Pullulan production by a non-pigmented strain of Aureobasidium pullulans using batch and fed-batch culture |
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Institution: | 1. Department of Biotechnology, Engineering School of Lorena, University of São Paulo, Lorena, Brazil;2. Department of chemical engineering, MNS University of Engineering and Technology, Multan, Pakistan;1. College of Marine Life Sciences, Ocean University of China, Yushan Road, No. 5, Qingdao, China;2. Department of Biology, Shantou University, Shantou 515063, China;3. Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266003 Qingdao, China |
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Abstract: | The production of pigment-free pullulan by Aureobasidium pullulans in batch and fed-batch culture was investigated. Batch culture proved to be a better fermentation system for the production of pullulan than the fed-batch culture system. A maximum polysaccharide concentration (31.3 g l−1), polysaccharide productivity (4.5 g l−1 per day), and sugar utilization (100%) were obtained in batch culture. In fed-batch culture, feed medium composition influenced the kinetics of fermentation. For fed-batch culture, the highest values of pullulan concentration (24.5 g l−1) and pullulan productivity (3.5 g l−1 per day) were obtained in culture grown with feeding substrate containing 50 g l−1 sucrose and all nutrients. The molecular size of pullulan showed a decline as fermentation progressed for both fermentation systems. At the end of fermentation, the polysaccharide isolated from the fed-batch culture had a slightly higher molecular weight than that of batch culture. Structural characterization of pullulan samples (methylation and enzymic hydrolysis with pullulanase) revealed the presence of mainly α-(1→4) (∼66%) and α-(1→6) (∼31%) glucosidic linkages; however, a small amount (<3%) of triply linked (1,3,4-, 1,3,6-, 1,2,4- and 1,4,6-Glc p) residues were detected. The molecular homogeneity of the alcohol-precipitated polysaccharides from the fermentation broths as well as the structural features of pullulan were confirmed by 13C-NMR and pullulanase treatments followed by gel filtration chromatography of the debranched digests. |
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