A marine microorganism is not a freshwater one that happens to live in a salty place. Its membrane lipids, its transporters and its whole osmotic strategy are built around dissolved salts at roughly seawater strength, and the standard medium still used to grow these isolates carries a little over 31 grams of salts per litre. Move such a strain onto an ordinary low-salt plate and it often survives without thriving, quietly dropping the traits that made it interesting: exopolysaccharide production slows, pigment formation fades, and the cold-adapted or barotolerant behaviour that was the reason for isolating it in the first place stops showing up. For anyone buying rather than culturing, the consequence is simple to state. A marine biomass is a defined material with a salinity history attached to it, not a generic fermentation powder that can be swapped in from another supplier without checking anything.
Eata Marisource supplies that material in whatever state the work requires. Some customers need the organism alive and able to divide, so we ship slants, plates, broth cultures, cryopreserved tubes and freeze-dried ampoules. Others need the cells as a raw material and have no interest in their viability at all, so we supply chilled wet paste, spray- or freeze-dried powder, heat- or chemically inactivated biomass, washed resting cells for biotransformation, alginate-immobilised preparations, and cell-wall or lysate fractions separated from the rest of the cell. The organism groups behind those formats run from common coastal heterotrophs through halophilic archaea and marine yeasts to the thraustochytrids that accumulate most of their dry weight as lipid. What follows is a description of each format, the numbers that come with it, and the points where a batch can go wrong.
The first difference most laboratories notice is nutritional, and it is easy to misread. A marine isolate plated onto a rich low-salt medium may grow reasonably well and still be the wrong material six transfers later. Salt tolerance is not a single switch. Some strains are merely tolerant and grow across almost the whole range from fresh water to saturated brine; others are genuinely halophilic and will not divide below a threshold that can sit anywhere between one and ten per cent sodium chloride. Halophilic archaea take the strategy further and keep their cytoplasm at molar salt concentrations, which is why their proteins need salt to hold their shape and why a lysate prepared in deionised water loses activity before the assay even starts.
Two further habits of marine cells shape everything downstream. Many of them live wrapped in exopolysaccharide, either attached to the cell surface or released into the broth, and that layer changes how the broth behaves during harvesting: it raises viscosity, fouls membranes and makes a pellet that slides instead of packing. And a great many marine bacteria regulate their internal osmotic balance with small organic solutes rather than with salt, accumulating compounds such as ectoine and glycine betaine when the outside gets salty. Those molecules contain nitrogen. A laboratory that measures nitrogen and multiplies by a protein factor will therefore over-report the protein content of a halophilic biomass, sometimes by a wide margin, without any analytical error having occurred. We flag this on the specification sheet whenever a batch was grown at high salinity.
Provenance is not decoration. The environment a strain was isolated from predicts, fairly reliably, the temperature, salinity and nutrient conditions it will tolerate, and it also predicts how awkward the material will be to produce at scale. Our own catalogue is built around six collection environments, and we keep the isolation record with every strain so that a customer can judge whether a particular isolate is likely to behave in their process.
| Source environment | What it usually yields | Why that matters to a buyer |
| Coastal seawater and surface sediment | Fast-growing Gram-negative heterotrophs that divide best at 1 to 4% sodium chloride | The quickest route to a robust production strain with well-documented growth behaviour |
| Mangrove leaf litter and decaying wood | Thraustochytrids and marine fungi with high lipid or strong hydrolytic output | Lipid-rich biomass in 48 to 96 hours of fed-batch growth, without any light supply |
| Hypersaline brines, salt pans and solar salterns | Halophilic archaea and Halomonas-type bacteria that grow at 10 to 25% salt | Processes that can be run open and unsterile because almost nothing else survives the brine |
| Deep sediment and hydrothermal plumes | Actinomycetes and slow-growing specialists | Secondary metabolite producers that need pressure or elevated temperature to behave normally |
| Sea ice and cold surface water | Psychrophiles carrying cold-active enzymes | Conversions run at 10 to 20 °C, where spoilage of the reaction mixture is slow |
| Sponge and invertebrate surfaces | Symbionts with chemistry the host does not make itself | Material that will not grow on its own in most laboratories, so it has to be taken from the tissue |
Six organism groups cover nearly every enquiry we receive, and each one has a characteristic that decides how the biomass has to be handled. The table below is the blunt version: what we routinely hold, what customers use it for, and the single point that most often causes trouble after delivery.
