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A step change in craft brewing

New Wave: Petar Puškarić used yeast isolated from the Adriatic Sea to make a beer he named Morski Kukumar (sea cucumber).1 credit

Petar Puškarić is an engineer, environmentalist and beer production manager at LAB Split, a craft brewery in Split, Croatia. He received a master’s degree from the Department of Marine Studies at the University of Split last year, after successfully making a beer from Candida reporta yeast that can be isolated from seawater. He now hopes to commercially brew this sea yeast beer. He talks to Nature on some of the challenges of moving from thesis to commercialization.

How was your marine yeast beer born?

I have had a long interest in brewing beer and started brewing as a hobby when I was a student. During a marine microbiology class for my bachelor’s degree in ecology, my mentor Marin Ordulj and I started talking about marine yeasts, and one question led to another. We wondered if sea yeast could ferment beer.

We have searched the literature and found no one who has made a beer with yeast isolated from the sea. Perhaps we could become the first to do so? The idea stuck with me for a few years as I continued my education and moved on to master’s. When choosing my dissertation topic, I decided it was time to put the idea to the test. I spoke with Marin, and he agreed to help me plan an experiment. At that time, I was working part-time at the LAB Split brewery, so I had some brewing experience to bring to our investigations.

Our first task was to isolate the yeasts from the sea. We then tested the fermentation abilities of the isolated yeasts and grew cultures from the most promising samples. Finally, we used these cultures to brew beer.

How did you manage your time between brewing and your degree?

I wasn’t overorganized, but I always made sure to be disciplined and do what was needed as the tasks came. I also remained active outside of work, continuing to play as a mandolinist in an orchestra, for example.

I didn’t think too much about my career and took the time to do the things I loved. I would recommend other students to try to enjoy life and spend as much time as possible with friends. After all, life isn’t just about building a career. I was lucky enough to come up with a graduation topic that I found interesting and that my mentor liked: it got me through the most boring and difficult times.

What was the hardest part of the process?

The biggest problem was created by the marine bacteria, which grew too large for the yeast colonies and thus made yeast isolation more difficult. We solved this problem by using selective nutrient media, which inhibit the growth of bacteria. Eventually, this resulted in pure yeast cultures.

How did the beer taste?

The first beer tasting after all that research, thought and anticipation was really exciting. We noted clove and fruit aromas and a slightly tart tone. It didn’t taste like the sea; the flavor was closest to that of sour beer.

What impact do you hope this work will have?

Beer is an exciting product of my graduate studies, but I also hope that my thesis will encourage others to explore yeasts from the Adriatic Sea in more detail and realize their potential in ecology, medicine and nutrition. Split is on the Adriatic coast and I like the idea that we contribute in some way to the protection of this coastline.

Sea cucumber, as we named beer, may not directly help much in this regard, but hopefully it can raise awareness of how many useful things there are in the sea.

Do you plan to take sea yeast further in your career?

Any experience in microbiology helps in the food industry. Sea yeast could prove useful in brewing, but we need to consider the finances and infrastructure we would need to support its commercial use. For now, we are focusing on brewing more standard beers. In the future, I hope to brew some of my own recipes, whether it’s sea cucumber or something else. I would really like to combine brewing with researching new yeasts that can be used not only in beer making, but also in other industries.

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