The yield and composition of the biocrude obtained by hydrothermal liquefaction (HTL) of Nannocloropsis gaditana using heterogeneous catalysts were evaluated. The catalysts were based on metal oxides (CaO, CeO 2 , La 2 O 3 , MnO 2 , and Al 2 O 3 ). The reactions were performed in a batch autoclave reactor at 320 • C for 10 min with a 1:10 (wt/wt) microalga:water ratio. These catalysts increased the yield of the liquefaction phase (from 94.14 ± 0.30 wt% for La 2 O 3 to 99.49 ± 0.11 wt% for MnO 2 ) as compared with the thermal reaction (92.60 ± 1.20 wt%). Consequently, the biocrude yields also raised in the metal oxides catalysed HTL, showing values remarkably higher for the CaO (49.73 ± 0.9 wt%) in comparison to the HTL without catalyst (42.60 ± 0.70 wt%). The N and O content of the biocrude obtained from non-catalytic HTL were 6.11 ± 0.02 wt% and 10.50 ± 0.50 wt%, respectively. In this sense, the use of the metal oxides decreased the N content of the biocrude (4.62 ± 0.15-5.45 ± 0.11 wt%), although, they kept constant or increased its O content (11.39 ± 2.06-21.68 ± 0.03 wt%). This study shows that CaO, CeO 2 and Al 2 O 3 can be promising catalysts based on the remarkable amount of biocrude, the highest values of C, H, heating value, energy recovery, and the lowest content of N, O and S.

The production of fatty acids ethyl esters (FAEEs) to be used as biodiesel from oleaginous microalgae shows great opportunities as an attractive source for the production of renewable fuels without competing with human food. To ensure the economic viability and environmental sustainability of the microbial biomass as a raw material, the integration of its production and transformation into the biorefinery concept is required. In the present work, lipids from wet Isochrysis galbana microalga were extracted with ethyl acetate with and without drying the microalgal biomass (dry and wet extraction method, respectively). Then, FAEEs were produced by lipase-catalyzed transesterification and esterification of the extracted lipids with ethanol using lipase B from Candida antarctica (CALB) and Pseudomonas cepacia (PC) lipase supported on SBA-15 mesoporous silica functionalized with amino groups. The conversion to FAEEs with CALB (97 and 85.5 mol% for dry and wet extraction, respectively) and PC (91 and 87 mol%) biocatalysts reached higher values than those obtained with commercial Novozym 435 (75 and 69.5 mol%). Due to the heterogeneous nature of the composition of microalgae lipids, mixtures with different CALB:PC biocatalyst ratio were used to improve conversion of wet-extracted lipids. The results showed that a 25:75 combi-lipase produced a significantly higher conversion to FAEEs (97.2 mol%) than those produced by each biocatalyst independently from wet-extracted lipids and similar ones than those obtained by each lipase from the dry extraction method. Therefore, that optimized combi-lipase biocatalyst, along with achieving the highest conversion to FAEEs, would allow improving viability of a biorefinery since biodiesel production could be performed without the energy-intensive step of biomass drying.

The purpose of this work is to define optimal growth conditions to maximise biomass for batch culture of the cyanobacterium Arthrospira maxima and the microalgae Chlorella vulgaris, Isochrysis galbana and Nannochloropsis gaditana. Thus, we study the effect of three variables on cell growth: i.e., inoculum:culture medium volume ratio (5:45, 10:40, 15:35 and 20:30 mL:mL), light:dark photoperiod (8:16, 12:12 and 16:8 h) and type of culture medium, including both synthetic media (Guillard’s F/2 and Walne’s) and wastewaters. The results showed that the initial inoculum:culture medium volume ratio, within the range 5:45 to 20:30, did not affect the amount of biomass at the end of the growth (14 days), whereas high (18 h) or low (6 h) number of hours of daily light was important for cell growth. The contribution of nutrients from different culture media could increase the growth rate of the different species. A. maxima was favoured in seawater enriched with Guillard’s F/2 as well as C. vulgaris and N. gaditana, but in freshwater medium. I. galbana had the greatest growth in the marine environment enriched with Walne’s media. Nitrogen was the limiting nutrient for growth at the end of the exponential phase of growth for C. vulgaris and N. gaditana, while iron was for A. maxima and I. galbana. The growth in different synthetic culture media also determines the biochemical composition of each of the microalgae. All species demonstrated their capability to grow in effluents from a wastewater treatment plant and they efficiently consume nitrogen, especially the three microalga species.

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Phaeodactylum tricornutum is an interesting source of biomass to produce biocrude by hydrothermal liquefaction (HTL). Its biochemical composition, along with its biomass productivity, can be modulated according to this specific application by varying the photoperiod, the addition of CO2 or the variation of the initial nitrate concentration. The lab-scale culture allowed the production of a P. tricornutum biomass with high biomass and lipid productivities using a 18:6 h light:dark photoperiod and a specific CO2 injection. An initial concentration of nitrates (11.8 mM) in the culture was also essential for the growth of this species at the lab scale. The biomass generated in the scale-up photoreactor had acceptable biomass and lipid productivities, although the values were higher in the biomass cultivated at the lab scale because of the difficulty for the light to reach all cells, making the cells unable to develop and hindering their growth. The biocrudes from a 90-L cultivated microalga (B-90L) showed lower yields than the ones obtained from the biomass cultivated at the lab scale (B-1L) because of the lower lipid and high ash contents in this biomass. However, the culture scaling-up did not affect significantly the heteroatom concentrations in the biocrudes. A larger-scale culture is recommended to produce a biocrude to be used as biofuel after a post-hydrotreatment stage.

Hospitals are one of the key contributors of pharmaceutical contaminants of emerging concern to the sewer systems. Hospitals wastewaters contain concentrations of pharmaceutical compounds between 3 and 150, which are higher than urban wastewater streams. However, dedicated treatments of the hospital effluents before discharge to the sewer system are not compulsory. Besides, conventional wastewater treatment plants have not been designed to remove pharmaceutical compounds effectively, and consequently, these micropollutants can reach the aquatic ecosystems. The removal of pharmaceutical compounds in real hospital wastewater was gaged using three different microbial cultures (white rot-fungus Trametes versicolor, microalga Isochrysis galbana, and a mixed culture of non-sulfur purple phototrophic bacteria). Before and after bioassays of the hospital wastewater, environmental hazard quotients were used to evaluate the biological treatment efficiency. Up to 45 out of the 79 compounds included in the analytical method were noticed in the hospital wastewater, with a predominance of analgesics/anti-inflammatories (acetaminophen, ibuprofen, ketoprofen, and naproxen). It was followed by antibiotics (azithromycin, ciprofloxacin, and ofloxacin, out of which the first two are included in the watch list of substances for monitoring in water in 2020) and anti-hypertensive drugs. Isochrysis galbana reached a reduction of 45% of the total concentration of pharmaceuticals, whereas Trametes versicolor and mixed culture of purple phototrophic bacteria improved the reductions up to 69% and 76%, respectively. Moreover, potential environmental risk compounds (antibiotics, particularly ciprofloxacin and ofloxacin) were removed by Trametes versicolor in higher extension, obtaining a total hazard quotient reduction higher than the other two cultures. Removal efficiency and environmental risk assessment of remaining PhACs were used to evaluate the performance of the new biological systems for the treatment of emerging pollutants. According to both criteria, T. versicolor seems the most capable alternative for removing pharmaceutical compounds in hospital wastewater effluents.

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