Cocultivating aerobic heterotrophs and purple bacteria for microbial protein in sequential photo- and chemotrophic reactors

Aerobic heterotrophic bacteria (AHB) and purple non-sulfur bacteria (PNSB) are typically explored as two separate types of microbial protein, yet their properties as respectively a bulk and added-value feed ingredient make them appealing for combined use. The feasibility of cocultivation in a sequential photo- and chemotrophic approach was investigated. First, mapping the chemotrophic growth kinetics for four Rhodobacter, Rhodop-seudomonas and Rhodospirillum species on different carbon sources showed a preference for fructose (mu(max) 2.4-3.9 d(-1) 28 degrees C; protein 36-59%(DW)). Secondly, a continuous photobioreactor inoculated with Rhodobacter capsulatus (VFA as C-source) delivered the starter culture for an aerobic batch reactor (fructose as C-source). This two-stage system showed an improved nutritional quality compared to AHB production: higher protein content (45-71%(DW)), more attractive amino/fatty acid profile and contained up to 10% PNSB. The findings strengthen protein production with cocultures and might enable the implementation of the technology for resource recovery on streams such as wastewater.

Automated summary

Recent research shows that combining aerobic heterotrophic bacteria with purple non-sulfur bacteria can improve protein production and nutritional quality, potentially enabling resource recovery in areas like wastewater treatment.