Organism
Saccharomyces bayanus
A name applied both to a hybrid Saccharomyces lineage and, loosely, to a whole class of commercial high-alcohol yeasts, and one of the least stable names in fermentation microbiology.
- Kind
- Yeast
- Binomial
- Saccharomyces bayanus
- Role
- Primary fermentation, Secondary fermentation
What it does
- Ferments sugar to ethanol, with lineages sold under this name generally selected for tolerance of high alcohol and of restarting conditions.
- Ferments fructose comparatively well, which is why yeasts labelled bayanus are commonly recommended for restarting a stuck ferment, where fructose is what remains.
- Withstands the low pH, high alcohol and low nutrient state of a stalled cider better than most, at the cost of a generally more neutral aroma contribution.
- Carries out secondary fermentation in bottle or tank under pressure in traditional-method and transfer-method production, where alcohol tolerance and flocculation matter more than aroma.
- Dominated the opening and middle stages of spontaneous Asturian ferments at 12–15 °C, reaching 33 to 41 per cent of all isolates, before S. cerevisiae displaced it towards the end — so the two share a ferment in sequence rather than one running it throughout.
- Is associated in the literature with cold regions and described as cryotolerant, which is the explanation the Asturian survey offers for finding it where it did.
Conditions it works in
What the organism tolerates and what suppresses it. These are the levers a maker actually has: temperature, acidity, air, alcohol and sulphite.
| Condition | What is recorded |
|---|---|
| Temperature | Ferments across roughly 10–30 °C, with commercial preparations often specified for the cooler half of that range. |
| pH | Tolerates pH down to around 3.0 and below, which is part of why it is used for restarts. |
| Oxygen | Facultative, with the usual *Saccharomyces* sterol requirement at the start. |
| Alcohol tolerance | High: preparations under this name are typically specified to 14–16% ABV or beyond, well above cider’s range. |
| Sulphite tolerance | High relative to wild yeasts, and unaffected by sulphite at normal cider dosing. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
Ethanol
The alcohol yeast makes from fruit sugar, which converts a perishable juice into a keepable drink and carries most of its aroma to the nose.
Carbon dioxide
The other product of fermentation, which protects a cider from air while it is being made and, dissolved in the finished drink, changes both its texture and its perceived acidity.
Glycerol
A syrupy three-carbon alcohol yeast produces as a side reaction of fermentation, which adds weight to a dry cider and is the raw material for one of its more obscure faults.
Succinic acid
An acid made by the yeast rather than the fruit, which adds a salty-bitter edge to a dry cider and, unlike malic acid, cannot be removed by malolactic fermentation.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Stuck fermentation
A fermentation that has stopped before the sugar is gone and will not restart, leaving a sweet, low-alcohol cider that is vulnerable to everything.
Sluggish fermentation
A fermentation that is still moving but far more slowly than it should, extending the period during which the cider is weak, sweet and exposed.
Unwanted refermentation
Fermentation restarting in a sealed container, generating carbon dioxide that was not planned for and pressure that a bottle may not withstand.
Nitrogen deficiency character
The set of characters a nitrogen-starved fermentation produces together — sulphide, a stalled or dragging ferment, harsh higher alcohols and a thin, hard cider.
Excessive sediment
More deposit in the bottle or vessel than the presentation intends, ranging from a normal conditioning yeast layer to a loose sludge that clouds every pour.
Under-carbonation
A cider intended to sparkle that has little or no dissolved gas, usually because the bottle conditioning never started or the closure did not hold.
Yeast haze
Cloudiness from yeast cells that have not settled out, usually because the strain flocculates poorly or the cider has not been left alone long enough.
Where in the process it appears
Inoculated fermentation
Starting a ferment by pitching a chosen yeast culture so that one known strain, rather than the fruit’s resident population, does the work.
Yeast selection
Choosing which cultured strain to pitch, on the basis of the temperature, nitrogen, alcohol and aroma behaviour that separates one commercial yeast from another.
Restarting a stuck fermentation
Diagnosing why a ferment has stopped with sugar remaining, then building an acclimatised starter and stepping the cider into it rather than pitching yeast into the problem.
