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Öğe Bioactive and technological properties of an ?-D-glucan synthesized by Weissella cibaria PDER21(Elsevier Sci Ltd, 2022) Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Taylan, Osman; Alamoudi, Mohammed; Dertli, EnesA slimy-mucinous-type colony of EPS-producing Weissella cibaria PDER21 was isolated and identified. The monomer composition was glucose, showing that the EPS is a glucan type homopolysaccharide, The core structure of (1 -> 6)-linked alpha-D-glucose units including (1 -> 3)-linked alpha-D-glucose branches at a ratio of 93.4/6.6 was revealed by H-1 and C-13 NMR spectra and confirmed by FTIR analysis. The glucan showed a superior thermal stability with almost no degradation in structure up to 300 degrees C. XRD analysis revealed the amorphous structure while SEM analysis confirmed the layer-like morphology. The glucan had an antioxidant activity (89.5%), water-holding capacity (103.7%) and water solubility index (80.7%) values, suggesting that the glucan had a strong level of antioxidant properties; good water binding capacity and excellent solubility. The glucan PDER21 is a polysaccharide possessing a good combination of technical and functional attributes, suggesting a great deal of potential for use in the food industry.Öğe Biosynthesis of alternan-stabilized selenium nanoparticles: A study on characterization and applications for antibacterial and antifungal purposes(Taylor & Francis Inc, 2024) ElObeid, Tahra; Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Sagdic, Osman; Taylan, Osman; Basahel, Abdulrahman; Karaboga, DervisIn this study, the alternan/selenium nanoparticles (Alt/SeNPs) were characterized with respect to their formation, morphology, size, selenium distribution, molecular, crystallographic, and thermal properties using UV-Vis spectroscopy, SEM, TEM, EDAX, FTIR, XRD, DSC and TGA measurements. UV-VIS measurements confirmed the synthesis of nanoparticles by observing a maximum surface plasmon resonance peak at 212 nm. In this study, alternan contributed to stabilizing the dispersion of SeNPs, resulting in a cluster of spherical and well-dispersed nanoparticles ranging in size from 50 to 90 nanometers. Nanoparticles were found to be highly thermally stable and in a nanocrystalline structure. The ABTS and CUPRAC radical scavenging activities of Alt/SeNPs were remarkable (95% and 78% at 4 and 6 mg/mL levels of Alt/SeNPs, respectively). Alt/SeNPs had also good inhibitory activities (3.5-4.0 and 4-15 mm of inhibition zone levels at 5 mg/mL level of Alt/against foodborne pathogenic bacteria and fungi, respectively).Öğe Characterisation and functional roles of a highly branched dextran produced by a bee pollen isolate Leuconostoc mesenteroides BI-20(Elsevier, 2022) Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Taylan, Osman; Tasdemir, Volkan; Sagdic, Osman; Dertli, EnesLactic Acid Bacteria (LAB) from different niches can be responsible for the production of distinct exopoly-saccharides (EPS) that might possess important structural and technological features. In this respect, the aim of this study was to isolate an EPS producer LAB strain from bee pollen environment. Leuconostoc mesenteroides BI-20 with a slimy-mucoid colony morphology was identified from bee pollen and the structural, technological and functional characteristics of EPS produced by this strain were determined. EPS BI-20 was a highly branched dextran containing 20% (1 -> 3)-linked alpha-D-glucose branches determined by H-1 and C-13 NMR analysis. The presence of (1 -> 6)/(1 -> 3)-linked alpha-D-glucose linkages in dextran BI-20 was also confirmed by FTIR analysis. Dextran BI-20, with a molecular weight of 1 x 10(8) Da, possessed strong thermal properties, amorphous nature and highly branched and fibrous microstructural characteristics determined by DSC, TGA, XRD and SEM analysis, respectively. In terms of functional roles, dextran BI-20 demonstrated strong antioxidant capacity detected by ABTS and CUPRAC tests. Finally, no digestion was observed in dextran BI-20 under simulated gastric conditions. Results of this study unveiled techno-functional characteristics of dextran BI-20 produced by a bee pollen isolate LAB strain.