| Group | Typical forms | Common uses | The point to watch |
| Marine bacteria, including Pseudoalteromonas, Vibrio, Bacillus and Halomonas | Wet paste, spray-dried or freeze-dried powder, live slant, cryopreserved tube | Inoculum, enzyme source, whole-cell biocatalysis, metal-binding biomass | Residual medium salts inflate the dry mass unless the wash regime is agreed in advance |
| Halophilic archaea | Dried orange-red powder, wet paste, live slant | Salt-tolerant enzymes, carotenoid-rich biomass, high-salinity process studies | Their proteins need salt to stay folded, so lysis in low-salt buffer destroys the activity |
| Marine yeasts and filamentous fungi | Dried cream or tan powder, plates, slants | Glucan-rich cell walls, lipases and proteases, nutrient-grade biomass | The cell wall resists simple disruption and usually needs mechanical or enzymatic breakage |
| Thraustochytrids, including Schizochytrium and Aurantiochytrium | Dried powder, lipid-rich flakes, wet cream | DHA-rich biomass, single-cell oil work, nutrition and aquaculture research | The lipid oxidises readily, so headspace and packaging decide the shelf life |
| Marine cyanobacteria | Dried blue-green powder, liquid culture, immobilised preparations | Pigment recovery, nitrogen fixation studies, biosorption of metals | Filamentous strains shear in a stirred tank; growth geometry has to be chosen carefully |
| Washed resting cells and immobilised cells | Chilled cell suspension, alginate beads, packed columns | Stereo- and regioselective conversions that need no growth | Activity drifts as the culture leaves exponential phase, so harvest timing is part of the specification |
One strain can leave us in eight different states, and the choice between them is about logistics rather than biology. A slant is the cheapest way to move a living culture, and also the shortest-lived: the agar dries out long before the cells die, which is why we quote weeks rather than years for that format. A cryopreserved tube at minus eighty degrees is the most reliable way to move a living culture and the least convenient to use, because it has to travel on dry ice and it cannot be refrozen after it thaws. A freeze-dried ampoule sits between the two: it ships at ambient temperature, has a long shelf life, and needs one round of revival and subculture before it is fully awake.
Slant cultures are the simplest way to move a living marine strain, and the shortest-lived of the living formats.
Where the customer wants material rather than a culture, viability stops mattering and the specification shifts to composition. We supply wet paste straight from the centrifuge for processors who intend to use it within days, and dried powder for everyone else, with the drying route chosen to suit the cell. Spray drying is cheaper per kilogram but exposes the cells to an inlet air temperature that a fragile strain will not survive in large numbers, while freeze-drying is gentler and produces a porous cake that rehydrates quickly. Washed resting cells are a different product again: no nutrients, no growth medium, just a dense suspension of cells whose enzymes are still working, which is what a biotransformation needs. The same batch can be split at any of those points, so a customer can order a kilogram of dried biomass and a cryopreserved tube of the identical culture in the same shipment.
Almost every marine isolate in circulation is grown on a formulation that was first described decades ago and has never been improved on in any practical sense. Its salt content is the reason the medium exists. Roughly thirty-one grams of dissolved salts per litre sit behind the carbon and nitrogen sources, and if a customer's own protocol substitutes a general-purpose medium, the first symptom is usually a lag phase that never quite ends.
