Organism
Lachancea thermotolerans
A non-Saccharomyces yeast that makes lactic acid out of sugar, and the one organism that can lower the pH of a cider juice without anything being added to it.
Also called Kluyveromyces thermotolerans.
- Kind
- Yeast
- Binomial
- Lachancea thermotolerans
- Role
- Primary fermentation
What it does
- Diverts part of the sugar it consumes into lactic acid rather than ethanol, so a fermentation it participates in finishes more acidic than it started — the opposite of what malolactic bacteria do.
- Lowers pH as a consequence, by around 0.3 to 0.4 units on apple mash in the one study CiderHQ has found on apple rather than grape.
- Ferments weakly and is not alcohol-tolerant, so it is used sequentially: given the juice for a day or two before Saccharomyces is pitched over it.
- Raises ethyl lactate, which contributes a soft, milky note, and shifts the ester profile more broadly.
- Offers something no other tool in a cider maker’s hands does. Acidifying juice otherwise means adding malic or citric acid, or blending in sharp fruit; this lowers pH biologically.
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 | Grows from roughly 10 °C to 30 °C, tolerating the upper end better than most non-*Saccharomyces* yeasts, which is what the epithet records. |
| pH | Active across juice acidity and drives its own environment downwards as it works. |
| Oxygen | Facultative; used in the aerobic early phase of a sequential inoculation. |
| Alcohol tolerance | Low, generally around 5–9% ABV depending on strain, so it cannot finish a ferment on its own. |
| Sulphite tolerance | Moderate at best. A juice sulphited to suppress spoilage will also suppress this. |
What it produces
Compounds this organism makes. Which organism made a compound usually decides whether it reads as a feature or as a symptom.
Lactic acid
The softer acid that replaces malic when malolactic fermentation runs, halving the acid a cider carries and changing its texture as much as its sharpness.
Ethyl lactate
The slow-forming ester of lactic acid and ethanol, which accumulates after malolactic fermentation and contributes the soft, milky roundness of a long-matured traditional cider.
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.
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.
2-Phenylethanol
The yeast-made alcohol responsible for the rose and honey note in cider, produced from phenylalanine and one of the few floral aromas that is not carried in from the fruit.
Faults it causes
Faults this organism is implicated in. Several are faults only against a particular expectation — the same activity is a signature elsewhere.
Low acidity
A cider without enough acid to give it definition, tasting soft, heavy and dull — and sitting at a pH that leaves it exposed to spoilage organisms.
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.
Microbial haze
Cloudiness caused by a growing population of spoilage organisms, and therefore a symptom of something worse rather than a clarity problem in itself.
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.
Acid adjustment
Correcting the acidity of low-acid juice before fermentation, usually with malic acid, and the difference between the pH question and the titratable acidity question.
Acid balancing
Bringing a cider to the sharpness it needs, which requires separating perceived sharpness from titratable acidity from pH — three related things that do not move together.
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.
Measured figures
Growth limits, tolerances and population counts, shown with the context each was taken in rather than averaged into a constant.
Lactic acid1.1–1.3 g/L
context not recorded · Pre-fermentative acidification of apple mash, reported jointly for L. thermotolerans and Lactiplantibacillus plantarum · Fejzullahu, Kun-Farkas and Kun, Acta Alimentaria 53(3):360–372
The study reports 1.05–1.26 g/L; CiderHQ stores figures at the precision it displays them to, so this is rounded to one decimal and the published values are given here instead of implied by a rendering. Two further limits matter more than the rounding. The range covers both organisms together rather than separating them, and the mash was destined for spirit rather than cider, so the fermentation was not run to the same end point. It is recorded because it is the only figure CiderHQ has for this effect on apple rather than on grape. In the same experiments the pH of the mash fell by 0.29 to 0.40 units — a change rather than a level, which the measurement model has no field for and which is therefore stated in prose on this page rather than tabulated as though it were a pH.
The acid malolactic bacteria make out of malic acid — softer on the palate than the acid it replaces, and in a fully malolactic cider the dominant one. Measured in grams per litre.
About Lachancea thermotolerans
Almost everything a cider maker can do to acid moves it in one direction. Fermentation does not change titratable acidity much; malolactic conversion halves it; ageing on lees and blending with sweet fruit both soften it. The one biological process that goes the other way is this yeast. Lachancea thermotolerans routes part of the sugar it metabolises into lactic acid instead of ethanol, so its fermentation acidifies rather than merely converting.
That matters more in cider than in wine, and it is worth being clear about why, because the literature on this organism is overwhelmingly a wine literature. Traditional cider fruit is defined by low acid, and low acid means high pH — commonly 3.8 or above for a bittersweet-dominated juice. At that pH sulphur dioxide barely functions, lactic bacteria are comfortable, and the ferment is exposed. The conventional answers are to blend in sharp fruit or to add acid directly. A yeast that lowers pH while fermenting is a third option, and it does not depend on having sharp fruit available.
The honest qualification is that the evidence base on apple is thin. One study CiderHQ has found tested it on apple mash — for spirit rather than cider — and reported around 0.3 to 0.4 pH units of reduction and roughly a gram of lactic acid per litre, jointly with a lactic bacterium rather than separately. Everything else transfers from grape must, and grape must is a different substrate at a different pH with twice the sugar. The mechanism is real and well described; how much of it survives the move to a low-nitrogen, low-sugar, high-pH apple juice is not something the published work answers yet.
It is also not a fermenting yeast on its own. It runs out of tolerance well before a cider is dry, so it is used sequentially, with Saccharomyces pitched over it after a day or two — which means anyone using it is running two organisms and inherits the risks of both.
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.
- How does cider ferment — Yeast consumes the sugar in apple juice and produces roughly equal masses of ethanol and carbon dioxide, along with the esters and higher alcohols that give cider much of its aroma. In a wild ferment several yeast species take turns before *Saccharomyces* finishes the job.
- 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 balance acid and tannin in a blend — Acid and tannin do different jobs and cannot substitute for each other: acid gives freshness and microbiological safety, tannin gives structure and length. A blend short of acid tastes flabby however tannic it is.
- How many calories are in cider — Roughly 40 to 60 kcal per 100 ml for most ciders, so a UK pint falls somewhere around 200 to 250 kcal. Alcohol contributes about 7 kcal per gram and residual sugar about 4, so both strength and sweetness matter.
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.
Enhancing fruit spirit quality: Novel approaches to mash acidification techniques
Fejzullahu, Kun-Farkas and Kun, Acta Alimentaria 53(3):360–372 · peer-reviewed literature · retrieved 2026-08-24
Registered because it is the one study CiderHQ found that tests biological acidification on apple mash rather than on grape must. That distinction matters: the extensive Lachancea thermotolerans literature is a wine literature, and a result obtained in grape juice at pH 3.5 with 220 g/L of sugar does not transfer to apple juice at pH 3.9 with 110. Bibliographic record verified through Crossref and the abstract read on 2026-08-24; the full text is behind the publisher’s wall.
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.