Developmental strategies and regulation of cell-free enzyme system for ethanol production: a molecular prospective

Khattak, Waleed Ahmad,Ullah, Muhammad Wajid,Ul-Islam, Mazhar,Khan, Shaukat,Kim, Minah,Kim, Yeji,Park, Joong Kon Springer-Verlag 2014 Applied microbiology and biotechnology Vol.98 No.23

<P>Most biomanufacturing systems developed for the production of biocommodities are based on whole-cell systems. However, with the advent of innovative technologies, the focus has shifted from whole-cell towards cell-free enzyme system. Since more than a century, researchers are using the cell-free extract containing the required enzymes and their respective cofactors in order to study the fundamental aspects of biological systems, particularly fermentation. Although yeast cell-free enzyme system is known since long ago, it is rarely been studied and characterized in detail. In this review, we hope to describe the major pitfalls encountered by whole-cell system and introduce possible solutions to them using cell-free enzyme systems. We have discussed the glycolytic and fermentative pathways and their regulation at both transcription and translational levels. Moreover, several strategies employed for development of cell-free enzyme system have been described with their potential merits and shortcomings associated with these developmental approaches. We also described in detail the various developmental approaches of synthetic cell-free enzyme system such as compartmentalization, metabolic channeling, protein fusion, and co-immobilization strategies. Additionally, we portrayed the novel cell-free enzyme technologies based on encapsulation and immobilization techniques and their development and commercialization. Through this review, we have presented the basics of cell-free enzyme system, the strategies involved in development and operation, and the advantages over conventional processes. Finally, we have addressed some potential directions for the future development and industrialization of cell-free enzyme system.</P>

Mapping evolution of dynamic web ontologies

Khattak, A.M.,Pervez, Z.,Khan, W.A.,Khan, A.M.,Latif, K.,Lee, S.Y. Elsevier science 2015 Information sciences Vol.303 No.-

Information on the web and web services that are revised by stakeholders is growing incredibly. The presentation of this information has shifted from a representational model of web information with loosely clustered terminology to semi-formal terminology and even to formal ontology. Mediation (i.e., mapping) is required for systems and services to share information. Mappings are established between ontologies in order to resolve terminological and conceptual incompatibilities. Due to new discoveries in the field of information sharing, the body of knowledge has become more structured and refined. The domain ontologies that represent bodies of knowledge need to be able to accommodate new information. This allows for the ontology to evolve from one consistent state to another. Changes in resources cause existing mappings between ontologies to be unreliable and stale. This highlights the need for mapping evolution (regeneration) as it would eliminate the discrepancies from the existing mappings. In order to re-establish the mappings between dynamic ontologies, the existing systems require a complete mapping process to be restructured, and this process is time consuming. This paper proposes a mapping reconciliation approach between the updated ontologies that has been found to take less time to process compared to the time of existing systems when only the changed resources are considered and also eliminates the staleness of the existing mappings. The proposed approach employs the change history of ontology in order to store the ontology change information, which helps to drastically reduce the reconciliation time of the mappings between dynamic ontologies. A comprehensive evaluation of the performance of the proposed system on standard data sets has been conducted. The experimental results of the proposed system in comparison with six existing mapping systems are provided in this paper using 13 different data sets, which support our claims.

Production, Characterization and Physico-mechanical Properties of Bacterial Cellulose from Industrial Wastes

Khattak, W. A.,Khan, T.,Ul-Islam, M.,Wahid, F.,Park, J. K. Springer Science + Business Media 2015 Journal of polymers and the environment Vol.23 No.1

Enhanced production of bioethanol from waste of beer fermentation broth at high temperature through consecutive batch strategy by simultaneous saccharification and fermentation

Khattak, W.A.,Khan, T.,Ha, J.H.,Ul-Islam, M.,Kang, M.K.,Park, J.K. IPC Science and Technology Press ; Elsevier Scienc 2013 Enzyme and microbial technology Vol.53 No.5

Malt hydrolyzing enzymes and yeast glycolytic and fermentation enzymes in the waste from beer fermentation broth (WBFB) were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). A new 'one-pot consecutive batch strategy' was developed for efficient bio-ethanol production by simultaneous saccharification and fermentation (SSF) using WBFB without additional enzymes, microbial cells, or carbohydrates. Bio-ethanol production was conducted in batches using WBFB supernatant in the first phase at 25-67<SUP>o</SUP>C and 50rpm, followed by the addition of 3% WBFB solid residue to the existing culture broth in the second phase at 67<SUP>o</SUP>C. The ethanol production increased from 50 to 102.5g/L when bare supernatant was used in the first phase, and then to 219g ethanol/L in the second phase. The amount of ethanol obtained using this strategy was almost equal to that obtained using the original WBFB containing 25% solid residue at 33<SUP>o</SUP>C, and more than double that obtained when bare supernatant was used. Microscopic and gel electrophoresis studies revealed yeast cell wall degradation and secretion of cellular material into the surrounding medium. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) supported the existence of enzymes in WBFB involved in bioethanol production at elevated temperatures. The results of this study will provide insight for the development of new strategies for biofuel production.

