Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 10Citation - Scopus: 11Synthesis of Adsorbents With Dendronic Structures for Protein Hydrophobic Interaction Chromatography(Elsevier Ltd., 2016) Mata-Gomez, Marco A.; Yaman, Sena; Valencia-Gallegos, Jesus A.; Tarı, Canan; Rito-Palomares, Marco; Gonzalez-Valdez, JoseHere, we introduced a new technology based on the incorporation of dendrons-branched chemical structures-onto supports for synthesis of HIC adsorbents. In doing so we studied the synthesis and performance of these novel HIC dendron-based adsorbents. The adsorbents were synthesized in a facile two-step reaction. First, Sepharose 4FF (R) was chemically modified with polyester dendrons of different branching degrees i.e. third (G3) or fifth (G5) generations. Then, butyl-end valeric acid ligands were coupled to dendrons via ester bond formation. UV-vis spectrophotometry and FTIR analyses of the modified resins confirmed the presence of the dendrons and their ligands on them. Inclusion of dendrons allowed the increment of ligand density, 82.5 ± 11 and 175.6 ± 5.7 μmol ligand/mL resin for RG3 and RG5, respectively. Static adsorption capacity of modified resins was found to be ~60 mg BSA/mL resin. Interestingly, dynamic binding capacity was higher at high flow rates, 62.5 ± 0.8 and 58.0 ± 0.5 mg/mL for RG3 and RG5, respectively. RG3 was able to separate lipase, β-lactoglobulin and α-chymotrypsin selectively as well as fractionating of a whole proteome from yeast. This innovative technology will improve the existing HIC resin synthesis methods. It will also allow the reduction of the amount of adsorbent used in a chromatographic procedure and thus permit the use of smaller columns resulting in faster processes. Furthermore, this method could potentially be considered as a green technology since both, dendrons and ligands, are formed by ester bonds that are more biodegradable allowing the disposal of used resin waste in a more ecofriendly manner when compared to other exiting resins.Article Citation - WoS: 52Citation - Scopus: 72Production of Bioethanol From Apple Pomace by Using Cocultures: Conversion of Agro-Industrial Waste To Value Added Product(Elsevier Ltd., 2015) Evcan, Ezgi; Tarı, CananDirect fermentation of cellulosic biomass to bioethanol has been very promising and hence attracted attention in recent years. In this study, bioethanol production from apple pomace hydrolysate (agro-industrial waste product) was investigated by coculturing Trichoderma harzianum, Aspergillus sojae and Saccharomyces cerevisiae using statistical approaches. Screening and optimization experiments were conducted in order to determine the significant factors and their optimum levels for maximum bioethanol production. Inoculation rates, aeration and agitation speed were considered as factor variables and bioethanol production as response variable. Highest bioethanol (EtOH) concentration and ethanol yield on total reducing sugar content (YP/S) were 8.748 g/L and 0.945 g/g, respectively. Optimum conditions were 6% (w/v) inoculation rates of T.harzianum and A.sojae, and 4% (v/v) inoculation rate of S.cerevisiae with vented aeration method and agitation speed of 200 rpm. To best of our knowledge to date, no reports are available in literature regarding the coculturing of T.harzianum, A.sojae and S.cerevisiae for bioethanol production. Therefore, this study will serve as a base line of initial studies in this field. The method can create a renewable alternative feedstock for fossil fuel production and suggest a feasible solution to multiple environmental problems simultaneously creating a sink for waste utilization.Article Citation - WoS: 28Citation - Scopus: 38Bioconversion of Wheat Bran for Polygalacturonase Production by Aspergillus Sojae in Tray Type Solid-State Fermentation(Elsevier Ltd., 2016) Demir, Hande; Tarı, CananWheat bran was tested as the solid substrate for the tray-type solid-state fermentation (SSF) production of polygalacturonase (PG) enzyme by A. sojae mutant strain - a high-PG activity producer. PG production of A. sojae was found to reduce as the thickness of the substrate increase from 8 mm to 14 mm at 90% relative humidity. An interaction between the thickness of the bed and relative humidity of the environment was determined with the help of experimental design and statistical analysis tools. As a result, the PG activity could be enhanced by 31% as the process conditions optimized. Additionally, 11 mm thickness and 70% relative humidity were selected as the PG production favoring