Plant microbial fuel cells (P-MFCs) are sustainable and eco-friendly technologies, which use plant root exudates to directly nourish the electrochemically active bacteria (EABs) to generate sustainable electricity. However, their use in evaluating plant growth has been insufficiently studied. In this study, interconnection between plant growth and the production of bioelectricity was evaluated by using P-MFCs inoculated with 642.865 mL ≅ 643 mL of livestock’s urine such as cow urine, goat urine, and sheep urine. The greatest mean stem diameter of 0.52 ± 0.01 cm was found in P-MFC-3 inoculated with goat urine, while the P-MFC-2 treated with cow urine reached a higher average number of roots with a value of 86 ± 2.50 (95% improvement) (p < 0.05). Besides, P-MFC-4 presented greater height of 50.08 ± 0.67 cm. For polarization curve experiment a higher maximum power density of 132 ± 11.6 mW m⁻² (931 mA m⁻²) was reached with cow urine; in turn, with regard to the long-term operation, the same reactor indicated a higher maximum average power density of 43.68 ± 3.05 mW m⁻². The study’s findings indicated that Stevia P-MFC inoculated with urine was a good option to increase the biomass amount for the agricultural plants along with power generation. Further, this study opens the way for more investigation of evaluating the impact of P-MFC on plant growth.

Microalgae hold great potential for producing purified high-value products (e.g. pigments and polyunsaturated fatty acids) and represent a source of bioavailable nutrients in aquaculture feeds; however, its production is limited by the high costs of harvesting. Recently, microalgae autoflocculation has been considered a useful solution due to the easy recovery of cell aggregates and natural increase in pH that prevents cell lysis. This work evaluates some cultivation conditions that could contribute to autoflocculation, such as natural pH increase and precipitate formation over the productivity and flocculation of 16 microalgae consortia. Results showed a biomass production of 1.4 to 4.4 dry weight (g L-1) and high flocculation of 81 to ~100%, probably due to Ca3(PO4)2 formation. Moreover, the alkaline pH could have facilitated the assimilation of CO2 and explained the increase of inorganic carbon in the solution obtained. Likewise, results showed a marked descent in electrical conductivity (EC) in solution and high mineral content in the biomass (21.4-35.9%). Finally, this study suggests that the studied culture conditions facilitated microalgae harvest, and the resulting biomass could be a source of bioavailable dietary minerals. Therefore, some of these results might be addressed in future studies with individual microalgae species.

Editorial: Advances and Trends in Development of Plant Factories

Hydroponic system requires periodic labor, a systematic approach, repetitive motion and a structured environment. Automation, robotics and IoT have allowed farmers to monitoring all the variables in plant, root zone and environment under hydroponics. This research introduces findings in design with real time operating systems based on microcontrollers; pH fuzzy logic control system for nutrient solution in embed and flow hydroponic culture; hydroponic system in combination with automated drip irrigation; expert system-based automation system; automated hydroponics nutrition plants systems; hydroponic management and monitoring system for an intelligent hydroponic system using internet of things and web technology; neural network-based fault detection in hydroponics; additional technologies implemented in hydroponic systems and robotics in hydroponic systems. The above advances will improve the efficiency of hydroponics to increase the quality and quantity of the produce and pose an opportunity for the growth of the hydroponics market in near future.