Impact of ammonia concentration on Spirulina platensis growth in an airlift photobioreactor

Spirulina platensis was cultivated in a bench-scale airlift photobioreactor using synthetic wastewater (total nitrogen 412 mg L(-1), total phosphorous 90 mg L(-1), pH 9-10) with varying ammonia/total nitrogen ratios (50-100% ammonia with balance nitrate) and hydraulic residence times (15-25 d). High average biomass density (3500-3800 mg L(-1)) and productivity (5.1 g m(-2) d(-1)) were achieved when ammonia was maintained at 50% of the total nitrogen. Both high ammonia concentrations and mutual self-shading, which resulted from the high biomass density in the airlift reactor, were found to partially inhibit the growth of S. platensis. The performance of the airlift bioreactor used in this study compared favorably with other published studies. The system has good potential for treatment of high strength wastewater combined with production of algae for biofuels or other products, such as human and animal food, food supplements or pharmaceuticals.     

Molecular docking analysis of Clostridium perfringens beta toxin model with potential inhibitors from the ZINC database

Beta toxin from Clostridium perfringens after being secreted in gut is capable of causing necrotic enteritis in humans and several other animal species and does not respond to routinely used antibiotics. Therefore, there is a need to design an effective inhibitor for the Clostridium perfringens beta toxin (CPB) using cutting edge drug discovery technologies. Hence, potential CPB inhibitors were identified using computer aided screening of compounds from the ZINC database. Further, we document the molecular docking analysis of Clostridium perfringens beta toxin model (that revealed 4 binding pockets, A-D) with the identified potential inhibitors. We show that ZINC291192 [N-[(1-methylindol-3-yl) methyl eneamino]-7,10-dioxabicyclo[4.4.0]deca-2,4,11-triene-8- carboxamide] has optimal binding features with calculated binding energy of -10.38 kcal/mol and inhibition constant of 24.76 nM for further consideration.     

Access of cellulase to cellulose and lignin for poplar solids produced by leading pretreatment technologies

Adsorption of cellulase on solids resulting from pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid (DA), flowthrough (FT), lime, and sulfur dioxide (SO₂) and pure Avicel glucan was measured at 4°C, as were adsorption and desorption of cellulase and adsorption of β‐glucosidase for lignin left after enzymatic digestion of the solids from these pretreatments. From this, Langmuir adsorption parameters, cellulose accessibility to cellulase, and the effectiveness of cellulase adsorbed on poplar solids were estimated, and the effect of delignification on cellulase effectiveness was determined. Furthermore, Avicel hydrolysis inhibition by enzymatic and acid lignin of poplar solids was studied. Flowthrough pretreated solids showed the highest maximum cellulase adsorption capacity (σ_solids = 195 mg/g solid) followed by dilute acid (σ_solids = 170.0 mg/g solid) and lime pretreated solids (σ_solids = 150.8 mg/g solid), whereas controlled pH pretreated solids had the lowest (σ_solids = 56 mg/g solid). Lime pretreated solids also had the highest cellulose accessibility (σ_cellulose = 241 mg/g cellulose) followed by FT and DA. AFEX lignin had the lowest cellulase adsorption capacity (σ_lignin = 57 mg/g lignin) followed by dilute acid lignin (σ_lignin = 74 mg/g lignin). AFEX lignin also had the lowest β‐glucosidase capacity (σ_lignin = 66.6 mg/g lignin), while lignin from SO₂ (σ_lignin = 320 mg/g lignin) followed by dilute acid had the highest (301 mg/g lignin). Furthermore, SO₂ followed by dilute acid pretreated solids gave the highest cellulase effectiveness, but delignification enhanced cellulase effectiveness more for high pH than low pH pretreatments, suggesting that lignin impedes access of enzymes to xylan more than to glucan, which in turn affects glucan accessibility. In addition, lignin from enzymatic digestion of AFEX and dilute acid pretreated solids inhibited Avicel hydrolysis less than ARP and flowthrough lignin, whereas acid lignin from unpretreated poplar inhibited enzymes the most. Irreversible binding of cellulase to lignin varied with pretreatment type and desorption method. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Clinical proteomics of the neglected human malarial parasite Plasmodium vivax

Recent reports highlight the severity and the morbidity of disease caused by the long neglected malaria parasite Plasmodium vivax. Due to inherent difficulties in the laboratory-propagation of P. vivax, the biology of this parasite has not been adequately explored. While the proteome of P. falciparum, the causative agent of cerebral malaria, has been extensively explored from several sources, there is limited information on the proteome of P. vivax. We have, for the first time, examined the proteome of P. vivax isolated directly from patients without adaptation to laboratory conditions. We have identified 153 proteins from clinical P. vivax, majority of which do not show homology to any previously known gene products. We also report 29 new proteins that were found to be expressed in P. vivax for the first time. In addition, several proteins previously implicated as anti-malarial targets, were also found in our analysis. Most importantly, we found several unique proteins expressed by P. vivax.This study is an important step in providing insight into physiology of the parasite under clinical settings.     