Öğe Effect of electrospun nisin and curcumin loaded nanomats on the microbial quality, hardness and sensory characteristics of rainbow trout fillet(Elsevier, 2019) Meral, Raciye; Alav, Aslihan; Karakas, CananYagmur; Dertli, Enes; Yilmaz, Mustafa Tahsin; Ceylan, ZaferNisin and curcumin loaded (NCL) nanomats having 172 nm mean diameter were successfully fabricated. The effect of NCL nanomats in terms of limitation of Total Mesophilic Aerobic (TMAB) and Lactic acid bacteria (LAB) in fish fillets was tested during the analysis period. On the 4th day, while TMAB load of C was 6.61 log CFU g(-1), that of the sample coated with NCL nanomats was found to be 3.28 log CFU g(-1). TMAB load of control samples reached above 6 log CFU g(-1) on the 4th day of cold storage, TMAB load of fish samples coated with nanomats reached the same level up to the 12th day. The shelf life of coated fillets was extended to 12 day. 3-4 logarithmic decrease was obtained in LAB count by NCL nanomats during the analysis period. On the 4th storage day, the hardness value of C sample decreased 21% compared to NCL samples. All sensory attributes of C samples were acceptable by the 4th day of the storage; while sensory attributes of NCL samples were acceptable by the 10th day of storage. The study revealed that nisin and curcumin loaded nanomats could be effectively used to improve the quality of fish fillets.Öğe The effect of flours of different immature cereal grains on sourdough and sourdough bread: Microbiological, rheological, textural and sugar profiles(Wiley, 2022) Alkay, Zuhal; Yilmaz, Mustafa Tahsin; Can, Asli Muslu; Ispirli, Humeyra; Dertli, EnesIn this study, the utilization of LAB (Lactiplantibacillus plantarum, Levilactobacillus brevis, Furfurilactobacillus rossiae, Weissella cibaria) cultures with selected flours of different immature cereal grains (wheat, barley, oat and rye) on sourdough and sourdough bread was investigated. In total, 16 different sourdough breads were produced and microbiological, pH, TTA and rheological properties of sourdoughs at 0, 8 and 24 h were determined. At the beginning of the fermentation, while sourdoughs showed elasticity, they showed viscoelastic properties after 24 h of fermentation. The sugar profile of cereal grains at the stage of milk formation and the sugar groups presented in EPSs isolated from sourdoughs were revealed by HPLC analysis. The sugar groups in sourdoughs were glucose, xylose and arabinose, while the sugars in the immature cereal grains were glucose, fructose and mannose. The highest EPS production level (1882.69 +/- 8.16) was observed in immature barley flour and Lpb. plantarum containing sourdough and all sourdoughs were found to contain glucan type EPSs. It was observed that the amount of EPS produced by the related species differed significantly under different grain conditions. Besides, it was observed that the sourdough breads produced were harder than the control bread. Novelty Impact Statement Wheat, barley, oat and rye immature grains and four distinct LAB strains were used during sourdough fermentation. Immature grain type and LAB strain used were determinants for in situ exopolysaccharide (EPS) production. Viscoelastic properties of sourdough and textural properties of sourdough bread were affected by grains and LAB strain utilized.Öğe EFFECT OF IN SITU EXOPOLYSACCHARIDE PRODUCTION ON SENSORY PROPERTIES OF TURKISH-TYPE FERMENTED SAUSAGE(Yildiz Technical Univ, 2016) Yilmaz, Mustafa Tahsin; Toker, Omer Said; Tatlisu, Nevruz Berna; Arici, Muhammet; Dertli, EnesIn this study, effect of in situ exopolysaccharide (EPS) production on sensory properties of Turkish-type fermented sausage (sucuk) was determined. Sausage mixes were prepared as four groups: (a) Control group, control sausage samples produced without LAB addition, with natural flora, (b) Strain 1 group, sausage samples produced by using Strain 1 (EPS+ Lactobacillus plantarum 162 R strain), (c) Strain 2 group: sausage samples produced by using Strain 2 (EPS+ Leuconostoc mesenteroides N6) and (d) Mixture group, sausage samples produced by using mixture of Strain 1 and Strain 2. These mixes were fermented at 14, 16 and 18 degrees C for 8, 12 and 16 days. Fermentation conditions remarkably affected the sensory properties of the sausage using different EPS producing EPS. These results of this study demonstrated the importance of in situ EPS production on final sensory properties of sausage.