| Component | g per litre | Component | g per litre |
| Peptone | 5.0 | Potassium chloride | 0.55 |
| Yeast extract | 1.0 | Sodium carbonate | 0.16 |
| Ferric citrate | 0.1 | Potassium bromide | 0.08 |
| Sodium chloride | 19.45 | Strontium chloride | 0.034 |
| Magnesium chloride | 5.98 | Boric acid | 0.022 |
| Sodium sulfate | 3.24 | Disodium phosphate | 0.008 |
| Calcium chloride | 1.80 | Sodium silicate | 0.004 |
| pH, measured at 25 °C | 7.4 to 7.8 | Sodium fluoride | 0.0024 |
| Inorganic salts, summed | about 31.3 | Agar, for solid medium only | 15.0 |
Salt is also the reason halophiles have become commercially interesting. A vessel running at high salinity and alkaline pH is a hostile place for the organisms that normally spoil a fermentation, so the process can be run open and unsterile, without the energy cost of sterilising everything in contact with the broth. Pilot work on Halomonas bluephagenesis has reached 82.6 g per litre of cell dry weight in a thousand-litre open fermentation within 48 hours, and 100 g per litre in 36 hours after scale-up to five thousand litres. The same high salinity then becomes a downstream cost, because the salts have to be washed out of the product, and engineered variants adapted to low salt have since reached 76 g per litre of cell dry weight at only 5 g per litre of sodium chloride in 44 hours, still without contamination. Read from the buying side, the message is that the salinity of the growth medium belongs in the specification, because it follows the cells out of the vessel.
Centrifugation gives a paste, and a paste is mostly liquid. That liquid is spent medium, and spent medium is brine. A worked example makes the size of the problem clear. One gram of dry cells harvested as a paste at twenty per cent solids carries about four millilitres of residual broth with it, and at just over thirty-one grams of salts per litre that is roughly 125 milligrams of salt, or about twelve per cent of the declared dry mass. Nothing is wrong with the analysis in that number; the material simply contains what it contains. Any quotation that specifies ash without specifying how many washes precede it is leaving the most variable figure in the whole specification undefined.
Wet paste leaving the centrifuge still carries spent medium, and with it the salts that decide the ash figure.
Washing has a sharp edge, and it is worth knowing where it lies. Rinsing marine cells with deionised water removes the salt beautifully and also bursts a good proportion of the cells by osmotic shock, which is exactly what you want if the product is a biosorbent and exactly what you must avoid if the product is a live culture. The wash therefore has to run at a defined salinity, and the temperature matters too, because a marine strain that tolerates four degrees in the growth vessel can still lose viability in a slow chilled centrifuge.
| Wash regime | Liquid left with the cells | Salt carried per gram of dry cells | Effect on the cells |
| None | About 4 mL of spent broth | Roughly 125 mg, or about 12% of the dry mass | Cells intact; any low-ash specification is impossible to meet |
| One wash, 2% sodium chloride, 4 °C | About 1 mL | Roughly 31 mg, or about 3% | Viable count essentially unchanged |
| Two washes, cold, same salinity | Well under 0.5 mL | Under 15 mg | A small fall in count if the centrifuge is run slowly |
| Deionised water rinse | Negligible | Salt almost entirely removed | Marine cells lyse; correct for a biosorbent, wrong for a living culture |
Freeze-drying is described as gentle, and compared with spray drying it is, but a cell passing through it is exposed to four stresses in sequence: ice crystals forming around it, an osmotic gradient as the solutes concentrate, dehydration of the membrane, and a pH shift in the remaining liquid. Damage accumulates across the whole cycle rather than arriving at one step, which is why the protectant, the cooling rate and the cell density all have to be settled together. Some preparations are almost entirely lost. One controlled study found no survival at all in a freeze-dried sample that was suspended in quarter-strength Ringer's solution without a protectant, which is the clearest possible argument for not skipping that part of the formulation.
A freeze-dried cake broken into fragments; the open pore structure is what allows it to rehydrate quickly.
The protectant has to suit the step. Glycerol is a good cryoprotectant for freezing and a poor one for drying, because it protects against ice damage rather than against the loss of the water shell around a membrane. The sugars work the other way. Trehalose holds an anhydrous glass transition near 110 °C, so a dried matrix containing it stays rigid and unreactive at room temperature. Skim milk has a glass transition near 92 °C, but water lowers it fast: at a moisture content of about 4.5 grams per hundred grams of powder the transition drops to roughly 47 °C, and once the storage temperature approaches that figure the matrix starts to move and the cells inside it lose viability. That single number explains why the same powder keeps for years at four degrees and fails within months on a shelf at twenty-five.