Secondary fermentation
Any fermentative event that follows the primary ferment — residual sugar refermenting, a deliberate second alcoholic fermentation, or the malolactic conversion of the maturation phase.
Traditional method
A second fermentation in the bottle the cider will be sold in, followed by riddling the deposit into the neck and expelling it, so the drink is both bottle-fermented and clear.
Bottle conditioning
Carbonating cider by letting a second fermentation finish inside the sealed bottle, so the gas is generated where it is going to stay.
Ice concentration
Freezing pressed juice and drawing off the unfrozen fraction, so that water is removed as ice and everything else in the juice is left behind more concentrated.
Wild fermentation
Letting the microflora already present on the fruit and in the press house carry the ferment, in a succession rather than as a single organism.
Fermentation temperature control
Managing the temperature at which a ferment runs, which sets not only how fast it goes but which aromatics survive it and what the finished cider tastes of.
Microbial succession
The ordered handover of a spontaneous ferment from apiculate yeasts to *Saccharomyces* to lactic acid bacteria, and the spoilage organisms waiting at the end of it.
Lees ageing
Deliberately holding a cider or perry on its fine yeast deposit so that autolysing cells release material that changes texture and foam behaviour.
Tank conditioning
Running a second fermentation in a sealed pressure tank so the gas is generated by yeast but the sediment never reaches the bottle.
Yeast nutrition
What a fermenting yeast population actually needs from apple juice — assimilable nitrogen, vitamins and membrane lipids — and what goes wrong when the juice cannot supply it.
Yeast rehydration
Reviving active dried yeast in warm water before pitching, so the cells restore their membranes without being ruptured by the sugar concentration of juice.
Measured figures
Growth limits, tolerances and population counts, shown with the context each was taken in rather than averaged into a constant.
Fermentation temperature12.0–15.0 °C
Villaviciosa, Asturias, Spain, 2001–2002 · Cellar temperature during spontaneous fermentation, no sulphite added · Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31
The conditions in which this species was found to dominate the first and middle thirds of a spontaneous Asturian ferment, reaching 33–41% of all isolates. It is the temperature of an unheated Asturian cellar rather than a preference the organism was tested for, and the finding belongs to it.
The temperature a ferment was actually run at, which governs how much aroma is made and how much is blown off with the gas. Measured in degrees celsius.
Described in full
- Shape
- Two stacked bar charts one above the other, each with four bars. Bars are sampling days 1, 4, 16 and 28 after pressing. Each bar is divided into three segments summing to 100 per cent, and every segment carries its own percentage as a number so the reading does not depend on seeing the fill.
- What is counted
- The share of identified yeast isolates belonging to each group, not the number of cells. A group at 100 per cent was the only thing cultured from that sample; it does not mean nothing else was alive.
- The three groups
- Apiculate yeasts are Hanseniaspora valbyensis, H. uvarum and H. osmophila. Oxidative non-Saccharomyces are Metschnikowia pulcherrima and Pichia guillermondii. Saccharomyces is S. bayanus and S. cerevisiae together.
- Upper chart, pneumatic pressing
- Day 1: apiculate 84, oxidative 16, Saccharomyces 0. Day 4: apiculate 4, oxidative 10, Saccharomyces 86. Day 16: Saccharomyces 100. Day 28: apiculate 38, Saccharomyces 62. This is the textbook succession — non-Saccharomyces first, then a Saccharomyces takeover — except for the tail, where an apiculate yeast comes back at more than a third of isolates.
- Lower chart, traditional pressing
- Day 1: apiculate 66, oxidative 14, Saccharomyces 20. Day 4: apiculate 48, oxidative 4, Saccharomyces 48. Day 16: apiculate 90, Saccharomyces 10. Day 28: apiculate 94, Saccharomyces 6. Here the succession does not happen. Saccharomyces is present from the first day, never dominates, and the ferment finishes overwhelmingly apiculate.
- Why it matters
- Both ferments completed. Both gave dry cider of 6.4 to 6.5 per cent alcohol. The difference between them was how the fruit was pressed, and the account of cider fermentation as a fixed sequence of organisms does not survive it. Apiculate yeasts are usually described as dying out within days under rising alcohol; at 12 to 15 degrees Celsius, without sulphite, and on a must under 110 grams of sugar per litre, one of them ran the whole ferment.
