Integrated bioprocesses

Schügerl, K.; Hubbuch, Jürgen

doi:10.1016/j.mib.2005.01.002

Cited by 117 publications

(72 citation statements)

References 60 publications

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“…Enzyme synthesis and cofactor regeneration are related to host metabolism, which in turn may be affected by the toxicity of organic substrates and products. Such toxicity can efficiently be attenuated by regulated substrate feeding (1,11) and in situ product removal (7,38,61,66,74). Yet, microbial cells, especially in a nongrowing state, often lose biooxidation activity over time, which may be due to oxygenase inactivation and/or the metabolic burden imposed by redox-coenzyme withdrawal and reactive oxygen species formed via uncoupled oxygen reduction.…”

mentioning

confidence: 99%

NADH Availability Limits Asymmetric Biocatalytic Epoxidation in a Growing Recombinant Escherichia coli Strain

Bühler

Park

Blank

et al. 2008

Appl Environ Microbiol

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Styrene can efficiently be oxidized to (S)-styrene oxide by recombinant Escherichia coli expressing the styrene monooxygenase genes styAB from Pseudomonas sp. strain VLB120. Targeting microbial physiology during whole-cell redox biocatalysis, we investigated the interdependency of styrene epoxidation, growth, and carbon metabolism on the basis of mass balances obtained from continuous two-liquid-phase cultures. Full induction of styAB expression led to growth inhibition, which could be attenuated by reducing expression levels. Operation at subtoxic substrate and product concentrations and variation of the epoxidation rate via the styrene feed concentration allowed a detailed analysis of carbon metabolism and bioconversion kinetics. Fine-tuned styAB expression and increasing specific epoxidation rates resulted in decreasing biomass yields, increasing specific rates for glucose uptake and the tricarboxylic acid (TCA) cycle, and finally saturation of the TCA cycle and acetate formation. Interestingly, the biocatalysis-related NAD(P)H consumption was 3.2 to 3.7 times higher than expected from the epoxidation stoichiometry. Possible reasons include uncoupling of styrene epoxidation and NADH oxidation and increased maintenance requirements during redox biocatalysis. At epoxidation rates of above 21 mol per min per g cells (dry weight), the absence of limitations by O 2 and styrene and stagnating NAD(P)H regeneration rates indicated that NADH availability limited styrene epoxidation. During glucose-limited growth, oxygenase catalysis might induce regulatory stress responses, which attenuate excessive glucose catabolism and thus limit NADH regeneration. Optimizing metabolic and/or regulatory networks for efficient redox biocatalysis instead of growth (yield) is likely to be the key for maintaining high oxygenase activities in recombinant E. coli.Oxygenases catalyze regio-and enantioselective oxyfunctionalization reactions and have a considerable potential in the area of asymmetric organic synthesis (2, 35). These enzymes typically depend on coenzymes such as NAD(P)H and are unstable outside cells, and they often consist of multiple components. Thus, for synthetic applications, their use in whole cells is favored over the use of isolated enzymes (7,18).The productivity of oxygenase-based whole-cell biocatalysts is influenced by various factors, such as maximal enzyme activity, enzyme level, substrate mass transfer, substrate and/or product inhibition/toxicity, and cofactor regeneration (7,13,54,68). Enzyme synthesis and cofactor regeneration are related to host metabolism, which in turn may be affected by the toxicity of organic substrates and products. Such toxicity can efficiently be attenuated by regulated substrate feeding (1, 11) and in situ product removal (7,38,61,66,74). Yet, microbial cells, especially in a nongrowing state, often lose biooxidation activity over time, which may be due to oxygenase inactivation and/or the metabolic burden imposed by redox-coenzyme withdrawal and reactive oxygen species formed via...

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mentioning

confidence: 99%

NADH Availability Limits Asymmetric Biocatalytic Epoxidation in a Growing Recombinant Escherichia coli Strain

Bühler

Park

Blank

et al. 2008

Appl Environ Microbiol

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“…It has many benefits for the overall fermentation process by facilitating the product recovery, eliminating feedback inhibition, overcoming product degradation, avoiding product autotoxicity, reducing cost, and improving the product yield efficiently [18,19]. The strategy of employing in situ macroporous resin adsorption has been successfully applied in increasing metabolite yields in some fungal culture systems, such as Fusarium redolens Dzf2 culture for beauvericin production [20], and Hyalodendriella sp.…”

Section: Discussionmentioning

confidence: 99%

Enhanced Production of Palmarumycins C12 and C13 in Mycelial Liquid Culture of the Endophytic Fungus <i>Berkleasmium<?i> sp. Dzf12 with <i>In situ</i> Macroporous Resin Adsorption

Mou¹,

Li²,

Zhou³

et al. 2015

Trop. J. Pharm Res

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“…Because esterification is essential to astaxanthin, but unnecessary to β-carotene, we hypothesized that the effect of fatty acids synthesis on the accumulation of secondary carotenoid was more likely to create a sequestering structure, which could absorb the newly synthesized astaxanthin or β-carotene constantly. This mechanism did just like an effectively functioned "in situ extraction system" which could ensure metabolism going on wheels by separating the metabolic production from the synthesis site in time [24] . Therefore, we hypothesize that the "in situ extraction system" would break and astaxanthin or β-carotene could not be separated timely from the synthesis site as long as fatty acid synthesis was inhibited, and the synthesis of astaxanthin or β-carotene would be interrupted.…”

Section: The Effect Of Fatty Acid Synthesis On Astaxanthin Esters Synmentioning

confidence: 99%

The synthesis of astaxanthin esters, independent of the formation of cysts, highly correlates with the synthesis of fatty acids in Haematococcus pluvialis

Miao

Zhang

et al. 2008

SCI CHINA SER C

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The compositions and contents of astaxanthin esters and fatty acids in four types of Haematococcus pluvialis cells were studied by HPLC and GC-MS. Results showed that the synthesis and accumulation of astaxanthin was independent of the formation of cysts, but was highly correlated with the synthesis and accumulation of fatty acids, though it is an well known phenomenon that the accumulation of astaxanthin is usually accompanied by the formation of cyst. The red cysts contain more than 30% of fatty acids, with 81% of the unsaturated fatty acids. Taken together, besides a resource of astaxanthin, H. pluvialis would be a good resource of valuable fatty acids.Haematococcus pluvialis, astaxanthin esters, cyst formation, fatty acids, GC-MS

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Integrated bioprocesses

Cited by 117 publications

References 60 publications

NADH Availability Limits Asymmetric Biocatalytic Epoxidation in a Growing Recombinant Escherichia coli Strain

NADH Availability Limits Asymmetric Biocatalytic Epoxidation in a Growing Recombinant Escherichia coli Strain

Enhanced Production of Palmarumycins C12 and C13 in Mycelial Liquid Culture of the Endophytic Fungus <i>Berkleasmium<?i> sp. Dzf12 with <i>In situ</i> Macroporous Resin Adsorption

The synthesis of astaxanthin esters, independent of the formation of cysts, highly correlates with the synthesis of fatty acids in Haematococcus pluvialis

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