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Lipid extraction directly from the wet oleaginous microorganisms for biodiesel production is preferred as it reduces the energy input for traditional processes which require extensive drying of the biomass prior to the extraction. The high water content (≥80% on cell dry weight) in the wet biomass hinders the extraction efficiency due to the mass transfer limitation. This limitation can be overcome by pretreating wet biomass prior to the lipid extraction using pressurized gas that can be used alone or combined with other pretreatments to disrupt the cell wall. In this review, an extensive discussion on different pretreatments and the subsequent lipid extraction using these pretreatments is presented. Furthermore, a detailed account of the cell disruption using pressurized gas (e.g., CO2) treatment for microbial cell lysing is also presented. Finally, a new technique on lipid extraction directly from wet biomass using the combination of pressurized CO2 and microwave pretreatment is proposed.

The use of ecological engineering tools for the development of a more sustainable aquaculture is crucial. In this context, seaweed based Integrated Multi-Trophic Aquaculture (IMTA) systems are being designed to mitigate the environmental problems caused by several forms of fed aquaculture. Several macroalgal species, namely some from the genus Gracilaria, have been shown to be efficient biofilters,. Gracilaria vermiculophylla thrives in Ria de Aveiro lagoon, Portugal (40°38N, 8°43°W). It has been an unexploited resource for the production of agar. A seaweed cultivation system with 1200 L tanks was installed at a sole and turbot land-based aquaculture facility to evaluate the potential of this species as the biofilter component of an IMTA system. A year round, full factorial experiment was done, testing for the influence of stocking density (3, 5 and 7 kg m− 2 (fw)), water exchange rate (100 and 200 L h− 1) and time of the year on G. vermiculophylla's relative growth rates (RGR), productivity and nutrient removal.

G. vermiculophylla was able to maintain a good overall performance; however, results indicate that the culture conditions require adaptations throughout the year in order to attain successful productivities. In general, biomass production and nutrient removal were negatively related to the cultivation densities in the system. In the tanks seeded with 3 kg fw m− 2, the production of G. vermiculophylla was 0.7 ± 0.05 kg dw m− 2 month− 1; this biomass removed 221 ± 12.82 g m− 2 month− 1 of carbon and 40.54 ± 2.02 g m− 2 month− 1 of nitrogen (± 0.03% of the monthly fish N inputs). Temperature and light were the main environmental factors conditioning the growth and nutrient removal performance of the seaweed. With the appropriate upscaling, this pilot IMTA system is ready for implementation at fish aquaculture operations. G. vermiculophylla has proved to be an efficient component of land-based IMTA systems with environmental and potentially economic benefits for the fish farm.

Most photophysiological studies of marine macroalgae have focussed on algae in waters shallower than 30 m. However some species are abundant at depths in excess of 100 m with irradiances less than 1 mmol photons m2 s 1 . We examined, for the first time, the in situ efficiency of photochemical energy conversion of a variety of epilithic macroalgal species at depths from 86 to 201 m using a piloted submersible and multiple-turnover modulated chlorophyll fluorescence measurements based on the PAM technique. The irradiance at which electron transport rate reached a maximum (Ek) for green algae declined from 50 mmol photons m2 s 1 (at 90 m) to less than 10 mmol photons m2 s 1 at their lower depth limit of 140 m; photochemical quenching in response to light exposure declined markedly at depths below 100 m, while non-photochemical quenching remained low at all depths, indicating minimal photoprotective capacity in these algae. Values of Ek for encrusting Corallinales at 201 m were 4 mmol photons m2 s 1 , which exceeded by 400 times the maximum ambient irradiance at that depth. In the short term, the deep-water red algae examined (in particular the encrusting species) were able to tolerate and take advantage of irradiances orders of magnitude greater than the estimated noonday surface irradiance. Non-photochemical quenching of the red algae also increased with depth, indicating these algae retain their capacity for coping with high light even when in very deep waters. Carbon stable isotope data of deep algae confirmed the diffusion of inorganic carbon with its minimal energy requirement is probably the primary means of inorganic carbon uptake. The observed lower depth limits of selected macroalgae at Penguin Bank are shallower than depth limits for comparable species reported in the literature. Occasional smothering of algae by sediment, observed at Penguin Bank, would reduce the annual photon dose, thereby reducing the depth limit.

Six antimicrobial-producing seaweed-derived Bacillus strains were evaluated in vitro as animal probiotics, in comparison to two Bacillus from an EU-authorized animal probiotic product. Antimicrobial activity was demonstrated on solid media against porcine Salmonella and E. coli. The marine isolates were most active against the latter, had better activity than the commercial probiotics and Bacillus pumilus WIT 588 also reduced E. coli counts in broth. All of the marine Bacillus tolerated physiological concentrations of bile, with some as tolerant as one of the probiotics. Spore counts for all isolates remained almost constant during incubation in simulated gastric and ileum juices. All of the marine Bacillus grew anaerobically and the spores of all except one isolate germinated under anaerobic conditions. All were sensitive to a panel of antibiotics and none harbored Bacillus enterotoxin genes but all, except B. pumilus WIT 588, showed some degree of β-hemolysis. However, trypan blue dye exclusion and xCELLigence assays demonstrated a lack of toxicity in comparison to two pathogens; in fact, the commercial probiotics appeared more cytotoxic than the majority of the marine Bacillus. Overall, some of the marine-derived Bacillus, in particular B. pumilus WIT 588, demonstrate potential for use as livestock probiotics.