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Constitutive expression of Vitreoscilla haemoglobin in Sphingomonas elodea to improve gellan gum production
Author(s) -
Wu X.C.,
Chen Y.M.,
Li Y.D.,
Li O.,
Zhu L.,
Qian C.D.,
Tao X.L.,
Teng Y.
Publication year - 2011
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2010.04896.x
Subject(s) - gellan gum , strain (injury) , sucrose , erlenmeyer flask , bioreactor , aeration , food science , biology , sphingomonas , biochemistry , botany , chemistry , chromatography , gene , 16s ribosomal rna , ecology , anatomy
Aims: To improve a commercially used strain for gellan production by exogenous Vitreoscilla haemoglobin (VHb). Methods and Results: VHb gene was expressed in Sphingomonas elodea under the control of constitutive bla promoter. Biochemical activity of expressed VHb was confirmed by CO‐difference spectra analysis that exhibited a characteristic absorption maximum at 419 nm. During cultivation, not only enhanced cell growth was detected, but also 20% improvement in gellan production was observed after 48 h of incubation, with a maximum yield of 16·82 g l −1 . Moreover, maximum sucrose conversion efficiency (g gellan per g sucrose) was 57·8, 20% higher than that of the parental strain. We further examined the polysaccharide production of VHb‐expressing strain at different aeration levels in Erlenmeyer flasks. Again, in all cases, a significant enhancement of gellan production was observed, and the enhancement was more significant under oxygen‐limiting conditions (up to 26·8%). Conclusions: VHb exhibited positive effect on cell growth and gellan yield of S . elodea , especially under hypoxic conditions. Significance and Impact of the Study: This is the first application of VHb as an effective metabolic engineering strategy in S . elodea to regulate cell growth and optimize gellan yield.