Öğe Fabrication of propolis loaded electrosprayed nanoparticles(Elsevier Science Bv, 2018) Ozmen, Duygu; Karakas, Canan Yagmur; Yilmaz, Azime; Dertli, Enes; Bayram, Nesrin Ecem; Yilmaz, Mustafa Tahsin[Abstract Not Available]Öğe Facile biomimetic synthesis of AgNPs using aqueous extract of Helichrysum arenarium: characterization and antimicrobial activity(Taylor & Francis Inc, 2022) Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Taylan, Osman; Balubaid, Mohammad; Dertli, EnesThe present study focuses on synthesis of silver nanoparticles (AgNPs) by employment of a green and facile synthesis method. Aqueous extract of Helichrysum arenarium was used as a reducing and capping agent. The bioreduction of silver particles was monitored using UV-Vis spectroscopy based on increase in color intensity led by surface plasmon resonance. SEM, TEM, FTIR, DSC, and XRD analyses were followed for characterization, divulging that the nanoparticles were thermally resistant in the size of approximately 20 nm with a quasi-spherical shape without any agglomeration. AgNPs possessed a nanocrystal form with presence of crystalline Ag. EDAX analysis was used to verify that the nanoparticles were silver as revealed by a typical optical absorption peak of metallic silver nanocrystallites. The AgNPs were shown to have strong antibacterial and antifungal effects on some foodborne pathogens. The method developed in this study could offer a green, facile biomimetic, and cost-effective method.Öğe Functional properties of lactic acid bacteria (LAB) playing crucial roles on sourdough biotechnology(Elsevier Science Bv, 2016) Dertli, Enes; Yilmaz, Mustafa Tahsin[Abstract Not Available]Öğe A green nano-biosynthesis of selenium nanoparticles with Tarragon extract: Structural, thermal, and antimicrobial characterization(Elsevier, 2021) Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Taylan, Osman; Dertli, EnesIn this study, tarragon extract was used as a reducing agent to perform green nano-biosynthesis of selenium nanoparticles (SeNPs). The synthesized SeNPs were characterized using measurements of UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy disperse analysis of X rays (EDAX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and differential scanning analysis (DSC). Synthesis of nanoparticles was confirmed by observing a peak at 212 nm in UV-VIS, indicating the surface plasmon resonance of SeNPs. Tarragon extract enabled a stable dispersion of SeNPs, giving rise to formation of the nanoparticles in the shape of quasi-spheres without clustering with the sizes between 20 and 50 nm. The SeNPs were shown to be in the form of nanocrystals, having Se embedded in the nanostructure with high thermal stability (a high resistance to thermal process over 200 degrees C). The SeNPs synthesized with tarragon extract could remarkably increase the inhibition zones from approximately 13 to 18 mm against the pathogenic bacteria and from 10 to 14 mm, 17-36 mm, 8-12 mm, 15-24.5 mm and 9-14 mm, against A. alternata, A. niger, A. parasiticus, B. cinerea, F. oxysporum and P. chrysogenum, respectively.Öğe Impact of glucan type exopolysaccharide (EPS) production on technological characteristics of sourdough bread(Elsevier Sci Ltd, 2020) Ispirli, Humeyra; Ozmen, Duygu; Yilmaz, Mustafa Tahsin; Sagdic, Osman; Dertli, EnesIn this study, technological role of a-glucan with (alpha 1-3) and (alpha 1-6) glycosidic linkages produced by Lactobacillus reuteri E81 on sourdough rheology and bread texture was investigated. To achieve this, a glucan deficient Delta gtfA mutant was produced by the deletion of the glucansucrase gene from strain E81. By comparison of glucan-positive and glucan-negative strains for rheological properties of sourdough revealed that in situ a-glucan production resulted in higher elasticity in sourdough. However, no additional effect of in situ glucan on textural characteristics of bread was observed although addition of glucan ex situ at 0.09% level significantly decreased bread hardness. Scanning Electron Microscopy (SEM) images of lyophilized sourdoughs confirmed association of glucan and starch granules forming a film like structure in sourdough.Öğe An integrated neural-fuzzy methodology for characterisation and modelling of exopolysaccharide (EPS) production levels of Leuconostoc mesenteroides DL1(Pergamon-Elsevier Science Ltd, 2020) Kabli, Mohammad; Yilmaz, Mustafa Tahsin; Taylan, Osman; Kaya, Yasemin; Ispirli, Humeyra; Basahel, Abdulrahman; Sagdic, OsmanOptimisation of exopolysaccharides (EPS) production in Lactic Acid Bacteria (LAB) is an important task as EPS production can be affected by different parameters. In this respect, this study aimed to characterise the structure of an EPS from Leuconstoc mesenteroides DL1 strain and to optimise the EPS production by determination of the effects of incubation time, sucrose concentration, incubation