- What this is not
- One cellar, one harvest, four ferments. It is evidence that the succession varies, not a measurement of how often it varies this way.
About Saccharomyces bayanus
This is a record about a name as much as about an organism. Saccharomyces bayanus was described from wine and has been used ever since as a label for alcohol-tolerant, cool-fermenting yeasts, but genome sequencing has shown that the reference material for the species is not a simple lineage: it carries genetic contributions from S. uvarum and from at least one further Saccharomyces species. Meanwhile a substantial proportion of yeast sold commercially as bayanus is, on analysis, S. cerevisiae or a cerevisiae hybrid.
CiderHQ therefore treats bayanus as a functional label with an unsettled taxonomic referent, and says so rather than presenting the name as though it identified one organism. Where a cider maker reaches for a “bayanus” yeast, what they are buying is a specification — high alcohol tolerance, good fructose utilisation, tolerance of adverse restart conditions — and not a guarantee about species identity.
That specification is genuinely useful, and it is why these preparations dominate two jobs in cider: restarting a ferment that has stalled, where the remaining sugar is fructose-rich and the environment is already alcoholic and nutrient-poor; and secondary fermentation in a sealed bottle, where the yeast has to work under pressure against alcohol already present. What they contribute in aroma is usually described as neutral, which for those two jobs is the point.
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- What yeast should i use for cider — CiderHQ does not recommend brands. The choice is between a neutral, reliable strain that lets the fruit show, an aromatic wine strain that adds its own esters, and no addition at all. Alcohol tolerance, cold tolerance and nitrogen demand are the properties worth comparing.
- Why did my cider stop fermenting — The usual causes are a shortage of yeast-available nitrogen, a temperature that has dropped, too much sulphite at the start, or a yeast that has reached its alcohol limit. Check the gravity before assuming anything is wrong: many ciders simply finish.
- Can you make cider from shop bought apple juice — Yes, provided the juice contains no preservative — check for potassium sorbate or benzoate on the label. Pasteurised juice ferments perfectly well once yeast is added, because pasteurisation removes the organisms but not the sugar.
- How do i restart a stuck cider fermentation — Warm the batch gently, then build an active starter and acclimatise it to the cider in stages rather than pitching dry yeast straight in. Yeast dropped into a cold, alcoholic, nutrient-poor liquid usually dies without restarting anything.
- How is sparkling cider made
- Why did my sweetened cider start fermenting again — Live yeast met the sugar that was added back. Sweetening is only stable if the yeast has been removed by sterile filtration, killed by pasteurisation, or held in check by sorbate together with sufficient sulphite.
Where to go next
- All organisms — Grouped by what each does in the ferment, and by what kind of organism it is.
- Compounds — The chemistry this microbiology produces.
- Troubleshooting — Work from the symptom in the glass back to the organism.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
Peer-reviewed literature on cider fermentation microbiology
Various journals · peer-reviewed literature · registered as competent for this subject
Covers the microbial succession of spontaneous cider fermentation, the role of non-Saccharomyces yeasts in the early stages, malolactic conversion by Oenococcus and Lactobacillus species, and the organisms behind the principal spoilage faults.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
Yeast species associated with the spontaneous fermentation of cider
Suárez Valles, Pando Bedriñana, Fernández Tascón, Querol Simón and Rodríguez Madrera, Food Microbiology 24(1):25–31 · peer-reviewed literature · passage verified 2026-08-24 · covers 2001–2002
SERIDA’s survey of what is actually growing in an Asturian cellar during a spontaneous ferment, across two harvests and two pressing technologies. Read in full from the author institution’s open repository (ria.asturias.es, handle 123456789/925) on 2026-08-24. Two things make it worth citing rather than summarising: it identifies its isolates molecularly rather than by colony appearance, and it publishes the analytical composition of the finished ciders alongside the microbiology, so a reader can see the organisms and the numbers they produced in the same paper. It also contradicts the textbook account of apiculate yeasts dying out early, which is why CiderHQ cites it on that point specifically.