| Method | Protectant | What to expect | Best suited to |
| Freezing at −80 °C | 15% v/v glycerol | The established laboratory default, but recovery after thaw varies widely between strains | Working stocks that will be revived within a year or two |
| Freezing at −80 °C | 10% w/v skim milk | In a six-species comparison skim milk kept cells viable significantly longer after thawing than 15% glycerol, and over 90% of strains frozen in it were recovered | Strains that survive a freeze-thaw cycle badly |
| Liquid nitrogen | 8% glycerol with 3.5% trehalose, frozen rapidly | In a ten-year study this gave the highest survival and held productivity at 92.9% of the original level | Master stocks kept for many years |
| Freeze-drying | Skim milk with about 6% trehalose | The best format for shipping at ambient temperature; skim milk matrices have given recoveries above 99% in published work | Ampoules and vials sent long distances |
| Spray drying | Carrier plus a protective colloid | Lower cost per kilogram, with the inlet air temperature setting the ceiling on survival | Bulk biomass where a partial loss of count is acceptable |
Not every application needs a living cell, and the numbers on inactivated material are better than most buyers expect. A marine Bacillus tested against lead held 216.8 milligrams of metal per gram as living biomass and 207.4 milligrams per gram after the cells had been killed, which is a difference of about four per cent. The same pattern held for cadmium on a halophilic strain: 280.2 milligrams per gram alive and 269.6 milligrams per gram dead. What that four per cent buys is a material that needs no cold chain, no nutrients, no incubation and no containment, and that cannot start growing in a customer's wastewater stream at three in the morning.
Steam sterilisation is one of several ways live biomass is converted into a stable, non-viable biosorbent.
Immobilising the cells changes the arithmetic far more than killing them does. A marine actinomycete tested as free cells removed cadmium at 5.1 milligrams per gram, and the same organism immobilised in alginate reached 114.5 milligrams per gram, because the beads hold a dense population in contact with the liquid instead of letting it settle out. That is more than a twenty-fold difference in capacity per gram of biomass, and it is achieved with less than a twentieth of the cell mass in the vessel.
| Sorption target | Live biomass | Inactivated biomass | Conditions |
| Lead(II), marine Bacillus xiamenensis PbRPSD202, isolated from a port environment | 216.8 mg per g | 207.4 mg per g | 4% w/v sodium chloride, pH 6.0, 35 °C, 140 rpm, 1 g per litre dose |
| Cadmium(II), halophilic Bacillus altitudinis CdRPSD103, from sea sediment | 280.2 mg per g | 269.6 mg per g | 500 mg per litre initial metal; the strain grows at up to 13% w/v sodium chloride |
| Cadmium(II), marine actinomycete Nocardiopsis dassonvillei, free cells | 5.1 mg per g with 2.5 g of biomass | Not tested as a separate case | 600 mg per litre cadmium, 86% of the metal removed |
| Cadmium(II), same strain immobilised in alginate beads | 114.5 mg per g with 0.12 g of biomass | Not tested as a separate case | 600 mg per litre cadmium, 92.4% of the metal removed |
| Copper(II), marine cyanobacterial cultures | Up to 83.9 mg per g of dry weight | Not applied | The highest of four marine strains compared in a single study |
Two practical points follow from that table. First, the sorbent dose has an optimum and it is not the highest one. In the cyanobacterial comparison the most concentrated suspensions gave the lowest uptake per gram, because the binding sites end up competing with each other for the same metal. Second, the binding chemistry is ordinary surface chemistry: hydroxyl, carboxyl, carbonyl and amine groups on the cell envelope, with the metal held by ion exchange, by complexation and in places by precipitation onto the surface. That is why the capacity is sensitive to pH, and why a supplier who quotes a capacity without quoting the pH at which it was measured has not told you very much.
A viable count is a number produced by a defined procedure, and it is meaningless without the procedure attached. Take the same marine culture and plate it on a medium containing two per cent sodium chloride and on one containing none, and the two counts can differ by orders of magnitude, not because the cells changed but because a proportion of them cannot divide without the salts they evolved with. Add the well-documented viable-but-not-culturable state, in which cells are alive and metabolically active but will not form colonies on any plate, and the gap between a plate count and the true number of living cells becomes something a buyer should know about before writing it into a purchase specification.
Automated counting returns a total cell figure, which is not the same quantity as a colony count.
