Person: SAYAR, AHMET ALP
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SAYAR
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AHMET ALP
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Publication Metadata only Retro-techno-economic evaluation of acetic acid production using cotton stalk as feedstock(SPRINGER, 2018) SAYAR, AHMET ALP; Sayar, Nihat Alpagu; Kazan, Dilek; Pinar, Orkun; Akbulut, Berna Sariyar; Sayar, Ahmet AlpIn value-added chemical industries, use of agricultural wastes as raw materials remains to be a major challenge in commercialization due to lack of competitiveness with respect to petrochemical processes. This work presents the techno-economic analysis of a novel bioprocessing plant converting 356,400MT/year cotton stalks into 147,000MT/year acetic acid. A production scheme integrating lignin separation with the main bioconversion stages has been proposed. Techno-economic assessment was performed through economic feasibility and retro-techno-economic analysis (RTEA) methods. The RTEA method has been extended to include the estimation of research and development funding for improving economic feasibility. Carbon offset of the proposed technology has been estimated and carbon credit results have been incorporated into the economic feasibility metrics.Publication Metadata only A sigmoidal model for biosorption of heavy metal cations from aqueous media(ELSEVIER SCIENCE INC, 2015) SAYAR, AHMET ALP; Ozen, Rumeysa; Sayar, Nihat Alpagu; Durmaz-Sam, Selcen; Sayar, Ahmet AlpA novel multi-input single output (MISO) black-box sigmoid model is developed to simulate the biosorption of heavy metal cations by the fission yeast from aqueous medium. Validation and verification of the model is done through statistical chi-squared hypothesis tests and the model is evaluated by uncertainty and sensitivity analyses. The simulated results are in agreement with the data of the studied system in which Schizosaccharomyces pombe biosorbs Ni(II) cations at various process conditions. Experimental data is obtained originally for this work using dead cells of an adapted variant of S. Pombe and represented by Freundlich isotherms. A process optimization scheme is proposed using the present model to build a novel application of a cost-merit objective function which would be useful to predict optimal operation conditions. (C) 2015 Elsevier Inc. All rights reserved.Publication Metadata only Schizosaccharomyces pombe and its Ni(II)-insensitive mutant GA1 in Ni(II) uptake from aqueous solutions: a biodynamic model(SPRINGER, 2014) SAYAR, AHMET ALP; Sayar, Nihat Alpagu; Durmaz-Sam, Selcen; Kazan, Dilek; Sayar, Ahmet AlpIn the present study, Ni(II) uptake from aqueous solution by living cells of the Schizosaccharomyces pombe haploid 972 with h (-) mating type and a Ni(II)-insensitive mutant GA1 derived from 972 was investigated at various initial glucose and Ni(II) concentrations. A biodynamic model was developed to predict the unsteady and steady-state phases of the uptake process. Gompertz growth and uptake process parameters were optimized to predict the maximum growth rate mu (m) and the process metric C (r), the remaining Ni(II) content in the aqueous solution. The simulated overall metal uptake values were found to be in acceptable agreement with experimental results. The model validation was done through regression statistics and uncertainty and sensitivity analyses. To gain insight into the phenomenon of Ni(II) uptake by wild-type and mutant S. pombe, probable active and passive metal transport mechanisms in yeast cells were discussed in view of the simulation results. The present work revealed the potential of mutant GA1 to remove Ni(II) cations from aqueous media. The results obtained provided new insights for understanding the combined effect of biosorption and bioaccumulation processes for metal removal and offered a possibility for the use of growing mutant S. pombe cell in bioremediation.Publication Metadata only What Are the Multi-Omics Mechanisms for Adaptation by Microorganisms to High Alkalinity? A Transcriptomic and Proteomic Study of a Bacillus Strain with Industrial Potential(MARY ANN LIEBERT, INC, 2018) SAYAR, AHMET ALP; Kaya, Fatma Ece Altinisik; Avci, Fatma Gizem; Sayar, Nihat Alpagu; Kazan, Dilek; Sayar, Ahmet Alp; Akbulut, Berna SariyarAlkaliphilic organisms are among an industrially important class of extremophile microorganisms with the ability to thrive at pH 10-11.5. Microorganisms that exhibit alkaliphilic characteristics are sources of alkali-tolerant enzymes such as proteases, starch degrading enzymes, cellulases, and metabolites such as antibiotics, enzyme inhibitors, siderophores, organic acids, and cholic acid derivatives, which have found various applications in industry for human and environmental health. Yet, multi-omics mechanisms governing adaptation to high alkalinity have been poorly studied. We undertook the present work to understand, as a case study, the alkaliphilic adaptation strategy of the novel microorganism, Bacillus marmarensis DSM 21297, to alkaline conditions using a multi-omics approach that employed transcriptomics and proteomics. As alkalinity increased, bacteria remodeled the peptidoglycan layer by changing peptide moieties along with the peptidoglycan constituents and altered the cell membrane to reduce lipid motility and proton leakiness to adjust intracellular pH. Different transporters also contributed to the maintenance of this pH homeostasis. However, unlike