Improvement in ethanol productivity of engineered <Emphasis Type="Italic">E. coli</Emphasis> strain SSY13 in defined medium via adaptive evolution

E. coli has the ability to ferment both C5 and C6 sugars and produce mixture of acids along with small amount of ethanol. In our previous study, we reported the construction of an ethanologenic E. coli strain by modulating flux through the endogenous pathways. In the current study, we made further changes in the strain to make the overall process industry friendly; the changes being (1) removal of plasmid, (2) use of low-cost defined medium, and (3) improvement in consumption rate of both C5 and C6 sugars. We first constructed a plasmid-free strain SSY13 and passaged it on AM1–xylose minimal medium plate for 150 days. Further passaging was done for 56 days in liquid AM1 medium containing either glucose or xylose on alternate days. We observed an increase in specific growth rate and carbon utilization rate with increase in passage numbers until 42 days for both glucose and xylose. The 42nd day passaged strain SSK42 fermented 113 g/L xylose in AM1 minimal medium and produced 51.1 g/L ethanol in 72 h at 89% of maximum theoretical yield with ethanol productivity of 1.4 g/L/h during 24–48 h of fermentation. The ethanol titer, yield and productivity were 49, 40 and 36% higher, respectively, for SSK42 as compared to unevolved SSY13 strain.     

Association of IFN-gamma and IL-10 gene variants with the risk of extrapulmonary tuberculosis

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) is a chronic infectious disease. Interferon-gamma (IFN-γ) is an important cytokine imparting resistance to mycobacterial diseases. It is believed that IFN-γ and Interleukin-10 (IL-10) play divergent roles in the host immune system against MTB infection. IL-10 is an important inhibitory cytokine and helps balancing the inflammatory and immune responses. IL-10 is involved in down regulation of Th1 cytokines, MHC class II antigen and co-stimulatory molecular expression on macrophages, while IFN-γ results in macrophage activation allowing them to exert the microbicidal role. The objectives were to find out the association of IL-10 (?1082 A/G) and IFN-γ (+874 A/T) single nucleotide polymorphisms (SNPs) with extrapulmonary tuberculosis in ethnic Kashmiri population. A total of 100 extrapulmonary tuberculosis cases and 102 healthy controls were analyzed for IL-10 (?1082 A/G) and IFN- γ (+874 A/T) SNPs using Allele-Specific PCR. We found a significant association of IFN-γ + 874 ‘TT’ genotype with extrapulmonary tuberculosis (p = 0.006) and in case of IL-10 (?1082 A/G) we found a significant association with extrapulmonary tuberculosis under recessive model (GG vs GA + AA) (p = 0.03) in Kashmiri population. IL-10 (?1082 A/G) and IFN-γ (+874 A/T) have a significant association with extrapulmonary tuberculosis in ethnic Kashmiri population.     

Enzymatic synthesis of L‐lactic acid from carbon dioxide and ethanol with an inherent cofactor regeneration cycle

Efficient conversion of carbon dioxide is of great interests to today's endeavors in controlling greenhouse gas emission. A multienzyme catalytic system that uses carbon dioxide and ethanol to produce L ‐lactate was demonstrated in this work, thereby providing a novel reaction route to convert bio‐based ethanol to an important building block for synthesis biodegradable polymers. The synthetic route has a unique internal cofactor regeneration cycle, eliminating the need of additional chemical or energy for cofactor regeneration. Lactate was successfully synthesized with 41% of ethanol converted in a batch reaction, while a turnover number of 2.2 day⁻¹ was reached for cofactor regeneration in a reaction with continuous feeding of ethanol. A kinetic model developed based on reaction kinetic parameters determined separately for each reaction step predicted well the reaction rates and yields of the multienzyme reaction system. Biotechnol. Bioeng. 2011;108: 465–469. © 2010 Wiley Periodicals, Inc.     