Formation and dynamic alterations of horizontal microdomains in sperm membranes during progesterone-induced acrosome reaction

A peptidomics approach was applied to determine the peptides in the larval central nervous system of the grey flesh fly, Neobellieria bullata. Fractions obtained by high performance liquid chromatography were analysed by MALDI-TOF and ESI-Q-TOF mass spectrometry. This provided biochemical evidence for the presence of 18 neuropeptides, 11 of which were novel Neobellieria peptides. Most prominently present were the FMRFamide-related peptides: 7 FMRFamides, 1 FIRFamide, and Neb-myosuppressin. The three putative capa-gene products Neb-pyrokinin and the periviscerokinins Neb-PVK-1 and -2 were detected, as well as another pyrokinin. This Neb-PK-2 was also present in the ring gland along with corazonin, Neb-myosuppressin, and Neb-AKH-GK, an intermediate processing product of the adipokinetic hormone. Furthermore, the central nervous system contained Neb-LFamide, proctolin, and FDFHTVamide, designated as Neb-TVamide. With this study, we considerably increased our knowledge of the neuropeptidome of the pest fly N. bullata, which is an important insect model for physiological research.     

Molecular determinants of the cofactor specificity of ribitol dehydrogenase, a short-chain dehydrogenase/reductase

Ribitol dehydrogenase from Zymomonas mobilis (ZmRDH) catalyzes the conversion of ribitol to d-ribulose and concomitantly reduces NAD(P)(+) to NAD(P)H. A systematic approach involving an initial sequence alignment-based residue screening, followed by a homology model-based screening and site-directed mutagenesis of the screened residues, was used to study the molecular determinants of the cofactor specificity of ZmRDH. A homologous conserved amino acid, Ser156, in the substrate-binding pocket of the wild-type ZmRDH was identified as an important residue affecting the cofactor specificity of ZmRDH. Further insights into the function of the Ser156 residue were obtained by substituting it with other hydrophobic nonpolar or polar amino acids. Substituting Ser156 with the negatively charged amino acids (Asp and Glu) altered the cofactor specificity of ZmRDH toward NAD(+) (S156D, [k(cat)/K(m)(,NAD)]/[k(cat)/K(m)(,NADP)] = 10.9, where K(m)(,NAD) is the K(m) for NAD(+) and K(m)(,NADP) is the K(m) for NADP(+)). In contrast, the mutants containing positively charged amino acids (His, Lys, or Arg) at position 156 showed a higher efficiency with NADP(+) as the cofactor (S156H, [k(cat)/K(m)(,NAD)]/[k(cat)/K(m)(,NADP)] = 0.11). These data, in addition to those of molecular dynamics and isothermal titration calorimetry studies, suggest that the cofactor specificity of ZmRDH can be modulated by manipulating the amino acid residue at position 156.     

Salt Stress-induced Responses in Growth and Metabolism in Callus Cultures and Differentiating In Vitro Shoots of Indian Ginseng (Withania somnifera Dunal)

In vitro-grown shoots and calli of Withania somnifera, an important medicinal plant, were exposed to various types of salts under in vitro culture conditions. Membrane permeability, lipid peroxidation, and the antioxidant system increased in shoots as well as in unorganized callus tissues under all the three concentrations of KCl, NaCl, KNO₃, NaNO₃, and CaCl₂. The growth responses of shoots and callus cultures under various salt treatments revealed that the tissue could grow better under NaCl and KNO₃ compared to other salts and the in vitro shoots appeared healthy at 50?mM concentration of NaCl and KNO_3. The activity of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase, guaiacol peroxidase, lipoxygenase, polyphenol oxidase, and glutathione reductase increased under salt treatments, especially at higher concentrations. The greatest activity increase was recorded for peroxidases, whereas CAT was the least responsive. Only two isoforms, Mn-superoxide dismutase (Mn-SOD) and Fe-SOD, could be visualized in callus tissue while Cu/Zn-SOD was absent. Diaphorase 4 was totally missing in callus tissue and was detected only in shoots. Phenolics accumulated at all the concentrations of the salts tested as an induced protective response. The higher concentration of CaCl₂ produced maximum increases in antioxidants and enzymatic activities compared to other salts. Thus, for W. somnifera the presence of excess calcium in the growing medium is most deleterious compared to other salts. Results also suggest that the nonenzymatic and enzymatic antioxidant systems of both the tissues played a primary role in combating the imposed salt stress.     

Arsenic affects mineral nutrients in grains of various Indian rice (Oryza sativa L.) genotypes grown on arsenic-contaminated soils of West Bengal

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29–167 mg kg^?1 dw), as well as As transfer factor (4–45%). Grains retained the least level of As (0.7–3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05–0.12 mg kg^?1 dw), whereas that of As was high (0.4–1.68 mg kg^?1 dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas.