Learning basic microbiology before you apply for brewing jobs

Why microbiology matters on day one

A new assistant brewer spends a large share of their time cleaning. Tanks, hoses, heat exchangers, kegs and fittings. Every one of those jobs exists because of microbes. Understanding why you clean and what you are trying to remove makes you better at it and less likely to cut corners when you are tired.

It also shows at interview. A candidate who can explain the difference between cleaning and sanitising, or why wort is far more vulnerable than finished beer, stands out from one who just says they are hard working. Our guide to jobs in a brewery shows how much of entry level work is hygiene.

Yeast is the microbe you want

Brewing yeast is a single-celled fungus, mostly Saccharomyces cerevisiae for ales and Saccharomyces pastorianus for lagers. It eats sugar and makes alcohol, carbon dioxide and flavour compounds. Learn the basics of its life cycle in the fermenter:

• Lag phase. Yeast adapts to the wort, takes up oxygen and nutrients and prepares to grow.
• Growth phase. Cells multiply and fermentation becomes vigorous.
• Stationary phase. Growth slows, yeast cleans up by-products such as diacetyl and settles out.

Know the typical numbers too. Ale fermentations often run at around 18 to 22 °C and lagers at around 8 to 13 °C. Brewers commonly pitch about 0.75 million cells per millilitre per degree Plato for ales and roughly double for lagers.

The microbes you do not want

Beer is a hostile place for most microbes. Alcohol, low pH, hop compounds, carbon dioxide and a lack of oxygen keep most of them out. A few have adapted to live in it anyway:

• Lactobacillus makes lactic acid and sours beer.
• Pediococcus sours beer and produces diacetyl, giving a buttery taste. It can also make beer ropy.
• Acetobacter turns alcohol into acetic acid where oxygen gets in, giving a vinegar note.
• Wild yeasts, including Brettanomyces and diastatic Saccharomyces, can over-attenuate beer, add unwanted flavours and cause gushing in packs.

Wort is more at risk than beer, because it has sugar, oxygen and no alcohol yet. That is why the cold side of the brewery, from heat exchanger to fermenter, needs the strictest hygiene.

Cleaning and sanitising are different jobs

Cleaning removes soil: protein, hop residue, yeast and beer stone. Sanitising reduces the remaining microbes to a safe level. You cannot sanitise a dirty surface properly, because soil protects the microbes underneath.

A typical cleaning in place (CIP) cycle in a brewery runs a pre-rinse, a hot caustic wash, a rinse, often an acid wash to remove beer stone and mineral deposits, a final rinse and then a sanitiser before use. Caustic is often used at around 1 to 2% and well above room temperature. Know the safety rules for these chemicals before you touch them: gloves, eye protection and never mixing chemicals.

Simple lab skills that help

Even a small brewery does some microbiology. Learning these basics before you apply puts you ahead:

• Using a microscope and focusing on yeast cells.
• Counting cells with a haemocytometer.
• Staining with methylene blue to check viability.
• Aseptic technique: flaming loops, working near a flame and keeping plates closed.
• Streaking and reading simple plates.

Know the basic arithmetic of a count too. On a standard haemocytometer, the cell count in the large central square multiplied by 10,000 gives cells per millilitre, before you correct for any dilution. Getting that dilution factor wrong is the most common reason a count comes out ten or a hundred times off.

If you have no lab access, a basic student microscope and a sachet of dried yeast are enough to practise focusing and counting. It will not make you a lab technician, but it will make the words familiar.

How to learn it without a degree

Start with the brewing side, not general microbiology textbooks. Read about yeast and fermentation in a good brewing book. Learn the names and effects of the common spoilers. Then learn cleaning and sanitising in detail, because that is what you will do every day. Our guide to brewing careers for microbiology graduates shows the deeper path if you want it.

The weakness of self-study is that it stays abstract. You can read about diacetyl and still not know what a buttery lager smells like, or how a brewer decides a slow fermentation needs action. A structured course with a working brewer closes that gap faster.

Your first step: write down, from memory, the steps of a CIP cycle and the job each step does. Then check your list against a brewing textbook or ask a brewer. Every gap is something to learn before your interview.