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Recent progress in the field of reinforcement learning has been accelerated by virtual learning environments such as video games, where novel algorithms and ideas can be quickly tested in a safe and reproducible manner. We introduce the Google Research Football Environment, a new reinforcement learning environment where agents are trained to play football in an advanced, physics-based 3D simulator. The resulting environment is challenging, easy to use and customize, and it is available under a permissive open-source license. In addition, it provides support for multiplayer and multi-agent experiments. We propose three full-game scenarios of varying difficulty with the Football Benchmarks and report baseline results for three commonly used reinforcement algorithms (IMPALA, PPO, and Ape-X DQN). We also provide a diverse set of simpler scenarios with the Football Academy and showcase several promising research directions.

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In this paper, the production of the microalga Nannochloropsis gaditana using centrate from the anaerobic digestion of treated urban wastewater is studied. For this, semicontinuous cultures were performed indoors at laboratory scale, under controlled conditions, supplying seawater with different centrate percentages from a real wastewater treatment plant as the culture medium. It was demonstrated that N. gaditana can be produced using solely centrate as the nutrient source but only at percentages below 50%. Above this level, inhibition is caused by an excess of ammonia, thus reducing productivity. In the 30-50% centrate range, biomass productivity was 0.4 g·l −1 ·day −1 , equal to that measured when using Algal culture medium. Moreover, the biochemical composition of the biomass was also equal to that measured when using Algal culture medium, with the protein content in the 30-40% d.wt. range; whereas the lipid content ranged from 20 to 25% d.wt. Under these conditions, phosphorus depuration from the culture medium was in the 80-90% range while nitrogen depuration was only between 20 and 40%, indicating an excess of nitrogen in the centrate with respect to phosphorus. In spite of this phosphorus limitation, in the optimal centrate range (30-50% in the culture medium), the cells performed under optimal conditions, removing up to 35 mg N ·l −1 ·day −1 and 5.7 mg P ·l −1 ·day −1 , with quantum yield values measuring 1.0-1.3 g·E −1 . By supplying additional phosphorus, it was possible to enhance productivity and increase nitrate and phosphorus depuration to over 80%. The use of centrate is confirmed as a useful method for reducing microalgae production costs while also increasing process sustainability, especially when using biomass for bioenergy applications.

Unicellular microalgae generally grow in the presence of bacteria, particularly when they are farmed massively. This study analyzes the bacteria associated with mass culture of Botryococcus braunii: both the planktonic bacteria in the water column and those forming biofilms adhered to the surface of the microalgal cells (∼10⁷-10⁸ culturable cells per gram microalgae). Furthermore, we identified the culturable bacteria forming a biofilm in the microalgal cells by 16S rDNA sequencing. At least eight different culturable species of bacteria were detected in the biofilm and were evaluated for the presence of quorum-sensing signals in these bacteria. Few studies have considered the implications of this phenomenon as regards the interaction between bacteria and microalgae. Production of C4-AHL and C6-AHL were detected in two species, Pseudomonas sp. and Rhizobium sp., which are present in the bacterial biofilm associated with B. braunii. This type of signal was not detected in the planktonic bacteria isolated from the water. We also noted that the bacterium, Rhizobium sp., acted as a probiotic bacterium and significantly encouraged the growth of B. braunii. A direct application of these beneficial bacteria associated with B. braunii could be, to use them like inoculants for large-scale microalgal cultures. They could optimize biomass production by enhancing growth, particularly in this microalga that has a low growth rate.