Cell Disruption Methods Research Articles

Investigation of the antioxidant capacity of cell-free extracts from Lactobacillus plantarum NJAU-01 obtained by different cell disruption methods

The antioxidant capacity of cell-free extracts from Lactobacillus plantarum NJAU-01 obtained by using different cell disruption methods was determined. The efficacy of various methods, including high-pressure treatment (HIP), lysozyme combined with ultrasound treatment (LCU), glycine treatment (GLY), and frozen-thawed treatment (FAT) was studied. The results showed that the bacterial suspension in the HIP group visibly had the least intact cells per visual field compared with the other groups, followed by the LCU group. The HIP group possessed 5.12 lg CFU/mL viable bacteria, which was significantly lower than that of the other groups after cell disruption from the initial 9 lg CFU/mL. The protein concentration of the cell-free extract from the HIP group was higher than that of the other groups with abundant protein bands and band intensities. The HIP group presented significantly higher total antioxidant capacity and superoxide dismutase and glutathione peroxidase activities than the other groups. Our data suggest that HIP can be a preferable method to obtain cell-free extracts with excellent antioxidant capacity for further exploring the underlying antioxidant mechanism of Lactobacillus plantarum NJAU-01.

Filamentous Fungi Producing l-Asparaginase with Low Glutaminase Activity Isolated from Brazilian Savanna Soil.

l-asparaginase is an enzyme used as treatment for acute lymphoblastic leukemia (ALL) due to its ability to hydrolyze l-asparagine, an essential amino acid synthesized by normal cells unlike neoplastic cells. The adverse effects of l-asparaginase formulations are associated with its glutaminase activity and bacterial origin; therefore, it is important to find new sources of l-asparaginase-producing eukaryotic microorganisms with low glutaminase activity. This work evaluated the biotechnological potential of filamentous fungi isolated from Brazilian Savanna soil and plants for l-asparaginase production. Thirty-nine isolates were screened for enzyme production using the plate assay, followed by measuring enzymatic activity in cells after submerged fermentation. The variables influencing l-asparaginase production were evaluated using Plackett–Burman design. Cell disruption methods were evaluated for l-asparaginase release. Penicillium sizovae 2DSST1 and Fusarium proliferatum DCFS10 showed the highest l-asparaginase activity levels and the lowest glutaminase activity levels. Penicillium sizovae l-asparaginase was repressed by carbon sources, whereas higher carbon concentrations enhanced l-asparaginase by F. proliferatum. Maximum enzyme productivity, specific enzyme yield and the biomass conversion factor in the enzyme increased after Plackett–Burman design. Freeze-grinding released 5-fold more l-asparaginase from cells than sonication. This study shows two species, which have not yet been reported, as sources of l-asparaginase with possible reduced immunogenicity for ALL therapy.

Identifying critical corridors during an area-wide disruption by evaluating network bottleneck capacity

This paper applies the min-cut max-flow theorem combined with a grid cell disruption method over a large transportation network, to identify the importance of network locations in providing travel capacity when a community is evacuating (say, from wildfire). We develop metrices that look at the importance and contribution of individual links to network bottleneck capacity in traveling from the evacuating community to the shelter community. The purpose of this is to determine the network location that is the most restrictive of all, and more importantly, where it is in reference to the evacuating community location. We apply this method to the highway network of Alberta, Canada, with evacuating communities identified as those that have been under wildfire threat historically and/or are expected to in the future. We find that in all cases, network locations that contribute the greatest share of bottleneck capacity, are located adjacent to these evacuating communities. Next, we look at combining the measure for several communities, finding that the highways in remote northern Alberta are important despite some of them having lower capacity than the multi-lane highways in the south. Application of this simple method can support provincial and local municipal governments in deciding which communities require more detailed emergency evacuation studies to better identify and communicate transportation network deficiencies to provincial and federal bodies that would be making infrastructure investments towards community health and resilience.

Distinct Human Gut Microbial Taxonomic Signatures Uncovered With Different Sample Processing and Microbial Cell Disruption Methods for Metaproteomic Analysis.