It also helps to know what counts are realistically achieved in a dried product. A patented route to marine bacterial powder reports 2.43 × 10¹⁰ CFU per gram after adsorption onto a carrier and milling to 300 mesh, while commercial single-cell-protein biomass is traded with a stated figure of 1 × 10⁹ CFU per gram. Those two numbers describe different organisms and different drying routes, and the honest conclusion is that a count cannot be transferred from one product to another.
Which number you need depends entirely on what you intend to do with the material. A laboratory reviving a culture for experiments needs a colony count on the medium the strain was isolated with, together with the incubation time, because that is the only figure it can act on. A processor using the biomass as a biosorbent does not need a count at all and should be asking for ash, moisture, particle size and surface chemistry instead. A group using washed cells for a conversion needs a defined activity, measured on a stated substrate under stated conditions, because a viable count correlates with that activity rather than equalling it.
| Method | What it actually measures | Where it misleads |
| Colony count on the strain's own medium | Cells able to divide and form a visible colony | Falls sharply if the plating medium is lower in salt than the one the strain was isolated with |
| Direct microscopic or flow count | All cells with an intact structure | Cannot distinguish a live cell from one that died an hour ago |
| Automated image-based counting | Cells separated by shape and staining | Entirely dependent on the staining chemistry the instrument is configured for |
| Gene copy quantification | Genomes present in the sample | Says nothing about whether the cells carrying them are alive |
| Optical density or dry weight | Total biomass | The conversion factor is strain-specific and shifts with medium and growth phase |
| Defined enzyme or conversion activity | The function the customer actually needs | Has to be measured under the conditions of use, so it cannot be a generic catalogue number |
Composition figures for microbial biomass are wide because the material genuinely is variable, and the widest ranges belong to the oleaginous organisms. Across the thraustochytrids, total lipid in the dry biomass has been reported anywhere between 36 and 84 per cent, with an average near 62 per cent, and most of that spread comes from strain and harvest time rather than from analytical method. A buyer who needs a reproducible feedstock should therefore treat the range as a starting point and ask for the value on the lot in front of them.
| Parameter | Reported range | Why it is worth reading carefully |
| Total lipid in the dry biomass | 36 to 84%, averaging about 62% | The spread reflects strain and harvest point more than the extraction method used |
| Triacylglycerol share of the total lipid | Above 90% | Neutral lipid stored in bodies rather than membrane lipid, which is why the oil separates cleanly |
| DHA as a share of total fatty acids | 32 to 38% in Schizochytrium limacinum SR21, approaching 40% in some strains | Palmitic acid sits at 45 to 51% in the same material and competes for the same price |
| DHA as a share of whole dry biomass | Above 10% of dry matter in commonly traded material | The figure to compare against a fish oil at roughly 24% when setting a formulation cost |
| Dry biomass reached in 96 hours | Above 100 g per litre in high-productivity strains | Fed-batch over 48 to 96 hours is the usual production route |
| Cell diameter | 9 to 14 µm | Large enough to harvest gently, which is why these organisms tolerate simple separations |
Every lot leaves with a sheet that names the method as well as the result, because the same material gives different answers under different assays and a number without a method behind it cannot be compared with a previous lot, let alone with another supplier's. Where a test depends on a choice, the choice is printed next to it. Protein figures name the conversion factor used and flag whether the culture was grown at high salinity. Viable counts name the medium and the incubation time. Sorption capacities are only ever quoted with the pH, temperature and salinity at which they were measured.
| Test | What it establishes | How it is reported |
| Appearance and odour | Consistency from one batch to the next | A written description with a retained photograph of the lot |
| Moisture | How the powder will behave in storage | Loss on drying or Karl Fischer titration, whichever was agreed with the customer |
| Ash and residual salt | How much of the declared mass is not cell material | Gravimetric, quoted against a stated number of washes at a stated salinity |
| Viable count | Living cells per gram or per millilitre | Colony count on the isolation medium, with incubation time and temperature given |
| Purity | That nothing else is growing alongside the intended organism | Streak plate plus a read of the ribosomal gene, checked against the deposited sequence |
| Protein, lipid or pigment content | The part of the composition that carries the value | The assay is named, since nitrogen conversion and spectroscopic methods diverge on the same sample |
| Particle size | How the powder will flow and disperse in the customer's process | Laser diffraction on the dried form |
| Heavy metals and residual solvents | Process hygiene from medium to final drying | Measured by an external laboratory and reported for the lot |
Three things destroy stored biomass, and all three are controllable. Moisture is the first: a dry powder whose water activity is low enough is effectively inert, and one that has picked up water from the air is neither inert nor stable. Oxygen is the second, and it attacks the lipid fraction long before it attacks anything else, which is why oleaginous biomass is packed with an inert headspace. Heat is the third, and it works through the glass transition described earlier, softening the protective matrix until the cells inside it start to degrade. Dust control is a fourth consideration at production scale and a straightforward one to meet: an enclosed transfer line keeps the powder out of the room and the room's humidity out of the powder.
