Rafael Garcia Lopes

There is a notable lack of standardised and validated protocols for evaluating the potential of aquaculture effluents as culture media for microalgae. This study addresses this gap by developing and validating a comprehensive protocol for assessing the suitability of aquaculture effluents for microalgal production. The protocol was designed and standardised based on effluent characterisation, effluent pre-treatment, standardised inoculation, assessment of microalgal growth performance, and evaluation of nutrient removal. Validation was conducted through the cultivation of Phaeodactylum tricornutum in biofloc technology (BFT) shrimp (Penaeus vannamei) effluent, demonstrating the protocol’s reliability, robustness, and adaptability across media with varying nutrient profiles. The approach effectively identified nitrate and orthophosphate removal patterns of up to 97.34 ± 2.15% and 87.88 ± 1.61%, respectively, in culture media containing 100% shrimp effluent, while providing consistent and accurate growth performance data across different treatments. The treatment containing 100% shrimp effluent achieved a maximum cell density of 8488 ± 772 (×10⁴ cells mL⁻¹). As the proposed framework is based on broadly applicable performance indicators, it provides a methodological basis that can be adapted for evaluating other aquaculture effluents, microalgal species, and cultivation systems. However, additional validation under these conditions is required before broader application can be confirmed.

Wheat (Triticum aestivum) is an important crop produced worldwide. Natural or synthetic products including phytostimulants, biofertilisers, biostimulants, bioregulators or phytoprotectors have been developed over the years. The objective of this study was to evaluate the effects of foliar application of micronutrients (essential minerals), growth regulators, extracts of the microalga Porphyridium cruentum and their mixtures on variables related to the growth and production of wheat (height of the plants at harvest, number of tillers per plant, weight of 1000 grains, pod length and yield). The experiment consisted of randomised blocks with four replications, consisting of 16 treatments (control, Zn, B, Cu, Mn, Zn+Cu+B+Mn, indolebutyric acid (AIB), 6-benzylaminopurine (BAP), Zn+Cu+B+Mn+AIB+BAP, P. cruentum freeze-dried polysaccharide (PS), P. cruentum freeze-dried material (FM), Zn+Cu+B+Mn+PS+FM, AIB+BAP+FM+gibberellic acid (GA), commercial-B, commercial-A and commercial-E). The single foliar application of micronutrients, commercial products containing micronutrients, growth regulators (indolbutyric acid, 6-bezylaminopurine, gibberellic acid and their mixtures), freeze-dried polysaccharide and biomass of P. cruentum, and mixtures of micronutrients and growth regulators did not potentiate the development and productivity of the wheat crop. The average height of wheat plants at harvest was 77.81 cm and ranged from 80.05 cm when the comercial-E product was applied to 74.43 cm with the application of P. cruentum polysaccharide extract at a dose of 62 g ha-1, which resulted in lower crop yield, although the difference was not significant. Additionally, the individual application of the P. cruentum polysaccharide extract did not significantly influence on plant growth.

Algae are known for their rich nutrients, which can enhance productivity of agricultural crops, making them valuable biostimulants. However, the use of microalgae for this purpose is still in its early stages, and there have been no studies conducted on lupine crops in Brazil so far. This study aimed to investigate the impact of microalgae extracts on the growth and productivity of white lupine. The experiment included four different microalgae extracts (Limnospira platensis, Nannochloropsis oculata, Tetradesmus obliquus, and Chaetoceros muelleri), applied either once or twice, along with a control group. The results showed that there was no interaction between the number of applications and the type of microalgae extract applied via foliar application in white lupine crops. The microalgae extracts did not have a significant impact on the 100-grain weight and yield of white lupine crops. The average height of white lupine plants at harvest was 117.04 cm, regardless of the treatment. However, there was a significant increase (13.12%) in the number of seeds per pod of white lupine with a single application of microalgae extract, regardless of the specific extract used. The height of the white lupine plants was not affected by the treatments during both the vegetative and reproductive phases. Further research is needed to optimise the bioactive extraction process, identify metabolites with biostimulant potential in the extracts, and determine the most effective application method (soil, seed, or foliar), as well as the optimal timing and frequency of foliar applications based on the crop's phenological stages.