The use of metaproteomics for studying the human gut microbiota can shed light on the taxonomic profile and the functional role of the microbial community. Nevertheless, methods for extracting proteins from stool samples continue to evolve, in the pursuit of optimal protocols for moistening and dispersing the stool sample and for disrupting microbial cells, which are two critical steps for ensuring good protein recovery. Here, we evaluated different stool sample processing (SSP) and microbial cell disruption methods (CDMs). The combination of a longer disintegration period of the stool sample in a tube rotator with sonication increased the overall number of identified peptides and proteins. Proteobacteria, Bacteroidetes, Planctomycetes, and Euryarchaeota identification was favored by mechanical cell disruption with glass beads. In contrast, the relative abundance of Firmicutes, Actinobacteria, and Fusobacteria was improved when sonication was performed before bead beating. Tenericutes and Apicomplexa identification was enhanced by moistening the stool samples during processing and by disrupting cells with medium-sized glass beads combined with or without sonication. Human protein identifications were affected by sonication. To test the reproducibility of these gut metaproteomic analyses, we examined samples from six healthy individuals using a protocol that had shown a good taxonomic diversity and identification of proteins from Proteobacteria and humans. We also detected proteins involved in microbial functions relevant to the host and related mostly to specific taxa, such as B12 biosynthesis and short chain fatty acid (SCFA) production carried out mainly by members in the Prevotella genus and the Firmicutes phylum, respectively. The taxonomic and functional profiles obtained with the different protocols described in this work provides the researcher with valuable information when choosing the most adequate protocol for the study of certain pathologies under suspicion of being related to a specific taxon from the gut microbiota.

Polyvalent Bacterial Lysate Protects Against Pneumonia Independently of Neutrophils, IL-17A or Caspase-1 Activation.

Polyvalent bacterial lysates have been in use for decades for prevention and treatment of respiratory infections with reported clinical benefits. However, besides claims of broad immune activation, the mode of action is still a matter of debate. The lysates, formulated with the main bacterial species involved in respiratory infections, are commonly prepared by chemical or mechanical disruption of bacterial cells, what is believed influences the biological activity of the product. Here, we prepared two polyvalent lysates with the same composition but different method of bacterial cell disruption and evaluated their biological activity in a comparative fashion. We found that both bacterial lysates induce NF-kB activation in a MyD88 dependent manner, suggesting they work as TLR agonists. Further, we found that a single intranasal dose of any of the two lysates, is sufficient to protect against pneumococcal pneumonia, suggesting that they exert similar biological activity. We have previously shown that protection against pneumococcal pneumonia can also be induced by prior S. pneumoniae sub lethal infection or therapeutic treatment with a TLR5 agonist. Protection in those cases depends on neutrophil recruitment to the lungs, and can be associated with increased local expression of IL-17A. Here, we show that bacterial lysates exert protection against pneumococcal pneumonia independently of neutrophils, IL-17A or Caspase-1/11 activation, suggesting the existence of redundant mechanisms of protection. Trypsin-treated lysates afford protection to the same extent, suggesting that just small peptides suffice to exert the protective effect or that the molecules responsible for the protective effect are not proteins. Understanding the mechanism of action of bacterial lysates and deciphering the active components shall allow redesigning them with more precisely defined formulations and expanding their range of action.

PHYSICAL PRETREATMENT OF ULVA FASCIATA FOR ENHANCINGBIODIESEL PRODUCTION AND QUALITY

The green algae Ulva faciata was subjected to different physical pretreatments comprising thermal and mechanical techniques at different experimental conditions to state the most appropriate method of cell disruption for increasing the quantity of the extracted lipid and hence improve the quality of the produced biodiesel with low cost. Thermal pretreatment was autoclaving of either wet or dry algal biomass, while mechanical pretreatments include microwave and ultrasonication at different time intervals. The control was the alga without pretreatment extracted at optimum conditions: 60 min, 55oC, shaking speed at 250 rpm, < 0.16 mm particle size with 25:1 v/w solvent to solid ratio. The results showed that the quantity of extracted lipids in case of using all physical pretreatments increased the Total fatty acids yield significantly by about 2-folds of the control for wet algae in hydrothermal treatment with optimum time of treatment 40 minutes, and 1.4 folds for dry algae in thermal pretreatment of the dried alga for 60minutes autoclaving period. The sharp increase by 2.2 folds of extracted lipids was recorded by microwave pretreatment for radiation period (5 min), while ultrasonication showed 2.1-fold increase in lipid yield at 15minutes ultrasound exposure time. Concerning the physical properties of the produced biodiesel after all physical pretreatments, the results indicated that the produced biodiesel had very high quality as all its properties are almost complied with the ASTM D6751 and EN14214 standards. These results were confirmed statistically where all physical pretreatments had high significant effect on fatty acids yield and Biodiesel properties.

