Enhanced <Emphasis Type="SmallCaps">l</Emphasis>-phenylalanine production by recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis> BR-42 (pAP-B03) resistant to bacteriophage BP-1 via a two-stage feeding approach |
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Authors: | Haiyan Zhou Xianyan Liao Long Liu Tianwen Wang Guocheng Du Jian Chen |
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Institution: | (1) State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, Jiangsu, China;(2) School of Biotechnology, Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China;(3) School of Life Sciences, Shanghai University, Shanghai, 200444, China; |
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Abstract: | The l-phenylalanine (l-Phe) production by Escherichia
coli WSH-Z06 (pAP-B03) was frequently prevented by bacteriophage BP-1 infestation. To cope with the bacteriophage BP-1 problem
for an improved l-Phe production, one bacteriophage BP-1-resistant mutant, E. coli BR-42, was obtained from 416 mutant colonies of E. coli WSH-Z06 after N-methyl-N’-nitro-N-nitrosoguanidine (NTG) mutagenesis by selection for resistance to bacteriophage BP-1. The recombinant E. coli BR-42-carrying plasmid pAP-B03 had a high capacity in l-Phe production and a remarkable tolerance to 1 × 1010 pfu (plaque-forming unit)/ml bacteriophage stock. For an enhanced l-Phe production by E. coli BR-42 (pAP-B03), the effects of different feeding strategies including pH–stat, constant rate feeding, linear decreasing
rate feeding, and exponential feeding on l-Phe production were investigated; and a two-stage feeding strategy, namely exponential feeding at μ
set = 0.18 h−1 in the first 20 h and a following linear varying rate feeding with F = (−0.55 × t + 18.6) ml/h, was developed to improve l-Phe production. With this two-stage feeding approach, a maximum l-Phe titer of 57.63 g/l with a high l-Phe productivity (1.15 g/l/h) was achieved, which was 15% higher than the highest level (50 g/l) reported so far according
to our knowledge. The recombinant E. coli BR-42 (pAP-B03) is a potential l-Phe over-producer in substantial prevention of bacteriophage BP-1 infestation compared to its parent strain WSH-Z06 (pAP-B03). |
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