Beer, as we know it today, would not exist without nature’s idiosyncrasies. Not only is it remarkable that nature appears tailored to producing beer, but it is also considered suspicious by some. Is it possible that beer provides evidence for intelligent design? Before answering this question, it is first necessary to understand a little about the brewing process and the history of beer.

Hops, History and Hygiene

Historically, beer aided the nourishment of people living without the guarantee of safe drinking water.[1] As a low alcohol, high calorie beverage, beer was pathogen-free and nutritious. Throughout the world, beer-drinking communities have enjoyed these benefits.

Bacteria introduced at any stage of the beer-making process, from grain cultivation to bottling, have the potential to spoil beer. Beer-spoiling bacteria may:

(1) oxidise ethanol to acetate, making the beer taste of vinegar (acetobacteria)
(2) acidify the beer by facilitating redox reactions (lactobacillus)
(3) create unwanted flavours by producing esters, biogenic amines, other alcohols, sulphides, phenol and other compounds (various bacteria)

It is therefore essential that unwanted contamination is prevented when brewing enjoyable, safe-to-drink beer. To achieve this, brewing adopts rigorous hygiene practises. Among other strategies, beer benefits from antimicrobial compounds derived from hop flowers.

Evidence for Intelligent Design?

Given the historical (and practical) significance of hop flowers, it is unsurprising that their flavours and aromas have become indispensable components of beer as it is known today. It turns out that the compounds produced from boiled hop flowers kill bacteria but leave yeast cells unscathed. If these tolerances were reversed, yeast could not coexist with hop-derived compounds and instead bacteria would prosper, transforming beer into a toxic, vinegar-flavoured solution. On this basis, churchgoers could consider beer as evidence for intelligent design.

The Details (Science)

When hop flowers are boiled, as is done during the standard brewing procedure, iso-alpha acids are produced through a process called isomerisation. These iso-alpha acids inflict a number of damaging effects on bacterial cells but do not affect yeast cells.

In bacteria, iso-alpha acids act as proton ionophores. This means that the iso-alpha acids transport protons through the cell membrane into the bacterium. Doing so decreases the cytoplasmic pH, resulting in slowed enzymatic activity that inevitably halts cell growth, causing cell death. The iso-alpha acids also promote redox reactions with manganese that cause oxidative stress to the bacterium, further disrupting cell functions (Graphic accompanying article – The damaging effects of iso-alpha acids (iso-α) and bacterial cell functions.)

Unlike bacteria, yeast cells have a number of unique features that prevent cell damage from iso-alpha acids. These include modifying the cell wall in response to hop stress; reducing the concentration of alpha acids in the cell vacuole; and actively purging alpha acids from the cell itself.

Unfortunately for brewers and beer-lovers alike, some bacteria have developed resistance to iso-alpha acids, therefore beer spoilage is sometimes unavoidable. So perhaps beer is not evidence for intelligent design after all.

Even if beer is not the Holy fluid, we can still drink heartily knowing that evolutionary fortune has granted us the miracle of beer.

Graphic adapted from Bokulich & Bamforth 2013.

[1] This statement is contentious. See Chevallier J., 16 November 2013, “The great Medieval water myth”, Les Leftovers sort of a food history blog, accessed 5 April 2015, available at http://leslefts.blogspot.com.au/2013/11/the-great-medieval-water-myth.html
[2] Bokulich N. A. & Bamforth C. W., 2013, The Microbiology of Malting and Brewing, Microbiology and Molecular Biology Reviews, vol. 77, no. 2, p. 157-172, June 2013