Mechanical Cell Disruption Technologies for the Extraction of Dyes and Pigments from Microorganisms: A Review

The production of pigments using single cell microorganisms is gaining traction as a sustainable alternative to conventional syntheses, which rely, in no negligible proportions, on petrochemicals. In addition to depending on petroleum, these syntheses involved the use of toxic organic solvents, which may be inadequately disposed of across a range of industries, thus compounding the deleterious effects of fossil fuel exploitation. Literature suggests that notable research efforts in the area of sustainable pigment production using single cell microorganisms are focused on the production of pigments coveted for their interesting qualities, which transcend their mere capacity to dye various fabrics both natural and synthetic. As interest in sustainable pigment biosynthesis grows, the need to devise effective and efficient cell disruption processes becomes more pressing given that the viability of pigment biosynthesis is not only dependent on microorganisms’ yield in terms of production, but also on researchers’ ability to recover them. This review chiefly reports findings as to mechanical cell disruption methods, used individually or in various combinations, and their aptitude to recover biosynthetic pigments.

Current Pretreatment/Cell Disruption and Extraction Methods Used to Improve Intracellular Lipid Recovery from Oleaginous Yeasts.

The production of lipids from oleaginous yeasts involves several stages starting from cultivation and lipid accumulation, biomass harvesting and finally lipids extraction. However, the complex and relatively resistant cell wall of yeasts limits the full recovery of intracellular lipids and usually solvent extraction is not sufficient to effectively extract the lipid bodies. A pretreatment or cell disruption method is hence a prerequisite prior to solvent extraction. In general, there are no recovery methods that are equally efficient for different species of oleaginous yeasts. Each method adopts different mechanisms to disrupt cells and extract the lipids, thus a systematic evaluation is essential before choosing a particular method. In this review, mechanical (bead mill, ultrasonication, homogenization and microwave) and nonmechanical (enzyme, acid, base digestions and osmotic shock) methods that are currently used for the disruption or permeabilization of oleaginous yeasts are discussed based on their principle, application and feasibility, including their effects on the lipid yield. The attempts of using conventional and “green” solvents to selectively extract lipids are compared. Other emerging methods such as automated pressurized liquid extraction, supercritical fluid extraction and simultaneous in situ lipid recovery using capturing agents are also reviewed to facilitate the choice of more effective lipid recovery methods.

Microwave-Assisted One-Pot Lipid Extraction and Glycolipid Production from Oleaginous Yeast Saitozyma podzolica in Sugar Alcohol-Based Media.

Glycolipids are non-ionic surfactants occurring in numerous products of daily life. Due to their surface-activity, emulsifying properties, and foaming abilities, they can be applied in food, cosmetics, and pharmaceuticals. Enzymatic synthesis of glycolipids based on carbohydrates and free fatty acids or esters is often catalyzed using certain acyltransferases in reaction media of low water activity, e.g., organic solvents or notably Deep Eutectic Systems (DESs). Existing reports describing integrated processes for glycolipid production from renewables use many reaction steps, therefore this study aims at simplifying the procedure. By using microwave dielectric heating, DESs preparation was first accelerated considerably. A comparative study revealed a preparation time on average 16-fold faster than the conventional heating method in an incubator. Furthermore, lipids from robust oleaginous yeast biomass were successfully extracted up to 70% without using the pre-treatment method for cell disruption, limiting logically the energy input necessary for such process. Acidified DESs consisting of either xylitol or sorbitol and choline chloride mediated the one-pot process, allowing subsequent conversion of the lipids into mono-acylated palmitate, oleate, linoleate, and stearate sugar alcohol esters. Thus, we show strong evidence that addition of immobilized Candida antarctica Lipase B (Novozym 435®), in acidified DES mixture, enables a simplified and fast glycolipid synthesis using directly oleaginous yeast biomass.

Mechanical/Physical Methods of Cell Disruption and Tissue Homogenization.

This chapter covers the various methods of mechanical cell disruption and tissue homogenization that are currently commercially available for processing small samples s<1mL) to larger multikilogram production quantities. These mechanical methods of lysing do not introduce chemicals or enzymes to the system. However, the energies required when using these "harsh," high mechanical energy methods can be enough to damage the very components being sought.The destruction of cell membranes and walls is effected by subjecting the cells (a) to shearing by liquid flow, (b) to exploding by pressure differences between inside and outside of cell, (c) to collision forces by impact of beads or paddles, or (d) a combination of these forces.Practical suggestions to optimize each method, where to acquire such equipment, and links to reference sources are included. Several novel technologies are presented.

