Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 1Citation - Scopus: 2Partial Purification of a Polygalacturonase From a New Aspergillus Sojae Mutant and Its Application in Grape Mash Maceration(John Wiley and Sons Inc., 2017) Yıldız, Semanur; Mata-Gomez, Marco A.; Tarı, Canan; Rito-Palomares, MarcoThe use of polygalacturonase (PG) preparations in winemaking promotes the release of phenolic compounds. A PG from a new source, Aspergillus sojae mutant, was semi-purified and tested for grape mash maceration. Crude extract (CE), a commercial pectinase, and two high PG activity semi-purified preparations, FI and FII , were applied for maceration at PG activity of 3.5 U g−1 of grape for 46 h. Enzyme-assisted maceration significantly (P < 0.05) increased the total phenolic content from 255.8 to 916.3 ± 5.2, 5732.9 ± 9.9, 563.4 ± 6.7 and 620.6 ± 18.4 mg L−1 for CE, commercial pectinase, FI and FII, respectively. The content of individual phenolics such as gallic, protocatechuic, chlorogenic and p-coumaric acids was improved. Principal component and hierarchical clustering analyses suggested that CE has a better performance upon the release of phenols. Semi-purified preparations acted similar to commercial pectinase. These findings open an opportunity for the potential use of PG from the mutant strain as an alternative macerating enzyme.Article Citation - WoS: 18Citation - Scopus: 19Control of Agitation Rate and Aeration for Enhanced Polygalacturonase Production in Submerged Fermentation by Aspergillus Sojae Using Agro-Industrial Wastes(John Wiley and Sons Inc., 2017) Fratebianchi, Dante; Crespo, Juan Manuel; Tarı, Canan; Cavalitto, SebastianBACKGROUND: The koji mold Aspergillus sojae, an industrially important microorganism, can produce high levels of pectinases utilizing agro-industrial wastes. This study introduces apricot and peach pomace, two agro-industrial wastes barely considered as raw material for the generation of value-added products, and focuses on its utilization together with orange peel for polygalacturonase production in submerged cultures using A. sojae. RESULTS: A Doehlert response surface methodology design conducted in shake flasks and applied individually with these three by-products led to 60–80 U mL−1 polygalacturonase activity. In bioreactor studies performed with a mixture of apricot pomace and orange peel, by fixing stirrer speed to 600 rpm and cascading airflow to the dissolved oxygen tension up to 1.7 vvm, oxygen limitation problems were overcome and polygalacturonase activity values of 380 U mL−1 were achieved. CONCLUSION: A simple and efficient strategy to minimize oxygen limitation with the lowest possible shear stress is provided for stirred-tank bioreactors working with highly viscous broths, so as to ultimately enhance microbial enzyme production. The polygalacturonase activity yields obtained in our study are among the highest reported in the literature.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: 10Citation - Scopus: 11Colloid Deposition Experiments as a Diagnostic Tool for Biomass Attachment Onto Bioproduct Adsorbent Surfaces(John Wiley and Sons Inc., 2008) Tarı, Canan; Vennapusa, Rami Reddy; Cabrera, Rosa B.; Fernandez-Lahore, MarceloBackground: Detrimental processing conditions can be expected in any downstream operation where direct contacting between a crude feedstock and a reactive solid phase is supposed to occur. In this paper we have investigated the factors influencing intact yeast cells deposition onto anion and cation exchangers currently utilized for expanded-bed adsorption of biotechnological products. The aim of this study was twofold: (a)to confirm previous findings relating biomass deposition with surface energetics according to the extended Derjaguin, Landau, Verwey and Overbeek theory (XDLVO) theory; and (b) to provide a simple experimental tool to evaluate biomass deposition onto process surfaces. Results: Biomass deposition experiments were performed on an automated workstation utilizing a packedbed format. Two commercial ion exchangers intended for the direct capture of bioproducts in the presence of suspended biological particles were employed. Intact yeast cells in the late exponential phase of growth were selected as model bio-colloids. Cell deposition was systematically evaluated as a function of fluid-phase conductivity and quantitatively expressed as a biomass deposition parameter (α). Conclusion: α ≤ 0.15 was established as a criterion to reflect negligible biomass adhesion to the process support(s). Biomass deposition experiments further confirmed predictions made on the basis of free interfacial energy calculations as per the extended DLVO approach.