conditions with the maximum PG activity of 298 U/g substrate in tray type of SSF without the addition of any nutritive or inducing supplements into wheat bran. The kinetic study conducted in the trays revealed the presence of reduction in the water activity on the 4th day of the SSF process under stated conditions. The productivity of the process conducted under optimized conditions was 3.41 U/g substrate-1 h-1 for the 4th day of the SSF. © 2015 Elsevier Ltd.Article Citation - WoS: 48Citation - Scopus: 58Valorization of Wheat Bran for the Production of Polygalacturonase in Ssf of Aspergillus Sojae(Elsevier Ltd., 2014) Demir, Hande; Tarı, CananWheat bran, among various agro industrial by products, screened for the production of polygalacturonase (PG) in solid-state fermentation of Aspergillus sojae mutant strain, was found to be the most suitable substrate without the addition of any nutritive or inducing supplement. It was further characterized for its physicochemical composition and particle size distribution. The process conditions that favored the PG production using this substrate were determined as; 107 spore/g substrate inoculum concentration, 4 days of fermentation, 37°C of incubation temperature, 62% initial moisture content, water as the moistening agent, 100-250μm particle size of wheat bran, 3 times/day agitation and spore solution as the inoculum type which resulted into maximum PG activity of 535.4U/g substrate. Overall, this optimization process resulted in 7.3 and 3.9 fold of significant enhancement in the PG activity and productivity, respectively.Article Citation - WoS: 18Citation - Scopus: 18Surface Energetics To Assess Biomass Attachment Onto Hydrophobic Interaction Adsorbents in Expanded Beds(Elsevier Ltd., 2009) Vennapusa, Rami Reddy; Tarı, Canan; Cabrera, Rosa; Fernandez-Lahore, MarceloCell-to-support interaction and cell-to-cell aggregation phenomena have been studied in a model system composed of intact yeast cells and Phenyl-Streamline adsorbents. Biomass components and beaded adsorbents were characterized by contact angle determinations with three diagnostic liquids and zeta potential measurements. Subsequently, free energy of interaction vs. distance profiles between interacting surfaces was calculated in the aqueous media provided by operating mobile phases. The effect of pH and ammonium sulphate concentration within the normal operating ranges was evaluated. Calculation indicated that moderate interaction between cell particles and adsorbent beads can develop in the presence of salt. Cell-to-cell aggregation was suspected to occur at high salt concentration and neutral pH. Predictions based on the application of the XDLVO approach were confirmed by independent experimental methods like biomass deposition experiments and laser diffraction spectroscopy. Understanding biomass attachment onto hydrophobic supports can help in alleviating process limitations normally encountered during expanded bed adsorption of bioproducts.Article Citation - WoS: 48Citation - Scopus: 59Biochemical and Thermal Properties of Ss-Galactosidase Enzymes Produced by Artisanal Yoghurt Cultures(Elsevier Ltd., 2010) Üstok, Fatma Işık; Tarı, Canan; Harsa, Şebnemβ-Galactosidases, produced by pure and mixed cultures of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey, were characterised with respect to their biochemical and thermal properties. Optimum pH and temperature for maximum activity were determined and these enzymes were stable in the pH range 7-9 and in the temperature range 20-37 °C, retaining 80-90% of their initial activities. The inactivation energies of β-galactosidase from Lb 77, St 95/2 and mixed culture (Lb 77 and St 95/2) were 51.3, 44.0 and 48.3 kcal mol-1, respectively. Moreover, thermodynamic (ΔG, ΔS, ΔH) and kinetic constants (Km and Vmax) were determined and effects of metal ions were investigated. As a result, these enzymes could be considered as potential candidates for lactose hydrolysis of milk and milk products. © 2009 Elsevier Ltd. All rights reserved.Article Citation - WoS: 19Citation - Scopus: 22Optimization of the Associative Growth of Novel Yoghurt Cultures in the Production of Biomass, Ss-Galactosidase and Lactic Acid Using Response Surface Methodology(Elsevier Ltd., 2009) Tarı, Canan; Üstok, Fatma Işık; Harsa, Hayriye ŞebnemThe associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL-1), lactic acid (22.50 g L-1) and biomass (7.11 g L-1) production at optimum conditions were very close to the actual experimental values (2.14 U mL-1, 22.94 g L-1 