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Öğe Biochemical characterization and stability of bacillus subtilis polygalacturonase produced using hazelnut shells by submerged fermentation(Taylor & Francis Ltd, 2020) Uzuner, Sibel; Çekmecelioğlu, DenizBiochemical and bio-catalytic properties of an enzyme are essential to evaluate its potential industrial applications in food, pharmaceutical, textile, paper and pulp. More specifically, identifying optimal pH and temperature, and their effects on the residual enzyme activity are of high priority in biochemical characterisation. Therefore, in this study, polygalacturonase (PGase) produced as an extracellular enzyme in an earlier study growing Bacillus subtilis on hazelnut shell hydrolysate was evaluated under varying pH and temperature for its stability. The optimal pH and temperature values of the enzyme were found as 7.0, and 50 degrees C, respectively. The enzyme K-m and V-max values were identified as 0.52 mg/mL and 3.27 mu mol/min. The enzyme retained about 93 and 78% of its initial activity at 50 and 60 degrees C after 7 h, respectively. SDS-PAGE revealed a single activity band with molecular weight of 50 kDa. The half-life of PGase at 50 and 60 degrees C were 57.8 and 23 h, respectively. Thus, the results prove the potential of the B. subtilis pectinase produced using hazelnut shells in food processing e.g. extraction and clarification processes or treatment of pectic waste water.Öğe Comparison of artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models in simulating polygalacturonase production(North Carolina State Univ Dept Wood & Paper Sci, 2016) Uzuner, Sibel; Çekmecelioğlu, DenizThe artificial neural network (ANN) method was used in comparison with the adaptive neuro-fuzzy inference system (ANFIS) to describe polygalacturonase (PG) production by Bacillus subtilis in submerged fermentation. ANN was evaluated with five neurons in the input layer, one hidden layer with 7 neurons, and one neuron in the output layer. Five fermentation variables (pH, temperature, time, yeast extract concentration, and K2HPO4 concentration) served as the input of the ANN and ANFIS models, and the polygalacturonase activity was the output. Coefficient of determination (R-2) and root mean square values (RMSE) were calculated as 0.978 and 0.060, respectively for the best ANFIS structure obtained in this study. The R-2 and RMSE values were computed as 1.00 and 0.030, respectively for the best ANN model. The results showed that the ANN and ANFIS models performed similarly in terms of prediction accuracy.Öğe Enhanced pectinase production by optimizing fermentation conditions of Bacillus subtilis growing on hazelnut shell hydrolyzate(Elsevier, 2015) Uzuner, Sibel; Çekmecelioğlu, DenizThis study describes optimization of polygalacturonase (PG) production using Bacillus subtilis in submerged fermentation by Plackett-Burman (PB) design and response surface methodology (RSM). Five variables (pH, time, temperature, yeast extract concentration and K2HPO4), which were determined to be significant by the PB analysis, were further optimized using Box-Behnken response surface method. The optimization results indicated that a maximal PG activity of 5.60 U mL(-1) was achieved at pH 7.0, 72 h, and 30 degrees C using 0.5% (w/v) yeast extract and 0.02% (w/v) K2HPO4 in the fermentation medium. The results implied a 2.7-fold increase in PG activity of B. subtilis under the optimized conditions. Thus, it was concluded that hazelnut shell hydrolyzate have remarkable potential for low cost commercial PG production. (C) 2015 Elsevier B.V. All rights reserved.Öğe Enzymes in the beverage industry(Elsevier, 2018) Uzuner, Sibel; Çekmecelioğlu, DenizEnzymes are novel alternatives to chemical or mechanical methods for improving yield and quality in the beverage industry. Pectinases, amylases, cellulases, and xylanases are typical enzymes used in the extraction and clarification of fruit juices. Pectinases hold a 25% share in global food enzyme sales and industrial demands are still growing. Extraction yield increases up to 100% with synergy of other enzymes such as amylases and cellulases. This chapter aims to provide an updated review on uses of enzymatic methods in the beverage industry such as in the manufacture of fruit juices, coffee, and tea drinks. The role and action of mechanism, source, and advantages of enzyme use will be presented along with a brief description of beverage production, while the economy and suggestions for further improvement will be discussed at the end of the chapter. © 2019 Elsevier Inc. All rights reserved.