Article views PDF downloads 22 Cited by 0. Abstract: Seven strains possessing the ability of algae lysis were screened from the liver and intestine of the indigenous Hemibarbus maculatus, in Taihu Lake. One of them with the highest algae lysis was named as GHJ, and was identified as Microbacterium oleivoran by DNA sequencing and building phylogenetic trees.
In this study, Microcystis aeruginosa, which is the usual algae in Taihu Lake Basin, was employed as the target degradation algae. The GHJ algae lysis characteristic was determined with the change in the concentration of chlorophyll.
The growth kinetics of GHJ and the kinetic mechanism of degradation of Microcystis aeruginosa in the algae lysis process were preliminarily revealed. In addition, the correlation between the growth kinetics of GHJ and the kinetic mechanism of degration of Microbacterium oleivoran was expored.
The results showed that the algae lysis process of GHJ was accomplished by destroying and dissolving algae cells via the synergistic process of direct dissolution and indirect dissolution. The algae-lysis ratio is up to When the ratio of bacteria to algae is in the range of to , the relationship between the amount of chlorophyll reduction and the time of algae lysis is agreed with the first-order kinetic model, R2 is between 0.
This study provides basic theoretical support for the screening source of algae-lysis bacteria and other engineering applications of algal lysis processes. Title Author Keyword.
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Seven strains possessing the ability of algae lysis were screened from the liver and intestine of the indigenous Hemibarbus maculatus, in Taihu Lake. Importance of controlling pH-depended dissolved inorganic carbon to prevent algal bloom outbreaks. Bioresource Technology, , CaCl 2 applied to the extraction of Moringa oleifera seeds and the use for Microcystis aeruginosa removal[J]. Chemical Engineering Journal,, 15 Analysis of algae growth mechanism and water bloom prediction under the effect of multi-affecting factor.
Saudi Journal of Biological Sciences, , 24 3 Algicidal and cyanocidal effects of selected isoquinoline alkaloids[J]. These organisms can be eukaryotic or prokaryotic, the latter being the cyanobacteria, which are commonly referred to as microalgae. The nature of the cell wall of a given microalgae species can vary, making it easier or harder to access its valuable contents. The rigidity of the cell wall can be provided, for example, by high levels of polysaccharides in the cell wall structure, such as glucose and mannose, present in Chlorella zofingiensis , or by complex sugars composition such as arabinose, galactose, rhamnose, mannose and xylose, as found in Tetraselmis suecia and T.
Arthorspira spp. Thus, several methods can be applied to breakdown such molecules that, being part of the cell wall, present different level of rigidity and confer them protection against environment factors. The cell wall disruption methods include physical, chemical, enzymatic approaches. In this entry, it will be presented a brief description of these methods. Methods for microalgae cell disruption comprise mechanical, physical or non-mechanical techniques, usually employed to disrupt or disintegrate the cellular membrane, this way increasing the recovery yield of the desired component e.
Figure 1 shows the general differences between mechanical and non-mechanical cell-disruption methods. Figure 1. Comparison of different cell-disruption methods. Mechanical and physical methods may promote cell lysis through solid or liquid-shear forces e. The cell disruption principle in bead mill machines is to promote mechanical cell damage by forcing the collision between the cells and the beads. This collision is promoted by a rotating shaft present in the grinding chamber. The diameter and load of the beads are important parameters with a direct influence on the cell disruption effectiveness [ 1 ].
The most common materials used in the beads are zirconium high-density beads and glass low-density beads. Zirconium is preferred to process high viscosity media, while glass beads are more suitable for media with low viscosity [ 2 ]. The inventors evaluated the effect of specific parameters, such as bead material glass, zirconium silicate and zirconium oxide , diameter of milling beads 0. The configuration recommended by the applicant company in order to combine lower energy consumption with higher productivity is performed by lower diameter-zirconium silicate beads 0.
It was demonstrated that moderate conditions are preferable to reduce energy consumption to achieve a target degree of milling. Despite high-density beads based on zirconium presenting high specific energy, the glass beads low density were not efficient, requiring more passes to achieve the same degree of milling, which also increases the specific energy. Therefore, in order to overcome this issue, the inventors combined the use of zirconium silicate, which is less dense than zirconium oxide, with lower diameter to reduce the number of passes required.
The same criteria were applied to biomass concentration; higher concentrations lead to higher productivities, but also increase the energy consumption. Additionally, moderate peripheral speed was recommended to avoid excessive abrasion and the filling rate, however, did not present a significant impact on energy consumption among the tested conditions. It is also possible to reduce the specific energy consumption and the process cost by using higher dry cell weight concentrations 0.
Thus, despite the many advantages of using bead milling, including this being a suitable technique for large-scale production, and the aforementioned optimizations, this process still has high energy consumption [ 4 ]. Despite presenting some drawbacks such as high energy consumption and protein denaturation, this technique is suitable for industrial scale and requires short processing time.
