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  • Author or Editor: H.B. Coban x
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Phytase is an important feed and food additive, which is used in diets to increase the absorption of divalent ions, amino acids, and proteins in the bodies and to decrease the excessive phosphorus release in the manure to prevent negative effects on the environment. To date, phytase has been mostly produced in solid state fermentations with insignificant production volumes. Thus, there is a need to produce phytase in submerged fermentations, which can be scaled-up for commercial productions. Additionally, optimization of fermentation medium has not been studied well in the literature. Therefore, this study has been undertaken to improve Aspergillus ficuum phytase production in submerged fermentations by optimizing important nutrients in the fermentation medium (glucose, Na-phytate, and CaSO4) using Box-Behnken design of Response Surface Methodology. Also, effects of pH and temperature on phytase activity were studied. Optimum glucose, Na-phytate, and CaSO4 concentrations were determined as 126, 14, and 1.1 g l–1, respectively. Additionally, pH 5.5 and 55 ºC were determined as optimum for the produced A. ficuum phytase activity. Under these conditions, phytase activity was increased to 3.45 U ml–1, which is about 50% higher than the previous results. Furthermore, the lowest activity loss was observed under 4 ºC storage conditions during 1 week of storage.

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Alpha keto acids are important food additives, which commonly produced by microbial deamination of amino acids. In this study, production of phenylpyruvic acid (PPA), which is the alpha keto acid of phenylalanine was enhanced in 2-l bench scale bioreactors by optimizing of fermentation medium composition using the Box-Behnken Response Surface Methodology (RSM). Optimum glucose, yeast extract, and phenylalanine concentrations were determined to be 119.4 g 1−1, 3.7 g 1−1, and 14.8 g 1−1, respectively, for PPA production, and 163.8 g 1−1, 10.8 g 1−1, and 9.8 g 1−1, respectively, for biomass production. Under these optimum conditions, PPA concentration was enhanced to 1349 mg 1−1, which was 28% and 276% higher than the unoptimized bioreactor and shake-flask fermentations, respectively. Moreover, P. vulgaris biomass concentration was optimized at 4.36 g 1−1, which was 34% higher than under the unoptimized bioreactor condition. Overall, this study demonstrated that optimization of the fermentation media improved PPA concentration and biomass production in bench scale bioreactors compared to previous studies in the literature and sets the stage for scale up to industrial production.

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