Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 13Citation - Scopus: 18Effect of Physicochemical Parameters on the Polygalacturonase of an Aspergillus Sojae Mutant Using Wheat Bran, an Agro-Industrial Waste, Via Solid-State Fermentation(John Wiley and Sons Inc., 2016) Demir, Hande; Tarı, CananBACKGROUND: Polygalacturonases (PGs) are valuable enzymes of the food industry; therefore it is of great importance to discover new and GRAS PG-producing microbial strains. In this study, PG enzyme produced from a high PG activity producer mutant Aspergillus sojae using wheat bran at the flask scale under pre-optimized conditions of solid-state fermentation (SSF) was biochemically characterized. RESULTS: The crude PG enzyme showed optimum activity in the pH range 4.0–5.0 and was stable in the pH range 3.0–7.0. The optimum temperature for the PG was 40 °C and it retained 99% of its activity at 50 °C. The mutant A. sojae PG could preserve more than 50% of its stability between 25 and 50 °C, both for 30 and 60 min, and was found to be stable in the presence of most of the tested compounds and metal ions. The inactivation energy (Ed) was determined as 125.3 kJ mol−1. The enthalpy (ΔH*), free energy (ΔG*) and entropy (ΔS*) of inactivation were found to be stable with increasing temperature. CONCLUSION: The mutant A. sojae PG could be suitable for the clarification (depectinization) of orange and grape juices and wine. © 2015 Society of Chemical Industry.Article Citation - WoS: 12Citation - Scopus: 16Utilization of Orange Peel, a Food Industrial Waste, in the Production of Exo-Polygalacturonase by Pellet Forming Aspergillus Sojae(Springer Verlag, 2015) Büyükkileci, Ali Oğuz; Lahore, Marcelo Fernandez; Tarı, CananThe production of exo-polygalacturonase (exo-PG) from orange peel (OP), a food industrial waste, using Aspergillus sojae was studied in submerged culture. A simple, low-cost, industrially significant medium formulation, composed of only OP and (NH4)2SO4 (AS) was developed. At an inoculum size of 2.8 × 103 spores/mL, growth was in the form of pellets, which provided better mixing of the culture broth and higher exo-PG activity. These pellets were successfully used as an inoculum for bioreactors and 173.0 U/mL exo-PG was produced. Fed-batch cultivation further enhanced the exo-PG activity to 244.0 U/mL in 127.5 h. The final morphology in the form of pellets is significant to industrial fermentation easing the subsequent downstream processing. Furthermore, the low pH trend obtained during this fermentation serves an advantage to fungal fermentations prone to contamination problems. As a result, an economical exo-PG production process was defined utilizing a food industrial by-product and producing high amount of enzyme.Article Citation - WoS: 14Citation - Scopus: 12Enhanced Production of Exo-Polygalacturonase From Agro-Based Products by Aspergillus Sojae(North Carolina University, 2011) Büyükkileci, Ali Oğuz; Tarı, Canan; Fernandez-Lahore, MarcelloAspergillus sojae has been previously shown to produce exo-polygalacturonase (exo-PG) in synthetic media, where the potential of the organism to utilize agricultural substrates was not considered so far. In this study, the utilization of agro-based products was taken into account in the enhanced production of exo-PG using an A. sojae mutant by applying statistical design methods. Complex sources (orange peel, wheat bran, and corn meal), simple sugar sources (glucose, maltrin, and sugar beet syrup), and two phosphate salts were screened using D-optimal design method. Orange peel yielded the highest exo-PG activity with all simple sugars and phosphate sources. According to the results of response surface methodology (RSM), the optimum concentrations of orange peel, sugar beet syrup, and (NH 4) 2SO 4 were found to be 10, 60, and 8 g L -1, respectively. The exo-PG activity under these conditions was 145.4 U m L -1 in shake flask cultures. In bioreactor studies enzyme production was induced at low pH values; thus highest production was obtained under uncontrolled pH conditions, in which the pH dropped to 2.0 in 72 h. As a result high exo-PG could be produced by an A. sojae mutant using a cost-effective medium containing agro-industrial substrates. Another important advantageous outcome was the low optimal pH, which is especially desired in industrial fermentations prone to contamination problems. In fact this highlights the easy adaptation of this fermentation to industrial scales.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.