Design of a UHF wide-band antenna with a compact notch filter

Khattak, Muhammad Kamran,Kahng, Sungtek IET 2016 IET microwaves, antennas & propagation Vol.10 No.15

<P>A novel ultra high frequency (UHF) broadband polygonal monopole antenna with a notch is presented. The antenna is a wineglass-shaped geometry near two pairs of long-horn-shaped coupling elements located on the top and bottom surfaces to cover the band of 700 MHz-1.3 GHz with the size of 150 x 100 x 1.2 mm. The notch filtering is achieved at 900 MHz by using the open-terminated stub of a novel composite right/left handed transmission-line phase shifter. The phase shifter is 12 mm as 0.07 x (g). The validity of the proposed scheme is verified by designing and comparing the wide-band antenna with different notch-making approaches through electromagnetic simulation, fabrication and measurement. The simulated and measured results show high degrees of agreement. The suggested antenna is shown to be useful for UHF-band applications with a stopband at 900 MHz to avoid potential interference from the GSM-E service, Z-wave communication and UHF radio-frequency identification tag frequencies.</P>

A novel dipole antenna backed by a thin and small-area AMC for good impedance match and low SAR on human tissue

Khattak, Muhammad Kamran,Kahng, S. Informa UK (TaylorFrancis) 2016 Journal of electromagnetic waves and applications Vol.30 No.12

<P>This paper presents a new dipole antenna that has robust input impedance matching and electromagnetic radiation, and low SAR for human body contact. It is made possible by backing the main radiator with a thin and small-area artificial magnetic conductor (AMC). Different from the conventional AMC which occupies a multi-layered large area based on the full PEC ground for a high antenna directivity, the proposed structure works for 2.4-GHz-ISM band, and has a 1-mm thickness and a 50mm-by-50mm footprint with good impedance matching and radiation performances even near human tissue, and a low SAR below 1.6W/kg is obtained. This design method is validated by full-wave simulations and physical implementation.</P>

Ovarian Masses: Is Multi-detector Computed Tomography a Reliable Imaging Modality?

Khattak, Yasir Jamil,Hafeez, Saima,Alam, Tariq,Beg, Madiha,Awais, Mohammad,Masroor, Imrana Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.4

Background: Ovarian cancer continues to pose a major challenge to physicians and radiologists. It is the third most common gynecologic malignancy and estimated to be fifth leading cancer cause of death in women, constituting 23% of all gynecological malignancies. Multi-detector computed tomography (MDCT) appears to offer an excellent modality in diagnosing ovarian cancer based on combination of its availability, meticulous technique, efficacy and familiarity of radiologists and physicians. The aim of this study was to compute sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of 64-slice MDCT in classifying ovarian masses; 95% confidence intervals were reported. Materials and Methods: We prospectively designed a cross-sectional analytical study to collect data from July 2010 to August 2011 from a tertiary care hospital in Karachi, Pakistan. A sample of 105 women aged between 15-80 years referred for 64-MDCT of abdomen and pelvis with clinical suspicion of malignant ovarian cancer, irrespective of stage of disease, were enrolled by non-probability purposive sampling. All patients who were already known cases of histologically proven ovarian carcinoma and having some contraindication to radiation or iodinated contrast media were excluded. Results: Our prospective study reports sensitivity, specificity; positive and negative predictive values with 95%CI and accuracy were computed. Kappa was calculated to report agreement among the two radiologists. For reader A, MDCT was found to have 92% (0.83, 0.97) sensitivity and 86.7% (0.68, 0.96) specificity, while PPV and NPV were 94.5% (0.86, 0.98) and 86.7% (0.63, 0.92), respectively. Accuracy reported by reader A was 90.5%. For reader B, sensitivity, specificity, PPV and NPV were 94.6% (0.86, 0.98) 90% (0.72, 0.97) 96% (0.88, 0.99) and 87.1% (0.69, 0.95) respectively. Accuracy computed by reader B was 93.3%. Excellent agreement was found between the two radiologists with a significant kappa value of 0.887. Conclusion: Based on our study results, we conclude MDCT is a reliable imaging modality in diagnosis of ovarian masses accurately with insignificant interobserver variability.

