Polymer accumulation in mixed cyanobacterial cultures selected under the feast and famine strategy

In this study, a sequencing batch reactor (SBR), operated with transient carbon availability (feast and famine) and different nutrients loads, was used to select cyanobacteria accumulating poly (3-hydroxyalkanoate) (PHB) and carbohydrates from a mixed wastewater-borne microbial culture. The SBR was operated with 12 h aerobic light and 12 h anaerobic dark phases, evaluating the effect of three different operational conditions consisting on; 1) carbon limitation, 2) carbon and phosphorus limitation and 3) phosphorus limitation. Once a steady state was reached in each operational period of the SBR, part of the biomass was collected and submitted to separate batch tests in order to investigate the maximum PHB and carbohydrates accumulation levels. Batch tests were performed during 24 h of illuminated aerobic condition and 24 h of dark anaerobic condition, while inorganic carbon was constantly present. During the SBR operation, inorganic carbon was mostly used for biomass and carbohydrate production, showing very low PHB accumulation levels (<1%). Notwithstanding, in subsequent batch tests, PHB was accumulated after a complete depletion of nitrogen, reaching almost 4%. Concerning carbohydrates, it was found that phosphorus limitation (with and without carbon limitation) led to a culture mostly dominated by cyanobacteria and higher levels of carbohydrate content (43%–48%) than the culture with carbon limitation and high loads of nitrogen and phosphorus (29%). Such contents were obtained in only 24 h of incubation under aerobic illuminated conditions. Hence, these encouraging results indicate that carbon uptake and the consequent polymers production from cyanobacteria can be enhanced through carbon and nutrient feeding strategiesPeer ReviewedPostprint (author's final draft

Dynamics of Microbial Communities in Phototrophic Polyhydroxyalkanoate Accumulating Cultures

DFA/BD/8201/2020 UIDP/04378/2020 UIDB/04378/2020 LA/P/0140/2020Phototrophic 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.publishersversionpublishe

Raman spectrometry as a tool for an online control of a phototrophic biological nutrient removal process

UIDP/04378/2020 UIDB/04378/2020 PD/BD/114574/2016Real-time bioprocess monitoring is crucial for efficient operation and effective bioprocess control. Aiming to develop an online monitoring strategy for facilitating optimization, fault detection and decision-making during wastewater treatment in a photo-biological nutrient removal (photo-BNR) process, this study investigated the application of Raman spectroscopy for the quantifi-cation of total organic content (TOC), volatile fatty acids (VFAs), carbon dioxide (CO2 ), ammonia (NH3 ), nitrate (NO3 ), phosphate (PO4 ), total phosphorus (total P), polyhydroxyalkanoates (PHAs), total carbohydrates, total and volatile suspended solids (TSSs and VSSs, respectively). Specifically, partial least squares (PLS) regression models were developed to predict these parameters based on Raman spectra, and evaluated based on a full cross-validation. Through the optimization of spectral pre-processing, Raman shift regions and latent variables, 8 out of the 11 parameters that were investigated—namely TOC, VFAs, CO2, NO3, total P, PHAs, TSSs and VSSs—could be predicted with good quality by the respective Raman-based PLS calibration models, as shown by the high coefficient of determination (R2 > 90.0%) and residual prediction deviation (RPD > 5.0), and relatively low root mean square error of cross-validation. This study showed for the first time the high potential of Raman spectroscopy for the online monitoring of TOC, VFAs, CO2, NO3, total P, PHAs, TSSs and VSSs in a photo-BNR reactor.publishersversionpublishe

Polymer accumulation in mixed cyanobacterial cultures selected under the feast and famine strategy

In this study, a sequencing batch reactor (SBR), operated with transient carbon availability (feast and famine) and different nutrients loads, was used to select cyanobacteria accumulating poly (3-hydroxyalkanoate) (PHB) and carbohydrates from a mixed wastewater-borne microbial culture. The SBR was operated with 12 h aerobic light and 12 h anaerobic dark phases, evaluating the effect of three different operational conditions consisting on; 1) carbon limitation, 2) carbon and phosphorus limitation and 3) phosphorus limitation. Once a steady state was reached in each operational period of the SBR, part of the biomass was collected and submitted to separate batch tests in order to investigate the maximum PHB and carbohydrates accumulation levels. Batch tests were performed during 24 h of illuminated aerobic condition and 24 h of dark anaerobic condition, while inorganic carbon was constantly present. During the SBR operation, inorganic carbon was mostly used for biomass and carbohydrate production, showing very low PHB accumulation levels (<1%). Notwithstanding, in subsequent batch tests, PHB was accumulated after a complete depletion of nitrogen, reaching almost 4%. Concerning carbohydrates, it was found that phosphorus limitation (with and without carbon limitation) led to a culture mostly dominated by cyanobacteria and higher levels of carbohydrate content (43%–48%) than the culture with carbon limitation and high loads of nitrogen and phosphorus (29%). Such contents were obtained in only 24 h of incubation under aerobic illuminated conditions. Hence, these encouraging results indicate that carbon uptake and the consequent polymers production from cyanobacteria can be enhanced through carbon and nutrient feeding strategiesPeer Reviewe

Polymer accumulation in mixed cyanobacterial cultures selected under the feast and famine strategy

In this study, a sequencing batch reactor (SBR), operated with transient carbon availability (feast and famine) and different nutrients loads, was used to select cyanobacteria accumulating poly (3-hydroxyalkanoate) (PHB) and carbohydrates from a mixed wastewater-borne microbial culture. The SBR was operated with 12 h aerobic light and 12 h anaerobic dark phases, evaluating the effect of three different operational conditions consisting on; 1) carbon limitation, 2) carbon and phosphorus limitation and 3) phosphorus limitation. Once a steady state was reached in each operational period of the SBR, part of the biomass was collected and submitted to separate batch tests in order to investigate the maximum PHB and carbohydrates accumulation levels. Batch tests were performed during 24 h of illuminated aerobic condition and 24 h of dark anaerobic condition, while inorganic carbon was constantly present. During the SBR operation, inorganic carbon was mostly used for biomass and carbohydrate production, showing very low PHB accumulation levels