in most well-known alkaliphiles, not only sodium ions but also potassium ions were involved in this process. Interestingly, increased pH has triggered the expression of neither general stress proteins nor gene encoding proteins associated with heat, salt, and nutrient stresses. Only an increase in the expression of oxidative stress related genes was evident. Endospore formation, also a phenomenon closely linked to stress, was unclear. This questioned if high pH was a real stress for B. marmarensis. These new findings, corroborated using the multi-omics approach of the present case study, broaden the knowledge on the mechanisms of alkaliphilic adaptation and might also potentially offer useful departure points for further industrial applications with other microorganisms.Publication Metadata only Assessment of different carbon and salinity level on growth kinetics, lipid, and starch composition of Chlorella vulgaris SAG 211-12(TAYLOR & FRANCIS INC, 2020) SAYAR, AHMET ALP; Kaplan, Ecem; Sayar, Nihat Alpagu; Kazan, Dilek; Sayar, Ahmet AlpThe quality of microalgal biofuel depends on the fatty acid (FA) distribution. A high ratio of saturated fatty acids (SFAs) favors better biofuel characteristics. Palmitic acid (C16:0) and stearic acid (C18:0) are essential FAs for required biodiesel quality. In this study, combined effects of growth medium concentrations of NaCl, glucose and glycerol on cell composition and FA profile of the Chlorella vulgaris SAG 211-12 were investigated. A central composite design (CCD) based design of experiments (DoE) was used for experimental setup. According to experimental results, the maximum mass fraction for palmitic acid (C16:0), 40.67% of total fatty acids, was obtained in the medium supplemented with 0.9% (w/v) NaCl, 0.3% (w/v) glucose, and 0.3% (w/v) glycerol, whereas stearic acid (C18:0) percentage reached the highest value of 22.16% of total fatty acids in the presence of 2.5% NaCl, 0.6% glucose, and 0.6% glycerol. According to the same set of designed experiments, best starch content was found as 22.08% of dry cell weight in a medium containing 2.0% NaCl, 0.3% glucose, and 0.3% glycerol. C16:0 mass fraction as a function of three medium ingredient concentrations was modeled using a Kriging model. Optimum concentrations of NaCl, glucose and glycerol to reach maximum C16:0 fraction were predicted as 0.5, 1, and 1%, respectively.Publication Metadata only Biosorption of Ni (II) by Schizosaccharomyces pombe: kinetic and thermodynamic studies(SPRINGER, 2011) SAYAR, AHMET ALP; Durmaz-Sam, Selcen; Sayar, Nihat Alpagu; Topal-Sarikaya, Aysegul; Sayar, Ahmet AlpThe potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake of Ni(II) on S. pombe, q(e), was obtained at 25 degrees C as 33.8 mg g(-1). It decreased with increasing temperature within a range of 25-50 degrees C denoting an exothermic behaviour. Increasing initial Ni(II) concentration up to 400 mg L-1 also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L-1. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich-Peterson, and Kahn isotherm equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature. Gibbs free energy changes (Delta G degrees) of the system at 25, 30, 35 and 50 degrees C were found as -1.47E + 4, -1.49E + 4, -1.51E + 4, and -1.58E + 4 J mol(-1), respectively. Enthalpy change (Delta H degrees) was determined as -2.57E + 3 J mol(-1) which also supports the observed exothermic behaviour of the biosorption process. Entropy change (Delta S degrees) had a positive value (40.75 J mol(-1) K-1) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed to act as a separating agent for Ni(II) recovery from its aqueous solution.Publication Metadata only Bioethanol Production From Turkish Hazelnut Husk Process Design and Economic Evaluation(SPRINGER, 2019) SAYAR, AHMET ALP; Sayar, Nihat Alpagu; Pinar, Orkun; Kazan, Dilek; Sayar, Ahmet AlpThe main objective of the current study is to develop and assess the preliminary synthetic design steps of an innovative and unprecedented bioprocess plant converting Turkish hazelnut husk into lignocellulosic ethanol with an emphasis on economic evaluation. Valorization of this agricultural waste would provide a promising economic potential and long-term sustainability with acceptable environmental impact. Preliminary economic evaluations are performed on several scenarios where the effects of changing various process design and operational inputs such as designed plant capacity, evaporation unit operation efficiency, and biocatalyst and nitrogen source prices are simulated. The total capital investment for the base case scenario with an annual throughput of 180,000 metric tons (MT) hazelnut husk is just above USD 111million. The annual operational costs for this case amount to USD 61million. Assuming a sales price of USD 1.50 per kg of bioethanol (achieved via governmental subsidy and tax incentives) the return on investment of the project comes to 12.61% with a 8year payback period. An uncertainty analysis performed on the annual hazelnut husk availability and biocatalyst and nitrogen source price fluctuations establishes a basis for further design of the process taking into account the risk factors associated with the project. The case studies and the uncertainty analysis confirm the fact that production of second generation bioethanol from hazelnut husk in Turkey is a worthwhile endeavor with an economic potential especially with additional social and environmental advantages.