Influence of the algal microbiome on biofouling during industrial cultivation of Nannochloropsis sp. in closed photobioreactors

Industrial cultivation of microalgae is becoming increasingly important, yet the process is still hampered by many factors, including contamination and biofouling of the algal reactors. We characterized a subset of microorganisms occurring in the broth and different biofilm stages of industrial scale photobioreactors applied for the cultivation of Nannochloropsis sp. A total of 69 bacterial strains were isolated, belonging to at least 24 different species. In addition, a green microalga was isolated and identified as Chlamydomonas hedleyi. The effect of C. hedleyi and 24 of the bacterial isolates on the productivity of Nannochloropsis was evaluated through growth and biofilm assays. C. hedleyi was shown to reduce growth and induce biofilm formation in Nannochloropsis. These effects were however indirect as they could be attributed to the bacteria associated to C. hedleyi and not C. hedleyi itself. Although most bacterial strains reported no effect, several were able to induce biofilm formation

External validation of ¹⁸F-FDG PET-based radiomic models on identification of residual oesophageal cancer after neoadjuvant chemoradiotherapy

Objectives Detection of residual oesophageal cancer after neoadjuvant chemoradiotherapy (nCRT) is important to guide treatment decisions regarding standard oesophagectomy or active surveillance. The aim was to validate previously developed 18F-FDG PET-based radiomic models to detect residual local tumour and to repeat model development (i.e. 'model extension') in case of poor generalisability. Methods This was a retrospective cohort study in patients collected from a prospective multicentre study in four Dutch institutes. Patients underwent nCRT followed by oesophagectomy between 2013 and 2019. Outcome was tumour regression grade (TRG) 1 (0% tumour) versus TRG 2-3-4 (≥1% tumour). Scans were acquired according to standardised protocols. Discrimination and calibration were assessed for the published models with optimism-corrected AUCs &gt;0.77. For model extension, the development and external validation cohorts were combined. Results Baseline characteristics of the 189 patients included [median age 66 years (interquartile range 60-71), 158/189 male (84%), 40/189 TRG 1 (21%) and 149/189 (79%) TRG 2-3-4] were comparable to the development cohort. The model including cT stage plus the feature 'sum entropy' had best discriminative performance in external validation (AUC 0.64, 95% confidence interval 0.55-0.73), with a calibration slope and intercept of 0.16 and 0.48 respectively. An extended bootstrapped LASSO model yielded an AUC of 0.65 for TRG 2-3-4 detection. Conclusion The high predictive performance of the published radiomic models could not be replicated. The extended model had moderate discriminative ability. The investigated radiomic models appeared inaccurate to detect local residual oesophageal tumour and cannot be used as an adjunct tool for clinical decision-making in patients.</p

Impact of the Noise Penalty Factor on Quantification in Bayesian Penalized Likelihood (Q.Clear) Reconstructions of 68Ga-PSMA PET/CT Scans

Functional imaging with 68Ga prostate-specific membrane antigen (PSMA) and positron emission tomography (PET) can fulfill an important role in treatment selection and adjustment in prostate cancer. This article focusses on quantitative assessment of 68Ga-PSMA-PET. The effect of various parameters on standardized uptake values (SUVs) is explored, and an optimal Bayesian penalized likelihood (BPL) reconstruction is suggested. PET acquisitions of two phantoms consisting of a background compartment and spheres with diameter 4 mm to 37 mm, both filled with solutions of 68Ga in water, were performed with a GE Discovery 710 PET/CT scanner. Recovery coefficients (RCs) in multiple reconstructions with varying noise penalty factors and acquisition times were determined and analyzed. Apparent recovery coefficients of spheres with a diameter smaller than 17 mm were significantly lower than those of spheres with a diameter of 17 mm and bigger (p &lt; 0.001) for a tumor-to-background (T/B) ratio of 10:1 and a scan time of 10 min per bed position. With a T/B ratio of 10:1, the four largest spheres exhibit significantly higher RCs than those with a T/B ratio of 20:1 (p &lt; 0.0001). For spheres with a diameter of 8 mm and less, alignment with the voxel grid potentially affects the RC. Evaluation of PET/CT scans using (semi-)quantitative measures such as SUVs should be performed with great caution, as SUVs are influenced by scanning and reconstruction parameters. Based on the evaluation of multiple reconstructions with different β of phantom scans, an intermediate β (600) is suggested as the optimal value for the reconstruction of clinical 68Ga-PSMA PET/CT scans, considering that both detectability and reproducibility are relevant