It has been reported operational times of 30 or 60 s at 10, or 14, rpm for lipid and antioxidant extraction in Nannochloropsis sp. The authors tested five microalgae species Nannochloropsis sp. According to the cell wall properties, parameters such as operating pressure and number of homogenization passes can be optimized to enhance the process efficiency [ 8 ].
Additionally, other variables such as dry cell weight concentration, microalgae species and growth conditions, impacts on the specific energy consumption [ 2 ]. Bernaerts et al. However, despite the effective reduction of homogenization passes, the high pressure also heated the sample, resulting in aggregation of the intracellular components released. However, Elain et al. Thus, the major drawbacks of HPH comprise the non-selectivity, the formation of undesirable cell debris and the limitation to break harder cell walls.
However, despite these disadvantages, HPH is, together with bead milling and HSH, the preferred method for the industrial scale. Microwave irradiation is a simple and scalable method for cell disruption. This method has a well-established optimal operational value for heating MHz and the cell walls are disrupted by the electromagnetic effect induced by the microwave irradiance that interacts with polar e.
This method is not suitable when the target component is volatile, but it has been successfully reported as an effective cell disruption technique for lipid extraction. Also, the combination of microwave with solvents, called microwave-assisted extraction MAE , has been reported as the technique with lower operational costs and extraction time than the conventional techniques, and higher lipid extraction than other non-conventional methods e.
By comparing different cell disruption methods autoclaving, bead-beating, microwaves, sonication and osmotic shock , followed by chemical lipid extraction, Lee et al.
Also, Viner et al. The highest total lipids extraction yield 9. Recently, the use of ionic liquids in MAE has been studied as a greener technology to overcome the intrinsic toxicity of the conventional solvents e. The ultrasonication method for cell disruption is based on liquid-shear forces caused by emission of high frequency wave sounds up to 15—20 kHz. In liquid, these sound waves create gas bubbles or cavities that, after a certain number of cycles, achieve a critical size, collapsing and releasing large amounts of energy.
Additionally, acoustic cavitation occurs by increasing local temperature and forming hydroxyl radicals that damage the cell wall [ 1 ]. Besides being a scalable technique with low operational cost, it is possible to optimize some parameters e. Moreover, the promising use of ultrasonication for large-scale treatment of microalgal biomass has been previously pointed out by Adam et al. However, this technique is not very effective for some microalgae species and it is commonly combined with chemical treatments for efficiency improvement and to reduce energy demand [ 4 ] [ 8 ].
Besides being energetically efficient and scalable, PEF also presents selectivity and fast processing time. However, despite the low operational costs, equipment is expensive and the technique depends on medium conductivity, limiting its use [ 18 ]. The disruption mechanism induced by PEF is based on electroporation as a result of transient membrane-permeabilization and electrophoretic movements into the cell caused by charged species [ 19 ].
The electroporation can be reversible 0. Several parameters can influence PEF efficiency such as the electric field strength, pulse shape, width , frequency, physicochemical parameters temperature, pH and conductivity , operational time and cell wall properties [ 21 ].
Lam et al. These results demonstrate that despite being a promising technology, there are still challenges to overcome for its establishment as a suitable technology for mild or large-scale microalgae biorefinery. However, PEF is a widely employed technology in the food industry that counts on specialized companies that are also involved in projects, approaching the use of PEF to stimulate growth and improve extraction of high-value compounds from microalgae.
In this project the effectiveness of low-intensity PEF treatments to stimulate growth and also enhance the extraction of several compounds e. The group reported significant difference between the phycocyanin extraction yield in PEF-treated Thus, this kind of initiative may accelerate the implementation of PEF in microalgae biorefineries. Thermal treatments are physical methods that use heat to promote cell disruption, such as thermolysis [ 25 ] , autoclaving [ 26 ] and steam explosion [ 27 ].
Despite being simple technologies with low maintenance cost, the physical disruption is frequently associated with low efficiency, high energy consumption, generation of large amounts of undesirable cell debris and applicability limited by thermal resistance of the target product to be extracted.
However, as shown in Table 1, steam explosion has many advantages compared to conventional thermal treatments. The cell disruption occurs when the system is depressurized to return to room conditions [ 28 ]. Lorente et al. In this study, steam explosion as pretreatment showed the highest lipid yield for all species, especially for N.
Furthermore, this technique promotes carbohydrates hydrolysis, forming aqueous phase rich in monomeric sugars suitable for subsequent fermentation. In Table 1 are summarized the main mechanical and physical methods for cell disruption, highlighting the principle of cell disruption and the main advantages and disadvantages of each of them. Table 1.
