Green Extractants in Assisting Recovery of REEs: A Case Study.

The recycling of REEs from the end of life (EoL) products, such as nickel metal hydride batteries (NiMH), offers great opportunities for their supply in Europe. In the presented paper, the application of 'green' extractants such as citric (CA), metatartaric (TA), and ethylenediaminedisuccinic acid (EDDS) (also with H2O2 addition) for the recovery of REEs was studied. The studies were conducted considering the effects of the phase contact time, the initial concentration of CA, TA, and EDDS, as well as H2O2, pH, and temperature. It was found that the addition of TA to the CA solution meant that higher rates of metal ion binding and, thus, leaching was observed. The optimal conditions were obtained in the system: CA-TA and H2O2 for the concentration 0.6M-0.3 M-2%.

Early-stage sustainability assessment of biotechnological processes: A case study of citric acid production.

Sustainability assessment using a life-cycle approach is indispensable to contemporary bioprocess development. This assessment is particularly important for early-stage bioprocess development. As early-stage investigations of bioprocesses involve the evaluation of their ecological and socioeconomic effects, they can be adjusted more effectively and improved towards sustainability, thereby reducing environmental risk and production costs. Early-stage sustainability assessment is an important precautionary practice and, despite limited data, a unique opportunity to determine the primary impacts of bioprocess development. To this end, a simple and robust method was applied based on the standardized life-cycle sustainability assessment methodology and commercially available datasets. In our study, we elaborated on the yeast-based citric acid production process with Yarrowia lipolytica assessing 11 different substrates in different process modes. The focus of our analysis comprised both cultivation and down-stream processing. According to our results, the repeated batch raw glycerol based bioprocess alternative showed the best environmental performance. The second- and third-best options were also glycerol-based. The least sustainable processes were those using molasses, chemically produced ethanol, and soy bean oil. The aggregated results of environmental, economic, and social impacts display waste frying oil as the best-ranked alternative. The bioprocess with sunflower oil in the batch mode ranked second. The least favorable alternatives were the chemically produced ethanol-, soy oil-, refined glycerol-, and molasses-based citric acid production processes. The scenario analysis demonstrated that the environmental impact of nutrients and wastewater treatment is negligible, but energy demand of cultivation and down-stream processing dominated the production process. However, without energy demand the omission of neutralizers almost halves the total impact, and neglecting pasteurization also considerably decreases the environmental impact.

Paving the way for bioelectrotechnology: Integrating electrochemistry into bioreactors.

The reactor systems used for microbial electrosynthesis, i.e. bioelectrochemical systems for achieving bioproduction so far reported in literature are relatively small in scale and highly diverse in their architecture and modes of operation. The often diverging requirements of the electrochemical and the biological processes and the interdisciplinarity of the field make the engineering of these systems a special challenge. This has led to multiple, differently optimized approaches of reactor vessels, designs and operating conditions making standardization and normalization or even a systematic engineering almost impossible. Overcoming this lack of standardization, scalability and knowledge-driven engineering is the driving force for this work introducing an upgrade kit for bioreactors transforming these reversibly to bioelectroreactors. The prototypes of the bioreactor upgrade kit were integrated with commercial bioreactor (fermentor) systems and performances compared to a classic, small-scale bioelectrochemical glass cell system. The use of the upgrade kit allowed interfacing with the existing infrastructure of the conventional bioreactors for growing electroactive microorganisms in pure culture conditions, with the added electrochemical control and further process monitoring. The results of growing Shewanella oneidensis MR-1 clearly show that these systems can be used to control, monitor, and scale microbial bioelectrochemical processes, providing better resolution of the data for the tested experimental conditions.

Energetics and surface properties of Pseudomonas putida DOT-T1E in a two-phase fermentation system with 1-decanol as second phase.

The solvent-tolerant strain Pseudomonas putida DOT-T1E was grown in batch fermentations in a 5-liter bioreactor in the presence and absence of 10% (vol/vol) of the organic solvent 1-decanol. The growth behavior and cellular energetics, such as the cellular ATP content and the energy charge, as well as the cell surface hydrophobicity and charge, were measured in cells growing in the presence and absence of 1-decanol. Although the cells growing in the presence of 1-decanol showed an about 10% reduced growth rate and a 48% reduced growth yield, no significant differences were measured either in the ATP and potassium contents or in the energy charge, indicating that the cells adapted completely at the levels of membrane permeability and energetics. Although the bacteria needed additional energy for adaptation to the presence of the solvent, they were able to maintain or activate electron transport phosphorylation, allowing homeostasis of the ATP level and energy charge in the presence of the solvent, at the price of a reduced growth yield. On the other hand, significantly enhanced cell hydrophobicities and more negative cell surface charges were observed in cells grown in the presence of 1-decanol. Both reactions occurred within about 10 min after the addition of the solvent and were significantly different after killing of the cells with toxic concentrations of HgCl2. This adaptation of the surface properties of the bacterium to the presence of solvents seems to be very similar to previously observed reactions on the level of lipopolysaccharides, with which bacteria adapt to environmental stresses, such as heat shock, antibiotics, or low oxygen content. The results give clear physiological indications that the process with P. putida DOT-T1E as the biocatalyst and 1-decanol as the solvent is a stable system for two-phase biotransformations that will allow the production of fine chemicals in economically sound amounts.