temperature and initial levan concentration (input parameters) using integrated ANNs (Artificial neural networks) and fuzzy modelling approaches. The characterisation of the EPS monomeric composition by HPLC analysis revealed that EPS DL1 was composed of glucose and fructose. The H-1 and C-13 NMR spectra of EPS DL1 also confirmed the glucan and fructan production. The effects of the input parameters on glucan and fructan production levels as output parameters by DL1 were optimised using neural network and fuzzy modelling tools. The fuzzy model was developed based on the recognition of basic elements of input-output parameters, and the power of ANNs used for system identification. A structural analysis was carried out to improve the flexibility of fuzzy model, and to design the unknown mappings of the input and output parameters more robustly. The parameters then were fine-tuned by qualitative reasoning to establish the relations of input output parameters using membership functions (MFs) and their intervals determination. A hybrid training algorithm was employed for parameter identification, MFs and their interval determination to obtain the fuzzy model. The model can predict the outcome parameters; glucan and fructan with high accuracy for the predetermined input parameters.Öğe MACHINE LEARNING APPLICATION FOR OPTIMIZING ASYMMETRICAL REDUCTION OF ACETOPHENONE EMPLOYING COMPLETE CELL OF LACTOBACILLUS SENMAIZUKE AS AN ENVIRONMENTALLY FRIENDLY APPROACH(Health & Environment Assoc, 2020) Taylan, Osman; Yilmaz, Mustafa Tahsin; Balubaid, Mohammed; Alamoudi, Rami; El-Obeid, Tahra; Dertli, Enes; Sahin, EnginRecently, optimization of the bioreduction reactions by optimization methodologies has gained special interest as these reactions are affected by several extrinsic factors that should be optimized for higher yields. An important example for these kinds of reactions is the complete cell implications for the bioreduction of prochiral ketones in which the culture parameters play crucial roles. Such biocatalysts provide environmentally friendly and clean methodology to perform reactions under mild conditions with high conversion rates. In the present work, at the first step the Lactobacillus senmaizuke was isolated from sourdough and the complete cell application of Lactobacillus senmaizuke for the bioreduction of acetophenone was optimized by an Artificial Neural networks (ANNs) to achieve the highest enantiomeric excess (EE, %). The culture parameters, pH, temperature, incubation period and agitation speed were the experimental factors that were optimized to maximize EE (%) by machine learning algorithm of Artificial Intelligence modeling and the best conditions to maximize EE (95.5 %) were calculated to be pH of 5.7, temperature of 35 degrees C, incubation period of 76 h and agitation speed of 240 rpm with very low sum of squared error value (0.611236 %) to bioreduce acetophenone using complete cell of Lactobacillus senmaizuke as a sourdough isolate GRAS microbial species. Accordingly, The ANN was employed to correctly establish the enantiomeric excess values of the specimen with an average absolute error 0.080739 %.Öğe Nanoemulsion-based delivery systems to improve functionality of oregano essential oil: Molecular characterization and in vitro antifungal activity(Elsevier Science Bv, 2017) Ermis, Ertan; Cicek, Perihan Kubra; Meral, Raciye; Yilmaz, Azime; Dertli, Enes; Yilmaz, Mustafa Tahsin[Abstract Not Available]Öğe Non-linear rheological (LAOS) behavior of sourdough-based dough(Elsevier Sci Ltd, 2019) Yildirim-Mavis, Cigdem; Yilmaz, Mustafa Tahsin; Dertli, Enes; Arici, Muhammet; Ozmen, DuyguDuring processing, wheat dough is known to undergo large deformation led by mixing and fermentation processes. This deformation is much more pronounced when sourdough is used in the recipe of wheat dough whose gluten is considerably hydrolyzed during sourdough fermentation. This causes deeper effects on rheological properties and shelf life of bakery products. Traditional small amplitude oscillatory tests do not enable us to comprehend the viscoelasticity under large deformations. In this respect, large amplitude oscillatory shear ( LAOS) tests are useful for accurate characterization of the non-linear mechanical response. This study, therefore, is undertaken to investigate the non-linear mechanical response of dough prepared with different amounts of sourdough (0, 10, 20 30 and 40%) in a strain values ranging from 0.005 to 200% (frequency at 10 rad/s). As a result, sourdough