Öğe Hydrolysis of hazelnut shells as a carbon source for bioprocessing applications and fermentation(Walter De Gruyter Gmbh, 2014) Uzuner, Sibel; Çekmecelioğlu, DenizHazelnut shells are generated in large amounts from hazelnut processing. Currently, it is used as fuel. However, reuse in bioprocessing can release remarkable content of sugars, which can be used for production of additives such as enzymes widely used in the food industry. Thus, the present study was undertaken to determine the effect of single and combined chemical and enzymatic hydrolysis on the production of fermentable sugars from hazelnut shells. Batch hydrolysis was carried out under various conditions to select optimal conditions. The results revealed that an optimal sugar concentration of about 19.2 g/l was achieved after 3.42% (w/w) dilute acid pretreatment conducted at 130 degrees C for 31.7 min and enzymatic load of 200 U/g for 24 h. The overall sugar yield was calculated as 72.4% (g reducing sugar/g total carbohydrate). Therefore, hazelnut shells can be considered a suitable feedstock to compete with synthetic sugars used in fermentations.Öğe Improvement of pectinase production by co-culture of Bacillus spp. using apple pomace as a carbon source(Springer, 2019) Kuvvet, Ceren; Uzuner, Sibel; Çekmecelioğlu, DenizIncreasing interest in using food and agricultural wastes for low cost enzyme production continues in fermentation industry. Bacteria, especially Bacillus subtilis, are known to produce pectinases in synthetic media and media amended with agricultural wastes as a carbon source, whereas the potential of co-culturing Bacillus species to produce pectinases has not been fully studied yet. In this study, co-culture of B. subtilis and B. pumilus was optimized for solid load and pH to maximize pectinase production in submerged fermentation using apple pomace as the carbon source. Optimal pectinase activity was achieved as 11.25IU/mL with 15% apple pomace (solid load), pH 9.0, and 1/4 of culture ratio (B. subtilis/B. pumilus) at 30 degrees C after 24h of fermentation period according to the Box-Behnken response surface methodology. Thus, it was concluded that a twofold-increase in pectinase production was achieved by co-culturing of Bacillus spp. compared to our previous monoculture Bacillus study.Öğe A novel oxidative destruction of lignin and enzymatic digestibility of hazelnut shells(Elsevier Science Bv, 2018) Uzuner, Sibel; Sharma-Shivappa, Ratna R.; Çekmecelioğlu, Deniz; Kolar, PraveenThis study investigated the effect of sequential oxidative (ozonolysis) pretreatment and enzymatic hydrolysis of hazelnut shells on production of fermentable sugars. Two factors (ozone concentration and pretreatment time), which were determined to be significant by the Box-Behnken response surface methodology, were further maximized for total lignin removal, solid recovery, and total reducing sugar yield via enzymatic hydrolysis of the pretreated biomass using full-factorial design. The ozonolysis was performed by passing 30, 40, and 50 mg/L of ozone gas through a packed bed of ground hazelnut shells for up to 120 min at a flow rate of 0.25 L/min. The highest lignin reduction (20.5%) was obtained in the shells with 30% moisture content subjected to ozone concentration of 50 mg/L for 120 min, which corresponded to a high biomass recovery (94%). The reducing sugar yield also increased from 119.9 mg/g dry untreated biomass to 284.6 mg/g dry untreated biomass for hazelnut shells ozonated at 30 mg/L for 60 min. Thus, these results indicate remarkable benefits of ozonolysis during pretreatment of hazelnut shells.Öğe Optimising clarification of carrot juice by bacterial crude pectinase(Wiley, 2015) Uzuner, Sibel; Çekmecelioğlu, DenizThis study was undertaken to search for potential use of crude bacterial pectinase enzyme produced from Bacillus subtilis grown on hazelnut shell hydrolysate in clarification of carrot juice and to optimize the enzyme load, pH and time using the Box-Behnken response surface methodology (RSM). The carrot juice was treated with the crude pectinase enzyme (5.60 U mL(-1)) at different concentrations (0.1-0.5%), pH (4-7), and time (2-6 h). The obtained enzyme was also compared with commercial fungal pectinase at identical conditions. RSM provided optimal clarification conditions of 0.5% (w/v) enzyme load, 7.0 pH, and 6 h of time estimating 100% clarity, whose experimental counterpart was 94.47 +/- 0.01%. High values of coefficient of determination (R-2 = 0.9631), predicted R-2 (0.8989) and insignificant lack-of-fit (0.12) also showed that the model was successful in predicting % clarity for various combinations. This study also indicated that crude bacterial pectinase providing about 95% clarity is superior to commercial fungal pectinase, which gave 78% clarity under tested conditions, in terms of clarification ability for carrot juice.
