Bioaugmented sulfur-oxidizing denitrification system with <Emphasis Type="Italic">Alcaligenes defragrans</Emphasis> B21 for high nitrate containing wastewater treatment

The performance of enriched sludge augmented with the B21 strain of Alcaligenes defragrans was compared with that of enriched sludge, as well as with pure Alcaligenes defragrans B21, in the context of a sulfur-oxidizing denitrification (SOD) process. In synthetic wastewater treatment containing 100–1,000 mg NO₃⁻-N/L, the single strain-seeded system exhibited superior performance, featuring higher efficiency and a shorter startup period, provided nitrate loading rate was less than 0.2 kg NO₃⁻-N/m³ per day. At nitrate loading rate of more than 0.5 kg NO₃⁻-N/m³ per day, the bioaugmented sludge system showed higher resistance to shock loading than two other systems. However, no advantage of the bioaugmented system over the enriched sludge system without B21 strain was observed in overall efficiency of denitrification. Both the bioaugmented sludge and enriched sludge systems obtained stable denitrification performance of more than 80% at nitrate loading rate of up to 2 kg NO₃⁻-N/m³ per day.     

Selection of Trichoderma strains capable of increasing laccase production by Pleurotus ostreatus and Agaricus bisporus in dual cultures

Aims:  To select Trichoderma strains for enhanced laccase production in Pleurotus ostreatus or Agaricus bisporus cultures.
Methods and Results:  Laccase production by P. ostreatus and A. bisporus was evaluated in liquid (axenic) and solid (dual cultures) malt extract medium. Oxidation of ABTS, DMP and syringaldazine was evaluated in order to assess the potential of Trichoderma strains to enhance laccase production by basidiomycetes. Selected Pleurotus–Trichoderma interactions yielded higher increases in laccase volumetric activity and an additional laccase isoform was produced. By contrast, Agaricus–Trichoderma interactions lead to smaller increases on laccase volumetric activity, probably as result of repression (or degradation) towards one of the laccases isoforms.
Conclusions:  The strains of P. ostreatus and A. bisporus assessed in this work showed good potential as laccase producers. The Trichoderma -mediated biological stimulation of laccase production by P. ostreatus and A. bisporus is relevant in order to develop highly productive processes.
Significance and Impact of the Study:  Extracellular laccases from basidiomycetes are produced only in small amounts. It is therefore important to increase process productivity for potential industrial applications. The results from this study enable the selection Trichoderma strains capable of increasing laccase production by P. ostreatus or A. bisporus in dual cultures.     

Sequential Thermochemical Hydrolysis of Corncobs and Enzymatic Saccharification of the Whole Slurry Followed by Fermentation of Solubilized Sugars to Ethanol with the Ethanologenic Strain <Emphasis Type="Italic">Escherichia coli</Emphasis> MS04

Interest in the use of corncobs as feedstock for bioethanol production is growing. This study assesses the feasibility of sequential thermochemical diluted sulfuric acid pretreatment of corncobs at moderate temperature to hydrolyze the hemicellulosic fraction, followed by enzymatic hydrolysis of the whole slurry, and fermentation of the obtained syrup. The total sugar concentration after enzymatic hydrolysis was 85.21 g/l, i.e., 86 % of the sugars were liberated from the polymeric fractions, together with a low amount of furfural (0.26 g/l) and 4.01 g/l of acetic acid. The syrups, which contained 36.3, 40.9, 4.47, and 1.84 g/l of xylose, glucose, arabinose, and mannose, respectively, were fermented (pH 7, 37 °C, 150 rpm) to ethanol with the metabolically engineered acetate-tolerant Escherichia coli strain MS04 under non-aerated conditions, producing 35 g/l of ethanol in 18 h (1.94 g_EtOH/l/h), i.e., a conversion yield greater than 80 % of the theoretical value based on total sugars was obtained. Hence, using the procedures developed in this study, 288 l of ethanol can be produced per metric ton of dry corncobs. Strain MS04 can ferment sugars in the presence of acetate, and the amount of furans generated during the sequential thermochemical and enzymatic hydrolysis was low; hence, the detoxification step was avoided. The residual salts, acetic acid, and solubilized lignin present in the syrup did not interfere with the production of ethanol by E. coli MS04 and the results show that this strain can metabolize mixtures of glucose and xylose simultaneously.     

Trapped conformational states of semiquinone (D+*QB-*) formed by B-branch electron transfer at low temperature in Rhodobacter sphaeroides reaction centers

The reaction center (RC) from Rhodobacter sphaeroides captures light energy by electron transfer between quinones QA and QB, involving a conformational gating step. In this work, conformational states of D+*QB-* were trapped (80 K) and studied using EPR spectroscopy in native and mutant RCs that lack QA in which QB was reduced by the bacteriopheophytin along the B-branch. In mutant RCs frozen in the dark, a light induced EPR signal due to D+*QB-* formed in 30% of the sample with low quantum yield (0.2%-20%) and decayed in 6 s. A small signal with similar characteristics was also observed in native RCs. In contrast, the EPR signal due to D+*QB-* in mutant RCs illuminated while freezing formed in approximately 95% of the sample did not decay (tau >107 s) at 80 K (also observed in the native RC). In all samples, the observed g-values were the same (g = 2.0026), indicating that all active QB-*'s were located in a proximal conformation coupled with the nonheme Fe2+. We propose that before electron transfer at 80 K, the majority (approximately 70%) of QB, structurally located in the distal site, was not stably reducible, whereas the minority (approximately 30%) of active configurations was in the proximal site. The large difference in the lifetimes of the unrelaxed and relaxed D+*QB-* states is attributed to the relaxation of protein residues and internal water molecules that stabilize D+*QB-*. These results demonstrate energetically significant conformational changes involved in stabilizing the D+*QB-* state. The unrelaxed and relaxed states can be considered to be the initial and final states along the reaction coordinate for conformationally gated electron transfer.     