Main mechanical and physical methods for cell disruption: mechanism of disruption, advantages, disadvantages and remarks. High-pressure homogenization [ 1 ] [ 29 ] [ 30 ]. Microwave irradiation [ 2 ] [ 29 ] [ 30 ]. Pulsed electric fields [ 2 ] [ 30 ]. Autoclaving [ 28 ] [ 29 ]. Steam explosion [ 28 ] [ 29 ]. Websites: a www. Non-mechanical methods comprise chemical methods that may use acid or alkaline treatments [ 31 ] [ 32 ] [ 33 ] and detergents [ 34 ] , osmotic shock [ 35 ] or enzymatic treatments [ 36 ].
Chemicals such as solvents, acids, alkali, hypochlorites, antibiotics, detergents, among others, can interact with components of the microalgal cell wall causing deformations and promoting cell disruption. Despite being a simple and well-known technique, the use of chemicals raises several environmental and economic concerns, especially for industrial scale.
Further, the chemical contamination of the target product limits its application, once the active compound is generally classified as non-food grade [ 1 ]. However, the use of surfactants, which can both help harvesting biomass and promote cell disruption, is an interesting option in large scale for species whose harvest is a limiting factor. The most commonly used surfactants are long-chain alkyl groups C12 to C16 containing quaternary-ammonium cation.
These compounds have hydrophobic ends capable of adsorbing or attaching to cell membranes, and once this happens, the quaternary cation makes the cell charge to become less negative, favoring cell aggregation [ 37 ]. Lai et al. Moreover, small amounts of CTAB 0. Recently, Alhattab et al. However, they also observed that although the extraction was higher, the FAME composition changed significantly. This possibility of modulating FAME composition may be interesting depending on the desired application, but for biodiesel production, they found that the most suitable composition was obtained with pure sc-CO 2.
Figure 2 shows the SEM micrograph of the Phaeodactylum tricornutum cells treatead with acid [ 40 ]. Figure 2.
The presence of a high concentration of solute salt, dextran or polyethylene glycol PEG leads to a decrease of osmotic pressure, causing cell wall damage, increasing its permeability and, consequently, allowing the release of intracellular compounds. In this respect, Rakesh et al.
MCC30, Botryococcus sp. MCC31, Botryococcus sp. They found that by applying osmotic shock improved lipid extraction could be achieved for Botryococcus sp.
Furthermore, the composition of the extracts varied with the treatment used to facilitate the extraction. The primary concern should be to disrupt the lifecycle of a toxic cyanobacterial bloom in such a way as to preserve the dead cells with their toxins largely intact.
That way they are easier to remove using conventional or enhanced coagulation, flocculation and filtration methods. Depending on the method or chemical compound used, treatment of toxic cyanobacterial blooms can cause catastrophic cell lysis and a spike in the concentration of free cyanotoxins in the water column.
That much is true. But with the right testing and treatment strategy, you can reduce overall toxicity while preventing or minimizing spikes in cyanotoxin concentrations. Cell lysis is a natural part of the cell cycle. All cells die at some point, either through apoptosis programmed cell death or an external factor such as consumption and digestion by other organisms or contact with a biocidal agent. Like all organisms, cyanobacterial cells naturally phase through the different stages of their lifecycle.
They typically reach cell lysis and death at a pace that remains in balance with the surrounding environment. When cyanobacterial cells die at a steady rate, neighboring organisms consume the dead cells and any released cytoplasmic material.
The potential negative impacts of cell lysis can be avoided when treatment mimics this natural process. If a treatment is too harsh, cyanobacterial cells may die too quickly and release cyanotoxins into the water depending on what physical or chemical factor was responsible.
When the rate of catastrophic cell death surpasses what can be consumed by other organisms, the concentration of cyanotoxins in the water column spikes. On the other hand, controlled treatment can chemically induce cell death without forcing catastrophic cell ruptures and radically destabilizing the aquatic ecosystem. A well-designed treatment regimen can prevent cyanobacterial growth by inhibiting photosynthesis; this prevents further cell reproduction and cyanotoxin production.
However, the treatment must not cause rapid cell lysis. It should stop growth but not cause lysis to avoid spikes in the concentration of toxins in the water column. Cell death can result from various kinds of cellular malfunctions. Cell lysis is only one such malfunction. Some cells remain intact during cell death without releasing any cytoplasmic material. More often, cells die with only a small amount of membrane damage and cytoplasmic material leakage.
Their metabolic functions simply fail, and they die before releasing the majority of their toxins. Thus, cell lysis is not the only path to cell death. When cell lysis does occur, it has various degrees of severity.
Proper treatment can minimize the severity of cell lysis and reduce the chance that cells will release high concentrations of hard-to-remove cyanotoxins into the water column. The preferred process is to allow slow leakage of intracellular materials while the cells die.
Because some treatments cause aggressive and abrupt cell rupture lysis , there is a misconception that all treatments target the cell in the same way. In fact, cell lysis can be stabilized so that cells break down slowly and consistently rather than rupturing abruptly and catastrophically. With the right treatment, under controlled conditions, the rate of cell lysis is often compatible with the rate of bacterial decomposition of cyanobacterial cells and their cellular contents.
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