Moving dried biomass through an enclosed screw conveyor keeps both dust and ambient moisture away from the product.
| Format | Recommended storage | Working life we quote | Handling note |
| Freeze-dried powder in a sealed ampoule or vial | 2 to 8 °C | Several years for a well-protected preparation | Open once and use it; do not return a part-used vial to the cold room |
| Agar slant | 2 to 8 °C | About one to three months before subculture | The medium dries out well before the culture dies |
| Agar plate | 4 °C | About one week | Asked for only when a living plate is genuinely needed |
| Broth culture | 4 °C | About one week | Travels badly; a slant or a cryopreserved tube is usually the better choice |
| Cryopreserved tube | −80 °C or below | One to two years as a general rule | Never refreeze a tube that has thawed |
| Wet cell paste | Fresh, or −20 °C for longer periods | Days at 4 °C | Freeze slowly if the cells are expected to survive it |
| Dried bulk biomass | Cool, dry and sealed | Set by the water activity and the headspace of the pack | Lipid-rich material needs an inert gas headspace |
Most problems reported against a microbial biomass turn out to be conditions rather than material, and the list below covers the cases we see repeatedly. It is worth working through it before assuming a lot has failed, because in several of these situations the batch is behaving exactly as it should and the process around it is not.
| Symptom | Usual cause | What to do |
| Count on arrival below the figure on the sheet | Freeze-thaw damage in transit, or a vial that was opened and put back | Request a cryopreserved tube for strains that travel badly, or a dry format with a higher loading |
| Growth is slow, or the first plate stays empty | The plating medium is not the one the strain was isolated with, usually too little salt | Check the medium against the sheet; most of our marine isolates need 2 to 4% sodium chloride |
| Powder has caked into a hard block | Moisture taken up after the container was opened | Keep a desiccant in the container and let the vial reach room temperature before opening it |
| Colour has darkened over a few months | Oxidation of the lipid fraction | Ask for an inert headspace and an opaque pack on the next order |
| Biosorption capacity below the quoted figure | pH away from the optimum, or a biomass dose that is too high | Reduce the dose; uptake per gram falls once the suspension becomes crowded |
| The pellet will not resuspend | Cells lysed during drying and released their contents | Move to a gentler protectant, or accept the lysate and use it as a lysate |
| An odour of solvent in the powder | Carry-over from a downstream washing or extraction step | Increase the number of washes and record the change on the sheet |
The formats above are starting points rather than a fixed range, and most of what we ship is adjusted somewhere between the fermenter and the packing line. If a strain is not already in the catalogue, we will isolate from a sample you send and take it through to a material you can work with. If the growth conditions in your process differ from ours, we would rather match them than ask you to adapt, because a biomass grown under the customer's own temperature and salinity behaves far more predictably in the customer's own vessel.
| Element | Range we work in |
| Salinity of the growth medium | From 0.1% up to about 25% w/v sodium chloride |
| Growth temperature | From 4 °C for cold-adapted strains up to 45 °C |
| Inactivation | Thermal, chemical, or none at all if the cells are needed alive |
| Washing regime | None up to three chilled washes at a stated salinity |
| Drying route | Freeze-dried, spray-dried, or supplied as a wet paste |
| Particle size | Coarse granules through to a finely milled powder |
| Packaging | Laboratory units from 25 g, with bulk formats above 1 kg |
| Documentation | Whatever the receiving laboratory's quality system asks for |
| Strain sourcing | Isolation from a sample you provide, or material matched to a published record |
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