Antimicrobials: There’s more to blue cheese than just the stench

Some members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria. Other species are used in cheesemaking. CC Image: CDC, SA 3.0

The distinctive, colourful marbled veins of blue lines cross-cross across the antique white surface of some of the world’s best and most flavoursome cheese. These cheeses are not only renowned for their taste and texture, but also for their pungent smells.

For some, the smell is sufficient to entice the taste buds and to get your stomach acid churning. For others, the smell is revolting, similar to worn socks after a park run.

The highway-like network of blue veins that twist and turn through blue cheeses are the hyphae and mycelium networks of edible Penicillium moulds. These filamentous fungi not only impart flavour to cheese, they also, as those familiar with the work of Alexander Flemming will know, produce compounds with antifungal, antibacterial, and other biological properties in high doses.

How can these compounds be more efficiently captured and processed for the benefit of humanity? Virginia Tech researchers have discovered a new, efficient way to synthesize some of these beneficial blue cheese compounds. This has been achieved deploying methods that avoid the use of harmful chemicals.

Previous problems with attempting the capture of the active ingredients either resulted in extremely low yields or required the use of harmful or dangerous chemicals, which would then have to be removed from the extracted compound.

As to why the new renewed interest in these fungi, antibacterial resistance has become a growing problem for society, which was caused by the overuse of antimicrobials – from animal rearing to mis-prescribing by medical doctors.

As I’ve written elsewhere:

“This has been compounded not only by microorganisms that are resistant to one antimicrobial or another, but due to the rise of multi-drug resistant microorganisms (the so-termed ‘super bugs’). Prominent examples include MRSA (methicillin-resistant Staphylococcus aureus), VISA (vancomycin-intermediate S. aureus), VRSA (vancomycin-resistant S. aureus), ESBL (Extended spectrum beta-lactamase), VRE (vancomycin-resistant Enterococcus) and MRAB (multidrug-resistant Acinetobacter baumannii).”

By finding a way to synthesize on a large scale a naturally occurring compound that has not previously been used for antibacterial applications, Virginia Tech researchers were able to evade the existing antibacterial resistances.

The extraction was achieved using an enzyme that can help create a natural product that has a different structure. Enzymes are proteins that help speed up chemical reactions. For their experiment, researchers used an enzyme that produces something called roquefortine L. Parts of its chemical structure are biologically active, which means that it can have beneficial properties such as antimicrobial activities.

This enzyme attaches two hydroxyl groups to a nitrogen atom, which are functional groups found in sugars and alcohols. A hydroxyl group consists of one hydrogen and one oxygen atom. Through a complex chemical process, the hydroxyl groups then develop an entirely different functionality.

Consequently, the compound extracted is of a form that makes it difficult for pathogens to become resistant.

In addition, the production of roquefortine L is central to the production of other molecules called glandiclone, melegranin, and oxaline, which have been shown to have broad antimicrobial properties and promising anticancer effects against human breast and leukaemia cancer cells.

The research has been published in the journal ACS Biochemistry. The paper is titled “Mechanism of Nitrone Formation by a Flavin-Dependent Monooxygenase.”