Biostimulants obtained after pilot-scale high-pressure homogenization of Scenedesmus sp. grown in pig manure

Microalgae are becoming an important source of high-value products such as biostimulants, biopesticides, and other low-value products such as biofertilizers or aquafeed (fatty acids and carotenoids), among others. However, extracting the biomolecules contained in the microalgae cells is difficult due to the structure and composition of the microalgal cell wall. To overcome this difficulty, mechanical cell disruption methods, such as high-pressure homogenization (HPH), can be applied to facilitate the extraction of the compounds of interest.This work focuses on optimizing the extraction of biostimulants from microalgae biomass and obtaining amino acid concentrates that can be used in several applications. The research aims to study the effect of HPH pretreatment on the production of these different bioproducts using Scenedesmus sp. biomass grown in pig sludge as the raw material.For each product, the HPH pretreatment of the wet biomass must be optimized to select the optimal conditions and the number of passes. Soft treatment of the wet biomass at 200 bar is sufficient to observe a 10% increase in the germination index (GI) of watercress seeds, while greater treatment intensities reduce the GI with respect to the untreated biomass, possibly because this increases the concentration of the molecules responsible for the bioactivity, thus causing a toxic effect on the seeds. In the case of the amino acid concentrates, better results were obtained at 600 bar, achieving a hydrolysis level of 72.9%. Lastly, the concentrations of the phenolic compounds and the salicylic acid, related with enhanced biostimulant activity, were determined using spectrophotometric methods and High-Performance Liquid Chromatography- diode array (HPLC), respectively.

High Resolution Proteome of Lipid Droplets Isolated from the Pennate Diatom Phaeodactylum tricornutum (Bacillariophyceae) Strain pt4 provides mechanistic insights into complex intracellular coordination during nitrogen deprivation.

Lipid droplets (LDs) are an organelle conserved amongst all eukaryotes, consisting of a neutral lipid core surrounded by a polar lipid monolayer. Many species of microalgae accumulate LDs in response to stress conditions, such as nitrogen starvation. Here, we report the isolation and proteomic profiling of LD proteins from the model oleaginous pennate diatom Phaeodactylum tricornutum, strain Pt4 (UTEX 646). We also provide a quantitative description of LD morphological ontogeny, and fatty acid content. Novel cell disruption and LD isolation methods, combined with suspension-trapping and nanoflow liquid chromatography coupled to high resolution mass spectrometry, yielded an unprecedented number of LD proteins. Predictive annotation of the LD proteome suggests a broad assemblage of proteins with diverse functions, including lipid metabolism and vesicle trafficking, as well as ribosomal and proteasomal machinery. These proteins provide mechanistic insights into LD processes, and evidence for interactions between LDs and other organelles. We identify for the first time several key steps in diatom LD-associated triacylglycerol biosynthesis. Bioinformatic analyses of the LD proteome suggests multiple protein targeting mechanisms, including amphipathic helices, post-translational modifications, and translocation machinery. This work corroborates recent findings from other strains of P. tricornutum, other diatoms, and other eukaryotic organisms, suggesting that the fundamental proteins orchestrating LDs are conserved, and represent an ancient component of the eukaryotic endomembrane system. We postulate a comprehensive model of nitrogen starvation-induced diatom LDs on a molecular scale, and provide a wealth of candidates for metabolic engineering, with the potential to eventually customize LD contents.

Exploring the critical factors of algal biomass and lipid production for renewable fuel production by machine learning

In this work, the algal biomass productivity and its lipid content were explored using a database containing 4670 instances extracted from the experimental results reported in 102 published articles. First, the influences of critical factors such as microalgae species, cultivation conditions, light intensity, CO2 amount, nutrient concentrations, reactor type, stress conditions, cell disruption methods, and lipid extraction solvents on the biomass and lipid production were reviewed. Then, the database was analyzed using machine learning techniques; decision trees were utilized to determine the combination of variables leading to high biomass and lipid content while association rule mining was used to find the specific conditions leading to very high biomass and lipid levels. Decision tree analysis discovered 11 different combinations of variables leading to high biomass productivity and 13 combinations for high lipid content; whereas, association rule mining analysis helped to identify the levels of specific factors for very high biomass and lipid production. It was then concluded that machine learning methods can help to determine the best conditions for optimum biomass growth and lipid yield for microalgae to manufacture renewable biofuels, and this can guide the planning of new experimental works.