AUTOMOBILE OWNERSHIP, TRAVEL BEHAVIOR AND PHYSICAL ACTIVITY IN NEO-TRADITIONAL NEIGHBORHOOD DEVELOPMENTS

AsadJ.Khattak 대한교통학회 2005 대한교통학회 학술대회지 Vol.48 No.-

Many planning researchers and practitioners believe that individuals rely on automobiles partly to travel from place to place in conventional communities because land uses in the United States are separated and spread out. By contrast, when certain design features such as higher development densities and continuous sidewalks are combined with the mixed land uses typically found in neotraditional communities, many expect residents of these communities to shed their vehicles, drive less and walk and bike more, and have more physical activity. Although previous research has supported the view that neo-traditional developments result in more walking activity, this talk will empirically answer several questions about such developments: Do residents of these neighborhoods substitute walking for driving trips, or do they make more trips overall? What is the role of self-selection of residents in these developments? This paper aims to address these questions by examining differences in travel behavior in a matched pair of neighborhoods (one conventional and one neo-traditional) in Chapel Hill and Carrboro, North Carolina. A detailed behavioral survey of 453 households and two-stage regression models suggest that single-family households in the neo-traditional development make a similar number of total trips, but significantly fewer automobile trips and fewer external trips, and they travel fewer miles, than households in the conventional neighborhood, even after controlling for demographic characteristics of the households and for resident self-selection. The findings suggest that households in the neo-traditional development substitute driving trips with walking trips.

A Systematic Literature Review of the Environmental Upgrading in Global Value Chains and Future Research Agenda

Amira Khattak,Luisa Pinto 한국유통과학회 2018 유통과학연구 Vol.16 No.11

Purpose - The purpose of this study is to provide a systematic literature review related to environmental upgrading in Global Value Chains (GVCs) and suggest possible future research agendas in advancing environmental upgrading and ultimately GVC boundaries. Research design, data, and methodology - The academic databases such as Science Direct, EBSCO, ProQuest and Google Scholar were explored using a structured keywords searches to identify relevant research in the environmental upgrading area in GVCs. Only relevant papers were selected after reading the abstracts, and analyzed using qualitative content analysis. Results - Overall analysis of the literature review suggests two critical developments in the field of environmental upgrading. The first and foremost major development is an enhanced understanding of environmental upgrading as a concept and phenomenon. The second significant development is that environmental upgrading has been empirically proven to be fundamentally based on relationships and power structures within GVCs. Conclusions - Environmental upgrading in GVCs has been studied individually and not in relation to financial outcomes and social upgrading. Hence, the relationship of environmental upgrading with financial outcomes and social upgrading needs to be investigated. Furthermore, the impact of the interaction of varying institutional structures on environmental upgrading is worthy of future study.

Explainable Boosting Machine for Predicting Wind Shear-Induced Aircraft Go-around Based on Pilot Reports

Afaq Khattak,Pakwai Chan,Feng Chen,Haorong Peng 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

The go-around is a safety-critical procedure in civil aviation that is rarely executed but is essential to avoid risky landings. Analyzing the factors that trigger go-around events can aid in identifying measures that could lower their frequency. This involves circumstances that could be deemed abnormal and intrinsically harmful. The study employed the Explainable Boosting Machine (EBM), a contemporary transparent model, to predict aircraft go-arounds and interpret different influential factors. The model proposed exhibits comparable accuracy to black-box models. The study utilized pilot reports and applied SMOTE-ENN to address the imbalance problem. The EBM model was trained with treated data in conjunction with Bayesian optimization. The EBM model's performance was evaluated using holdout data and compared to binary logistic regression and decision tree models, as well as black-box models such as adaptive boosting, random forest, and extreme gradient boosting. The EBM model exhibited superior performance compared to other models in terms of precision (83.15%), recall (79.77%), geometric mean (77.29%), and Matthews’s correlation coefficient (0.453). The EBM algorithm enables the comprehensive interpretation of individual and pairwise factor interactions in predicting aircraft go-around outcomes from both global and local perspectives. This facilitates the assessment of the impact of different factors on go-around outcomes.