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: 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: 29Citation - Scopus: 29Microbial Strain Improvement for Enhanced Polygalacturonase Production by Aspergillus Sojae(Springer Verlag, 2014) Heerd, Doreen; Tarı, Canan; Fernandez Lahore, MarceloStrain improvement is a powerful tool in commercial development of microbial fermentation processes. Strains of Aspergillus sojae which were previously identified as polygalacturonase producers were subjected to the cost-effective mutagenesis and selection method, the so-called random screening. Physical (ultraviolet irradiation at 254 nm) and chemical mutagens (N-methyl-N′-nitro-N-nitrosoguanidine) were used in the development and implementation of a classical mutation and selection strategy for the improved production of pectic acid-degrading enzymes. Three mutation cycles of both mutagenic treatments and also the combination of them were performed to generate mutants descending from A. sojae ATCC 20235 and mutants of A. sojae CBS 100928. Pectinolytic enzyme production of the mutants was compared to their wild types in submerged and solid-state fermentation. Comparing both strains, higher pectinase activity was obtained by A. sojae ATCC 20235 and mutants thereof. The highest polygalacturonase activity (1,087.2±151.9 U/g) in solid-state culture was obtained by mutant M3, which was 1.7 times increased in comparison to the wild strain, A. sojae ATCC 20235. Additional, further mutation of mutant M3 for two more cycles of treatment by UV irradiation generated mutant DH56 with the highest polygalacturonase activity (98.8±8.7 U/mL) in submerged culture. This corresponded to 2.4-fold enhanced polygalacturonase production in comparison to the wild strain. The results of this study indicated the development of a classical mutation and selection strategy as a promising tool to improve pectinolytic enzyme production by both fungal strains.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: 45Citation - Scopus: 52Biochemical and Thermal Characterization of Crude Exo-Polygalacturonase Produced by Aspergillus Sojae(Elsevier Ltd., 2008) Tarı, Canan; Doğan, Nergiz; Göğüş, NihanCrude exo-polygalacturonase enzyme (produced by Aspergillus sojae), significant for industrial processes, was characterized with respect to its biochemical and thermal properties. The optimum pH and temperature for maximum crude exo-polygalacturonase activity were pH 5 and 55 °C, respectively. It retained 60-70% of its activity over a broad pH range and 80% of its initial activity at 65 °C for 1 h. The thermal stability study indicated an inactivation energy of Ed = 152 kJ mol-1. The half lives at 75 and 85 °C were estimated as 3.6 and 1.02 h, respectively. Thermodynamic parameters, ΔH*, ΔS* and ΔG*, were determined as a function of temperature. The kinetic constants Km and Vmax, using polygalacturonic acid as substrate, were determined as 0.424 g l-1 and 80 μmol min-1, respectively. SDS-PAGE profiling revealed three major bands with molecular weights of 36, 53 and 68 kDa. This enzyme can be considered as a potential candidate in various applications of waste treatment, in food, paper and textile industries.