Processing Nannochloropsis gaditana biomass for the extraction of high-value biocompounds

Extraction of carotenoids and fatty acids from microalgae is a technological bottleneck in processing. An improved extraction process was developed to scale the production of these bioproducts from Nannochloropsis gaditana. Different cell disruption methods were evaluated in terms of carotenoid release. Ethanol was substituted with isopropyl alcohol in a three-component solution of water:isopropyl alcohol:hexane (WIH), in which the extracts were separated by solution partitioning. This resulted in higher carotenoid and fatty acid recovery yields if compared with the standard method. The extraction method was replicated on a pilot scale, obtaining similar carotenoid recovery yields, higher than those of the standard method. Although fatty acid recovery was lower than that of the small-scale tests, yields above 85% were obtained. This demonstrated that the method was scalable for the extraction of high-value products from microalgae up to 10-L reactor volume. The use of isopropyl alcohol, which is cheaper than ethanol, and the separation of the solution phases by partitioning (avoiding drying) could contribute to reduce operation costs of downstream processing.

Comparative assessment of pretreatment strategies for production of microalgae-based biodiesel from locally isolated Chlorella homosphaera

The yield and quality of lipids extracted from microalgal biomass are critical factors in the production of microalgae-based biodiesel. The green microalga Chlorella homosphaera, isolated from Beira Lake, Colombo, Sri Lanka was employed in the present study to identify the effect of chlorophyll removal and cell disruption methods on lipid extraction yield, fatty acid methyl ester (FAME) profile and quality parameters of biodiesel; including cetane number (CN), iodine value (IV), degree of unsaturation (DU) and high heating value (HHV). In the first section of this study, chlorophyll was removed from dry microalgae biomass prior to lipid extraction. Through the analysis of FAME profiles, it was observed that chlorophyll removal yielded biodiesel of enhanced quality, albeit with a lipid loss of 44.2% relative to the control. In the second section of the study, mechanical cell disruption strategies including grinding, autoclaving, water bath heating and microwaving were employed to identify the most effective method to improve lipid recovery from chlorophyll-removed microalgae biomass. Autoclaving (121 °C, 20min sterilization time, total time 2h) was the most effective cell disruption technique of the methods tested, in terms of lipid extraction yield (39.80%) and also biodiesel quality. Moreover, it was observed that employing cell disruption subsequent to chlorophyll removal has a significant impact on the FAME profile of microalgae-based biodiesel, and consequently served to increase HHV and CN although IV and DU did not vary significantly.

Extraction of chlorophylls and carotenoids from dry and wet biomass of isolated Chlorella Thermophila: Optimization of process parameters and modelling by artificial neural network

Chlorophylls and carotenoids can be extracted from microalgae using various solvents. However, there is lack of studies regarding the comparison of extraction yield of these pigments from wet and dry microalgal biomass using different combination of cell disruption methods. Therefore, in this work, we have investigated the comparison of the extraction yield of chlorophylls and carotenoids from the wet and heat-dried microalgal biomass (isolated Chlorella thermophila) using ethanol. Extraction parameters such as homogenisation time, homogenisation speed, solvent temperature, solid-solvent ratio, boiling time and microwave time have been optimised. Chlorophyll extraction yield was observed to be 2.7 fold higher from wet biomass than dry biomass while carotenoid yield was 6.7 fold higher. Highest chlorophyll yield (∼60 mg/g-dry biomass) was observed at 6 min of homogenisation time, 10,000 rpm, solid solvent ratio of 1 mg/mL and 58 °C of solvent temperature from wet biomass with extraction efficiency of ∼94 %. Highest carotenoid yield was noticed following the same conditions of chlorophyll extraction except 4 °C of solvent temperature. The modelling of the extraction process was performed using artificial neural network (ANN) which may be useful for the scale-up of the extraction process at the industrial level.

Improved extraction of bioactive compounds from biomass of the marine dinoflagellate microalga Amphidinium carterae

The extraction of three families of compounds (carotenoids, fatty acids and amphidinols) from the biomass of two strains of Amphidinium carterae (ACRN03 and Dn241EHU) was improved by tuning cell disruption and solvent extraction operations. The extraction of carotenoids was evaluated using alkaline saponification (0%-60% KOH d.w.) at different temperatures (25–80 °C). High levels of carotenoids were obtained at 60 °C using freeze-dried biomass, not subjected to cell disruption methods. The ACRN03 strain required 20% KOH whereas the Dn241EHU strain did not require saponification since carotenoid degradation was observed. The extraction efficiencies were determined with a wide range of pure solvents and mixtures thereof. Two empirical non-linear equations were used to correlate extraction percentages for each family of compounds with the Hildebrand solubility parameter (δT) and the polarity index of the solvents (PI). Thresholds of δT and PI of around 20 MPa1/2 and 6, respectively, were determined for the extraction of amphidinols, consistent with antiproliferative activity measurements.

