Dynamics of Microbial Communities in Phototrophic Polyhydroxyalkanoate Accumulating Cultures

Abstract

Phototrophic mixed cultures (PMC) are versatile systems which can be applied for waste streams, valorisation and production of added-value compounds, such as polyhydroxyalkanoates (PHA). This work evaluates the influence of different operational conditions on the bacterial communities reported in PMC systems with PHA production capabilities. Eleven PMCs, fed either with acetate or fermented wastewater, and selected under either feast and famine (FF) or permanent feast (PF) regimes, were evaluated. Overall, results identified Chromatiaceae members as the main phototrophic PHA producers, along with Rhodopseudomonas, Rhodobacter and Rhizobium. The findings show that Chromatiaceae were favoured under operating conditions with high carbon concentrations, and particularly under the PF regime. In FF systems fed with fermented wastewater, the results indicate that increasing the organic loading rate enriches for Rhodopseudomonas, Rhizobium and Hyphomicrobiaceae, which together with Rhodobacter and Chromatiaceae, were likely responsible for PHA storage. In addition, high-sugar feedstock impairs PHA production under PF conditions (fermentative bacteria dominance), which does not occur under FF. This characterization of the communities responsible for PHA accumulation helps to define improved operational strategies for PHA production with PMC.

The biotechnological potential of the Chloroflexota phylum

“…PHA are natural polyesters with thermoplastic properties that are internally accumulated by bacteria as carbon and energy reserves, being considered interesting candidates for substituting traditional plastics ( 131 ). Recently, purple phototrophic bacteria have been described as suitable PHA-accumulating organisms ( 132 ), and its upscale challenges have been reviewed ( 133 ). There are several examples of phototrophic production of PHA using purple bacteria or cyanobacteria ( 134 – 138 ), and these bacteria have been reviewed as suitable phototrophic factories to couple resource recovery with the production of value-added substances ( 139 ).…”

Photobioreactor Design for Polyhydroxyalkanoate Production Using Anoxygenic Photoheterotrophs: A Review

“…Quantitative studies on PHA metabolism using phototrophic PNSB are limited only to a few species, such as Rhodobacter sphaeroides [36,37], Rhodospirillum rubrum [38][39][40], Rhodopseudomonas palustris [41], Afifella marina [42], Rhodopseudomonas julia [43,44], Rhodopseudomonas sp. S16-VOGS3 [45,46], Rhodovulum tesquicola, Roseovarius goensis, and Roseovarius visakhapatnamensi [47].…”

Achieving Discharge Limits in Single-Stage Domestic Wastewater Treatment by Combining Urban Waste Sources and Phototrophic Mixed Cultures

“…These anoxygenic photosynthetic microorganisms have gained interest due to their metabolic versatility, as they can grow chemotrophically in aerobic conditions and photoheterotrophically by obtaining energy from light in the IR spectrum [ 21 ]. Their secondary metabolism allows them to store C in the form of polyhydroxyalkanoates for the production of bioplastics [ 22 , 23 , 24 , 25 , 26 ], to accumulate P in the form of poly-P to be used as fertilizer [ 27 ], or to assimilate N to synthesize protein [ 28 , 29 ] of high biological quality due to their amino acids profile [ 30 ]. Also, mixed PPB cultures do not need strict anaerobic conditions to sustain the culture but rather a negative oxidation-reduction potential (ORP) [ 31 ].…”