Glutathione modulates Ca(2+) influx and oxidative toxicity through TRPM2 channel in rat dorsal root ganglion neurons

Glutathione (GSH) is the most abundant thiol antioxidant in mammalian cells and maintains thiol redox in the cells. GSH depletion has been implicated in the neurobiology of sensory neurons. Because the mechanisms that lead to melastatin-like transient receptor potential 2 (TRPM2) channel activation/inhibition in response to glutathione depletion and 2-aminoethyldiphenyl borinate (2-APB) administration are not understood, we tested the effects of 2-APB and GSH on oxidative stress and buthionine sulfoximine (BSO)-induced TRPM2 cation channel currents in dorsal root ganglion (DRG) neurons of rats. DRG neurons were freshly isolated from rats and the neurons were incubated for 24 h with BSO. In whole-cell patch clamp experiments, TRPM2 currents in the rat were consistently induced by H₂O₂ or BSO. TRPM2 channels current densities and cytosolic free Ca²⁺ content of the neurons were higher in BSO and H₂O₂ groups than in control. However, the current densities and cytosolic Ca²⁺ release were also higher in the BSO + H₂O₂ group than in the H₂O₂ alone. When intracellular GSH is introduced by pipette TRPM2 channel currents were not activated by BSO, H₂O₂ or rotenone. BSO and H₂O₂-induced Ca²⁺ gates were blocked by the 2-APB. Glutathione peroxidase activity, lipid peroxidation and GSH levels in the DRG neurons were also modulated by GSH and 2-APB inhibition. In conclusion, we observed the protective role of 2-APB and GSH on Ca²⁺ influx through a TRPM2 channel in intracellular GSH depleted DRG neurons. Since cytosolic glutathione depletion is a common feature of neuropathic pain and diseases of sensory neuron, our findings are relevant to the etiology of neuropathology in DRG neurons.     

Biophysical Variability and Pastoral Rights to Resources: West African Transhumance Revisited

This paper focuses on a conundrum that has dominated the literature on pastoral mobility and institutions in dryland regions of the world, where livestock production is the main livelihood system. High spatiotemporal variability of rainfall and forage resources are seen to require flexible rules and porous social boundaries to facilitate pastoral mobility—characteristics that run counter to conventional views of the requirements for effective common property institutions. We seek to explore this paradox by investigating the spatiotemporal variability of forage availability (using satellite derived vegetation indices as a proxy for green forage) in four transhumance zones (“transhumance sheds”) in Mali, West Africa. For each transhumance shed, three characteristics with important institutional implications are evaluated over an eleven-year period between 2000 and 2010: the inter-annual variability of forage phenology, seasonal changes in connectivity of green forage patches, and the degree to which key forage locations exist in the form of consistently early green-up and/or late senescence. Periods of vegetation green-up and senescence, which determine the timing of transhumant livestock movements, are found to be sufficiently regular from year to year to be governed by conventional institutions. Seasonal changes in the north-south connectivity of green patches are sufficiently rapid for customary systems of sharing of pasture information to be effective (rather than more technologically sophisticated systems of pasture information). Moreover, transhumance sheds contain key pastoral forage sites, which because of their consistently early greening or late senescence, are strong candidates for territorial protection from alternative land uses such as agriculture. These findings support local herders’ views of transhumance as composed of regular patterns of herd movements along prescribed corridors between key pastoral sites. The seasonal regularity of key pastoral resources has been obscured by an overemphasis on environmental unpredictability that characterizes dryland systems at certain spatial and temporal scales. This paper suggests that policies directed at improving pastoral resource governance must focus instead on securing pastoralists’ access rights to movement corridors, specific pastures and water points.     

Effect of reverse photoperiod on in vitro regeneration and piperine production in Piper nigrum L.

In this study, a novel approach for in vitro regeneration of Piper nigrum L. has been applied in order to increase healthy biomass, phytochemicals and piperine production via reverse photoperiod (16hD/8hL). Leaf portions of the seed-derived plants were placed on an MS-medium fortified with different PGRs. Under 16hD/8hL, thidiazuron (TDZ; 4.0 mg L⁻¹) and BA (1.5 mg L⁻¹) was found to be the most effective (< 90%) in callus induction. Two concentrations (1.5, 2.0 mg L⁻¹) of the IBA produced > 80% shoots from callus cultures. Healthy shoots were transferred to rooting medium and higher percentage of rooting (< 90%) was observed on IBA (1.5 mg L⁻¹). These in vitro tissues were subjected to amino acid analysis, spectrophotometry, and HPLC. ARG, SER, THR, and TYR were the most abundant components out of 17 amino acids. Higher amino acid production was observed under normal photoperiod (16hL/8hD) than under reverse photoperiod (16hD/8hL). The highest total phenolic content (TPC; 9.91 mg/g-DW) and flavonoid content (7.38 mg/g-DW) were observed in callus cultures incubated under 16hL/8hD than other tissues incubated under 16hD/8hL photoperiod. Higher DPPH and PoMo activities were observed in tissues incubated under 16hL/8hD photoperiod, while ABTS and Fe²⁺ chelating activities were found higher in tissues incubated under reverse photoperiod. Significant quantities of piperine content were observed in all tissues except callus cultures. These results suggest that reverse photoperiod is a promising approach for callus induction, phytochemicals and piperine production for commercial applications.     

