Nitrogen-fixing cell factories
Large-scale culture of microalgae, which have an average composition of CH1.7O0.4N0.15P0.0094, might represent a high-nitrogen-intensive bioprocess, if wastewater and/or other alternatives are not used as partial or complete substitutes for nitrogen fertilizers [51–53]. Although promotion of symbiotic N2 fixation represents a remarkable strategy in agriculture, the sophisticated interplay of recognition signals that underlay most known N2-fixing symbiosis [28] has complicated the development of exchangeable N2-fixing parts for synthetic biology approaches.
Most free-living diazotrophs normally fix enough N2 for their needs and excrete low to undetectable amounts of N2fixation products into the medium. Recently, it was shown that disruption of the genetic system signaling the nitrogen status in an Az. vinelandii mutant strain by inactivation of the nifL gene, expresses nitrogenase constitutively and excretes ammonium into the surrounding medium. Con- versely to wild type Az. vinelandii, the ammonium-excreting strain engaged in carbon–nitrogen mutualistic relations with the oleaginous microalgae Chlorella sorokiniana, Pseudokirchneriella sp., and Scenedesmus
Nitrogen-fixing cell factories
Large-scale culture of microalgae, which have an average composition of CH1.7O0.4N0.15P0.0094, might represent a high-nitrogen-intensive bioprocess, if wastewater and/or other alternatives are not used as partial or complete substitutes for nitrogen fertilizers [51–53]. Although promotion of symbiotic N2 fixation represents a remarkable strategy in agriculture, the sophisticated interplay of recognition signals that underlay most known N2-fixing symbiosis [28] has complicated the development of exchangeable N2-fixing parts for synthetic biology approaches.
Most free-living diazotrophs normally fix enough N2 for their needs and excrete low to undetectable amounts of N2fixation products into the medium. Recently, it was shown that disruption of the genetic system signaling the nitrogen status in an Az. vinelandii mutant strain by inactivation of the nifL gene, expresses nitrogenase constitutively and excretes ammonium into the surrounding medium. Con- versely to wild type Az. vinelandii, the ammonium-excreting strain engaged in carbon–nitrogen mutualistic relations with the oleaginous microalgae Chlorella sorokiniana, Pseudokirchneriella sp., and Scenedesmus
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