was determined to have considerable effects on the non-linear viscoelastic response of dough. Strain-stiffening and shear-thinning behaviors were considerably influenced by sourdough incorporation and the dough started to show strain-softening and lowered shear-thinning behavior after giving a peak around at 100% strain due to the onset of the breakdown of the gluten network and suspension of starch matrix as consequence of the metabolic activity of the starter culture (Lactobacillus brevis E25) used in the preparation of sourdough. The physicochemical (pH and TTA), microbiological properties (LAB count) and extensographic properties were also shown to support the LAOS results. LAOS tests could be effectively and clearly used to reveal the effect of processing conditions (sourdough content and deformation by large strain amplitude) on the non-linear mechanical response of wheat dough.Öğe A novel perspective for Lactobacillus reuteri: Nanoencapsulation to obtain functional fish fillets(Elsevier, 2019) Ceylan, Zafer; Uslu, Emin; Ispirli, Humeyra; Meral, Raciye; Gavgali, Mehmet; Yilmaz, Mustafa Tahsin; Dertli, EnesEnrichment of food products with beneficial Lactic Acid Bacteria (LAB) is an important methodology used to develop functional food products. Lactobacillus reuteri E81 was successfully nanoencapsulated into poly (vinyl alcohol)-based nanofibers for its application to the surface of fish fillets. The Scanning Electron Microscopy analysis confirmed the nanoencapsulation of L. reuteri E81 in electrospun nanofibers (LRNF) that had an average diameter of 381.83 +/- 130.69 nm. LAB growth in rainbow trout fillets and fatty fish (mackerel) and were found to be 2.92 and in the range of 3.27 and 2.66 log CFU/g, respectively. Importantly, the antioxidative characteristics of fish fillets significantly increased following their coating with LRNF. The results revealed a significant increase in the inhibition of free radicals in the samples treated with nanoencapsulated L. reuteri as compared to control group fish fillet samples. DPPH activity significantly increased to 40.24%, 44.96%, 44.97 in mackerel samples treated with nanoencapsulated L. reuteri (MLR) and increased to 19.76%, 20.87%, 21.46% in rainbow samples treated with nanoencapsulated L. reuteri (RLR). MLR samples exhibited the highest ABTS radical-scavenging activity (1631 mu mol TEAC/g). FRAP value of MLR samples was found to be 1.70 times higher than the control group samples.Öğe Optimization of asymmetric bioreduction conditions of 1-(thiophen-2-yl)ethanone by Weissella cibaria N9 using a desirability function-embedded face-centered optimization model(Taylor & Francis Inc, 2023) Bolubaid, Mohammed; Ozdemir, Akin; Dertli, Enes; Alamoudi, Mohammed; Taylan, Osman; Karaboga, Dervis; Yilmaz, Mustafa TahsinProchiral ketones can be effectively bio-reduced to chiral secondary alcohols by whole-cell biocatalysts, which are possible useful precursors to synthesize physiologically active chemicals and natural products. When whole-cell biocatalysts strains are used, bioreduction process can be influenced by various cultural factors, and it is vital to optimize these factors that affect selectivity, conversion rate, and yield. In this study, Weissella cibaria N9 was used as whole-cell biocatalyst for bioreduction of 1-(thiophen-2-yl)ethanone, and cultural design factors were optimized using a desirability function-embedded face-centered optimization model. For this, effects of pH (4.5-5.5-6.5, x(1)), (2) temperature (25-30-35 degrees C, x(2)), (3) incubation period (24-48-72 h, x(3)), and (4) agitation speed (100-150-200 rpm, x(4)) on two response variables; (1) ee (%) and (2) cr (%) were tested. Next, desirability function-embedded face-centered optimization model revealed that a pH of 6.43, a temperature of 26.04 degrees C, an incubation period of 52.41 h, and an agitation speed of 150 rpm were the optimum levels and the estimated ee and cr responses were 99.31% and 98.16%, respectively. Importantly, the actual experimental ee and cr responses were similar to the estimated values indicating the capability of the offered desirability function-embedded face-centered optimization model when using the optimum cultural conditions.