Correction: Rijnsdorp et al. Impact of the Noise Penalty Factor on Quantification in Bayesian Penalized Likelihood (Q.Clear) Reconstructions of 68Ga-PSMA PET/CT Scans. Diagnostics 2021, 11, 847

In the original article [...

Combining medium recirculation with alternating the microalga production strain : a laboratory and pilot scale cultivation test

Reuse of growth medium after biomass harvesting is a cost-saving approach to improve the economic feasibility of algae mass cultivation. Algal exudates, cell debris and varying amounts of residual nutrients, impose challenges to the recycling of spent medium. In this study, the potential of combining reused medium from different algae species for growing monocultures of other algal strains was evaluated by making use of three successive cultivation setups with increasing volume; 400 mL in turbidostat mode, 2.6 L and 220 L in semi-continuous mode. Cultivation on replenished medium derived from Nannochloropsis sp. and Tisochrysis lutea, had no adverse effect on the productivity of either of the strains, regardless of whether they were grown in their own recycled medium or that of the other alga. Microfiltration of the reused medium proved to be sufficient to avoid cross-contamination. Moreover, a substantial average reduction in water footprint (77%) and nutrient cost (68% or 9 €·kg−1 dry biomass) was achieved. Extension and validation of the medium recycling approach to other economically interesting algae species can contribute to improving the economic feasibility of large scale microalgae production systems

Exergy and life cycle analysis of microalgae as feed for aquaculture

In this study, the environmental sustainability of 3 algal production scenarios is analysed by using Exergy Analysis (EA) and Exergetic Life Cycle Assessment (ELCA). Next to the pilot plant of 240m² photobioreactors (pilot 2012), also 2 upscaled scenarios have been developed to examine the entire production process and to optimize the configuration for a more sustainable algae cultivation. The second scenario uses 1320 m² PBR bags (pilot 2013) and the first production scale scenario 2.5 hectare (2015). Patented ProviAPT photobioreactors are used to cultivate the oil-rich microalgae Nannochloropsis sp. and the biomass is semi-continuously harvested through an overflow system. This renewable resource is then purified and concentrated in a filtration and centrifugation step. At the end, the algal biomass is dried to obtain 95% dry weight (DW) in order to have good conservation properties. The biomass has a promising application in aquaculture as fish feed because algae could substitute traditional fish oil and fish meal, lowering the intensive fish farming. The EA reveals that the drying and cultivation step have the lowest efficiencies at process level, even at the 2.5 ha scale (72.8% and 3.58% respectively). The results of the ELCA clearly shows an improvement in resource efficiency upon upscaling: 1280.7 MJex,CEENE is extracted from the natural environment in the first scenario to produce 1 kg DW biomass, which is reduced to 499.6 and 56.83 MJex,CEENE/kg DW for the second and third scenario respectively. Also due to upscaling and optimization, the impact on climate change declines with a factor 20 (2.1 kg CO2,eq/kg DW at 2.5 ha scale). Comparing these results to the resource consumption and impact on climate change of traditional fish feed containing terrestrial biomass products (133.29 MJex,CEENE and 0.8 kg CO2,eq per kg DW), it becomes clear that algae production for aquacultural purposes is possible from a resource sustainability point of view but only when upscaling, recycling and reuse of waste streams are implemented into microalgae biorefineries