Data center energy efficient resource scheduling

The information and communication technology (ICT) sector has grown exponentially in the recent years. An essential component of the ICT organizations is constituted by the data centers that are densely populated with redundant servers and communicational links to ensure the provision of 99.99 % availability of services; a fact responsible for the heavy energy consumption by data centers. For energy economy, the redundant elements can be powered off based on the current workload within the data center. We propose a Data Center-wide Energy-Efficient Resource Scheduling framework (DCEERS) that schedules data center resources according to the current workload of the data center. Minimum subset of resources to service the current workload are calculated by solving the Minimum Cost Multi Commodity Flow (MCMCF) using the Benders decomposition algorithm. The Benders decomposition algorithm is scalable: it solves the MCMCF problem in linear time for large data center environments. Our simulated results depict that DCEERS achieves better energy efficiency than the previous data center resource scheduling methodologies.     

Digoxin Derivatives with Enhanced Selectivity for the α2 Isoform of Na,K-ATPase: EFFECTS ON INTRAOCULAR PRESSURE IN RABBITS*

In the ciliary epithelium of the eye, the pigmented cells express the α1β1 isoform of Na,K-ATPase, whereas the non-pigmented cells express mainly the α2β3 isoform of Na,K-ATPase. In principle, a Na,K-ATPase inhibitor with selectivity for α2 could effectively reduce intraocular pressure with only minimal local and systemic toxicity. Such an inhibitor could be applied topically provided it was sufficiently permeable via the cornea. Previous experiments with recombinant human α1β1, α2β1, and α3β1 isoforms showed that the classical cardiac glycoside, digoxin, is partially α2-selective and also that the trisdigitoxose moiety is responsible for isoform selectivity. This led to a prediction that modification of the third digitoxose might increase α2 selectivity. A series of perhydro-1,4-oxazepine derivatives of digoxin have been synthesized by periodate oxidation and reductive amination using a variety of R-NH₂ substituents. Several derivatives show enhanced selectivity for α2 over α1, close to 8-fold in the best case. Effects of topically applied cardiac glycosides on intraocular pressure in rabbits have been assessed by their ability to either prevent or reverse acute intraocular pressure increases induced by 4-aminopyridine or a selective agonist of the A3 adenosine receptor. Two relatively α2-selective digoxin derivatives efficiently normalize the ocular hypertension, by comparison with digoxin, digoxigenin, or ouabain. This observation is consistent with a major role of α2 in aqueous humor production and suggests that, potentially, α2-selective digoxin derivatives could be of interest as novel drugs for control of intraocular pressure.     

Multi-point enzyme immobilization,surface chemistry,and novel platforms: a paradigm shift in biocatalyst design

Engineering enzymes with improved catalytic properties in non-natural environments have been concerned with their diverse industrial and biotechnological applications. Immobilization represents a promising but straightforward route, and immobilized biocatalysts often display higher activities and stabilities compared to free enzymes. Owing to their unique physicochemical characteristics, including the high-specific surface area, exceptional chemical, electrical, and mechanical properties, efficient enzyme loading, and multivalent functionalization, nano-based materials are postulated as suitable carriers for biomolecules or enzyme immobilization. Enzymes immobilized on nanomaterial-based supports are more robust, stable, and recoverable than their pristine counterparts, and are even used for continuous catalytic processes. Furthermore, the unique intrinsic properties of nanomaterials, particularly nanoparticles, also confer the immobilized enzymes to be used for their broader applications. Herein, an effort has been made to present novel potentialities of multi-point enzyme immobilization in the current biotechnological sector. Various nano-based platforms for enzyme/biomolecule immobilization are discussed in the second part of the review. In summary, recent developments in the use of nanomaterials as new carriers to construct robust nano-biocatalytic systems are reviewed, and future trends are pointed out in this article.