Öğe Optimization of asymmetric bioreduction conditions of 1-indanone by Leuconostoc mesenteroides N6 using a face-centered design-based multi-objective optimization model(Taylor & Francis Inc, 2024) Alamoudi, Mohammed; Ozdemir, Akin; Dertli, Enes; Bolubaid, Mohammed; Alidrisi, Hassan M.; Taylan, Osman; Yilmaz, Mustafa TahsinThere has been an increasing interest in biocatalysts over the past few decades in order to obtain high efficiency, high yield, and environmentally benign procedures aiming at the manufacture of pharmacologically relevant chemicals. Lactic Acid Bacteria (LAB), a microbial group, can be employed as biocatalysts while performing asymmetric reduction of prochiral ketones. In this study, Leuconostoc mesenteroides N6 was used for the asymmetric bioreduction 1-indanone. And then, a novel and innovative face-centered design-based multi-objective optimization model was used to optimize experimental conditions. Also, the experimental design factors were defined as agitation speed, incubation period, pH, and temperature for optimization to acquire the maximum enantiomeric excess (ee) and conversion rate (cr) values. When using the face-centered design-based multi-objective optimization model, the optimum culture conditions corresponded to 96.34 and 99.42%, ee and cr responses, respectively, were pH = 5.87, incubation temperature = 35 degrees C, incubation period = 50.88 h, and agitation speed = 152.60 rpm. Notably, the validation experiment under the optimum model conditions confirmed the model results. This study demonstrated the importance of the optimization and the efficiency of the face-centered design-based multi-objective model.Öğe Optimization of cryoprotectant formulation to enhance the viability of Lactobacillus brevis ED25: Determination of storage stability and acidification kinetics in sourdough(Wiley, 2020) Gul, Latife Betul; Gul, Osman; Yilmaz, Mustafa Tahsin; Dertli, Enes; Con, Ahmet HilmiIn this study, various kinds of cryoprotectant (skim milk, lactose, and sucrose) formulations were tested to enhance the survival of Lactobacillus brevis ED25 after freezing and freeze-drying. A Box-Behnken experimental design was used to optimize cryoprotective medium and the highest cell survival was observed with the 17.28% skim milk, 2.12% lactose, and 10% sucrose cryoprotectant as the optimum condition. The structural and physicochemical characteristics of freeze-dried powder were acceptable for application with regards to particle surface morphology, moisture and water activity (A(w)), glass transition temperature (Tg), Fourier transform infrared spectra, X-ray structure, and also storage stability under the refrigeration and room temperature conditions. Accelerated storage test based on Arrhenius equation could be used to predict the freeze-dried bacterial shelf life but only with a certain degree of predictability for long-term storage. The acidification kinetics of fresh and stored culture in sourdough fermentation was also described on the basis of the Gompertz equation. Practical applications Freezing and storage are crucial factors for the viability and acidification power of starter culture. Therefore, various types and concentrations of cryoprotectants have been used to preserve the microorganisms. L. brevis ED25 has been a good potential for the manufacture of industrial sourdoughs and this research has aimed to investigate long-term protective effects of optimum cryoprotectant formulations on the viability of bacteria and also determine the acidification power in sourdough. The results showed the potential value of freeze-dried L. brevis ED25 culture for commercialization.Öğe Optimization of exopolysaccharide production of Lactobacillus brevis E25 using RSM and characterization(2020) Ermiş, Ertan; Poyraz, Ecem; Dertli, Enes; Yilmaz, Mustafa TahsinResponse surface methodology was used to determine the exopolysaccharide production of Lactobacillus brevis E25. The effects of three variables, temperature (30, 36 and 42°C), incubation time (18, 33 and 48 h) and initial pH of growth medium (4.5, 5.5, and 6.5) were studied. Under optimum growth conditions, the amount of exopolysaccharide derived from Lactobacillus brevis E25 ranged from 10 to 35 gL-1. The size of EPS molecules ranged from 105 to 107Da. Infra red spectrum analysis showed characteristics absorption peaks indicating the presence of -OH, C=O and C-H groups. Furthermore, only glucose was detected as monosaccharide in exopolysaccharide structure, revealing that the structure of exopolysaccharide is a homopolymeric glucan type. Based on the differential scanning calorimeter thermograms, exopolysaccharide’s melting temperature was observed around 116 °C.Keywords: Lactic acid bacteria, exopolysaccharide, response surface methodology, molecular characterization
