Amino acids concentrates derived from microalgae biomass through enzymatic protein hydrolysis can improve plant growth by saving the energy that is required for amino acid synthesis from conventional mineral fertilizer resources. To obtain high enzymatic hydrolysis yields, pre-treatment of microalgae biomass prior to enzymatic hydrolysis is suggested for facilitating enzyme access to proteins.Pulsed electric field (PEF) treatment was introduced as a pre-treatment to fresh and concentrated (50 g•kg sus −1 to 80 g•kg sus −1) Scenedesmus almeriensis biomass prior to enzymatic hydrolysis. The concentrated microalgae suspension was treated at an initial conductivity of σ = 1 mS•cm −1 with 1 μs long pulses at an electric field strength of 40 kV•cm −1 and a treatment energy of 75 kJ•kg sus −1 and 150 kJ•kg sus −1 . For benchmarking, additional biomass samples were processed by high pressure homogenization (HPH) at 2 kbar and up to 5 passes. Enzymatic hydrolysis was performed by applying the commercial enzymes Alcalase 2.5 L and Flavourzyme 1000 L for 180 min. The amino acids content in supernatant was determined by using the ortophthaldialdehyde (OPA) assay. PEF treatment at both energy inputs and HPH treatment at 2 kbar, 5 passes, revealed the same hydrolysis kinetics and the same final value of the degree of hydrolysis (DH) of 50% ± 2%. The energy demand for PEF pre-treatment amounts to 0.75 MJ•kg dw −1 when processing biomass at 100 g dw •l −1 . After both pretreatments, incomplete protein hydrolysis could be detected by SDS-PAGE analysis of residual biomass. Most feasible, hydrophobic protein fractions and protein aggregation impede complete protein hydrolysis by the applied enzyme cocktail.Since PEF treatment preserves cell shape and biomass separability and thus enables cascade processing, it is suggested as alternative downstream processing method for the production of amino acids concentrates from microalgae biomass.

A fatty acid hydroperoxide lyase from grapevine promotes defence-related cell death and generates 3-cis-hexenal, which specifically activates actin disruption.

Background Microalgae have attracted considerable interest due to their ability to produce a wide range of valuable compounds. Pulsed Electric Fields (PEF) has been demonstrated to effectively disrupt the microalgae cells and facilitate intracellular extraction. To increase the commercial viability of microalgae, the entire biomass should be exploited with different products extracted and valorized according to the biorefinery scheme. However, demonstrations of multiple component extraction in series are very limited in literature. This study aimed to develop an effective lipid extraction protocol from wet Scenedesmus almeriensis after PEF-treatment with 1.5 MJ·kgDW−1. A cascade process, i.e., the valorization of several products in row, was tested with firstly the collection of the released carbohydrates in the water fraction, then protein enzymatic hydrolysis and finally lipid extraction. Biomass processed with high pressure homogenization (HPH) on parallel, served as benchmark. Results Lipid extraction with ethanol:hexane (1:0.41 vol/vol) offered the highest yields from the different protocols tested. PEF-treatment promoted extraction with almost 70% of total lipids extracted against 43% from untreated biomass. An incubation step after PEF-treatment, further improved the yields, up to 83% of total lipids. Increasing the solvent volume by factor 2 offered no improvement. In comparison, extraction with two other systems utilizing only ethanol at room temperature or elevated at 60 °C were ineffective with less than 30% of total lipids extracted. Regarding cascade extraction, carbohydrate release after PEF was detected albeit in low concentrations. PEF-treated samples displayed slightly better kinetics during the enzymatic protein hydrolysis compared to untreated or HPH-treated biomass. The yields from a subsequent lipid extraction were not affected after PEF but were significantly increased for untreated samples (66% of total lipids), while HPH displayed the lowest yields (~ 49% of total lipids). Conclusions PEF-treatment successfully promoted lipid extraction from S. almeriensis but only in combination with a polar:neutral co-solvent (ethanol:hexane). After enzymatic protein hydrolysis in cascade processing; however, untreated biomass displayed equal lipid yields due to the disruptive effect of the proteolytic enzymes. Therefore, the positive impact of PEF in this scheme is limited on the improved reaction kinetics exhibited during the enzymatic hydrolysis step.

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Pulsed electric field (PEF) was conducted for the extraction of proteins/C-Phycocyanins from Arthrospira platensis. The cyanobacterial suspension was treated with 1 µs long pulses at an electric field strength of 40 kV•cm-1 and a treatment energy of 114 kJ•kgsus −1 and 56 kJ•kgsus −1. For benchmarking, additional biomass was processed by high pressure homogenization. Homogeneity of the suspension prior to PEF-treatment influenced the protein/C-phycocyanin extraction efficiency. Stability of C-Phycocyanin during post-PEF incubation time was affected by incubation temperature and pH of the external medium. Biomass concentration severely affect proteins/C-Phycocyanins extraction yield via PEF-treatment. The optimum conditions for extraction of proteins/C-Phycocyanin was obtained at 23 °C while incubating in pH 8-buffer. The energy demand for PEF-treatment amounts to 0.56 MJ•kgdw-1 when processing biomass at 100 gdw•kgsus −1. PEF treatment enhances the C-Phycocyanin purity ratio, thus, it can be suggested as preferential downstream processing method for the production of C-Phycocyanin from A. platensis biomass.