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Beet molasses-based feeding strategy enhances recombinant thermostable glucose isomerase production by Escherichia
Sena Yaman1,2, Pınar Çalık1,2
1Industrial Biotechnology and Metabolic Engineering Laboratory, Department of Chemical Engineering, Middle East Technical University, Ankara, Turkey.
Abstract:
The aim of this work was to develop an effective fed-batch feeding strategy to enhance recombinant glucose isomerase (r-GI) production by recombinant Escherichia coli BL21 (DE3) pLysS on an industrially relevant feedstock without the application of an exogenous inducer. Following the batch operation (0 < t < 7 H), the effects of pulse and/or continuous feeding of hydrolyzed beet molasses were investigated under five different feeding strategies. The two most promising strategies with respect to r-GI activity were (i) PM-0.05, designed with one pulse feed (t = 7 H) followed by a continuous feed and (ii) 2PMF -0.05, designed with two consecutive pulse feeds (t = 7 and 10 H) followed by a continuous feed. The continuous feeding of molasses for both fermentation strategies employed the same precalculated feeding rate, μo = 0.05 H-1 . The maximum r-GI activities exhibited by PM-0.05 and 2PMF -0.05 were 29,050 and 30,642 U dm-3 , respectively. On the one hand, compared to PM-0.05 r-GI activity reached its maximum within a shorter cultivation time (∆tmax = 2 H) at 2PMF -0.05, which could be preferable in terms of manufacturing costs and possible risks; on the other hand, PM-0.05 is a simpler fermentation regime compared to 2PMF -0.05 with respect to manipulations that should be considered in large-scale production.