and 7.86 g L-1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.Article Citation - WoS: 50Citation - Scopus: 59Characterization of Three-Phase Partitioned Exo-Polygalacturonase From Aspergillus Sojae With Unique Properties(Elsevier Ltd., 2008) Doğan, Nergiz; Tarı, CananExo-polygalacturonase enzyme produced by Aspergillus sojae ATCC 20235 was purified using three-phase partitioning (TPP), an emerging bio-separation technique where a single step as compared to the classical multi-step purification was used. Using this technique, crude enzyme solution (pH 6.6) saturated to 30% (w/v) with ammonium sulphate and with a crude extract to tert-butanol ratio of 1:1 (v/v) at 25 °C resulted in 25.5% recovery of exo-polygalacturonase with a 6.7-fold purification. The purified enzyme was characterized with respect to its activity and stability at various pH and temperature ranges. Optimum pH and temperature for maximum activity were determined as pH 4 and 55 °C. The enzyme was stable at both acidic and alkaline pH for 2 h at 30 °C. The thermal stability study showed that the purified enzyme had an inactivation energy of 68.41 kcal/mol and a half-life (t1/2) value of 3.6 h at 75 °C presenting a large thermal stability. The kinetic constants Km and Vmax using polygalacturonic acid as substrate were 0.75 g l-1 and 1.14 μmol min-1, respectively. SDS-PAGE profiling revealed that the purified exo-polygalacturonase had two bands with the molecular weights of 36 and 53 kDa. The enzyme was completely inhibited in the presence of Mn2+ and SDS and induced significantly by EDTA, glycerol and β-mercaptoethanol.Article Citation - WoS: 124Citation - Scopus: 144Use of Uv-C Radiation as a Non-Thermal Process for Liquid Egg Products (lep)(Elsevier Ltd., 2008) Ünlütürk, Sevcan; Atılgan, Mehmet Reşat; Baysal, Ayşe Handan; Tarı, CananThe efficacy of short wave ultraviolet light (UV-C) as a non-thermal process for liquid egg products (LEP) was investigated. Non-pathogenic Escherichia coli strain (ATCC 8739), which shows lower sensitivity to UV-C light than E. coli O157:H7 and Salmonella typhimurium, was chosen as a target microorganism. The inactivation of UV resistant strain of E. coli in LEP was examined by evaluating the effects of depth of liquid food medium (0.5, 0.3 and 0.153 cm), UV light intensity (1.314, 0.709 and 0.383 mW/cm2) and exposure time (0, 5, 10, and 20 min) by using a collimated beam apparatus. The best reduction (>2-log) was achieved in liquid egg white (LEW) when the fluid depth and UV intensity were 0.153 cm and 1.314 mW/cm2, respectively. Maximum inactivation was 0.675-log CFU/ml in liquid egg yolk (LEY) and 0.316-log CFU/ml in liquid whole egg (LWE) at the same conditions. The kinetics of UV inactivation of E. coli in LEP was nonlinear. Our results emphasize that UV-C radiation can be used as a pre-treatment process or combined with mild heat treatment to reduce the adverse effects of thermal pasteurization of LEP.Article Citation - WoS: 52Citation - Scopus: 62Solid-State Production of Polygalacturonase by Aspergillus Sojae Atcc 20235(Elsevier Ltd., 2007) Üstok, Fatma Işık; Tarı, Canan; Göğüş, NihanThe effect of solid substrates, inoculum and incubation time were studied using response surface methodology (RSM) for the production of polygalacturonase enzyme and spores in solid-state fermentation using Aspergillus sojae ATCC 20235. Two-stage optimization procedure was applied using D-optimal and face-centered central composite design (CCD). Crushed maize was chosen as the solid substrate, for maximum polygalacturonase enzyme activity based on D-optimal design. Inoculum and incubation time were determined to have significant effect on enzyme activity and total spore (p < 0.01) based on the results of CCD. A second order polynomial regression model was fitted and was found adequate for individual responses. All two models provided an adequate R2 of 0.9963 (polygalacturonase) and 0.9806 (spores) (p < 0.001). The individual optimum values of inoculum and incubation time for maximum production of the two responses were 2 × 107 total spores and 5-6 days. The predicted enzyme activity (30.55 U/g solid) and spore count (2.23 × 107 spore/ml) were very close to the actual values obtained experimentally (29.093 U/g solid and 2.31 × 107 spore/ml, respectively). The overall optimum region considering the two responses together, overlayed with the individual optima. Solid-state fermentation provided 48% more polygalacturonase activity compared to submerged fermentation under individually optimized conditions.