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.

The solubility of aqueous electrolyte solutions is a critical property for absorption refrigeration and heat pump working fluids. In this paper, we report a systematic study on the solubility of 21 alkaline nitrate and nitrite mixtures determined by a visual polythermal method. The solubility of the mixtures (LiNO 3 + NaNO 3 + KNO 3 ) + H 2 O with salt mass ratios of 53:19:28 and 53:05:42 and (LiNO 3 + KNO 3 + NaNO 2 ) + H 2 O with salt mass ratios of 53:35:12 and 60:36:04 was further determined accurately by differential scanning calorimetry. Saturation temperature data of these mixtures were correlated with the total salt mass fraction using empirical polynomial equations. The mixtures of LiNO 3 + NaNO 3 + KNO 3 (53:05:42) and LiNO 3 + KNO 3 + NaNO 2 (53:35:12) showed the highest solubility in water.

Thermal energy storage (TES) is seen today as a key technology to reduce the existing gap between energy demand and energy supply in many energy systems. There are, currently, three well known methods to store thermal energy and they are: sensible heat storage (SHS), latent heat storage (LHT) and thermochemical heat storage. Every method has its own thermophysical requirements for the mediums of storage, such as thermal stability, high enthalpy of phase change or reaction, high heat capacity and suitable temperature of the thermal phenomenon for a respective application, among others. In this regard, the composition of materials usually needs to be modified in order to improve their performance or to reach a determined requirement. As a consequence, the costs of potential TES materials to be applied in renewable energy systems are too high to compete with traditional systems using fossil fuels. On the other hand, several wastes and by-products from the non-metallic mining, such as salt hydrates and double salts, are available without any application but accumulating in the mining sites. This is the case for astrakanite (Na 2 SO 4 •MgSO 4 •4H 2 O) and lithium carnallite (LiCl•MgCl 2 •7H 2 O) with no current application, and potassium carnallite (KCl•MgCl 2 •6H 2 O) used as a supplementary raw material to obtain KCl. Since the costs of these materials are close to zero, they were characterized as TES materials taking into account the properties required for the three methods of storage. Results showed that astrakanite and potassium carnallite have potential to be applied as thermochemical material at low-medium temperature (<300°C). Also, a dehydrated product obtained from astrakanite showed potential to be applied as phase change material (PCM) at high temperature, from 550°C to 750°C. Nevertheless, lithium Δ H H Enthalpy of Hydration J/g wt.% Percentage of weight loss %

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