT of Newcastle disease virus, and its growth and distribution in some selected tissues as assayed by the enumeration of plaques are reported.