Abstract:
The behaviour of a locally isolated diazotrophic consortium was investigated with the
prospect of agricultural applications. A repeatable culture was obtained in a non-sterile bioreactor.
Metagenomic analysis indicated Chryseobacterium ssp. and Flavobacterium ssp. were the dominant
species, making up approximately 50% of the microbial community. The oxygen supply was varied
and mass-transfer limited growth was attained under all experimental conditions. Negligible
amounts of aqueous metabolites were formed, indicating a high selectivity towards biomass production.
High oxygen availability resulted in decreased growth efficiencies i.e., the specific energy
requirements for biomass synthesis. This was attributed to reduced electron transport chain efficiencies
and nitrogenase protection mechanisms. Mass and energy balances indicated that sessile
biomass with a high C:N served as a carbon sink. The most efficient growth was measured at an
aeration feed composition of 21% oxygen and 79% nitrogen. The study presents one of the only
known investigations of operational conditions on diazotrophic growth in a non-sterile bioreactor.
In addition, it provides a strong foundation for the development of a Biological Nitrogen Fixation
process with scaling potential.