The aquafeed industry evolved alongside fish farming, utilizing scientific and technological advancements to incorporate a variety of feed additives, supplements, and alternative ingredients in the nutrition and feeding of fish in aquaculture. These advances played a significant role in improving the production, health, and welfare of farmed fish. Recent research in Brazil highlighted the importance of using fish feed additives, such as vitamins, minerals, and amino acids, to ensure that farmed fish receive all the necessary nutrients for growth and health. Functional additives can enhance the immune system, boosting disease resistance and promoting the overall health of fish. Antimicrobial and antiparasitic additives help prevent and treat infections and infestations, reducing the occurrence of disease outbreaks. Additionally, some additives improve feed digestibility, leading to better nutrient absorption and reduced feed requirements. Overall, nutritional strategies are essential for optimizing fish farming practices in Brazil and globally, promoting fish health and sustainability in the industry. This review emphasizes the significance of certain additives, supplements, and ingredients strategically incorporated into experimental feeds for research in Brazilian fish farming. It also underscores the necessity for ongoing research. There is a noticeable trend towards developing more sustainable and efficient feeds, which is essential for the future of sustainable aquaculture. The goal is to minimize environmental impacts while maintaining economic viability in aquaculture operations.

The study assessed flat-panel photobioreactors (FP-PBRs) for superintensive microalgae cultivation. FP-PBRs were constructed with a metallic skeletal structure and galvanized metal grids for support. FP-PBRs were made with plastic bags with dimensions of 2.30 m × 0.75 m × 0.1 m and a useful volume of 150 L. The operation included a filtered aeration system, CO2 injection, and automated pH and temperature control. To start the FP-PBR operation, an aeration rate of 0.067 vvm and an overall mass transfer coefficient KLa(O2) of 54.29 h-1 were used. An irradiance of 400 µmol photons m-2 s-1 suitable for Nannochloropsis oculata cultivation was applied. Two surface-to-volume ratios (S/V) were used: 10.5 m-1 with one-sided illumination and 21 m-1 with illumination on both sides. At the end of 264 h (11 days), the FP-PBR system made with alternative materials proved to be efficient. The highest biomass of N. oculata biomass was achieved with a S/V ratio of 21.0 m-1 (1.91 ± 0.15 g L-1 day-1), compared to 1.13 ± 0.08 g L-1 day-1 in the S/V 10.5 m-1 treatment. By using a FP-PBR that cost around US$ 544.00, it was feasible to attain high productivity in cultures where the algal cells received increased light exposure, while still ensuring control and safety.

Sulfated polysaccharides (SPs), especially those with immunostimulant effects on shrimp and fish, are bioactive compounds with potential use in aquaculture. In this study, Pacific white shrimp (Penaeus vannamei) were fed diets containing 0%, 0.5%, 1.0%, 1.5%, or 2.0% crude extracts from the microalga Porphyridium cruentum for 30 days. After dietary supplementation, the shrimp were exposed to Vibrio alginolyticus, allowing the assessment of phenoloxidase activity (PO) and total hemocyte count (THC) pre- and post-challenge, as well as shrimp survival rates. Shrimp that received the 1.0% treatment had greater survival (90%) at 48 h post-challenge, while the 0% and 2.0% treatments had survival rates close to 63% in the same period. Furthermore, at 48 h post-challenge, THC was significantly greater (p < 0.05) in the shrimp that received crude extract supplementation compared to that in shrimp of the control group (0%). PO showed a proportional increase according to crude extract inclusion levels. Such dose-dependency in response to PO increases became significantly greater (p < 0.05) in the 2.0% treatment group compared to that in the 0% treatment group in the pre-challenge period and that in the 0% and 0.5% treatment groups in the post-challenge period. These results showed that crude extracts from P. cruentum could be considered immunostimulants by increasing the resistance of P. vannamei exposed to V. alginolyticus, potentially representing a major breakthrough for marine shrimp farming.

The present study shows the characterization of the bacterial communities associated with different systems during the cultivation of the microalga Tetradesmus obliquus. For that, sequential cultivation was performed in three different systems: (1) Photobioreactor bench‐scale; (2) flat‐panel photobioreactor; and (3) thin‐layer cascade. Cultures were monitored daily for growth parameters and biomass samples were collected for characterization of bacterial communities using metagenomic. A total of 195,177 reads were produced, resulting in the identification of 72 OTUs. In the grouping of bacterial communities, 3 phyla, 6 classes, 28 families, and 35 taxa were found. The bacteria Brevundimonas and Porphyrobacter had a higher relative abundance compared with other taxa found. These taxa were present in all cultivation systems forming a possible core community. Bacterial communities associated with different cultivation systems of the microalga T. obliquus showed an increase in taxa richness and diversity in the super‐intensive and intensive systems.