Browsing by Author "Ozdemir, Mustafa"

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Invertase Production and Molasses Decolourization by Cold-Adapted Filamentous Fungus Cladosporium Herbarum Er-25 in Non-Sterile Molasses Medium
(Elsevier, 2016) Taskin, Mesut; Ortucu, Serkan; Unver, Yagmur; Tasar, Ozden Canli; Ozdemir, Mustafa; Kaymak, Haluk Caglar
This study was undertaken to remove the coloring compounds of molasses as well as produce extracellular (exo) invertase in sterile and non-sterile molasses medium by using cold-adapted filamentous fungus Cladosporium herbarum ER-25. It was determined that a combination of low culture pH (5.5), temperature (20 degrees C) and high molasses concentration (6%) could completely prevent undesired bacterial contamination during the cultivation of C. herbarum ER-25. Under the optimized non-sterile culture conditions, the maximum invertase activity (36.1 U/mL) was attained after 72 h. On the other hand, the fungus could remove toxical dark brown pigments (melanoidins) in non-sterilized molasses medium through biodegradation and bioadsorption mechanisms. A color removal rate of 64.8% in non-sterile medium could be achieved at the end of 144-h cultivation period. It was found that lac case and manganese peroxidase were responsible for biodegradation. No ligninase activity was detected for the fungus during the cultivation. Maximum laccase (4.6 U/mL) and manganese peroxidase (3.5 U/mL) activities could be reached after 120 h. Higher invertase activity and color removal rate were achieved in non-sterilized medium compared to sterilized one. This is the first report on invertase production from cold-adapted microorganisms under non-sterile culture conditions. As an additional contribution, use of cold-adapted fungi for molasses decolourization was investigated for the first time in the present study. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Lipase Production with Free and Immobilized Cells of Cold-Adapted Yeast Rhodotorula Glutinis HL25
(Elsevier Science BV, 2016) Taskin, Mesut; Ucar, Muhammed Hanifi; Unver, Yagmur; Kara, Ayse Aydan; Ozdemir, Mustafa; Ortucu, Serkan
This study was undertaken to produce the lipase by free and immobilized cells of cold-adapted yeast Rhodotorula glutinis HL25 using waste frying oils as substrate. The optimization of culture parameters was performed using traditional one-factor-at-a-time protocol. The temperature 20 degrees C and initial pH 6.0 were optimal for lipase production by both free and immobilized cells. An inoculum size of 40 mL/L for free cells and beads number of 150 g/L for immobilized cells were optimal for lipase production. Optimal waste frying oil concentration and incubation time were 30 mL/L and 84 h for free cells but 40 mL/L and 72 h for immobilized cells, respectively. The maximum increases for free and immobilized cells were achieved at the Triton X-100 concentrations of 5 and 7.5 mL/L, respectively. The maximum lipase activities were determined as 54.4 and 75.2 U/L for free and immobilized cells, respectively. Immobilized cells could be used in five successive reaction cycles without any loss in the maximum activity. Immobilized cells could retained about 70% of their maximum activity by the end of the cycle 10. This is the first attempt on lipase production potential of a cold-adapted strain of the yeast R. glutinis. Furthermore, lipase production using immobilized cells of cold-adapted yeasts was investigated for the first time. (C) 2016 Elsevier Ltd. All rights reserved.