Inosine triphosphatase allele frequency and association with ribavirin-induced anaemia in Brazilian patients receiving antiviral therapy for chronic hepatitis C

Inosine triphosphatase (ITPA) single nucleotide polymorphisms (SNPs) are stronglyassociated with protection against ribavirin (RBV)-induced anaemia in European,American and Asian patients; however, there is a paucity of data for Brazilianpatients. The aim of this study was to evaluate the ITPA SNP (rs7270101/rs1127354)frequency in healthy and hepatitis C virus (HCV)-infected patients from Brazil andthe association with the development of severe anaemia during antiviral therapy. ITPASNPs were determined in 200 HCV infected patients and 100 healthy individuals bysequencing. Biochemical parameters and haemoglobin (Hb) levels were analysed in 97patients who underwent antiviral therapy. A combination of AArs7270101+CCrs1127354(100% ITPase activity) was observed in 236/300 individuals. Anaemia was observed in87.5% and 86.2% of treated patients with AA (rs7270101) and CC genotypes (rs1127354),respectively. Men with AA (rs7270101) showed a considerable reduction in Hb at week12 compared to those with AC/CC (p = 0.1475). In women, there was no influence ofgenotype (p = 0.5295). For rs1127354, men with the CC genotype also showed a suddenreduction in Hb compared to those with AC. Allelic distribution of rs7270101 andrs1127354 shows high rates of the genotypes AA and CC, respectively, suggesting thatthe study population had a great propensity for developing RBV-induced anaemia. Aprogressive Hb reduction during treatment was observed; however, this reduction wasgreater in men at week 12 than in women.     

Relation of polyamine synthesis and titer to aging and senescence in oat leaves

Polyamine biosynthesis in senescing leaves of Avena sativa L. was measured by determining the activities of arginine decarboxylase (EC 4.1.1.19), ornithine decarboxylase (EC 4.1.1.17) and S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50). Polyamine content was also estimated by thin layer chromatography and high performance liquid chromatography. Arginine decarboxylase activity decreases progressively in aging attached first leaves and in senescing excised leaves in the dark. Conversely, it increases during light exposure of excised leaves, which retards senescence. Ornithine decarboxylase activity is high and constant in the attached leaf, irrespective of age; it decreases in excised leaves kept in the dark and in the light, irrespective of senescence. S-Adenosyl-l-methionine decarboxylase shows no correlation with age or senescence. Levels of putrescine, diaminopropane, agmatine, and spermidine are high in young leaves and decline with age. The best single indicator of senescence is usually spermidine, which decreases in excised leaves incubated in the dark, but increases in such leaves with time of light exposure. Spermidine generally has a reciprocal relationship with putrescine, indicating that spermidine synthase, which converts putrescine to spermidine, may exert important physiological control. These data support the view that polyamines play an important role in the regulation of plant development.     

Arsenic Exposure Increases Monocyte Adhesion to the Vascular Endothelium,a Pro-Atherogenic Mechanism

Epidemiological studies have shown that arsenic exposure increases atherosclerosis, but the mechanisms underlying this relationship are unknown. Monocytes, macrophages and platelets play an important role in the initiation of atherosclerosis. Circulating monocytes and macrophages bind to the activated vascular endothelium and migrate into the sub-endothelium, where they become lipid-laden foam cells. This process can be facilitated by platelets, which favour monocyte recruitment to the lesion. Thus, we assessed the effects of low-to-moderate arsenic exposure on monocyte adhesion to endothelial cells, platelet activation and platelet-monocyte interactions. We observed that arsenic induces human monocyte adhesion to endothelial cells in vitro. These findings were confirmed ex vivo using a murine organ culture system at concentrations as low as 10 ppb. We found that both cell types need to be exposed to arsenic to maximize monocyte adhesion to the endothelium. This adhesion process is specific to monocyte/endothelium interactions. Hence, no effect of arsenic on platelet activation or platelet/leukocyte interaction was observed. We found that arsenic increases adhesion of mononuclear cells via increased CD29 binding to VCAM-1, an adhesion molecule found on activated endothelial cells. Similar results were observed in vivo, where arsenic-exposed mice exhibit increased VCAM-1 expression on endothelial cells and increased CD29 on circulating monocytes. Interestingly, expression of adhesion molecules and increased binding can be inhibited by antioxidants in vitro and in vivo. Together, these data suggest that arsenic might enhance atherosclerosis by increasing monocyte adhesion to endothelial cells, a process that is inhibited by antioxidants.