Evaluation of Downstream Processing, Extraction, and Quantification Strategies for Single Cell Oil Produced by the Oleaginous Yeasts Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194.

Single cell oil (SCO) produced by oleaginous yeasts is considered as a sustainable source for biodiesel and oleochemicals since its production does not compete with food or feed and high yields can be obtained from a wide variety of carbon sources, e.g., acetate or lignocellulose. Downstream processing is still costly preventing the broader application of SCO. Direct transesterification of freeze-dried biomass is widely used for analytical purposes and for biodiesel production but it is energy intensive and, therefore, expensive. Additionally, only fatty acid esters are produced limiting the subsequent applications. The harsh conditions applied during direct esterification might also damage high-value polyunsaturated fatty acids. Unfortunately, universal downstream strategies effective for all yeast species do not exist and methods have to be developed for each yeast species due to differences in cell wall composition. Therefore, the aim of this study was to evaluate three industrially relevant cell disruption methods combined with three extraction systems for the SCO extraction of two novel, unconventional oleaginous yeasts, Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194, based on cell disruption efficiency, lipid yield, and oil quality. Bead milling (BM) and high pressure homogenization (HPH) were effective cell disruption methods in contrast to sonification. By combining HPH (95% cell disruption efficiency) with ethanol-hexane-extraction 46.9 ± 4.4% lipid/CDW of S. podzolica were obtained which was 2.7 times higher than with the least suitable combination (ultrasound + Folch). A. porosum was less affected by cell disruption attempts. Here, the highest disruption efficiency was 74% after BM and the most efficient lipid recovery method was direct acidic transesterification (27.2 ± 0.5% fatty acid methyl esters/CDW) after freeze drying. The study clearly indicates cell disruption is the decisive step for SCO extraction. At disruption efficiencies of >90%, lipids can be extracted at high yields, whereas at lower cell disruption efficiencies, considerable amounts of lipids will not be accessible for extraction regardless of the solvents used. Furthermore, it was shown that hexane-ethanol which is commonly used for extraction of algal lipids is also highly efficient for yeasts.

Green extraction of polysaccharides from Arthrospira platensis using high pressure homogenization

The efficiency of high pressure homogenization as cell disruption method was investigated on the cyanobacterium Arthrospira platensis for the recovery of polysaccharides following the concept of green chemistry, mainly solvent and energy saving. The highest yield of polysaccharides (15.1 ± 0.8 g (100 g)−1 dry weight) was obtained at a solid concentration of 14.5% (w/w), inlet pressure of 500 bar and after 4 homogenization cycles. High-pressure treatment resulted in a 2.5-fold higher yield than the conventional hot water method. Purified polysaccharides extracted under the optimized conditions were isolated and characterized by ATR-FTIR and HPSEC. It was shown that polysaccharides of A. platensis can be extracted using high pressure homogenization under mild conditions (short time, ambient temperature, no chemicals, neutral pH) with a high yield of recovery and a specific energy consumption of 0.41 kWh $$ {\mathrm{kg}}_{\mathrm{DW}}^{-1}, $$ which is close to the minimum energy demand recommended for an extraction step within biorefinery processes.

Effect of growth conditions on the efficiency of cell disruption of Neochloris oleoabundans

The impact of four different growth conditions on the cell disruption efficiency of Neochloris oleoabundans was investigated. A mechanical and biological cell disruption methods were evaluated separately and combined. It has been established that microalgae grown in marine water under nitrogen deprivation were the most resistant against cell disruption methods and released the lowest amount of proteins. The release of lipids, however, followed the “hindered molecule diffusion phenomenon” because it did not follow the same release pattern as proteins. The enzymatic treatment was efficient enough to release the majority of the proteins without combining it with high-pressure homogenization. Regarding energy input, Neochloris oleoabundans grown in marine water under nitrogen deprivation required the highest energy input to release proteins (Ep = 13.76 kWh.kg−1) and to break the cells by high-pressure homogenization (Ex – HPH = 1.14 kWh.kg−1) or by the combination of enzymes and High-pressure homogenization (Ex – ENZ = 2.79 kWh.kg−1).