• Energy Research

Microalgae are sources of nutritional products and biofuels. However, their economical processing is challenging, because of (i) the inherently low concentration of biomass in algal cultures, below 0.5%, (ii) the high-water content in the harvested biomass, above 70%; and (iii) the variable intracellular content and composition. Cell wall structure and strength vary enormously among microalgae, from naked Dunaliella cells to robust Haematococcus cysts. High-value products justify using fast and energy-intensive processes, ranging from 0.23 kWh/kg dry biomass in high-pressure homogenization, to 6 kWh/kg dry biomass in sonication. However, in biofuels production, the energy input must be minimized, requiring slower, thermal or chemical pretreatments. Whichever the primary fraction of interest, the spent biomass can be processed into valuable by-products. This review discusses microalgal cell structure and composition, how it affects pretreatment, focusing on technologies tested for large scale or promising for industrial processes, and how these can be integrated into algal biorefineries.

Microalgae are sources of nutritional products and biofuels. However, their economical processing is challenging, because of (i) the inherently low concentration of biomass in algal cultures, below 0.5%, (ii) the high-water content in the harvested biomass, above 70%; and (iii) the variable intracellular content and composition. Cell wall structure and strength vary enormously among microalgae, from naked Dunaliella cells to robust Haematococcus cysts. High-value products justify using fast and energy-intensive processes, ranging from 0.23 kWh/kg dry biomass in high-pressure homogenization, to 6 kWh/kg dry biomass in sonication. However, in biofuels production, the energy input must be minimized, requiring slower, thermal or chemical pretreatments. Whichever the primary fraction of interest, the spent biomass can be processed into valuable by-products. This review discusses microalgal cell structure and composition, how it affects pretreatment, focusing on technologies tested for large scale or promising for industrial processes, and how these can be integrated into algal biorefineries.

An environmental friendly process was developed to produce Arthrospira maxima's biomass from sugarcane vinasse, which was generated in a bioethanol production chain, at laboratory and pilot scale. Peptides fractions were than obtained from enzymatically hydrolyzed biomass. High microalgae biomass productivities were reached (0.150 g L-1 day-1) coupled with a significant reduction of BOD and COD (89.2 and 81%, respectively). Three peptide fractions were obtained from microalgae biomass through single or sequential enzymatic hydrolysis. Antioxidant, antimicrobial, anti-inflammatory, and/or anti-collagenase activities of biopetides' fractions were observed. The PHS showed multi-biological activities. The three peptides fractions could be potential candidates for different applications in pharmaceutical, cosmetic and food industry.

An environmental friendly process was developed to produce Arthrospira maxima's biomass from sugarcane vinasse, which was generated in a bioethanol production chain, at laboratory and pilot scale. Peptides fractions were than obtained from enzymatically hydrolyzed biomass. High microalgae biomass productivities were reached (0.150 g L-1 day-1) coupled with a significant reduction of BOD and COD (89.2 and 81%, respectively). Three peptide fractions were obtained from microalgae biomass through single or sequential enzymatic hydrolysis. Antioxidant, antimicrobial, anti-inflammatory, and/or anti-collagenase activities of biopetides' fractions were observed. The PHS showed multi-biological activities. The three peptides fractions could be potential candidates for different applications in pharmaceutical, cosmetic and food industry.

The aim of the work was to study the production of the exopolysaccharides by Agaricus brasiliensis and the isolation of exopolysaccharides (EPSs) with biological effects. A brasiliensis LPB03 was cultured in submerged fermentation in a medium containing glucose, yeast extract, hydrolyzed soybean protein, and salts (pH 6.1) at 29 degrees C and 120 rpm for 144 h. The maximum biomass and EPS yield was 7.80 +/- 0.01 and 1,430.70 +/- 26.75 mg/L, respectively. To isolate the produced EPSs, two methods were compared: (1) with alcohol precipitation and (2) treatment with tricloroacetic acid (TCA), followed by alcohol precipitation. The use of TCA facilitated the purification of the EPS, reducing the amount of the contaminant soy proteins. For monosaccharide identification, the EPSs were hydrolyzed, derivatized to alditol acetates, and analyzed by gas chromatography (GC) and GC-mass spectrometry, which showed the presence (in molar percentage) of mannose (58.7), galactose (21.4), and glucose (13.1) as major sugars, with lower amounts of rhamnose (3.9) and xylose (2.8). Scanning electron microscopy was used to observe the morphological structure of the EPS. The experiments in vivo including EPS in the mice diet during 8 weeks indicated the hipocholesteremic and hypoglycemic effects.

The aim of the work was to study the production of the exopolysaccharides by Agaricus brasiliensis and the isolation of exopolysaccharides (EPSs) with biological effects. A brasiliensis LPB03 was cultured in submerged fermentation in a medium containing glucose, yeast extract, hydrolyzed soybean protein, and salts (pH 6.1) at 29 degrees C and 120 rpm for 144 h. The maximum biomass and EPS yield was 7.80 +/- 0.01 and 1,430.70 +/- 26.75 mg/L, respectively. To isolate the produced EPSs, two methods were compared: (1) with alcohol precipitation and (2) treatment with tricloroacetic acid (TCA), followed by alcohol precipitation. The use of TCA facilitated the purification of the EPS, reducing the amount of the contaminant soy proteins. For monosaccharide identification, the EPSs were hydrolyzed, derivatized to alditol acetates, and analyzed by gas chromatography (GC) and GC-mass spectrometry, which showed the presence (in molar percentage) of mannose (58.7), galactose (21.4), and glucose (13.1) as major sugars, with lower amounts of rhamnose (3.9) and xylose (2.8). Scanning electron microscopy was used to observe the morphological structure of the EPS. The experiments in vivo including EPS in the mice diet during 8 weeks indicated the hipocholesteremic and hypoglycemic effects.