From baker to brewer

In addition to his role on the executive management committee of the FABLS network, Rob Learmonth also draws on the network in his own research.

A senior academic in the Faculty of Sciences' Department of Biological & Physical Sciences at the University of Southern Queensland in Toowoomba, Learmonth also has the impressive title of USQ Wine Industry Liaison Coordinator.

His research centres on developing novel ways to identify micro-organisms as well as assessing yeast health using fluorescence technology, which can potentially be adapted to industrial bioprocesses such as bread, beer and wine making (all the major food groups, in other words).

In particular, Learmonth has a long-term interest in the biochemistry and biophysics of yeast fermentation and propagation. Completing a PhD at Monash University in Melbourne, Learmonth's early work was on immunopathology, followed by studies on red blood cell membranes. In the early 1990s he began working on baker's yeast in collaboration with Burn Philp and Mauri Foods.

Learmonth is specifically interested in yeast membranes and the properties of membrane fluidity that change during adaptation processes. Obviously attracted by the cooler winters on the Darling Downs in Queensland, Learmonth moved to USQ in 1994, also moving from the bakery to the brewery to source his yeast and research focus.

More recently, with the growth of the Queensland wine industry and USQ taking on a wine-science teaching program, Learmonth has turned his priorities to the yeast strains added to help the natural stuff on wine grapes turn into the yummy stuff in the glass.

"The funny thing is that when I moved from baker's to brewer's yeast, I suddenly had twice as many friends! Now I am even more popular as the guy who is going to make a better wine!"

Industrial processes that use micro-organisms such as yeast and bacteria require cultures of reproducible purity and vitality. This is what prompted Learmonth to turn his interest in yeast from a basic biochemistry and microbiology angle to a bioengineering one.

He is now aiming to use his research on the fluorescence properties of yeast and bacterial cultures to devise rapid and simple techniques to identify strains and monitor their vitality, and can be potentially slotted into a given bioprocess without disruption and without having to go through days of traditional microbiology.

Learmonth knows from his years of research that fluorescence techniques can differentiate between yeast strains or between yeast and some bacteria with high sensitivity. In simple terms, Learmonth does spectral analysis of microbial mixtures using laser scanning fluorescence microscopy and looks for inherent differences.

Image analysis work carried out by collaborator Ewa Goldys at Macquarie University proves that these differences can be reliably quantified among batches to show contamination or yeast-strain ratios.

One of the interesting questions from a science viewpoint for Learmonth is what is causing the fluorescent differences he is measuring. He has looked at many different features of the yeast membranes such as tryptophan residues in proteins and now knows a lot about what isn't causing the fluorescence, but the actual source of the emission remains elusive.

However, his desire to answer this basic question is being overridden at present by the pressures to accept that there are differences and use them to distinguish organisms in a mixture - in other words, to apply the technique.

"There are plenty of people in industry who want to monitor fermentations or look for contamination - cheaply and easily and reliably, and without doing anything to their process. So, we are trying to get this technology out as soon as we can."

Learmonth and Goldys have to work out a few parameters such as the critical wavelengths to use for a particular application, but the ultimate aim is to modify the technology to a small-instrument or miniaturised scale for installation in an on-line system, with instrumentation that is fairly cheap, robust and user-friendly.

The research is now at the proof of concept stage - measuring spectral differences in individual cultures and controlled mixtures.

The next step will test more industrial-type media with challenges such as background fluorescence or levels of opacity, such as what would be found in milk processing.

"We know the concept is OK but it is still a long way to implementation. This is another stage when I will really see the benefit of the FABLS network, because I now need to access lots of other expertise that I do not have such as bioprocess engineering."

Membrane fluidity

One of Learmonth's other main aims in life, and an extension of his identification work, is to measure membrane fluidity in live cells with fluorescence, and look at them while they are adapting in real time.

This sort of technology would be applicable even more widely than that currently under development. Yeast membranes are known to change dynamically with adaptation processes such as during a wine ferment when the nutrient source changes from glucose to ethanol.

Whilst others over the years have concentrated on changes to particular proteins and sterols in yeast membranes, Learmonth has worked out a relatively simple way to measure membrane fluidity by fluorescence.

"My hypothesis is that changes in membrane fluidity are important for cell signalling pathways. Now I want to find out how and why this is, particularly in response to stresses such as oxidation."

He is now examining a series of yeast mutants by spectroscopy and multi-photon fluorescence microscopy to track changes in membrane fluidity. "It is good to see what is going on in individual cells, and measuring the different responses in these mutants to environmental changes."

From his research, Learmonth believes that membrane adaptability is actually a good indicator of vitality in a given yeast strain.

"This is important for wine makers, and maybe even more so for brewers because they re-pitch their yeast and use it several times, and so need yeast that is going to behave reproducibly and stay vital."

A rapid, cheap and easy test for organism vitality based on membrane fluidity also has the potential to be used in any microbial-based bioprocess.

With collaborators in the FABLS network, Learmonth is also looking for other novel fluorescence-based techniques to characterise micro-organisms, with new probes becoming available all the time for specific membrane domains such as lipid rafts.

At this time of year, the fluorescence work has been temporarily put on hold. Apparently the vintage this year has been extremely large and he is far too with his students picking grapes and making wine.